No, 8984 
 
-^^^^ 
 
 x^^^^ * 
 
 0^00-,,% .^*\c^%^<L /..i^>>o /\c:,;l%\ --o^ 
 
 
 
 /% 
 
 •V. -"- .%>" ... V '" 
 
 
 ^^'^'^^. ^ 
 
 ^ o 
 
 
 
 
 
 
 
 
 
 ^a"^' Mi£^. V./^ *^^»'"' '"^^ -^^ ^^^ 
 
 ).♦ -^ />> 
 
 
 
 
 
 -^^^^ 
 
 65> »^- 
 
 ' '^. 
 
 ^^.'^'^ 
 
 * .♦'> 
 
 
 
 
 
 /.:^;fe%\. .>° .^^ °-.. ./Vi-i^'X .co^.^;:."°o ./\^^;^/\ co^ 
 
 
 f 
 
 °^ ^^<^ 
 
 
 
 
 
 
 
 ,*^'v 
 
 

 
 0^ "^o. *.-r.T^- ^ 
 
 ** -Jy^ ^<* 
 
 ,V 
 
 
 
 
 
 **„ ..** .'^-. *^^^# /^ \/ ..Jfe-, ^^^^^* 
 
 
 v.^' 
 
 
 
 
 ,'. -^^0^ -."-...^^Bl" '^^.^y :'£Sm>^\ ^^M.^ o^^m^'" V..-^' 
 
 ^oV 
 
 
 
 
 ^oV 
 
 
 "^Cf^^^ 
 
 
 
 
 
 
 r 
 
 
 ^* ^ %> -: 
 
 '•1^^^ 
 
 
 <*. c"^ »'^l^'. ' t.. A^ ^ /^'^^Ao^ "^^^ c'^^ ^^-Sl^'. ' ^ A-^ ' ♦tr(\'^^A- "^^ c;^*" »'^lg»Si'". 't.. .^^ 
 
 .<^v. 
 
 
 
 L ' » _ •<$*. 
 
 
 ^v^-*- 
 
 /% 
 
IC 
 
 8984 
 
 f: 
 
 0' 
 
 Bureau of Mines Information Circular/1984 
 
 Selected Pneumatic Gunites for Use 
 in Underground Mining: A Comparative 
 Engineering Analysis 
 
 By Gary W. Krantz 
 
 UNITED STATES DEPARTMENT OF THE INTERIOR 
 
Information Circular 8984 
 
 H 
 
 Selected Pneumatic Gunites for Use 
 in Underground Mining: A Comparative 
 Engineering Analysis 
 
 By Gary W. Krantz 
 
 UNITED STATES DEPARTMENT OF THE INTERIOR 
 William P. Clark, Secretary 
 
 BUREAU OF MINES 
 Robert C. Norton, Director 
 
V 
 
 A 
 
 < 
 
 .VX^# 
 
 k 
 
 ^' 
 
 
 UNIT OF MEASUREMENT 
 
 ABBREVIATIONS 
 
 USED IN THIS REPORT 
 
 A 
 
 angstrom 
 
 lb/gal 
 
 pound per gallon 
 
 "C 
 
 degree Celsius 
 
 Ib/h 
 
 pound per hour 
 
 cm 
 
 centimeter 
 
 lb/yd3 
 
 pound per cubic yard 
 
 cm2 
 
 square centimeter 
 
 m2/kg 
 
 square meter per kilogram 
 
 cm3 
 
 cubic centimeter 
 
 m^/min 
 
 cubic meter per minute 
 
 cm^/min 
 
 cubic centimeter 
 
 mg 
 
 milligram 
 
 
 per minute 
 
 mg/m^ 
 
 milligram per cubic meter 
 
 cP . 
 
 centipoise 
 
 mg/min 
 
 milligram per minute 
 
 °F 
 
 degree Fahrenheit 
 
 min 
 
 minute 
 
 ft 
 
 foot 
 
 mj 
 
 millijoule 
 
 ft^/mln 
 
 cubic foot per minute 
 
 mL/min 
 
 milliliter per minute 
 
 ft/s 
 
 foot per second 
 
 yL/min 
 
 microliter per minute 
 
 g , 
 
 gram 
 
 mm 
 
 millimeter 
 
 g/cm^ 
 
 gram per cubic 
 
 urn 
 
 micrometer (one millionth 
 
 
 centimeter 
 
 
 of a meter) 
 
 gal 
 
 gallon 
 
 02 
 
 ounce 
 
 h 
 
 hour 
 
 pet 
 
 percent 
 
 hp 
 
 horsepower 
 
 psi 
 
 pound per square inch 
 
 in 
 
 inch 
 
 psla 
 
 pound per square inch 
 
 in/ in 
 
 Inch per inch 
 
 
 (absolute) 
 
 keV 
 
 thousand electron volt 
 
 psig 
 
 pound per square inch (gauge) 
 
 L/min 
 
 liter per minute 
 
 s 
 
 second 
 
 lb 
 
 pound 
 
 yd3 
 
 cubic yard 
 
 lb/ft3 
 
 pound per cubic foot 
 
 ydVh 
 
 cubic yard per hour 
 
 Library of Congress Cataloging in Publication Data: 
 
 Krantz, Gary W 
 
 Selected pneumatic gunites for use in underground mining, 
 
 (Bureau of Mines information circular ; 8984) 
 
 Bibliography: p. 55-57. 
 
 Supt. of Docs, no.: I 28.27:8984. 
 
 1. Ground control (Mining). 2. Gunite. I. United States. Bureau 
 of Mines. II. Title. III. Series: Information circular (United States. 
 Bureau of Mines) ; 8984. 
 
 'N295.U4 [TN288] 622s [622'. 2] 84-600137 
 
.i 
 
 CONTENTS 
 
 Page 
 
 Abstract 1 
 
 Introduction 2 
 
 Background 4 
 
 Acknowledgments 5 
 
 Approach 5 
 
 Gunlte fibers 9 
 
 Gunlte additives and admixtures 11 
 
 Silica fume 11 
 
 Water reducers 12 
 
 Accelerators 13 
 
 Superplas ticizers 13 
 
 Polymer latex additives 13 
 
 Aggregate analysis 16 
 
 Gunlte specimen collection 17 
 
 Rebound analysis 23 
 
 Gunlte dust 27 
 
 Scanning electron microprobe analysis of silica fume 31 
 
 Compressive strength analysis 33 
 
 Flexural strength analysis 35 
 
 Porosity and permeability analyses 39 
 
 Delivery hose static discharge 45 
 
 Gunlte operation crew requirements 46 
 
 Gunlte cost analysis 48 
 
 Conclusions and recommendations 52 
 
 References 55 
 
 Appendix A. — Gunlte rebound data 58 
 
 Appendix B. — Air sampler dust data 59 
 
 Appendix C, — Gunlte pore volume, density, and porosity data 60 
 
 Appendix D, — Permeability data 61 
 
 Appendix E. — Cost data 63 
 
 Appendix F. — Toughness index discussion 64 
 
 ILLUSTRATIONS 
 
 1 . Dry-mix rotary gun used to apply gunlte specimen 4 3 
 
 2. Dry-mix double-hopper spray machine used to apply specimen 5 3 
 
 3 . Dry-mix rotary gun used to apply specimens 9 and 10 3 
 
 4. Wet-mix gunlte gun and mortar mixer used to apply specimens 1-3 4 
 
 5 . Location of the Lake Lynn Laboratory 6 
 
 6. Plan view of experimental mine workings showing gunlte demonstration panel 
 
 location 7 
 
 7. Geologic column of strata in vicinity of Lake Lynn Laboratory 8 
 
 8 . Gunlte fiber examples 9 
 
 9. Rotary gunlte gun used in polymer latex gunning 14 
 
 10. Styrene-butadiene latex polymer delivery pump 14 
 
 11. Polymer latex gunlte application 15 
 
 12. Water ring blockage by partially hydrated portland cement and polymer 15 
 
 13. Grain size accumulation curves for samples 1-3 18 
 
 14. Grain size accumulation curves for samples 4 and 5 19 
 
 15. Grain size accumulation curves for samples 6 and 7 20 
 
 16. Grain size accumulation curves for samples 8 and 9 21 
 
n 
 
 ILLUSTRATIONS—Continued 
 
 Page 
 
 17. Grain size accumulation curve for sample 10 22 
 
 18. NX-size cores of four gunite specimens 22 
 
 19. Wet-mix gunite sample acquisition for splitting tensile analysis 23 
 
 20. Six-inch-diameter by 12-in-long cylinders of six different gunite products 23 
 
 2 1 . Gunite rebound collected and ready for weighing 26 
 
 22 . Angled roof gunning produces very high rebound 26 
 
 23. Near-vertical wet-mix roof gunning gives low rebound 27 
 
 24. Near-vertical dry-mix roof gunning with reduced pressure gives low rebound 27 
 
 25 . Gunite dust monitoring equipment 28 
 
 26 . Gunite dust from the gun-loading operation 29 
 
 27. Gunite gun dust on mine floor caused by worn friction plate or wear pad... 29 
 
 28. Scanning electron microscope microphotograph of portland cement and silica 
 
 fume 31 
 
 29. Scanning electron microscope microphotograph of silica fume 31 
 
 30 . Electron probe microanalysis of portland cement 32 
 
 31. Electron probe microanalysis of silica fume 32 
 
 32. Tinius Olsen 120,000-lb testing machine used in gunite analysis 33 
 
 33. Stainless steel rotating bearing block used in gunite core compressive 
 
 strength analysis 34 
 
 34. Gunite compressive strength plot showing rapid failure 35 
 
 35. Gunite compressive strength plot showing gradual failure 35 
 
 36. Diamond-tipped saw used to cut steel-f ibered gunite specimens 37 
 
 37. Flexural strength curve of a steel-f ibered gunite sample 39 
 
 38. Gunite core air evacuation system for porosity analysis 41 
 
 39 . Gunite permeability analysis system diagram 42 
 
 40. Gunite permeability analysis equipment 43 
 
 41. Hassler tube and associated core permeability measuring apparatus 43 
 
 42. Linear regression curve fit of porosity and permeability 45 
 
 TABLES 
 
 1 . Gunite fibers tested at BOM Experimental Mine 10 
 
 2. Normal fiber mix rates and typical diameter sizes 11 
 
 3 . Polymer latex gunite materials tested 14 
 
 4. Sand-size fraction content in gunite 17 
 
 5 . Gunite rebound percentages 25 
 
 6. Gunite dust data 30 
 
 7 . Element X-ray spectrum data for silica fume 32 
 
 8. Element X-ray spectrum data for cement 32 
 
 9. Compressive strengths of f ibered-gunite specimens 36 
 
 10 . Flexural strength of f ibered-gunite specimens 38 
 
 11. Gunite density and porosity 41 
 
 12. Gunite mean permeability values 44 
 
 1 3 . Gunite crew requirements 46 
 
 14. Gunite shooting rate 47 
 
 15. Portland cement price data 49 
 
 16. Gunite fiber price data 49 
 
 17. Wet-mix gunite admixture costs 49 
 
 18. Cost estimate for prebagged, wet-mix, silica fume, steel-f ibered gunite...^ 51 
 
 19. Prebagged gunite cost comparison 51 
 
SELECTED PNEUMATIC GUNITES FOR USE IN UNDERGROUND MINING: 
 A COMPARATIVE ENGINEERING ANALYSIS 
 
 By Gary W, Krantz ^ 
 
 ABSTRACT 
 
 Fibered, portland-cement-based gunite products were applied in the 
 Bureau of Mines Lake Lynn Laboratory Experimental Mine using a variety 
 of pneumatic guns and gunning crews. The demonstrated wet-mix (with 
 silica fume), dry-mix, and surface bonding products were sampled by the 
 Bureau and subjected to a suite of engineering analyses. Gunite flex- 
 ural and compressive strength, rebound, permeability, porosity, dust 
 loading, shooting rate, crew requirements, and cost factors were evalu- 
 ated. Steel, fiberglass, or polypropylene fibers were contained in all 
 but two of the gunites tested. Both Bureau and private testing labora- 
 tory analyses are provided for some products. Electron probe micro- 
 analysis and X-ray diffraction analysis were performed on the silica 
 fume fraction of the wet-mix gunite to characterize the dust. Aggre- 
 gate size fraction distribution analyses were performed to provide 
 strength relationships. Results indicate that all of the commercially 
 available fibered-gunite materials tested can provide beneficial seal- 
 ant, spall prevention, or roof stability control attributes for under- 
 ground mining environments when applied by an experienced crew using a 
 well-maintained gun, in accordance with product manufacturers' recom- 
 mendations and when used for the designated purpose. 
 
 ^Engineering geologist, Pittsburgh Research Center, Bureau of Mines, Pittsburgh, PA. 
 
INTRODUCTION 
 
 Shotcrete, or pneumatically sprayed 
 concrete or mortar, originated in the 
 early 1900' s. The name "gunite" (former- 
 ly the registered trade-mark of the Al- 
 lentown Pneumatic Gun Co.) was coined by 
 the Cement Gun Co. Gunite or shotcrete 
 is defined by the American Concrete In- 
 stitute as mortar or concrete conveyed 
 through a hose and pneumatically pro- 
 jected at high velocity onto a surface 
 il) .^ The force of the pneumatically 
 propelled material impacting on the sur- 
 face causes compaction of the gunite into 
 the fine surface irregularities, giving 
 good adhesion. Pneumatic gunning results 
 in a dense, dry (low water-cement ratio) 
 coating that is capable of supporting 
 itself in vertical or horizontal (over- 
 head) applications. Gunite has been re- 
 ferred to by a variety of names, includ- 
 ing spraycrete, pneumatically applied 
 mortar or concrete, airblown mortar or 
 concrete, gunned mortar or concrete, and 
 shotcrete. 
 
 Aggregate size is the criterion used 
 here to distinguish between gunite and 
 shotcrete. Although sprayed mortar has 
 been used for more than 50 years, only 
 recent innovations in pneumatic equip- 
 ment have enabled the use of aggregate 
 as large as 1 in (25.4 mm). In gener- 
 al, the pneumatically applied material 
 is called shotcrete if it contains ag- 
 gregates larger than 5 mm and gunite if 
 the largest aggregate is smaller than 5 
 mm. The largest aggregate contained in 
 any material tested during this re- 
 search project passed through a No. 4 
 sieve (4.75 mm). Therefore, for purposes 
 of this discussion, the material is re- 
 ferred to as gunite or fibered gunite. 
 
 and compressive strength. The type and 
 amount of improvement are dependent upon 
 the amount of fibers and their type, 
 size, strength, and configuration (2^). 
 
 Fibered gunite has a wide variety of 
 uses including but not limited to the 
 following: 
 
 o Packwalls in longwall mining 
 
 o Mine roof and rib control and 
 support 
 
 o Rock tunnel linings 
 
 o Mine roof and rib sealant 
 
 o Mine shaft lining (hoist and vent 
 shafts) 
 
 o Mine shaft collar installation 
 
 o Underground joint or fault stabili- 
 zation in mines 
 
 o Highwall and rock slope 
 stabilization 
 
 o Dam construction 
 
 o High-strength protective concreting 
 for foundations 
 
 o Thin-shell dome construction 
 
 o Fire protection applications 
 
 o Bridge repair 
 
 The Bureau's major interest in the mate- 
 rial is its mining applications. 
 
 The inclusion of fibers in gunite im- 
 proves many of the desirable engineering 
 properties of the product. These include 
 ductility, toughness, flexural strength, 
 impact resistance, fatigue resistance, 
 
 ^Underlined numbers in parentheses re- 
 fer to items in the list of references 
 preceding the appendixes. 
 
 Gunite has two primary application 
 techniques — wet mix and dry mix. With 
 the dry mix, the ingredients are volume- 
 or weight-batched and mixed dry or pre- 
 bagged (mixed) . The dry material is nor- 
 mally fed to a pneumatically operated gun 
 which delivers a smooth, continuous flow 
 of material through the delivery hose and 
 to the nozzle. The nozzle is equipped 
 
with a manually operated water injection 
 ring system that provides even distribu- 
 tion and mixing of water with the dry in- 
 gredients as they are propelled through 
 the nozzle and onto the application sur- 
 face. Dry-mix machines are categorized 
 as either high velocity or low velocity, 
 depending on the application pressure and 
 nozzle size. Figures 1-3 show three of 
 the dry mix gunite guns used in this in- 
 vestigation. (A fourth dry-mix-type gun 
 is shown in figure 9.) 
 
 With wet mix, water is mixed with the 
 dry constituents in a batch mixture by 
 either weight or volume. Weight batch- 
 ing of the gunite ingredients is nor- 
 mally recommended. The batch is normally 
 tested for slump, entrained air con- 
 tent, and uniformity before delivery to 
 the application equipment. The mixture 
 is moved through the equipment deliv- 
 ery hose by a pump or with compressed 
 air and sprayed (with compressed air) 
 through the nozzle. Efficient, positive- 
 displacement-type wet-mix delivery equip- 
 ment has been recently introduced to the 
 
 FIGURE 2o " Dry-mix double=hopper spray ma= 
 chine used to apply specimen 5. 
 
 FIGURE L - Dry-mix rotary gun used to apply 
 gunite specimen 4. 
 
 FIGURE 3. - Dry-mix rotary gun used to apply 
 specimens 9 and lOo 
 
market. With this equipment, the wet 
 mixture is forced through the delivery 
 hose by a piston pump or screw-feed pump 
 to the nozzle, where a compressed air in- 
 jector ring pneumatically discharges the 
 mixture at high velocity onto the appli- 
 cation surface. A screw-feed type of 
 gunite pump was used for the wet-mix ap- 
 plication portion of this research proj- 
 ect. Figure 4 shows the wet-mix gunite 
 equipment and mixer used in this investi- 
 gation. Accelerator fluids are easily 
 added at the nozzle in quantities depen- 
 dent on the application surface. Plas- 
 ticizers and superplasticizers are added 
 at the mixer to improve the workabil- 
 ity (pumpability) of the material while 
 maintaining the low slump and low water- 
 cement ratio required in high-strength 
 material. 
 
 Various types of gunite guns and nozzle 
 assemblies are commercially available and 
 were used during this research product. 
 Gun and/or nozzle selection depends on 
 
 FIGURE 4. = Wet-mix gunite gun and mortar 
 mixer used to apply specimens 1-3. 
 
 the nature of the gunite product to be 
 used, desired engineering parameters of 
 the final product, quantity of material 
 to be applied, rate of application, oper- 
 ating gun-nozzle distance, cost, and 
 other factors. 
 
 BACKGROUND 
 
 As early as 1911, small-diameter metal 
 shavings and slivers of steel were tested 
 in concrete products (and patents were 
 issued) for the purpose of providing 
 structural reinforcement. In the late 
 1950' s, the Portland Cement Association 
 began conducting studies to determine 
 the strength properties of steel-fiber- 
 reinforced concrete and mortar. The 
 first detailed and documented crack- 
 arrest research on steel-f ibered concrete 
 products was conducted in 1963-64 at 
 Carnegie-Mellon University in Pittsburgh. 
 Experimentation with steel-f ibered shot- 
 crete and gunite was conducted in 1971 at 
 the Battelle Memorial Institute. During 
 the same year, the Bureau of Mines began 
 conducting research on the use of steel- 
 fibered shotcrete and gunite for use in 
 underground mine roof and rib structural 
 control O) . 
 
 By 1973, the use of steel fibers in 
 shotcrete and gunite had advanced to such 
 a degree that they were employed by the 
 U.S. Army Corps of Engineers in a tunnel 
 at the Ririe Dam in Idaho. Much of the 
 
 early work on fibered gunite was con- 
 ducted using relatively high fiber load- 
 ings (130 to 260 lb/yd ^) and using steel 
 fibers of relatively small diameter 
 (0.010 in) and relatively high aspect 
 ratios (up to 100) (3^). Aspect ratio of 
 the fibers refers to the fiber length 
 divided by its diameter, or equivalent 
 diameter in the case of nonround fibers. 
 The concrete material used in much of the 
 early research was actually a cement-sand 
 mortar containing no coarse aggregate. 
 The research was devoted primarily to 
 determining the effect of fiber content, 
 configuration, and aspect ratio on the 
 engineering properties of the mortar or 
 concrete, including tensile strength, 
 flexural strength, creep, impact resist- 
 ance, fatigue resistance, and durability. 
 As research on steel-f ibered mortar and 
 concrete progressed during the 1960's, 
 there was a trend to the use of concretes 
 in favor of mortars and to the use of 
 larger diameter, smaller-aspect-ratio 
 steel fibers. The change to the lower- 
 aspect-ratio fibers was necessitated by 
 the unacceptably low workability of 
 
mortars or concretes containing large 
 amounts of high-aspect-ratio fibers. The 
 shift from mortar to concrete was made 
 due to the high application volumes of 
 coarse aggregate materials O) . 
 
 The list of materials used for fibers 
 in gunite has now expanded to include 
 plastic, natural materials, steel (up to 
 2 pet by volume) , standard and alkaline- 
 resistant (AR) fiberglass, polypropylene, 
 nylon, and other materials. The search 
 continues to find inexpensive, high- 
 strength, nondeteriorating, easily ac- 
 cessible fibers with good workability 
 
 characteristics for use in general and 
 specialty applications. Additionally, 
 silica fume, fly ash, ground slag, poly- 
 mers , and latex-based additives have been 
 introduced into the pneumatically ap- 
 plied, cement-based products to impart 
 improved adhesion and engineering proper- 
 ties and to upgrade the sealant, chemical 
 attack, and freeze-thaw characteristics. 
 Use of the specialty materials has ex- 
 panded considerably in the past 5 years 
 and should continue to capture new mar- 
 kets in a diverse array of construction 
 and mining applications. 
 
 ACKNOWLEDGMENTS 
 
 The research effort, product demonstra- 
 tion, comparative analyses, and findings 
 compiled in this report were made possi- 
 ble by the participation and generosity 
 of four major gunite product manufactur- 
 ing companies: B Bond Industries, Inc., 
 Latrobe, PA; Burrell Construction and 
 Supply Co., New Kensington, PA; Coal In- 
 dustry Services Co., Pounding Mill, VA; 
 and Elborg Technology Co., Pittsburgh PA. 
 The author would also like to acknowledge 
 
 the Mine Safety and Health Administration 
 at Bruceton, PA, and the Department of 
 Energy at Bartlesville, OK, who provided 
 facilities and research testing equipment 
 for portions of the investigation. The 
 author is particularly indebted to the 
 staff and management of the Bureau of 
 Mines Lake Lynn Laboratory facility, who 
 provided physical, logistical, and tech- 
 nical assistance throughout the work. 
 
 APPROACH 
 
 The Bureau has been involved with 
 f ibered-gunite development (for mining 
 applications) since the early 1970' s. 
 The Bureau's general philosophy regarding 
 the material and the Bureau research lit- 
 erature published to date on the topic 
 support a generalized theory that the 
 various fibered, portland-cement-based 
 gunite materials can improve mine roof 
 and rib stability and contribute to a 
 safer underground mining environment when 
 properly applied. Past Bureau research 
 at the Spokane Mining Research Center 
 (1975) recognized fibered gunite as a new 
 and promising structural material for 
 ground support ( 4_) . Recent domestic, 
 f ibered-gunite product improvements have 
 made inroads on the problems encountered 
 in the early fibered-gunite research — 
 mainly fiber balling (birds' nesting), 
 lack of product homogeneity, fiber- 
 aspect-ratio-caused handling problems , 
 and high rebound or wastage. The advent 
 
 of prebagged mixes has essentially re- 
 solved the first three problems. Im- 
 proved gunning equipment has reduced the 
 latter problem considerably. A basic, 
 unbiased research effort designed to com- 
 pare several of the various fibered- 
 gunite materials was needed in order to 
 identify the properties of a cross sec- 
 tion of the generic products that might 
 be used at the Lake Lynn Laboratory. 
 
 A research program .was designed that 
 would allow wet-mix and dry-mix fibered- 
 gunite material comparisons for the fol- 
 lowing parameters: 
 
 o Ease of gun loading 
 
 o Gun-caused dust loadings 
 
 o Gun noise and operation 
 
 o Application ease 
 
o Rebound or wastage 
 
 o Down-drift dust (cumulative) loading 
 
 o Comparative engineering parameters:. 
 
 Splitting tensile strength 
 (Brazilian) 
 
 Flexural strength 
 
 Compressive strength 
 
 Porosity 
 
 Permeability 
 
 o Comparative product mechanical sieve 
 analysis 
 
 o Product cost comparisons 
 
 o Long-term durability (not reported 
 herein) 
 
 o Bonding strength (not reported 
 herein) 
 
 Owing to the vast number of gunlte fi- 
 ber types, sizes, and configurations, the 
 varying component mixture ratios (speci- 
 fications), and the variety of gunlte 
 guns, nozzles, and mix methods available, 
 a comparative gunlte product research 
 project had to be approached carefully. 
 This point became even more cogent when 
 product confidentiality was considered. 
 
 The Bureau elected to conduct the gun- 
 lte comparative research at the Lake Lynn 
 Laboratory Experimental Mine, approxi- 
 mately 60 miles south of Pittsburgh, PA, 
 on the Pennsylvania-West Virginia border 
 (fig. 5). Figure 6 presents a plan view 
 of the mine and identifies the gunlte 
 application area. 
 
 A 25-ft section of D drift in the Lake 
 Lynn Laboratory Experimental Mine was 
 used for each product on a separate 
 schedule basis that would allow approxi- 
 mately 1 week of application time per 
 product if needed. The four participat- 
 ing gunlte manufacturers were permitted 
 to prepare the roofs and ribs of their 
 
 ©Pittsburgh 
 ^ Bruceton 
 
 O Uniontown 
 
 ^ Lake L ynn Loborot ory 
 
 l__PA 
 
 WV 
 
 O Morgantown 
 FIGURE 5. - Location of the Lake Lynn Laboratory. 
 
 respective drift sections in accordance 
 with their particular product needs. In 
 some Instances, loose rock was barred 
 down and the fresh surface was air-blown 
 and/or water-mist-fogged prior to gunlte 
 application. Although roof or rib bolts 
 and/or wire mesh would have improved the 
 properties of some of the tested prod- 
 ucts, they were disallowed for this par- 
 ticular comparative research effort. 
 
 The experimental mine drifts at the 
 Lake Lynn Laboratory are developed in a 
 section of the Wymps Gap Limestone, a 
 formation comprised of Intercalated lime- 
 stones and calcareous shales. The lime- 
 stone is grey, crystalline, and fossilif- 
 erous. A 1-ft-thlck dark grey, calcare- 
 ous shale stringer occurs at the roof-rib 
 Interface in the mine drift where the 
 gunlte test applications were performed. 
 The shale stringer is prone to spalling 
 and provides a suitable test of the capa- 
 bility of the gunlte products to seal, 
 support , and protect the rock from mois- 
 ture absorption and subsequent expansion 
 and/or spalling. Figure 7 presents the 
 geologic column of the Lake Lynn Labora- 
 tory site. 
 
 Future mine explosion research to be 
 conducted in D drift will subject the ap- 
 plied gunlte to rigorous conditions. The 
 bonding strength and durability parame- 
 ters can be analyzed at a future time. 
 
Gunite application panels 
 
 Gas-mixing stub^k 
 Explosion-proof bwlkhead-"^ 
 
 Ventilation stub— 
 
 Explosion-proof bulkhead—* 
 
 Gas-mixing stub— 
 
 FIGURE 6. - Plan view of experimental mine workings showing gunite demonstration panel location. 
 
 The floor of the experimental mine is 
 concrete, which permitted rebound mate- 
 rial to be collected with shovels for 
 weighing. 
 
 Dust collection and monitoring were 
 performed. Mine temperature and relative 
 humidity were monitored , as were all oth- 
 er visible factors regarding the gunite 
 application. 
 
 Gunite product samples were collected 
 in 6-in-diam by 12-in-long containers for 
 splitting tensile strength tests. Four- 
 by four- by fourteen-inch samples were 
 sprayed directly into plywood forms for 
 the flexural strength tests. Additional 
 flexural tests were performed on sawn 
 beams. A 24-in-square metal container 
 was shot with an 8- to 10-in-thick sample 
 of the various gunite products for cor- 
 ing. NX-sized (2.1-in) diamond-drilled 
 cores were taken from these sample blocks 
 
 to perform uniaxial unconfined compres- 
 sive strength tests. Additional testing 
 for compressive strength was performed 
 using sawn cubes. The data tables indi- 
 cate the configuration of the sample used 
 in the respective test procedure. 
 
 The fibered gunite samples were tested 
 by the Bureau using a Tinius Olsen^ hy- 
 draulic universal testing machine. The 
 machine has a 120,000-lb maximum pressure 
 capacity and is equipped with multiscale 
 electronic load-indicating dials. The 
 loading rate was controlled with the use 
 of an auxiliary pacing disc. An elec- 
 tronic deflectometer was used to measure 
 specimen deflection under load and was 
 coupled to an x-y graph plotter to obtain 
 stress-strain curves for each specimen. 
 
 ^Reference to specific products does 
 not imply endorsement by the Bureau of 
 Mines. 
 
UPPER KITTANNING COAL 
 MIDDLE KITTANNING COAL 
 
 LOWER KITTANNING COAL 
 
 KITTANNING SANDSTONE 
 CLARION COAL 
 
 BROOKVILLE COAL 
 
 HOMEWOOD SANDSTONE 
 
 MERCER COAL 
 CONNOQUENE3SING SANDSTONE 
 
 QUAKERTOWN COAL 
 SHARON COAL 
 
 LAKE LYNN HIGHWALL FACE 
 
 ZITZISZ SHALE, EXTREMELY WEATHERED, FRACTURED 
 
 !^ 
 
 WYMPS GAP LIMESTONE 
 
 (FORMELY GREENBRIER LIMESTONE) ■ 
 
 ^■■i l i ' 
 
 I I I I I 
 
 I • I • I • ' 'T 
 
 DEER VALLEY LIMESTONE 
 
 CX3 
 
 a 
 
 w 
 
 XI 
 
 BURGOON SANDSTONE 
 
 :^->zV 
 
 MURRYSVILLE SANDSTONE ' 
 
 SHALE, RED. MEDIUM HARD, FISSILE 
 SHALE, GREEN, SILTY, SANDY SEAMS 
 
 rrrLLL-T SHALE, RED AND GREEN, MEDIUM HARD, FISSILE 
 
 LIMESTONE, GRAY. HARD. MASSIVE 
 SHALE, DARK GRAY. BADLY BROKEN 
 SHALE. RED. MEDIUM HARD. FISSILE 
 LIMESTONE. GRAY. HARD. MASSIVE 
 SHALE, GREEN, INTERBEDDED V\//LIMESTONE 
 LIMESTONE. GRAY. HARD. MASSIVE 
 
 LIMESTONE. DARK GRAY, HARD, MASSIVE 
 
 QUARRY FLOOR 
 
 FIGURE 7. - Geologic column of strata in vicinity of Lake Lynn Laboratory. 
 
GUNITE FIBERS 
 
 Many types of fibers are commercially 
 available for use in gunite. The fibers 
 of a particular composition come in vary- 
 ing lengths and/or diameters. Some are 
 collated with water-soluble glue into 
 bundles of 10 to 30 fibers to facilitate 
 handling and mixing O ) . Figure 8 shows 
 examples of some types of fibers. The 
 more common types of gunite fibers in- 
 clude E-f iberglass, AR-f iberglass , steel 
 (carbon and stainless), polypropylene, 
 and nylon. Polyethylene, polyvinyl chlo- 
 ride, and polytetraf luoroethylene fibers 
 may have limited gunite applications due 
 to their alkalai resistance. 
 
 E-fiberglass fibers are not highly rec- 
 ommended in fibered gunite unless pro- 
 tected by some means from expansive re- 
 actions and silica dissolution caused 
 by alkaline attack (introduced by the 
 Portland cement) (6^). Fiber deteriora- 
 tion has been reported when unprotected 
 E-fiberglass fibers were used in gunite 
 (2^, 6) . The alkaline attack results from 
 three major concrete and/or gunite alka- 
 lis: calcium, sodium, and potassium 
 hydroxide. Glasses are available that 
 exhibit very low reactivity, both in re- 
 duction from alkalinity and in silica 
 dissolved (upon exposure to alkalis) (7). 
 
 
 ^ 
 
 B 
 
 
 FIGURE 8. - Gunite fiber examples. A, 1-in cold-drawn wire, X 63; B, 1-in cold-drawn wire, X 200; 
 C, 2-in melt-extract carbon steel, X 63; D, 0.71-in slit sheet, enlarged end, X 63; E, 0.71=in slit 
 sheet, enlarged end, X 200; F, 1-in slit sheet carbon steel, X 63; G, 1-in slit sheet carbon steel, 
 X 200; H, 0.75°in Duform, cold-drawn, X 63; /, 0.75-in Duform, cold-drawn, X 200; J, l°in melt ex- 
 tract, X 63; K, 3/4-inmelt extract, X 63; L, 3/4-inmelt extract, X 200; M, 1/2-in polypropylene, X 63; 
 A', 1-in fiberglass, X 63; 0, 1-in steel, deformed, X 63; P, 1.5-in drawn wire, deformed, X 63; Q, 1/2- 
 in drawn wire, X 63; R, 1/2-in drawn wire, X 200. 
 
10 
 
 The E-fiberglass fibers are more connnonly 15 are 
 used in plastic or polymer reinforcement. fibers. 
 
 variations of slit-sheet steel 
 
 The more suitable, high-zirconia AR- 
 fiberglass fibers developed in the late 
 1960's are more commonly used in fibrous, 
 portland-cement-based gunite. Type I ce- 
 ment is normally recommended and commonly 
 used with fiberglass fibers for general 
 use, owing to cost and other factors. 
 Type II or III cement may be recommended 
 with some fibers if moderate sulfate 
 action is anticipated or if high early 
 strength is required. Five types of 
 fiberglass-fiber gunites or surface- 
 bonding cements were tested during the 
 research period. Table 1 presents the 
 various types of gunite fibers used in 
 this investigation, their length, and the 
 type of cement used. 
 
 2. Cold-drawn wire method — cold-drawn 
 wire is chopped to specified lengths. 
 The wire fibers may also be deformed, 
 kinked, or twisted. Sample 7 is a varia- 
 tion of this type of fiber. 
 
 3. Melt-extraction method — a process 
 whereby a rotating, cooled disc with 
 indentations the size of the fiber is 
 dipped (spinning) in the surface of a 
 molten pool of high-quality metal. The 
 fibers formed by this technique can be 
 altered in length, shape, and configura- 
 tion by altering the disc indentations. 
 This fiber type was not tested; however, 
 figure 8 shows variations of the fiber 
 type. 
 
 Steel fibers are manufactured by many 
 different processes for use in fibered 
 gunite, including — 
 
 1. Slit-sheet method — a sheet of steel 
 is cut or slitted, producing a square 
 or rectangular fiber. The fibers may 
 then be deformed at the ends, kinked, 
 or twisted. Samples 1-3, 6, 10, 11, and 
 
 The steel fibers range in strength from 
 50,000 to 300,000 psi ultimate strength. 
 Fiber sizes range from 1/2 by 0.010 in 
 to 2-1/2 by 0.030 in (_2 ) . Fibers with 
 kinks , deformed ends , or other locking 
 mechanisms develop higher ultimate flex- 
 ural and/or splitting tensile strength 
 gunite owing to the increased fiber 
 pullout resistance. Fibers with larger 
 
 TABLE 1. - Gunite fibers tested at BOM Experimental Mine 
 
 Sample 
 
 Fiber type 
 
 Length of 
 fiber, mm 
 
 Type of 
 cement 
 
 Type of 
 mix 
 
 1.. 
 
 2., 
 
 3., 
 
 4., 
 
 5I, 
 
 6., 
 
 7., 
 
 8l, 
 
 9., 
 
 10., 
 
 11.. 
 
 12.. 
 
 13.. 
 
 14.. 
 
 152, 
 
 162, 
 
 172, 
 
 Steel (slit-sheet). 
 
 . . .do 
 
 . . .do 
 
 AR-f iberglass 
 
 ...do 
 
 Steel (slit-sheet)... 
 Steel (cold-drawn),.. 
 
 E-fiberglass 
 
 AR-f iberglass 
 
 Steel (slit-sheet)... 
 
 . . .do 
 
 No fiber 
 
 Polypropylene 
 
 AR-f iberglass 
 
 Steel 
 
 No fiber 
 
 Polypropylene , 
 
 18 
 
 18 
 
 18 
 
 12.7 
 
 12.7 
 
 25.4 
 
 30 
 
 12.7 
 
 12.7 
 
 25.4 
 
 25.4 
 
 NAp 
 25.4 
 12.7 
 25.4 
 
 NAp 
 25.4 
 
 III 
 
 III 
 
 III 
 
 II 
 
 II 
 
 lA 
 
 lA 
 
 III 
 
 I 
 
 I 
 
 I 
 
 I 
 
 I 
 
 I 
 
 I 
 
 I 
 
 I 
 
 Wet 
 Wet 
 Wet 
 Dry 
 Dry 
 Dry 
 Dry 
 Dry 
 Dry 
 Dry 
 Dry 
 Dry 
 Dry 
 Dry 
 Dry 
 Dry 
 Dry 
 
 NAp Not applicable. 
 
 ^Samples 5 and 8 were surface-bonding mortars (cement), 
 
 2samples 15-17 were shot with latex polymer. 
 
11 
 
 surface area (square or rectangular as 
 compared to round) have more concrete 
 bonding area. Accordingly, fibers with 
 a scarified (pitted) surface have a 
 greater surface area than smooth-surfaced 
 fibers. 
 
 Corrosion of steel fibers in gunite 
 with a high water-cement ratio may pose a 
 deterioration problem. The free moisture 
 in wet concrete (and gunite) provides an 
 aqueous medium which facilitates trans- 
 port of soluble chemical substances, such 
 as oxygen, calcium hydroxide, alkalis, 
 and chlorides, toward the metal. It also 
 increases the electrical conductivity of 
 the material, thus aiding any tendency 
 for electrochemical corrosion (7^) . For 
 this reason, high-quality steel or stain- 
 less steel is used by many fiber manufac- 
 turers in an effort to prevent or at 
 least reduce corrosion. 
 
 Polypropylene fibers are essentially a 
 crystalline thermoplastic produced by 
 
 polymerizing polypropylene monomer in the 
 presence of a catalyst. The fibers are 
 chemically inert, are noncorrosive, and 
 have a high chemical resistance to min- 
 eral acids, bases, and inorganic salts. 
 The fibers are recommended for use as a 
 secondary type of reinforcement in con- 
 crete (maintains integrity of concrete 
 against cracking) rather than for primary 
 reinforcement (structural support). In 
 gunite the polypropylene fibers arrest 
 the cracking process during the plastic 
 shrinkage stage, creating microcracks 
 rather than large cracks (8^) . The poly- 
 propylene fiber tested in this research 
 effort is manufactured in a fibrillated 
 bundle which springs open during mixing. 
 
 A generalized mixing rate for the vari- 
 ous fiber types is presented in table 2. 
 A range of mix rates is provided, depend- 
 ing on manufacturers' specifications and 
 the strength or specialty requirements of 
 the gunite. 
 
 GUNITE ADDITIVES AND ADMIXTURES 
 
 Some gunite manufacturers, particularly 
 wet-mix gunite manufacturers, have re- 
 cently introduced a variety of additives 
 and admixtures into gunite to improve 
 strength, adhesiveness, cohesiveness , and 
 freeze-thaw and abrasion-resistance char- 
 acteristics, and to reduce rebound. Six 
 of the gunite products tested in this 
 investigation included known additives 
 or admixtures. A brief discussion is 
 provided of the major additives and 
 
 tures used in the wet-mix gunite in this 
 investigation. 
 
 SILICA FUME 
 
 Silica fume and ferrosilicon dust (es- 
 sentially the same material but with 
 slightly different chemical compositions) 
 are essentially by-products of silicon 
 metal and ferrosilicon alloy manufactur- 
 ing. The light grey to grey silica fume 
 
 TABLE 2. - Normal fiber mix rates and typical 
 diameter sizes ^ 
 
 Fiber type 
 
 pet (by vol) 
 
 lb/yd; 
 
 Typical diam, in 
 
 Fiberglass: 
 
 E type 
 
 AR type 
 
 Steel 
 
 Polypropylene. . 
 
 1 -5 
 
 1 -5 
 
 .4-2 
 
 .1 
 
 40 
 40 
 50-265 
 1.6 (av.) 
 
 0.0002 to 0.0006 
 
 0.010 to 0.030 
 0.0008 to 0.015 
 
 ^These figures represent the concentration of fibers 
 normally used in gunite products. The figures do not im- 
 ply that equivalent performance will be achieved by the 
 various fiber types at these concentrations. 
 
12 
 
 develops above the molten burden in an 
 electric arc furnace as escaping SiO gas 
 oxidizes and condenses into a solid vi- 
 treous particulate Si02 form (9^) , The 
 initial investigations on the effect of 
 silica fume in concrete were conducted in 
 the 1950' s (10) . The developmental work 
 and actual use of the material started in 
 1969 (U), 
 
 Silica fume production in the United 
 States and Canada is difficult to esti- 
 mate since it is directly tied to the 
 currently depressed ferroalloys industry, 
 but 500,000 tons per year of silica fume 
 are reportedly available in the Western 
 World and Japan. Total annual production 
 from the United States and Canada is ap- 
 proximately 205,000 tons of silica fume 
 with Si02 content higher than 70 pet. Of 
 this, only 80,000 to 120,000 tons is ex- 
 pected to be of suitable quality for con- 
 crete (and gunite) use. Silica fume from 
 15 sources in the United States and Can- 
 ada had 63.3 to 96 pet Si02 , 0.10 to 5.45 
 pet AI2O3, 0.10 to 12.2 pet Fe203, and 
 1.75 to 10 pet C (11). The silica fume 
 tested in this investigation was found by 
 the Bureau to have the above components 
 plus trace amounts of sulfur, potassium, 
 calcium, titanium, and chromium. Silica 
 fume size (diameter) was determined to be 
 0.5 to 1 ym in the Bureau scanning elec- 
 tron microscope. 
 
 Cost of the silica fume varies consid- 
 erably. Although it was once discarded 
 as an unwanted byproduct , research and 
 testing have turned it into a marketable 
 commodity ranging in price from $50/ton 
 to $75/ ton (bulk) at the plant. Expecta- 
 tions are that a price of $100/ ton may 
 be reasonable in the future. Silica fume 
 is available from a variety of sources 
 across the United States. 
 
 Silica fume is difficult to handle, 
 store, and transport owing to its ex- 
 tremely small particle size. Its bulk 
 density is very low at 12 to 20 Ib/ft^ 
 (12) . Caution had to be exercised in 
 handling the material in the drafty mine 
 environment at Lake Lynn. Silica fume is 
 highly pozzolanie and can be used to some 
 
 extent in most applications as a cement 
 replacement. The material is hard to 
 disperse in wet-mix gunite and consumes 
 considerable water. The specific area of 
 condensed silica fume is very high (up to 
 20,000 m^/kg compared to 600 m^/kg for 
 cement) (13) . Water reducers and/or su- 
 perplasticizers are used with silica fume 
 to control the workability and pumpabil- 
 ity of the mix. Mixing silica fume with 
 water as a slurry is a convenient way of 
 handling the material in bulk volume. 
 Reportedly 1 ton of water is mixed with 1 
 ton of the silica fume (13) . Superplas- 
 ticizer is frequently added to maintain 
 dispersion of the silica fume in the wa- 
 ter. The slurry can then be conveniently 
 added to the concrete or wet-mix gunite. 
 
 The use of silica fume in the wet-mix 
 gunite required the contained sand-sized 
 aggregate to have a specific fine aggre- 
 gate size fraction distribution. One 
 bulk volume of purchased sand was re- 
 jected by the wet-mix manufacturer when 
 lower-than-expected ultimate strengths 
 were discovered owing to an unacceptable 
 size fraction distribution. 
 
 The increased cohesiveness of the wet- 
 mix gunite with silica fume allowed a 
 thickness of more than 2-1/2 to 3 in to 
 be placed on the mine roof without sag- 
 ging or slumping. The fine silica fume 
 material contained in the wet mix tended 
 to give a smooth overall finish to the 
 gunite. Even the protruding steel fibers 
 appeared to have a paste coating on them. 
 The coating tended to prevent serious 
 puncture wounds and also added to the 
 strength of the material. 
 
 WATER REDUCERS 
 
 Water reducers, mainly of the lignosul- 
 fonate or hydroxylated carboxylic acid 
 type, are used to improve gunite (wet- 
 mix) workability and cohesiveness in the 
 plastic state. Once hardened, the mate- 
 rial adds to the product strength while 
 reducing permeability and increasing dur- 
 ability. When added to a wet-mix gunite 
 (or concrete) , the water reducer can give 
 a significant increase in slump with the 
 
13 
 
 same water-cement ratio, or the water- 
 cement ratio can be reduced to achieve 
 the same slump as for a mix not con- 
 taining the water reducer. (The reduced 
 water-cement ratio relates to a direct 
 increase in strength. ) The higher slump 
 adds to an increased workability or, in 
 the case of wet-mix gunite, an increased 
 pumpability. The wet-mix gunite tested 
 in this investigation had a slump ranging 
 from 3-1/2 to 5 in. 
 
 ACCELERATORS 
 
 Gunite accelerators are used to shorten 
 product set time, thereby reducing any 
 sagging or sloughing tendencies when 
 thick applications are to be made in 
 a single pass. The accelerators can 
 improve workability and increase final 
 product strength. Although some 
 chloride-containing accelerators are 
 known to reduce the ultimate gunite 
 strength, nonchloride accelerators are 
 available. 
 
 SUPERPLASTICIZERS 
 
 Superplasticizers are chemically dis- 
 tinct from normal plasticizers or water 
 reducers. They are better known as high- 
 range water reducers since they can be 
 used at high dosage levels without the 
 problems of set retardation or excessive 
 air entrainment associated with high 
 rates of addition of conventional plasti- 
 cizers or water reducers (14) . The su- 
 perplasticizers are grouped into several 
 chemical categories, including the sulfo- 
 nated melamine formaldehyde condensates, 
 sulfonated naphthalene formaldehyde con- 
 densates, and modified lignosulf onates 
 (15) . These chemicals are essentially 
 salts of organic sulfonates. Their names 
 are conveniently shortened to type M 
 (melamine) , type N (naphthalene) , and 
 type L (lignosulf onate) . Type M forms a 
 lubricating film on the particle sur- 
 faces, type N electrically charges the 
 particles and they repel each other, and 
 type L decreases the water surface ten- 
 sion. When well dispersed, the cement 
 particles not only flow around each other 
 more easily but also coat the aggregate 
 
 more completely. The result is a con- 
 crete that is both stronger and more 
 workable ( 16 ) . The investigated wet-mix 
 gunites containing the superplasticizer 
 took on a silky, almost lustrous feel and 
 could have been pumped for great dis- 
 tances without clogging the placement 
 and/or delivery hoses. The superplasti- 
 cizers' effect of dispersing "fines" 
 makes them perfect and needed admixtures 
 for gunite (wet-mix) containing silica 
 fume. 
 
 The gunite slump increase achieved by 
 adding conventional superplasticizers is 
 time and temperature dependent and can be 
 completely lost within 60 to 90 min after 
 mixing. Although higher dose rates can 
 slow the rate of slump loss, too much 
 superplasticizer results in a total loss 
 of cohesiveness and the initiation of 
 mix segration, a condition known as to- 
 tal collapse (16) . One such incident oc- 
 curred at the Lake Lynn Laboratory Mine 
 during the batching of the wet-mix gun- 
 ite. The sensitive balance of the silica 
 fume-water reducer-superplasticizer was 
 overexceeded in one batch, and the mix 
 had to be discarded and cleaned out of 
 the gunite pump system. The introduction 
 of a variety of specialty additives and 
 admixtures into wet-mix gunite, there- 
 fore, should only be attempted by a high- 
 ly trained specialist. Since many of the 
 admixtures are liquid, they cannot all be 
 conveniently measured and prebagged in 
 dry form at this time. 
 
 POLYMER LATEX ADDITIVES 
 
 Polymer latex additives have been used 
 in portland-cement-based products to im- 
 part special desired properties, includ- 
 ing adhesion improvement, permeability 
 reduction, resistance to chloride attack, 
 freeze-thaw deterioriation prevention, 
 impact resistance, reinforcement steel 
 protection, and strength improvement. 
 Owing to the prospective use of the addi- 
 tive in fibered gunite for mining pur- 
 poses, a test gunite demonstration was 
 arranged between one dry-mix gunite manu- 
 facturer and a polymer latex producer. 
 
14 
 
 The polymer latex used in the test ap- 
 plication (at the gunite manufacturer's 
 facilities) was a styrene-butadiene poly- 
 meric emulsion in which the polymer com- 
 prises 47±1 pet by weight and water makes 
 up the balance (53 pet). The polymer 
 contained 64±2 pet styrene and 36±2 pet 
 butadiene. Mean polymer particle size 
 was reported to be 2,034±300 A. The 
 polymer weighed 8.4 lb/gal. 
 
 The polymer latex gunite test was con- 
 ducted at the facilities of one of the 
 participating gunite manufacturers. Test 
 panels of a variety of fibered gunite 
 materials were shot. Table 3 lists test 
 panel shots and provides sample number 
 identification for the various products. 
 The gunite manufacturer's gunning crew 
 had no prior experience with polymer la- 
 tex and, therefore, relied solely on the 
 polymer manufacturer's representative for 
 guidance in mix-ratio proportioning. 
 
 The various prebagged gunite products 
 demonstrated during this phase of the 
 work were shot using the rotary gun shown 
 in figure 9. Sample blocks 15-17 were 
 shot with the polymer latex using a 
 gasoline-powered pump to deliver the 
 latex to the nozzle directly from a 55- 
 gal drum. The delivery system is shown 
 
 TABLE 3. - Polymer latex gunite 
 materials tested 
 
 Sample 
 
 Material 
 
 11 Steel fiber. 
 
 12 Sanded gunite , no fiber . 
 
 13 Polypropylene fiber . 
 
 14 AR-f iberglass (1 pct).^ 
 
 15 Steel fiber with polymer 
 
 latex. 
 
 16 Sanded gunite, no fiber, 
 
 polymer latex. 
 
 17 Polypropylene fiber with 
 
 polymer latex. 
 
 ^Prebagged, fibered or nonfibered mixes 
 were gunned into test panels with and 
 without polymer latex. 
 
 ^Polymer latex was not tested in a 
 fiberglass-fibered gunite. 
 
 in figure 10. Figure 11 shows the gun- 
 ning operation in progress. Antifoaming 
 agents were not employed , and flow cones 
 were not used to determine workability. 
 
 Considerable difficulty was experienced 
 in obtaining a consistent latex-gunite 
 flow from the nozzle. The polymer latex 
 caused partial blockage of the nozzle wa- 
 ter ring assembly (fig. 12) by partially 
 hydrating the cement fraction and forming 
 
 FIGURE 9. - Rotary gunite gun used in polymer 
 latex gunning. 
 
 FIGURE 10. - Styrene-butadiene latex polymer 
 delivery pump. 
 
15 
 
 FIGURE 11,- Polymer latex gunite application. 
 
 FIGURE 12, " Water ring blockage by partially hy- 
 drated portlond cement and polymer. 
 
 a sticky residue within the orifices. An 
 attempt was made to correct the situation 
 by drilling the orifices larger (+1/32 
 in) and increasing the latex polymer de- 
 livery pressure. The alterations par- 
 tially corrected the problem, and hydra- 
 tion of the dry-mix gunite appeared to be 
 adequate; however, the gunned material 
 had a very high slump and would not have 
 been suitable for application on a verti- 
 cal surface. The use of a longer hose 
 extension between the water nozzle body 
 water ring and the nozzle tip along with 
 higher latex polymer pump pressure and 
 lower volume would have provided a longer 
 wetting chamber, hence more thorough hy- 
 dration of the gunite by the latex poly- 
 mer. With the equipment setup used, how- 
 ever, an excess of polymer was required 
 to hydrate the dry mix in the short 
 water-ring-to-nozzle-tip distance. This 
 overabundance of latex polymer, plus the 
 variation of feed rate caused by air 
 compressor flow variation and subsequent 
 gun speed changes , gave less than opti- 
 mum test shot specimens for analysis. 
 The polymer specimens were seriously 
 laminated. 
 
 Tables 9 (p. 36) and 10 (p. 38) include 
 the comparative compressive and flexural 
 strengths for the seven products demon- 
 strated during the latex polymer tests 
 (samples 11-17) and presented in table 3. 
 The engineering properties were deter- 
 mined by Froehling and Robertson, Inc., 
 
 laboratories. Twenty-eight-day compres- 
 sive and flexural strength decreases (36 
 to 49 pet and 24 to 29 pet, respectively, 
 compared to nonpolymer steel and poly- 
 propylene specimens) were observed for 
 the steel- and polypropylene-fibered sam- 
 ples shot with the latex product (samples 
 15 and 17, respectively) owing to the 
 gunite mix hydration problems . The non- 
 fibered, sanded gunite with latex (sample 
 16) gave better results; however, this 
 was not due to the absence of fibers. 
 The equipment and gunning conditions were 
 optimum at the time this material was 
 gunned. The 28-day compressive strength 
 of the sanded gunite-latex polymer sample 
 (16) was only 90 pet of the nonpolymer 
 strength, but the sample showed a sig- 
 nificant increase in flexural 28-day 
 strength (173 pet of nonpolymer materi- 
 al) . The nonf ibered polymer specimen 
 (sample 16) had the best hydration char- 
 acteristics of the series. In general, 
 the compressive-flexural characteristics 
 of the three gunite-polymer materials are 
 considered to be less than those achiev- 
 able with the proper gunite-latex deliv- 
 ery equipment. 
 
 The permeability reduction achieved by 
 the polymer latex in specimens 15-17 
 compared to that with nonpolymer speci- 
 mens was impressive. Although each spec- 
 imen tested contained lamination zones 
 (hence the poor compressive and flexural 
 strengths), the permeabilities were less 
 
16 
 
 than the accurate measurable lower limit 
 of the research apparatus (1 >^ 10~^ dar- 
 cy). Permeability analyses are discussed 
 in more detail later in this report. The 
 permeability reduction obtained by the 
 use of a polymer latex additive should 
 impart beneficial freeze-thaw character- 
 istics and rebound percentage reduction; 
 however, the high cost of the material 
 
 could preclude its use in general appli- 
 cations. The material has excellent po- 
 tential for use in specialty (reduced 
 permeability) gunite applications in deep 
 mines such as high water intake zones , 
 where high sulfur or sulfate may be en- 
 countered, or where the gunite may be 
 exposed to large volumes of cold, moist 
 air, such as at or near shaft collars. 
 
 AGGREGATE ANALYSIS 
 
 Elandom samples of the tested prebagged 
 dry gunite products and of the sand- 
 sized fraction of the wet-mix were sub- 
 jected to mechanical sieving analysis. 
 The dry sieve samples were taken directly 
 from freshly opened bags. Multiple sam- 
 ple splitting was not performed owing to 
 the prospective high loss of the cement- 
 sized fraction and to the fibers. One- 
 thousand-gram random samples of each 
 product were placed in a stacked series 
 of screen sieves containing 4-, 10-, 20-, 
 40-, 100- , and 200-mesh screen (4.76, 
 2.0, 0.84, 0.42, 0.149, and 0.074 mm re- 
 spectively) plus the bottom pan. The 
 stacked sieve screens were covered with a 
 top section and placed in a RO-TAP shaker 
 for 10 min. The retained content of each 
 sieve was weighed, and a sample was col- 
 lected for microscopic analysis. Only 
 one random sample from one premixed bag 
 of dry -mix gunite was tested. The sample 
 analysis, therefore, may or may not be 
 totally representative of the product. 
 
 The steel-f ibered samples were sub- 
 jected to magnetic fiber separation. 
 Samples containing fiberglass fibers were 
 hand-picked of their fiber content. The 
 magnetic technique resulted in the col- 
 lection of 100 pet of the steel fibers. 
 The hand-picking procedure was only cap- 
 able of recovering 90 to 95 pet (esti- 
 mated) of the fiberglass fibers. The fi- 
 ber weight (and volume) percentages may, 
 therefore, differ from the manufacturer's 
 specifications. The sand-sized (10- to 
 200-mesh) fraction of the various gunite 
 products was analyzed for differences in 
 grain shape, nominal size, and size frac- 
 tion distribution. 
 
 The grain shape (roundness and spheri- 
 city) of the sand-sized materials had a 
 
 decisive effect upon the grain size col- 
 lected by the respective sieves. The 
 parameter also relates to gunite strength 
 properties. Grain fractions with three 
 equidimensional (nearly spherical) axes 
 (a=b=c) perpendicular to each other ex- 
 hibited size separation reflecting the 
 diameter characteristics of the grain. 
 Grain fractions with multidimensional 
 (elongate) axes (e.g., a=b^c or a^b^c) 
 exhibited size fraction separation depen- 
 dent primarily on the minor axis dimen- 
 sion. Some size fraction percentages, 
 therefore, may be slightly distorted. 
 
 The roundness classification of the 
 material is an empirical analysis which 
 can be described qualitatively as follows 
 (17): 
 
 1. Angular - all corners sharp, having 
 radius of curvature equal to zero; sur- 
 face not abraded. 
 
 2. Subangulav - corners not sharp but 
 having very small radius of curvature; 
 most of surface not abraded. 
 
 3. Suhvounded - corners very notice- 
 ably rounded but surface not completely 
 abraded. 
 
 4. Rounded - entire surface abraded; 
 radius of curvature of sharpest edges is 
 about equal to radius of maximum in- 
 scribed circle. 
 
 As seen in two dimensions, either in 
 sawn cores or cubes , the sand and aggre- 
 gate grains were either equidimensional 
 or elongate. Roundness of the aggregate 
 is very important owing to the interlock- 
 ing nature of the grains in the hardened 
 product. 
 
17 
 
 Sand-sized fraction (10- to 200-mesh) 
 analysis was critically important since a 
 major proportion of the material from the 
 samples tested (up to 97 pet) falls with- 
 in the size fraction category. Table 4 
 presents the percentage composition of 
 the sand-sized fraction of each sample 
 product tested. Figures 13 through 17 
 show the grain size accumulation curves 
 for the various gunites. Although the 
 sand-sized fraction appears to be quite 
 high for some products, the percentages 
 are somewhat misleading. The cement par- 
 ticles tended to agglomerate into small 
 round balls during screening and were re- 
 tained, in various proportions, on the 
 100- and 200-mesh screens. 
 
 TABLE 4. - Sand-size fraction (10- to 
 200-mesh) content in gunite 
 
 Sample 
 
 10 to 
 
 200 mesh. 
 
 10 to 100 mesh. 
 
 
 pet 
 
 (by wt) 
 
 pet (by wt) 
 
 1-3... 
 
 1 
 
 100 
 
 95.16 
 
 4 
 
 
 88.53 
 
 68.67 
 
 52.... 
 
 
 67.05 
 
 25.96 
 
 6 
 
 
 79.20 
 
 76.28 
 
 7 
 
 
 93.33 
 
 73.45 
 
 82.... 
 
 
 91.14 
 
 69.44 
 
 9 
 
 
 86.98 
 
 69.43 
 
 10 
 
 
 97.32 
 
 87.81 
 
 '^Raw sand tested. 
 
 '^Samples 5 
 cements. 
 
 and 8 are surface-bonding 
 
 The characteristics of the sand-sized 
 aggregate have a direct bearing on the 
 
 ultimate engineering properties of the 
 final gunite product. The influence of 
 aggregate grading and shape on the prop- 
 erties of concrete has been studied since 
 the invention of portland cement, and 
 many methods have been proposed for ar- 
 riving at an "ideal" grading. None, how- 
 ever, has been universally acceptable 
 (18) . In concrete, the coarser fractions 
 of aggregate cause bleeding and segrega- 
 tion while at the same time increasing 
 strength and reducing shrinkage, crack- 
 ing, and cost. The fine fraction (alone) 
 reduces workability unless high water- 
 cement ratios are used. In gunite, the 
 fine and intermediate fractions are re- 
 quired to fill in the matrix and contrib- 
 ute to the final product density. In 
 general, portland-cement-based products 
 take on the hardness and abrasion resist- 
 ance characteristics of the aggregate. 
 
 Although the pneumatically applied gun- 
 ite may have exhibited size-fraction- 
 induced rebound or slump characteristics 
 in this research, the major affected fac- 
 tors were the ultimate product engineer- 
 ing properties. Since each company pro- 
 vided its own application equipment and 
 nozzle operators for the test demonstra- 
 tions , the application variables were too 
 numerous to permit a more detailed evalu- 
 ation of the aggregate characteristics' 
 influence on the final product engineer- 
 ing properties. 
 
 GUNITE SPECIMEN COLLECTION 
 
 The most serious obstacle in the re- 
 search effort was obtaining high-quality 
 test specimens of the fibered gunite ma- 
 terial that were representative of the 
 applied product. Samples of the gunite 
 were carefully prepared and collected 
 and were left in the damp, moist mine 
 environment covered in plastic for 24 h 
 before being moved. The samples were 
 then moved, moistened, and covered to 
 protect them from rapid moisture loss 
 until testing. 
 
 Core drilling of the 24- by 24-in test 
 panels for compression test specimens 
 
 revealed that all of the steel-fibered 
 products of the dry-mix type contained 
 sandy, laminated zones up to 1/2 in 
 thick. The laminated zones were randomly 
 dispersed throughout the 7- to 9-in-thick 
 sample; therefore, they are not the re- 
 sult of side or bottom rebound aberra- 
 tions. Figure 18 shows (on the right) 
 three different dry-mix product cores 
 that contain laminations . The specimen 
 on the left is one of the wet-mix gunite 
 products , which contain silica fume and 
 additives. All four samples were rolled 
 on a damp sponge to show the preferential 
 water absorption of the lamination zones. 
 
18 
 
 r 
 
 
 
 
 
 
 
 MECHANICAL ANALYSIS GRAIN SIZE ACCUMULATION CURVE 
 
 
 
 2" 
 11/2" 
 
 1" 
 3/4" 
 
 1/2" 
 
 3/8" 
 1/4" 
 
 hit 
 
 Sieve Sizes - U.S. Standard 
 
 100 
 
 
 I III 
 
 ' 
 
 
 ^, 
 
 1 
 1 
 
 
 I ' 1 
 1 1 1 
 
 i-- 
 
 1 ' 1 
 
 I'll 
 
 
 10 
 
 
 
 
 
 \, 
 
 1 
 
 
 1 1 1 
 1 1 1 
 
 / 
 
 
 
 
 
 90 
 
 
 
 
 
 N 
 
 1 
 
 VI 
 
 
 1 1 1 
 1 1 1 
 
 / 
 
 
 
 
 
 20 
 
 
 
 
 
 
 y^ 
 
 
 y 
 
 
 
 
 
 
 80 
 
 
 
 
 
 
 ■■HMU. : 1/ 
 
 
 
 
 
 
 30 
 
 
 
 
 
 
 1 
 1 
 
 1 
 1 
 
 T--J/ 
 
 
 
 
 
 
 70 
 
 
 
 
 
 
 1 
 
 
 T 
 
 
 
 
 
 
 T3 
 
 c 40 
 
 10 
 
 
 
 
 
 
 1 
 1 
 
 
 1 1 1 
 
 
 
 
 
 
 60 1 
 <n 
 
 
 
 
 
 
 1 
 
 
 
 
 
 
 
 
 0) 
 
 t 50 
 
 
 
 
 
 
 1 
 
 
 
 
 
 
 
 
 50 t 
 
 c 
 
 
 
 
 
 
 1 
 
 
 
 
 
 
 
 
 a> 
 2 60 
 
 <?: 
 
 70 
 
 
 
 
 
 
 1 
 
 
 
 
 
 
 
 
 An " 
 
 
 SAMPLE 1-3 
 
 SAND FRACTIOI 
 
 ONLY 
 
 ' II 1 
 
 L 
 
 
 
 1 
 
 
 
 
 
 
 
 
 40 5; 
 
 1 
 
 
 
 1 
 
 
 
 
 
 
 
 
 30 
 
 1 
 
 
 
 1 
 
 
 
 
 
 
 
 
 80 
 
 yi 1— 
 
 
 
 1 
 1 
 
 
 
 
 
 
 
 
 20 
 
 1 
 
 
 
 1 
 
 
 
 
 
 
 
 
 90 
 
 1 
 
 
 
 1 
 1 
 
 
 
 
 
 
 
 
 10 
 
 1 
 
 
 
 1 
 
 
 
 
 
 
 
 
 100 
 
 
 > 1 1 M 1 
 
 
 
 1 
 
 1 
 
 
 
 
 1 1 1 
 
 1 1 1 1 
 
 1 1 1 
 
 
 -d dP °§§g 
 Particle Size Diameter in Millimeters , 
 
 
 Coarse Aggregate 
 
 Coarse Sand 
 
 Fine Sand 
 
 Silt 
 
 Clay 
 
 
 c 
 
 T 
 
 c 
 
 
 
 
 MECHANICAL ANALYSIS GRAIN SIZE ACCUMULATION CURVE 
 
 
 
 2" 
 1 1/2" 
 
 1" 
 3/4" 
 
 1/2" 
 
 3/8" 
 1/4" 
 
 Sieve Sizes - U.S. Standard 
 
 o o o 
 r 00° ^cMc5-» <B y- cge\j 
 
 100 
 
 
 1 III 
 
 1 
 
 
 V 
 
 1 
 
 1 
 1 
 
 
 1 1 
 1 1 
 
 /^- 
 
 1 1 
 
 'III 
 
 
 10 
 
 
 
 
 
 \ 
 
 1 
 1 
 
 1 
 
 
 [^ 
 
 
 
 
 
 
 90 
 
 
 
 
 
 \ 
 
 1 
 1 
 
 1 
 
 
 >l 
 
 
 
 
 
 
 20 
 
 
 
 
 
 \ 
 
 1 
 1 
 
 1 
 1 
 
 
 y 
 
 
 
 
 
 
 80 
 
 
 
 
 
 
 u 
 
 1 
 
 1 
 
 g 
 
 r^\ 
 
 
 
 
 
 
 30 
 
 
 
 
 
 
 i 
 
 1 
 
 1 > 
 
 * 
 
 
 
 
 
 
 
 70 
 
 
 
 
 
 
 1 
 
 -^ 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 1 
 
 T 
 1 
 
 
 
 
 
 
 
 
 60 1 
 in 
 
 c 40 
 
 
 
 
 
 
 1 
 
 1 
 1 
 
 
 
 
 
 
 
 
 0) 
 
 ^ 50 
 
 
 
 
 
 
 1 
 
 1 
 
 
 
 
 
 
 
 
 50 t 
 
 c 
 
 
 
 
 
 
 1 
 
 1 
 1 
 
 
 
 
 
 
 
 1 1 1 
 
 2 60 
 
 
 
 
 
 
 1 
 
 1 
 
 
 
 
 
 
 
 1 1 1 
 
 An " 
 
 - 
 
 SAMPLE 1-3 
 REJECT SAND 
 
 1 III 
 
 1 
 
 
 
 1 
 
 1 
 
 
 
 
 
 
 
 
 40 oj 
 a. 
 
 70 
 
 1 
 
 
 
 1 
 
 1 
 
 
 
 
 
 
 
 
 30 
 
 1 
 1 
 
 
 
 1 
 
 1 
 
 
 
 
 
 
 
 
 80 
 
 1 
 
 
 
 1 
 
 1 
 
 
 
 
 
 
 
 
 20 
 
 1 
 
 
 
 1 
 
 1 
 
 
 
 
 
 
 
 
 90 
 
 1 
 
 
 
 1 
 
 1 
 
 
 
 
 
 
 
 
 10 
 
 1 
 _ . 1 
 
 
 
 1 
 
 1 
 1 
 
 
 
 
 
 
 
 
 100 
 
 
 1 : 1 1 II 1 
 
 
 
 1 
 
 1 
 
 
 1 1 
 
 
 
 1 L 
 
 1 1 1 J 
 
 
 . 
 
 3 
 
 "" - -o dp pggc 
 
 Particle Size Diameter in Millimeters 
 
 
 Coarse Aggregate 
 
 Coarse Sand 
 
 Fine Sand 
 
 Silt 
 
 Clay 
 
 
 FIGURE 13. - Grain size accumulation curves for samples 1-3. 
 
19 
 
 
 
 
 MECHANICAL ANALYSIS GRAIN SIZE ACCUMULATION CURVE 
 
 
 
 2" 
 1 1/2" 
 
 1" 
 3/4" 
 
 1/2" 
 
 3/8" 
 1/4" 
 
 Sieve Sizes - U.S. Standard 
 
 inf) 
 
 
 
 
 
 1 
 
 
 \, 
 
 1 
 
 T 
 1 
 
 
 1 
 
 
 I ' 1 
 1 1 1 
 
 '111 
 
 1 1 1 
 
 
 
 
 
 ] 
 
 
 \ 
 
 
 1 
 
 
 
 1 
 
 
 L^l ! 
 
 
 
 90 
 
 10 
 
 
 
 
 
 \ 
 
 
 1 
 
 1 
 
 
 
 r , 1 
 .4 11 1 
 
 
 
 20 
 
 
 
 
 
 
 w_ 
 
 1 
 
 
 >U^' 
 
 ' 1 1 
 
 
 
 no 
 
 
 
 
 
 
 
 -9^ 
 
 1 
 
 
 1 
 
 
 
 
 
 
 30 
 
 
 
 
 
 
 
 1 
 
 1 
 
 
 1 
 
 
 
 
 
 70 
 
 
 
 
 
 
 
 1 
 
 
 1 
 
 
 
 
 
 
 T3 
 
 
 
 
 
 
 
 1 
 1 
 
 
 1 
 
 
 
 
 
 O) 
 
 60 i 
 
 CO 
 
 c 40 
 
 
 
 
 
 
 
 1 
 
 
 1 
 
 
 
 
 
 CC 50 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 50 °- 
 
 
 
 
 
 
 
 1 
 
 
 
 
 1 1 1 
 
 
 
 c 
 
 <s> 
 
 
 
 
 
 
 
 1 
 
 
 
 
 
 
 
 o 
 
 40 £ 
 
 Q. 
 
 Sf 60 
 
 0) 
 
 — 
 
 
 1 
 
 
 
 
 1 
 
 
 
 
 
 
 
 0. 
 
 SAMPLE 4 
 
 1 — 1 
 1 
 
 
 
 
 1 
 
 1 1 1 
 
 
 
 
 
 
 30 
 
 70 
 
 1 — ' 
 1 
 
 
 
 
 1 
 
 1 1 1 
 
 
 
 
 
 
 
 
 1 — ' 
 1 
 
 
 
 
 1 
 
 
 
 
 
 
 
 ?n 
 
 80 
 
 1 — ' 
 1 
 
 
 
 
 1 
 
 
 
 
 
 
 
 
 
 1 — ' 
 I 
 
 
 
 
 1 
 1 
 
 
 
 
 
 
 
 10 
 
 90 
 
 1 — 
 
 1 
 
 
 
 
 1 
 
 .— 1 
 
 
 — 1 
 
 
 
 
 
 
 
 II 1 1 1 1 
 
 
 
 
 1 
 
 
 
 
 
 1 1 1 1 
 
 
 . 
 
 100 
 
 >" '- -d oP °8pc 
 
 Particle Size Diameter in Millimeters 
 
 
 Coarse Aggregate 
 
 Coarse Sand 
 
 Fine Sand 
 
 Silt 
 
 Clay 
 
 
 c 
 
 c 
 
 
 
 
 MECHANICAL ANALYSIS GRAIN SIZE ACCUMULATION CURVE 
 
 
 
 2" 
 1 1/2" 
 
 1" 
 3/4" 
 
 1/2" 
 
 3/8" 
 
 1/4" 
 
 Sieve Sizes - U.S. Standard 
 
 -, <OOQOQ o pt^ 
 
 r 00? ^ c^ ^^ (S i= SfM 
 1 j^ ^ — 
 
 100 
 
 
 
 1 
 
 
 
 
 
 1\ 
 
 
 
 1 ' 1 
 
 ■ III 
 
 1 1 1 
 
 10 
 
 
 1 III 
 
 
 
 
 
 
 \ 
 
 
 
 
 
 
 90 
 
 
 
 
 
 
 
 
 \ 
 
 
 
 
 
 
 20 
 
 
 
 
 
 
 
 
 \ 
 
 \ 
 
 
 1 1 1 
 
 
 
 80 
 
 
 
 
 
 
 
 
 ^ 
 
 
 
 V\ 
 
 
 
 30 
 
 
 
 
 
 
 
 
 ^ 
 
 
 
 / 1 
 
 
 
 70 
 
 
 
 
 
 
 
 
 \ 
 
 
 f 
 
 
 
 
 •o 
 
 2 .in 
 
 
 
 
 
 
 
 
 
 \ 
 
 / 
 
 
 
 
 60 I 
 in 
 
 c 40 
 
 
 
 
 
 
 
 
 
 >J 
 
 » 
 
 
 
 
 ^ 50 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 50 t 
 
 c 
 
 
 
 
 
 
 
 ] 
 
 
 
 
 
 
 
 e 60 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 o 
 40 5 
 
 
 SAMPLE 5 
 
 1 
 
 
 
 
 
 
 
 
 
 
 
 70 
 
 1 
 
 
 
 
 
 
 
 
 
 
 
 30 
 
 1 
 1 
 
 
 
 
 
 
 
 
 
 
 
 80 
 
 1 
 
 
 
 
 
 
 
 
 
 
 
 20 
 
 1 
 
 
 
 
 
 
 
 
 
 
 
 90 
 
 \_ 
 
 
 
 
 
 
 
 
 
 II 1 1 
 
 
 10 
 
 1 
 
 
 
 
 
 
 
 
 
 
 
 100 
 
 
 .1 1 M 1 
 
 
 
 1 
 
 
 
 
 
 1 1 1 
 
 lJ_J_i 
 
 1 1 1 
 
 . 
 I 
 
 Particle Size Diameter in Millimeters 
 
 
 Coarse Aggregate 
 
 Coarse Sand 
 
 Fine Sand 
 
 Silt 
 
 Clay 
 
 
 FIGURE 14. - Grain size accumulation curves for samples 4 and 5. 
 
20 
 
 c 
 
 
 
 
 MECHANICAL ANALYSIS GRAIN SIZE ACCUMULATION CURVE 
 
 
 
 2" 
 1 1/2" 
 
 1" ■ 
 3/4" 
 
 1/2" 
 
 3/8" 
 1/4" 
 
 Sieve Sizes - U.S. Standard 
 _, tooooQ o or>- 
 
 100 
 
 
 T Til 
 
 T 
 
 
 
 Tv. 
 
 1 
 
 1 ' ' 
 
 ^ 
 
 1 i 1 
 
 ''If 
 
 1 1 1 
 
 10 
 
 
 
 
 
 
 1 \ 
 
 
 
 7 
 
 
 
 
 
 90 
 
 
 
 
 
 
 \ 
 
 
 
 { 
 
 \ 
 
 
 
 
 20 
 
 
 
 
 
 
 ' 
 
 V 
 
 1 1 1 ^ 
 
 
 \ 
 
 
 
 
 80 
 
 
 
 
 
 
 
 1 ■ 
 
 ■^1 / 
 
 
 
 
 
 
 30 
 
 
 
 
 
 
 
 
 Tl^^^ 
 
 — 1 
 
 
 
 
 
 70 
 
 
 
 
 
 
 
 
 1 1 T 
 
 1 
 
 
 
 
 
 ■D 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 60 1 
 
 c 40 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 rr 
 
 
 
 
 
 
 
 
 
 
 
 1 1 
 
 
 
 50 i 
 
 c 
 
 °- 50 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 9> 
 
 2 60 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 u 
 
 40 5 
 
 Q. 
 
 — 
 
 SAMPLE 6 
 
 1 
 
 
 
 
 
 
 
 
 
 
 
 70 
 
 1 
 
 
 
 
 
 
 
 
 
 
 
 30 
 
 1 
 1 
 
 
 
 
 
 
 
 
 1 1 1 
 
 
 
 80 
 
 1 
 
 
 
 
 
 
 
 
 
 1 1 1 1 
 
 
 20 
 
 1 
 1 
 
 
 
 
 
 
 
 
 
 II 1 1 
 1 1 1 1 
 
 
 90 
 
 1 
 
 
 
 
 
 
 
 
 
 1 1 II 
 1 1 1 1 
 
 
 10 
 
 1 
 
 _1 
 
 
 
 
 
 
 
 
 
 1 1 1 1 
 1 1 1 1 
 
 1 1 1 
 
 100 
 
 
 II 1 1 1 1 
 
 
 
 
 
 
 
 
 1 1 1 
 
 1 1 1 1 
 
 1 1 1 
 
 . 
 
 3 
 
 " - -o dp c=goc 
 
 Particle Size Diameter in Millimeters 
 
 
 Coarse Aggregate 
 
 Coarse Sand 
 
 Fine Sand 
 
 Silt 
 
 Clay 
 
 
 r 
 
 r 
 C 
 
 
 
 
 
 MECHANICAL ANALYSIS GRAIN SIZE ACCUMULATION CURVE 
 
 
 
 2" 
 1 1/2" 
 
 1" 
 3/4" 
 
 1/2" 
 
 3/8" 
 1/4" 
 
 Sieve Sizes ■ U.S. Standard 
 
 100 
 
 
 T 111 
 
 
 
 "■^i 
 
 k 
 
 1 
 
 
 1 1 
 
 1 
 
 1 i 1 
 
 'III 
 
 1 1 1 
 
 10 
 
 
 
 
 
 
 \ 
 
 1 
 
 
 
 1 / 
 1 / 
 
 
 
 
 90 
 
 
 
 
 
 
 \ 
 
 1 
 
 
 
 1 / 
 
 
 
 
 20 
 
 
 
 
 
 
 1 \ 
 
 1 
 
 \ 
 
 -1 
 
 ' 
 
 
 
 
 
 80 
 
 
 
 
 
 
 
 
 \ , 
 
 4 
 
 ^ L — -w- 
 
 1 
 
 
 
 
 30 
 
 
 
 
 
 
 
 1 
 
 
 
 
 
 
 
 70 
 
 
 
 
 
 
 
 1 
 1 
 
 
 
 
 
 III 
 
 
 T3 
 
 c 40 
 
 
 1 1 1 1 
 
 
 
 
 
 1 
 1 
 
 
 
 
 
 
 
 60 i 
 
 C/) 
 
 
 
 
 
 
 
 1 
 1 
 
 
 
 
 
 
 
 ^ 50 
 
 
 
 
 
 
 
 1 
 
 
 
 1 
 
 
 
 
 (0 
 
 50 t 
 
 c 
 
 
 
 
 
 
 
 1 
 
 1 
 
 
 
 1 
 
 
 
 
 ID 
 
 if 60 
 70 
 
 
 
 
 
 
 
 1 
 
 
 
 
 
 
 
 u 
 
 40 S 
 
 a. 
 
 
 SAMPLE 7 
 1 III 
 
 1 
 
 
 
 
 1 
 
 
 
 
 
 
 
 1 
 
 
 
 
 1 
 
 
 
 
 
 
 
 30 
 
 1 
 1 
 
 
 
 1 
 
 1 
 
 
 
 
 
 
 
 80 
 
 1 
 1 
 
 
 
 1 
 
 1 
 
 
 
 
 
 
 
 20 
 
 1 
 1 
 
 
 
 
 1 
 
 
 
 
 
 
 
 90 
 
 |_ 
 
 
 
 1 
 
 1 
 1 
 
 
 
 
 
 
 
 10 
 
 1 
 1 
 
 
 
 1 
 
 1 
 
 1 
 
 
 
 
 
 
 1 1 1 
 
 100 
 
 
 ' ' ' ' II ' 
 II 1 1 
 
 
 
 1 
 
 
 
 1 1 
 
 1 
 
 1 1 1 
 
 1 1 1 1 
 
 
 . 
 I 
 
 " - -d dP pggc 
 
 Particle Size Diameter in Millimeters 
 
 
 Coarse Aggregate 
 
 Coarse Sand 
 
 Fine Sand 
 
 1 
 Silt Clay 
 
 
 FIGURE 15. - Grain size accumulation curves for samples 6 and 7. 
 
21 
 
 c 
 
 r 
 
 
 
 
 
 MECHANICAL ANALYSIS GRAIN SIZE ACCUMULATION CURVE 
 
 
 
 : - ^ - •»■ <N 5 ■* 
 
 Sieve Sizes - U.S. Standard 
 
 r CO? $eas§s 1 i§ 
 
 100 
 
 
 ' 
 
 1 
 
 
 
 
 ~^\ 
 
 
 1 1 
 
 
 
 T ' T 
 
 '111 
 
 
 10 
 
 
 
 
 
 
 
 ' 
 
 ^ 
 
 k 1 1 
 
 
 i 
 
 
 II 1 1 
 
 
 90 
 
 
 
 
 
 
 
 
 ^ 
 
 \ 
 
 
 / 
 
 
 Mil 
 1 1 1 1 
 
 
 20 
 
 
 
 
 
 
 
 
 
 \ 
 
 — 1 
 
 / 
 
 
 Mil 
 
 
 80 
 
 
 
 
 
 
 
 
 -\ 
 
 \ 
 
 / 
 
 
 
 1 1 II 
 
 
 30 
 
 
 
 
 
 
 
 
 
 \ 
 
 / 
 
 
 
 II II 
 
 
 70 
 
 
 
 
 
 
 
 
 
 \ 
 
 1 
 
 
 
 ill! 
 
 
 c 40 
 
 
 
 
 
 
 1 
 
 
 
 \ y 
 
 
 
 
 II II 
 
 
 60 1 
 
 
 
 
 
 
 1 
 
 
 
 1 \ / 
 
 
 
 
 1 1 1 1 
 
 
 0) 
 
 0^ 50 
 
 c 
 
 
 
 
 
 
 
 
 
 \ / 
 
 
 
 
 1 1 1 1 
 1 1 1 1 
 
 
 50 t 
 
 c 
 
 
 
 
 
 
 
 
 
 \ / 
 
 
 
 
 MM 
 
 
 e 60 
 
 
 
 
 
 
 
 
 
 ¥ 
 
 
 
 
 II II 
 
 
 o 
 40 5; 
 
 Q. 
 
 - 
 
 SAMPLE 8 
 
 1 
 
 
 
 
 
 
 1 
 
 n 
 
 
 
 II 1 1 
 1 II 1 
 
 
 70 
 
 1 
 
 
 
 
 
 
 1 1 
 
 
 
 
 MM 
 
 
 30 
 
 I 
 
 
 
 
 
 
 
 
 
 
 1 M 1 
 
 
 80 
 
 \ 
 
 
 
 
 
 
 1 1 
 
 
 
 
 MM 
 Ml! 
 
 
 20 
 
 1 
 
 
 
 
 
 
 
 
 
 
 Mil 
 
 
 90 
 
 1 
 
 
 
 
 
 
 
 
 
 
 i M 1 
 
 1 1 1 1 
 
 
 10 
 
 1 
 
 
 
 
 
 ■ 
 
 
 
 
 
 MM 
 1 1 II 
 
 
 100 
 
 
 1 II 'Ml 
 II 1 1 1 1 
 
 
 
 1 
 
 1 
 
 
 L _ 1 . 1 
 
 
 
 i 1 1 
 
 Mil 
 
 1 1 1 
 
 
 Particle Size Diameter in Millimeters 1 
 
 
 Coarse Aggregate 
 
 Coarse Sand 
 
 Fine Sand 
 
 Silt 
 
 Clay 
 
 
 c 
 
 
 
 
 MECHANICAL ANALYSIS GRAIN SIZE ACCUMULATION CURVE 
 
 
 
 2" 
 1 1/2" 
 
 1" 
 3/4" 
 
 1/2" 
 
 3/8" 
 1/4" 
 
 Sieve Sizes - U.S. Standard 
 
 _. (OOOOO o o^- 
 r 00° ^<Mco¥<o T- cgcNj 
 
 100 
 
 
 1 ' I I 
 
 I 
 
 ' 
 
 ^. 
 
 1 
 1 
 
 
 I ' ' 
 
 1 
 
 ' i 1 
 
 1 1 1 1 
 
 T 1 1 
 
 10 
 
 
 
 
 
 ^ 
 
 
 
 
 
 — 1 
 
 
 
 
 90 
 
 
 
 
 
 
 \ 
 
 
 
 k 
 
 1 / 
 
 
 
 
 20 
 
 
 
 
 
 
 \ 
 
 
 
 ^ 
 
 
 
 
 80 
 
 
 
 
 
 
 ' \ 
 
 I 
 
 _1 J 
 
 
 T 
 1 
 
 
 1 1 II 
 
 
 30 
 
 
 
 
 
 
 
 V 
 
 / 
 
 
 1 
 
 
 
 
 70 
 
 
 
 
 
 
 
 > 
 
 f 
 
 
 1 
 
 1 
 
 
 
 
 S 
 
 
 
 
 
 
 
 
 
 
 1 
 
 
 
 
 O) 
 
 60 i 
 
 c 40 
 
 
 ■ 1 — )■ — 1 f ■ 
 
 
 
 
 
 
 
 1 
 1 
 
 
 
 
 « 
 
 
 
 
 
 
 
 
 
 1 
 
 
 
 
 50 t 
 
 c 
 
 "■ 50 
 
 
 
 
 
 
 
 
 
 1 
 
 
 
 
 0) 
 
 y 60 
 
 a. 
 70 
 
 
 
 
 
 
 
 
 1 1 1 
 
 1 
 
 
 
 
 o 
 
 40 a 
 
 a. 
 
 — 
 
 SAMPLE 9 
 
 1 
 1 
 
 
 
 
 
 
 1 
 1 
 
 
 
 
 1 
 
 
 
 
 
 
 1 
 
 
 
 
 30 
 
 1 
 
 1 
 
 
 
 
 
 
 1 
 1 
 
 
 
 
 
 80 
 
 1 
 
 
 
 
 
 
 1 
 
 
 
 
 90 
 
 I- 
 1 
 
 
 
 
 
 
 
 
 
 
 
 90 
 
 1 
 
 
 
 
 
 
 1 
 1 
 
 
 
 
 10 
 
 1 — ' 
 1 
 
 
 
 
 
 
 1 
 
 
 
 
 100 
 
 
 ' ' ' 1 1 1 
 
 II 1 1 
 
 
 
 1 
 
 
 1 1 1 
 
 1 
 1 
 
 1 1 1 
 
 
 
 . 
 
 5 
 
 Particle Size Dianneter in Millimeters 
 
 
 Coarse Aggregate 
 
 Coarse Sand 
 
 Fine Sand 
 
 Silt 
 
 Clay 
 
 
 FIGURE 16. - Grain size accumulation curves for samples 8 and 9. 
 
22 
 
 c 
 
 
 
 
 
 
 
 MECHANICAL ANALYSIS GRAIN SIZE ACCUMULATION CURVE 
 
 
 
 Sieve Sizes - U.S. Standard 
 
 100 
 
 
 T 
 
 
 
 ^ 
 
 1 
 1 
 
 I 
 1 
 
 
 I 1 
 1 1 
 
 1 / 
 
 1 i 1 
 
 '111 
 
 1 1 1 
 
 10 
 
 
 
 
 
 \, 
 
 1 
 1 
 
 1 
 
 -\ 
 
 1 1 
 1 1 
 
 / 
 
 
 
 
 90 
 
 
 
 
 
 S 
 
 1 
 1 
 
 1 
 
 1 
 
 ; 
 
 ^ 
 
 / 
 
 
 
 
 
 20 
 
 
 
 
 
 
 t^. 
 
 1 
 
 f\ 
 
 S 
 
 r 
 
 
 
 
 
 80 
 
 
 
 
 
 
 i ^. 
 
 y 
 
 
 |\ / 
 
 
 
 
 
 
 30 
 
 
 
 
 
 
 1 ^ 
 1 
 
 y 
 
 
 1 ^^ 
 
 
 
 
 
 
 70 
 
 
 
 
 
 
 1 
 
 T 
 
 
 1 
 
 
 
 
 
 
 T3 
 
 a> 
 c 40 
 
 
 
 
 
 
 1 
 1 
 
 1 
 1 
 
 
 1 1 
 1 1 
 
 
 
 
 
 
 60 i 
 
 (0 
 
 
 
 
 
 
 1 
 
 1 
 
 
 1 1 
 
 
 
 
 
 
 0) 
 
 
 
 
 
 
 1 
 
 1 
 
 
 1 1 
 
 
 
 
 
 
 to 
 
 50 t 
 
 c 
 
 •^ 50 
 
 
 
 
 
 
 1 
 1 
 
 1 
 
 1 
 
 
 1 1 
 
 
 
 
 
 
 ii 60 
 
 
 
 
 
 
 1 
 
 1 
 
 
 1 1 
 
 
 
 
 
 
 o 
 40 £ 
 
 Q. 
 
 ^ 
 
 SAMPLE 10 
 
 1 
 
 
 
 1 
 
 1 
 
 
 1 1 
 
 
 
 
 
 
 
 1 
 
 
 
 1 
 
 1 
 
 
 1 1 
 
 
 
 
 
 
 30 
 
 70 
 
 1 
 
 
 
 1 
 
 1 
 
 
 1 1 
 
 
 
 
 
 
 
 1 
 
 1 
 
 
 
 1 
 1 
 
 1 
 
 
 1 1 
 
 
 
 
 
 
 20 
 
 80 
 
 1 — 
 1 
 
 
 
 1 
 
 1 
 
 
 1 1 
 
 
 
 
 
 
 90 
 
 1 
 
 
 
 1 
 1 
 
 1 
 1 
 
 
 1 1 
 1 1 
 
 
 
 
 
 
 10 
 
 1 
 1 
 
 
 
 1 
 
 1 
 
 
 1 1 
 1 1 
 
 
 
 
 
 
 100 
 
 
 II 1 1 1 1 
 
 
 
 1 
 
 1 
 
 
 1 1 
 
 
 
 1 1 1 
 
 1 1 1 1 
 
 
 
 >" - -d dP pgog 
 
 Particle Size Diameter in Millimeters i 
 
 
 Coarse Aggregate 
 
 Coarse Sand 
 
 Fine Sand 
 
 Silt 
 
 Clay 
 
 
 FIGURE 17.- Grain size accumulation curve for sample 10. 
 
 FIGURE 18. - NX-size cores of four gunite specimens. 
 
 The laminated zones are thought to have 
 been caused by (1) poor hydration of the 
 dry-mix gunite during recurrent spurting 
 pulses of the nozzle, (2) flow pulsing of 
 the dry-mix through the hose, (3) erratic 
 loading of the rotating load chamber feed 
 cells in the rotary dry-mix gun, (4) noz- 
 zle operator water level control varia- 
 tions , or perhaps a combination of all 
 four factors. Sandy grains could easily 
 be picked out of the laminae by finger- 
 nail, even after 28 days of curing. The 
 wet-mix samples did not contain the 
 strength-reducing laminae. 
 
 Cores cut for compressive strength 
 testing were NX sized, 2.1 in in diameter 
 and 4.2 in long. The strength of cored 
 samples is greatly influenced by the 
 maximum size of the contained aggregate. 
 The rule of thumb for concrete-cored 
 specimens is that the core diameter ratio 
 should be at least three times the maxi- 
 mum aggregate size, as was the case for 
 all the fibered-gunite specimens. Addi- 
 tional testing was performed using cubes. 
 
 The flexure test specimens were made by 
 gunning directly onto a wooden panel 
 which contained 4- by 4- by 14-in molds. 
 The molds were coated with form-release 
 oil to prevent rapid water loss through 
 absorption. The glass-f ibered products 
 were uniform in cross section; however, 
 the steel-f ibered products had a slight 
 paucity of fibers at the bottom of the 
 samples owing to rebounding and contained 
 laminations. Additional flexure strength 
 samples were acquired in 3- by 3- by 12- 
 in sawn beam form. 
 
 An initial effort was made to collect 
 gunite samples for use in splitting 
 tensile strength (Brazilian) testing. 
 
23 
 
 FIGURE 19. - Wet-mix gunite sample acquisi- 
 tion for splitting tensile analysis. 
 
 Six-inch-diameter by 12-in-long plastic 
 molds were utilized. Extreme difficulty 
 was experienced in gunning the sample 
 containers when dry-mix products were be- 
 ing sampled. Samples of the wet-mix gun- 
 ite could be slowly pumped into the cyl- 
 inders, as shown in figure 19. Subse- 
 quent sample testing of the dry-mix prod- 
 ucts revealed multiple laminations , air 
 pockets , bleed-out exterior scale (around 
 the sides of the cylinder) , and other 
 problems. Figure 20 shows typical cylin- 
 ders of six different dry-mix products. 
 Four of the six shown are defective. 
 
 Splitting tensile strength was 
 mined using the formula 
 
 deter- 
 
 1^ 
 
 FIGURE 20. - Six-inch-diameter by 12-in-long 
 cylinders of six different gunite products. 
 
 2P 
 
 a='rrLD 
 
 where P is the maximum pressure applied 
 and L and D are length and diameter re- 
 spectively. The splitting tensile 28-day 
 strengths observed ranged from 350 to 400 
 psi for the fiberglass-fibered dry mixes, 
 to 500 psi for the steel-f ibered dry 
 mixes, to almost 800 psi for the high- 
 strength silica fume wet-mix gunite. The 
 data are not presented herein to prevent 
 misleading correlations or comparisons. 
 The splitting tensile strength testing of 
 the gunite products was abandoned since 
 collection methodology inconsistencies 
 (cylinder rodding, tamping, tapping, and 
 shooting or pouring) began to develop and 
 comparative analysis would not have been 
 meaningful. Sample acquisition problems 
 render the engineering test misleading in 
 comparing f ibered, pneumatic gunite prod- 
 uct strengths. The test is not recom- 
 mended for dry-mix gunites. 
 
 REBOUND ANALYSIS 
 
 The pneumatic application of f ibered, 
 portland-cement-based gunite imparts ben- 
 eficial compaction characteristics to the 
 finished gunned product. The application 
 technique, however, causes a relatively 
 high percentage of the high-velocity ag- 
 gregate and fibers (if metallic) to 
 bounce or rebound off the fresh rock sur- 
 face until a layer of cohesive material 
 has accumulated there and can cushion the 
 impact. ACI Standard 506-66 (Recommended 
 
 Practice for Shotcreting) approximates 
 shotcrete rebound generally as 15 to 30 
 pet for sloping and vertical walls and 25 
 to 50 pet for overhead work (l) . Gunite 
 with fine-sized aggregates must be able 
 to meet or hopefully exceed these percen- 
 tages to be economical. 
 
 When steel-fibered gunite is applied 
 to a hard rock surface, such as massive 
 limestone or silica-bearing strata (as at 
 
24 
 
 the Lake Lynn Laboratory Mine) , sparks 
 are commonly observed to occur at the 
 fiber-rock contact. High-speed photogra- 
 phy conducted in one experiment showed 
 that many of the steel fibers were in the 
 outer portion of the airstream and that 
 many of them were blown away radially 
 from near the point of intended impact 
 shortly before or after they hit (19) . 
 For high-velocity gunite work, the coarse 
 aggregate particles (and fibers) con- 
 tained in the pneumatic feed travel at 
 such a high velocity (reportedly 300 to 
 400 ft/s) (20) that they can inflict se- 
 vere eye injury when they ricochet off 
 the application surface. When suitable 
 protective gear is used in conjunction 
 with adequate precautionary measures, 
 however, the safety aspects of the term 
 "rebound" are upstaged by a more real- 
 istic concern — that being the economic 
 issues. 
 
 Rebound is, in fact, waste. It cannot 
 be reused or reprocessed. Except for 
 that portion of rebound attributed to 
 slough-off, the material is generally de- 
 ficient in one or more of the necessary 
 ingredients contained in the original 
 composite mixture and must be discarded. 
 In some applications , the gunning opera- 
 tion must be halted to clean areas of the 
 application surface that have been down- 
 graded by the accumulation of aberrant 
 rebound. If cleaning is not performed, 
 loss of bond will occur in the final 
 product. This problem is seldom cri- 
 tical, however, in mining applications 
 since the majority of the rib-roof appli- 
 cations involve vertical or horizontal 
 applications. 
 
 The application of high-quality fibered 
 gunite by an inexperienced crew using 
 poorly maintained equipment and/or incor- 
 rect pressure (air and water) settings 
 can easily result in rebounds approaching 
 50 pet. With a well-trained crew, the 
 most effective means to reduce rebound 
 include reduction of air pressure, use 
 of more fines, use of shorter fibers 
 (steel), predampening , and shooting at 
 
 the wettest stable consistency ( 19 ) . Re- 
 bound can also be reduced, according to 
 the results of this investigation, by 
 using more cement, finer aggregate top 
 size, and silica fume, crushed slag, or 
 fly ash. 
 
 The term "rebound" draws at least two 
 paradoxical thoughts to the minds of 
 prospective gunite material users: 
 
 1 . Although the term relates directly 
 to the percentage of the purchased mate- 
 rial that will result in useless waste, 
 job specifications seldom address it 
 specifically. 
 
 2. Since rebound is an elusive prop- 
 erty to quantify, the applications per- 
 sonnel generally estimate about 15 pet, 
 which, in this author's opinion, is very 
 hard to achieve, particularly for the 
 dry-mix gunite, unless an extremely pro- 
 ficient gunning crew performs the work. 
 
 Rebound calculations were performed on 
 most of the products tested in the Lake 
 Lynn Laboratory Experimental Mine. Sam- 
 ples 11-17 were demonstrated at the manu- 
 facturer's facilities and could not be 
 tested for rebound percentage. Samples 
 1-3 are wet-mix steel-f ibered silica fume 
 gunite products containing a variety of 
 ingredients that make the material more 
 cohesive, resulting in significantly low 
 rebound. The product manufacturer would 
 not release accurate batch mix quanti- 
 ties; therefore, a precise rebound per- 
 centage could not be provided. Based on 
 rebound cleanup comparisons, however, the 
 rebound was estimated to be approximately 
 10 pet. This is a significant improve- 
 ment over conventional wet-mix shotcrete 
 (without fiber, silica fume, or addi- 
 tives) used in the past. An average re- 
 bound of 47 pet was reported for a 6,618- 
 psi-compressive-strength (28-day) wet-mix 
 shotcrete used in an Arizona deep mine 
 (21). Wet mining conditions were experi- 
 enced during that particular application, 
 however, and shotcrete accelerators were 
 even found to be ineffective. 
 
25 
 
 For the 
 formulas : 
 
 dry-mix prebagged products, rebound was calculated using two different 
 
 A. Rebound (pet) = 
 
 gunite rebound collected (wet, lb) 
 
 Dry gunite shot (lb) + )-^ — ags gum e s o ^(cgjae^t ^i^/yd3)(^ater-cement ratio) 
 
 (No. bags/yd-' ) 
 
 X 100. 
 
 B. Rebound (pet) = 
 
 gunite rebound collected (wet, lb) 
 
 dry gunite shot (lb) + [(yd^ of gunite shot) (300 lb water/yd^)] 
 
 X 100. 
 
 Formula A assumes the specified water- 
 cement ratio was achieved in the gunning 
 operation. 
 
 Formula B assumes that 1 yd^ of gun- 
 ite weighs 4,000 lb and contains 3,700 lb 
 of solids and 300 lb of water. Normal- 
 ly, gunite products weigh from 143 to 
 154 Ib/ft^, resulting in a range from 
 
 3,861 to 4,158 lb/yd3; 4,000 Ib/yd^ is 
 frequently used in gunite quantity 
 calculations. The development and use of 
 these formulae for this investigation 
 were required owing to unavailability of 
 direct measurement of the water factor. 
 Although the rebound percentages calcu- 
 lated and presented in table 5 are based 
 
 TABLE 5. - Gunite rebound percentages 
 
 Sample 
 
 Gunite shot (wet) , 
 lb 
 
 Rebound (wet) , 
 lb 
 
 Rebound , pet 
 
 Formula A Formula B 
 
 1-3. 
 4.. 
 5., 
 6., 
 7., 
 8., 
 
 9., 
 
 10., 
 
 0) 
 
 8,850 
 1,350 
 6,960 
 3,540 
 2,050 
 7,500 
 11,040 
 5,760 
 
 NA 
 
 (2) 
 
 NA 
 
 1,050 
 
 850 
 
 1,090 
 
 1,500 
 
 1,900 
 
 1,020 
 
 ®10 
 
 NA 
 
 32 
 
 33 
 
 NA 
 
 NA 
 
 13-14 
 
 3i4 
 
 21 
 
 22 
 
 H3 
 
 449 
 
 18 
 
 18 
 
 15 
 
 16 
 
 16 
 
 16 
 
 ^Estimated. NA Not available. 
 
 ^Samples 1-3 are wet-mix gunites. With the number of additives included, the mate- 
 rial is extremely cohesive. Precise "shot" material weights were not provided by the 
 manufacturer; rebound calculations are, therefore, not available. Comparatively 
 (based on empirical observation) , the rebound mainly consisted of steel fiber and a 
 small amount of coarse aggregate and was significantly lower in quantity than for any 
 of the dry-mix types. An estimate of 10 pet is conservative. 
 
 ^3,550-350=3,200. Included in the rebound calculation is a 20-in by 5-ft by 3-in- 
 thick roof spall-off zone. At a density of approximately 2.1 g/cm^, the mass weighed 
 approximately 274 lb. Two other spall zones contributed to a total of approximately 
 350 lb of spall in the rebound calculation. 
 
 ^Extreme dust occurred at the gun. The calculated rebound is estimated to be low 
 by 3 to 5 pet. True rebound percent, therefore, may approach 20 pet. 
 
 ^Very high dust occurred at the gun; also, the material exhibited very high slump. 
 The manufacturer does not recommend pneumatic application, but rather, trowel appli- 
 cation. The pneumatic application technique for this product was conducted for test- 
 ing purposes only. 
 
 ^Product 9 was shot in 2 separate applications, each having rebound collection 
 performed. 
 
26 
 
 on actual rebound collected and weighed 
 (fig, 21), they may be slightly higher or 
 lower than actual owing to one or more of 
 the following: 
 
 1. Errors included in physically shov- 
 elling up the rebound from the flat con- 
 crete mine floor. 
 
 2. Errors due to weighing the rebound 
 on a truck scale (reported to be accurate 
 to 10 to 15 lb). 
 
 3. Use of an assumed water-cement ra- 
 tio of 0.4 in the water weight calcula- 
 tion, when more or less water may have 
 been used during application. It is im- 
 portant to note, however, that a water- 
 cement ratio change from 0.4 to 0.5 in 
 the calculation changed the rebound per- 
 centage factor only 1 or 2 pet. 
 
 4. The specific gravity of the rebound 
 differing considerably from that of the 
 in-place product. 
 
 5. Dewatering, bleeding, or dessica- 
 tion of the collected rebound mass before 
 physical weighing. 
 
 6. The ventilation-borne gunite dust 
 not being "estimated" and removed from 
 the "dry gunite shot (lb)" factor in the 
 divisor segment of the rebound equations. 
 
 The factor used, therefore, results in 
 slightly lower than actual rebound per- 
 centages for those products with very 
 little dust loss and in significantly 
 lower than actual rebound readings for 
 those products with extreme dust. 
 
 The complete listing of rebound data 
 used in the calculations is shown in ap- 
 pendix A. The mean dry-mix rebound per- 
 centage for all products tested, exclud- 
 ing the lowest and highest values, was 
 20.4 pet (std dev=±6.8) using values from 
 formila A and 21 pet (std dev=±7.1) using 
 formula B values. 
 
 One additional comparative test was 
 performed to determine the ratio of roof 
 rebound to rib rebound. Based on the 
 findings of the comparison analyses (of 
 one company's application), the roof -rib 
 rebound ratio was determined to be ap- 
 proximately 2:1 for one product. Angled 
 roof gunning such as is shown in figure 
 
 22 results in very high rebound. Figures 
 
 23 and 24 show more efficient roof gun- 
 ning positions. 
 
 FIGURE 21. - Gunite rebound collected and 
 ready for weighing. 
 
 FIGURE 22. = Angled roof gunning produces 
 very high rebound. 
 
27 
 
 FIGURE 23. = Near=vertical wet-mix roof gun- 
 ning gives low rebouncl = 
 
 FIGURE 24o = Near=vertical dry=mix roof gun= 
 ning with reduced pressure gives low rebound. 
 
 GUNITE DUST 
 
 The Federal Coal Mine Health and Safety 
 Act of 1969 required that deep coal mines 
 maintain their airborne respirable dust 
 (nominally less than 5 to 10 ym in size) 
 concentration at or below 2.0 mg/m^ over 
 an 8-h average time period after December 
 30, 1972 (22). When the respirable dust 
 in the mine atmosphere of active workings 
 contains more than 5 pet quartz , the res- 
 pirable concentration allowable is re- 
 duced significantly. The concentration 
 in milligrams per cubic meter is computed 
 by dividing the percent of quartz pres- 
 ent into the number 10 (23^) . Total dust 
 loading is required to be less than 10 
 mg/m^ in metal and nonmetal mines {2A) . 
 Consequently, all deep mining activities, 
 including gunite application, must be 
 performed in consideration of the total 
 respirable dust generated. Coal workers' 
 pneumoconiosis ("black lung"), asbesto- 
 sis, and silicosis are of primary con- 
 cern, therefore total dust exposure, re- 
 gardless of its composition, is monitored 
 by mine regulatory agencies. 
 
 Dust sample collection and analysis 
 were performed during gunite emplacement 
 for all four companies participating in 
 the comparative research. The dust moni- 
 toring was performed in the following 
 manner and with the equipment shown in 
 figure 25. 
 
 1. Dust sampler — filter assemblies 
 used were Dupont model P-2500 low-volume 
 gravimetric air samplers fitted with cy- 
 clones (for respirable dust measuring) 
 and 1-1/2-in diam MSA gravimetric cas- 
 sette membrane filters. The sampler is a 
 constant-flow model with an automatic 
 flow control system that maintains con- 
 stant airflow rate within ±5 pet over 
 pressure drop changes up to 15 in. The 
 samplers have a range of 1,000 to 2,500 
 cm^/min. A pump flow rate of 2,000 cm^/ 
 min (2 L/min) was used in this investiga- 
 tion. The cyclone-filter holder assembly 
 is designed to simulate the human respi- 
 ratory tract in its selectivity for the 
 respirable fraction of dust particles. 
 
28 
 
 FIGURE 25. - Gunite dust monitoring equipment. 
 
 The lO-tnm cyclone assembly separates out 
 
 the dust particles larger than 10 ym. 
 
 The membrane filter traps the particles 
 smaller than 10 ym. For the "total dust" 
 
 sample collection, the cyclone was 
 
 omitted from the assembly and only the 
 
 air sampler pump and filter assembly were 
 used. 
 
 2. Six filter assemblies were sus- 
 pended from the mine roof a nominal dis- 
 tance of 60 in above the mine floor and 
 85 to 90 ft downdrift of the gunite ap- 
 plication zone. The gun loading area 
 (the major dust loading area) was 15 to 
 25 ft updrift from the nozzle-application 
 zone; i.e., a minimum of 100 to 110 ft 
 updrift of the samplers. 
 
 3. Cyclones were used on two of the 
 six downdrift samplers. 
 
 4. Three filter assemblies (without 
 cyclones) were suspended 60 in above the 
 mine floor 135 ft updrift of the gunite 
 application zone in clean mine air to es- 
 tablish ambient total dust levels. A 
 control filter was provided at the up- 
 drift location during the application of 
 
 some gunite products. The filter ori- 
 fices were opened and exposed to the mine 
 air to evaluate the amount of moisture 
 absorption and other prospective filter 
 weight increases not related to the dust 
 sampling, 
 
 5. The mine temperature, relative hu- 
 midity, and ventilation conditions were 
 monitored to provide comparison charac- 
 teristics of the collected data. The 
 100-hp axivane ventilation fan was main- 
 tained on fourth speed forward during all 
 gunite applications. Bulkhead doors were 
 maintained in the full-open position. 
 The mine drift containing the gunite 
 equipment received 50 pet of the avail- 
 able 60,000 ft3/min of air (30,000 ftV 
 min) . 
 
 6. Air sampling periods were carefully 
 timed. 
 
 7. Gunite specimens 11 through 17 were 
 gunned during a demonstration at the man- 
 ufacturer's facilities and, therefore, 
 were not monitored for dust data. 
 
 Gunite application equipment , particu- 
 larly the dry-mix type, is notoriously 
 dusty. Although a concerted effort has 
 been made by the gunite equipment manu- 
 facturers to reduce gun dust, the problem 
 has been only marginally reduced for most 
 dry-mix gun types. Ventilation air dust 
 loadings result from three separate seg- 
 ments of the underground gunite appli- 
 cation operation. The major dust con- 
 butor was found to be the gun hopper 
 loading operation, in which 50- to 80-lb 
 paper bags of premixed gunite are opened 
 either manually or by the use of a gun 
 hopper knife, and dumped into the hop- 
 per — sometimes through a screen or griz- 
 zly to prevent clogging by lumps , fiber 
 balls, or other foreign materials. The 
 bag ripping, emptying, and shaking opera- 
 tion is a serious dust generator, 
 
 A second serious dust generator, par- 
 ticularly in the rotary, continuously 
 loaded dry-mix gunite gun, is the rotat- 
 ing airlock (rotor). The rotor takes 
 the dry gunite material from atmospheric 
 
29 
 
 pressure in the feed hopper, measures out 
 a slug of the product, and injects it 
 into the gunite placement hose under 
 pressure where a moving high-pressure 
 airstream (40 to 90 psi) carries it to- 
 ward the nozzle. In poorly maintained 
 guns in which either the rubber wear 
 plates, steel friction plates, or both 
 are worn or misaligned , a cyclic pulse of 
 gunite is puffed out of the rotor area 
 (and sometimes even the hopper area) each 
 time a chamber slug is emptied into the 
 hose. 
 
 Three of the companies involved in the 
 gunite comparative research used dry-mix 
 rotary guns. One company experienced se- 
 vere dust generation problems due to worn 
 wear and/or friction plates. Figure 26 
 shows gunite dust caused by bag unloading 
 and hopper puffing. Figure 27 shows the 
 same gun after the gunning operation was 
 completed. When gunning was completed, 
 dust thicknesses (from the malfunctioning 
 gun) of approximately 1/16 in were found 
 on the upper surface of air samplers sus- 
 pended from the mine roof 100 ft down- 
 drift. Not only was dust pulsing from 
 the rotor section of the gun, the loading 
 hopper was casting loaded gunite back 
 out of the hopper in large puffs, allow- 
 ing the moving mine ventilation air to 
 
 separate and carry the fines (e.g., ce- 
 ment fraction) downdrift, much like the 
 process used in nonautomated farming 
 areas to separate chaff from wheat on a 
 windy day. Some gunite samples collected 
 during the gun malfunction period were so 
 lean (cement-poor) they could be crumbled 
 by hand. 
 
 A third dust source characteristic of 
 dry-mix gunite application is pneumati- 
 cally ejected dust from the nozzle due to 
 incomplete hydration at the nozzle water 
 ring section. The internal mix water 
 spray through the nozzle water ring is 
 controlled manually by the nozzle opera- 
 tor, who must gauge water addition empir- 
 ically, based on the glisten of the ap- 
 plied product as observed in the poorly 
 lighted conditions of the mine. The noz- 
 zle operator is under constant pressure 
 to maintain a low water-cement ratio to 
 achieve optimum strength characteristics 
 of the product , while at the same time 
 making sure the water added sufficiently 
 hydrates the port land cement fraction. 
 Since most of the rotary guns tested 
 characteristically cough, speed up, slow 
 down, sputter, and pulse, the nozzle 
 operator must make continuous water ad- 
 justments to prevent dusty (too dry) or 
 slough-off (too wet) gun operation. 
 
 FIGURE 26. - Gunite dust from the gun-loading 
 operation. Gun malfunction was partially the 
 cause of the excessive dust. 
 
 FIGURE 27. - Gunite gun dust (fines) on mine 
 floor caused by worn friction plate or wear pad 
 (or both). 
 
30 
 
 Double-chamber guns (in which an upper 
 chamber is intermittently loaded while a 
 lower chamber is continuously flowing) , 
 single-batch guns , and gunite predampener 
 feeders are known to reduce dust loading 
 of mine air if space conditions and bud- 
 get permit their use. However, none were 
 demonstrated in this effort. 
 
 Table 6 summarizes the dust data; full 
 data are presented in appendix B. For 
 the "total" dust collected, the table 
 
 "Total" dust in air = 
 
 (0 
 
 provides an analysis of dust collected 
 per unit time (mg/min) , dust collected 
 per unit weight of dry gunite fed through 
 the gun (mg/ lb shot) , and dust collected 
 per unit volume of air moved through the 
 sampler (mg/m^ in air). The latter fig- 
 ure may be the most meaningful and was 
 calculated by dividing the weight of dust 
 collected by the volume of dust-laden air 
 moved through the sampler pump for the 
 duration of the sampling period : 
 
 1.57 mg 
 
 .002 m^/min) x 167 min 
 
 4.70 mg/m^. 
 
 Some of the dust loadings are extremely 
 high. Though they appear to violate the 
 permissible standards (2 mg/m^), they 
 must be taken in context of the fact that 
 the standards are given for an 8-h shift. 
 If the gunite equipment was the only sig- 
 nificant dust generator, the worst case 
 (sample 6) for the time period operated 
 (70 min) generated 99.2 pet of the allow- 
 able 8-h loading. 
 
 In comparing the gunite product dust 
 data, the following should be considered: 
 
 function of crew operation (hopper load- 
 ing and nozzle operation) and the mechan- 
 ical condition of the gun. The products 
 were quite similar in dust constituent 
 content. 
 
 2. The wet-mix products were dumped 
 into a mixer from bags, generating a ma- 
 jority of the products' dust. Very lit- 
 tle of the wet-mix product dust was from 
 the nozzle. The mixing operation turned 
 out to be quite dusty compared to some 
 dry-mix operations. 
 
 1. Dry-mix gunite product dust load- 
 ing differences were found to be a 
 
 3. Neither the respirable nor the to- 
 tal (nuisance) dust loadings exceeded the 
 
 TABLE 6. - Gunite dust data 
 
 Sample 
 
 Gunite 
 shot, 
 lb 
 
 Time, 
 min 
 
 Respirable 
 
 dust (av) , 
 
 mg 
 
 Total 
 dust (av) , 
 mg 
 
 Total dust, 
 mg/min 
 
 Total dust 
 per pound 
 shot, mg 
 
 Total dust 
 in air, 
 mg/m^ 
 
 3I 
 
 42 
 
 4 
 
 5 
 
 6 
 
 7 
 
 8 
 
 9 
 
 10 
 
 4,200 
 9,000 
 8,500 
 1,350 
 7,680 
 3,840 
 2,400 
 8,700 
 11,360 
 
 167 
 
 180 
 
 125 
 
 60 
 
 70 
 
 38 
 
 55 
 
 55 
 
 102 
 
 0.87 
 .37 
 
 4.81 
 .03 
 
 1.71 
 NA 
 
 1.60 
 .04 
 .06 
 
 1.57 
 8.03 
 7.97 
 
 .37 
 9.53 
 
 .59 
 3.45 
 
 .34 
 1.10 
 
 0.9 X 10-2 
 
 4.4 X 10-2 
 6.3 X 10-2 
 
 .6 X 10-2 
 13.6 X 10-2 
 
 1.5 X 10-2 
 6.2 X 10-2 
 
 .6 X 10-2 
 1.0 X 10-2 
 
 3.7 X 10-*^ 
 8.9 X lO-'* 
 
 9.4 X 10-*+ 
 2.7 X 10-^+ 
 
 12.4 X 10-*+ 
 
 1.5 X lO-'* 
 14.4 X lO-'^ 
 
 .4 X lO-^t 
 1.0 X lO-'^ 
 
 4.70 
 22.30 
 31.16 
 
 3.08 
 68.07 
 
 7.76 
 31.36 
 
 3.09 
 
 5.39 
 
 NA Not available. 
 
 ^Volume of wet-mix type 3 estimated at 1.05 yd^. At an estimated 4,000 lb/yd ^, the 
 total shot is 4,200 lb. 
 
 2two separate applications of product 4 were monitored for dust loading. 
 
31 
 
 standards for dust when taken in context 
 of an 8-h shift (480 min) . However, at 
 least four of the eight dry-mix samplings 
 produced loadings that would exceed the 
 
 standards if the crew were to gun at that 
 loading rate for a full shift or if they 
 were gunning near a working section. 
 
 SCANNING ELECTRON MICROPROBE ANALYSIS OF SILICA FUME 
 
 An electron probe microanalysis was 
 performed on the silica fume and cement 
 fractions of sample 3, to investigate the 
 particle size relationship (with cement) 
 and angularity of the silica fume as it 
 relates to respirable dust loading, A 
 qualitative elemental chemical analysis 
 was also performed both on the silica 
 fume and on portland cement because of a 
 concern that some ferroalloy fume byprod- 
 ucts, from which silica fume particles 
 are concentrated, contain relatively high 
 concentrations of toxic chromium and/or 
 cadmium when condensed from a furnace 
 burden melt containing those metals. 
 
 Figure 28 reveals the size relationship 
 between cement (large particles) and sil- 
 ica fume (small particles). Although 
 some of the silica fume particles appear 
 to be somewhat angular, they are, in 
 
 fact, agglomerations of smaller, amor- 
 phous particles, as shown in figure 29, 
 Silica fume size (diameter) ranged from 
 0,1 to 1 ym. The silica fume was also 
 analyzed in an XRD-5 X-ray dif f ractometer 
 and found to exhibit no characteristic 
 quartz (Si02) peak when bombarded with 
 copper K°^ radiation. Absence of the peak 
 confirms the amorphous nature of the 
 material. 
 
 The silica fume partice size is in 
 the range of respirable dust. Its amor- 
 phous surface characteristics and wet- 
 mix incorporation method into the gun- 
 ite, however, reduce the major potential 
 silicosis concerns. The bag opening 
 function for bulk mixing of the silica 
 fume or prebag mix, however, should al- 
 ways be performed using dust protection 
 equipment , 
 
 FIGURE 28. = Scanning electron microscope mi» 
 crophotograph of portlond cement and silica fume. 
 
 FIGURE 29. - Scanning electron microscope mi- 
 crophotograph of silica fume. 
 
32 
 
 An elemental qualitative chemical anal- 
 ysis was performed on the silica fume and 
 Portland cement using a scanning electron 
 microscope (SEM) and an energy-dispersive 
 X-ray (EDX) analyser. A small amount of 
 the sample was supported on a metallic 
 substrate, which was then inserted into 
 the SEM's sample chamber. The X-ray pho- 
 tons produced by the bombardment of the 
 sample by electrons are detected by a 
 solid state detector. The output signal 
 of the detector is fed into a multichan- 
 nel analyzer where the signals are sorted 
 
 according to energy to produce an X-ray 
 spectrum. The energy of the X-ray is 
 related to the atomic number of the atoms 
 present in the sample. The elemental 
 species present are, therefore, identi- 
 fied by the X-ray signals' different 
 energies. 
 
 Tables 7 and 8 present the count data, 
 energy readings , and the representative 
 elements associated with the various en- 
 ergy spectra peaks shown in figures 30 
 and 31 respectively. 
 
 TABLE 7. - Element X-ray spectrum data for silica fume 
 
 Energy , keV 
 
 Element 
 
 Count rate 
 
 Energy , keV 
 
 Element 
 
 Count rate 
 
 1.5 
 1.74 
 
 Aluminum 
 
 Silicon. ........ 
 
 NA 
 
 3,491 
 
 47 
 
 67 
 
 3.7 
 4.5 
 5.4 
 6.4 
 
 Calcium (K°:) .... 
 
 Titanium 
 
 Chromium 
 
 Iron 
 
 57 
 45 
 
 2.3 
 
 Sulfur 
 
 45 
 
 3.3 
 
 Potassium 
 
 38 
 
 NA Not available (unmeasurable) . 
 
 TABLE 8. - Element X-ray spectrum data for cement 
 
 Energy , keV 
 
 Element 
 
 Count rate 
 
 Energy, keV 
 
 Element 
 
 Count rate 
 
 1.5 
 1.74 
 
 Aluminum 
 
 Silicon. ........ 
 
 172 
 816 
 289 
 219 
 
 3.7 
 4.0 
 4.5 
 6.4 
 
 Calcium (K«) .... 
 Calcium (Kg) .... 
 
 Titanium 
 
 Iron 
 
 4,971 
 775 
 
 2.3 
 
 Sulfur 
 
 73 
 
 3.3 
 
 Potassium 
 
 146 
 
 NOTE: Calcium exhibits 2 detectable peaks (K°: and Kg) when it occurs in high 
 concentrations . 
 
 1,0 
 
 800 
 
 CO 
 
 h- 
 
 § 600 
 
 o 
 o 
 
 UJ 
 
 ^ 400 
 
 Q- 
 
 200 
 
 
 
 "T r 
 
 Off scale, 
 total count 4,971 
 
 Total count time 
 175s 
 
 Note^ 
 graphically reproduced 
 from microphotograph. 
 
 500 
 
 4 6 
 
 ENERGY, keV 
 
 FIGURE 30. - Electron probe microanalysis of 
 Portland cement. 
 
 400 - 
 
 CO 
 
 I- 
 
 i 300 
 
 o 
 
 o 
 
 UJ 
 CO 
 
 200 
 
 00 
 
 
 
 Off scale, total count 3,491 
 
 Total count tinne, 200 s 
 
 Note= graphically reproduced 
 from microphotograph 
 
 4 6 
 
 ENERGY, keV 
 
 FIGURE 31. - Electron probe microanalysis of 
 silica fume. 
 
33 
 
 Elements of low atomic number such as 
 are found in both the cement and silica 
 fume are difficult, at best, to identify 
 in a quantitative manner using conven- 
 tional X-ray emission spectrographic 
 equipment where the sample is bombarded 
 directly by X-rays. This is due to the 
 high background, absorption (X-ray), and 
 enhancement effects. In the silica- 
 alumina system, for example, silicon K"^ 
 is strongly absorbed by aluminum to ex- 
 cite aluminum K<^; the mass absorption co- 
 efficient in this case exceeds 3,000. 
 With an increasing content of alumina, 
 the intensity of silicon K°^ decreases 
 progressively. The intensity of alumi- 
 num K°^ behaves quite differently as the 
 silica content decreases (25) . Addi- 
 tionally, the relatively high background 
 
 tends to hide 
 chromium . 
 
 some elements , such as 
 
 By using a focused electron beam from 
 the SEM rather than X-rays to exite atoms 
 in the sample into producing essentially 
 a point source of strongly divergent 
 X-rays, as was used here, absorption and 
 enhancement effects are minimized. The 
 analyses produced by the technique, how- 
 ever, are purely qualitative and should, 
 in this case, be used only to indicate 
 the presence or absence of an element and 
 its relative composition. The analysis 
 presented indicates that some chromium 
 occurs in the silica fume but in very low 
 concentration. Cadmium was not detected 
 in the sample. 
 
 COMPRESSIVE STRENGTH ANALYSIS 
 
 The fibered-gunite products were ana- 
 lysed for unconfined uniaxial compressive 
 strength using conventional testing pro- 
 cedures. Samples 1-10 were tested by the 
 Bureau with additional analyses provided 
 by Pittsburgh Testing Laboratories. Sam- 
 ples 11-17 were tested by the Froehling 
 and Robertson, Inc. , Engineering Labora- 
 tory. For samples 1-10, full-length NX- 
 sized cores up to 8 in long were drilled 
 out of 24-in by 24-in by 8-in-thick sam- 
 ple blocks, and the best 4.2-in specimens 
 were selected and trimmed out. The near- 
 bottom and near-side areas of the sample 
 blocks were avoided in specimen selection 
 since they have high rebound (low fiber 
 and smaller aggregate characteristics). 
 Additionally, laminated sections were 
 avoided. Although an average of 15 cores 
 were taken from each product sample 
 block, some were so laced with lamina- 
 tions that specimens had to be tested 
 that contained minor laminations. Al- 
 though this procedure may not be con- 
 doned by the industry, which strives to 
 obtain perfect samples to provide optimum 
 strength characteristics, the use of lam- 
 inated samples may provide a more realis- 
 tic analysis of the product that was ap- 
 plied underground. 
 
 Core length was maintained at twice 
 the diameter. Correction factors for 
 
 long or short cores were, therefore, 
 unneeded. The length cuts were made with 
 a precision-self-feeding diamond saw 
 blade in order to obtain compression 
 bearing surfaces perpendicular to the 
 long axis of the cores. Compressive 
 strengths were analyzed by using a 
 120,000-lb pressure Tinius Olsen machine 
 (fig. 32). A 2.13-in-diameter stainless 
 steel, two-piece, universal rotating 
 bearing block was used to overcome minor 
 offset loading (fig. 33). 
 
 FIGURE 32. . Tinius Olsen 120,000.Ib test- 
 ing machine used in gunite analysis. 
 
34 
 
 Compressive strength tests were also 
 performed on sawn cubes of some samples. 
 The analyses were performed by testing 
 laboratories and funded by gunite prod- 
 uct manufacturers. It is important to 
 note that ACI Standard 506-66 indicates 
 that "cube strengths may be reported as 
 length/diameter or (L/D) determined or 
 converted to cylinder (L/D=2) strengths 
 by multiplying by the factor 0.85" 
 (_1_) . As contained in this report , the 
 strengths have not been converted. Addi- 
 tionally, it has been reported (26) that 
 the percentage reduction in strength of 
 drilled cores from concrete increases 
 with the increase in strength level of 
 the concrete. The reason given is that 
 stronger concrete offers more resist- 
 ance to drilling, whereby microcracks or 
 other damages are introduced into the 
 core. If this is true, then the drilled 
 cores used by the Bureau in this inves- 
 tigation would produce lower ultimate 
 compressive strengths for the higher 
 strength products than are produced from 
 the larger cubes normally used at testing 
 laboratories. A Bureau-performed com- 
 pressive strength analysis, therefore, 
 may be more than 15 pet lower than an 
 analysis received from a licensed testing 
 laboratory for an identical specimen. 
 
 FIGURE 33. = Stainless steel rotating bearing 
 block used in gunite core compressive strength 
 analysis. 
 
 Compressive strengths of the specimens 
 were derived by the standard formula 
 
 compressive strength = — '" —^ -> 
 
 where P{max) = maximum applied load, 
 
 lb. 
 
 and 
 
 r = radius of core, in. 
 
 The compressive strength of the samples 
 tested as cubes was derived using the 
 formula 
 
 compressive strength = 
 
 P( ma x) 
 
 area (cross section) 
 
 The applied compressive stress was con- 
 tinued until observable fracture was 
 noted and the stress-strain curve had 
 peaked and established a definitive irre- 
 versible negative trend after failure had 
 occurred. Stress in this paper relates 
 to the intensity of the internal compo- 
 nents of the forces in the gunite that 
 resist change in the form of the core. 
 Strain refers to axial strain only in the 
 direction of applied loading, since lat- 
 eral strain or deformation was not mea- 
 sured. Figures 34 and 35 are compressive 
 strength diagrams of two gunite samples 
 plotted with the applied load on the 
 
 ordinates and compressive deflection on 
 the abscissas, showing rapid and gradual 
 failure, respectively. 
 
 Although true hourglass or shear cone 
 rupture was observed in some specimens at 
 failure, this was a rarity. The random 
 failure patterns observed were due to 
 (1) the nonhomogeneous composition of the 
 gunite, (2) the isotropic distribution of 
 the fibers, and (3) the end section re- 
 straint to lateral expansion caused by 
 friction and/or loading of the platen and 
 bearing block. 
 
35 
 
 50,000 
 
 £ 40,000 
 
 2 3 4 5 6 7 
 
 DEFLECTION (COMPRESSIVE), 0.01 in/in 
 
 FIGURE 34. - Gunite compressive strength plot 
 showing rapid failure. 
 
 ASTM 39-66 recommends end capping for 
 concrete cylinders that are not within 
 0.002 in from plane (27) . For sample 
 convexity of only 0.01 in in a cylin- 
 der of 6-in diameter, tests have shown 
 reduction in strength of up to 20 pet 
 (28) . Accordingly, great effort was 
 made. to obtain planar ends on the sam- 
 ples by precision sawing. Slightly lower 
 compressive strength ratings may have 
 been obtained, however, since end cap- 
 ping was not performed on the Bureau 
 specimens. 
 
 Compression samples 11-17 were sawn 
 by the referenced testing laboratory 
 from the test panels in 3-in cubes. 
 According to the manager of the labo- 
 ratory, the test panels were trimmed 
 1-1/2 to 2 in to discard the high re- 
 bound zone. The ultimate load was re- 
 corded for compressive strength. Lami- 
 nations were somewhat problematical, 
 especially for sample 17. The labora- 
 tory reported that the cubes tended to 
 fail along dry lamination planes where 
 present. 
 
 2 5 4 5 6 7 
 
 DEFLECTION (COMPRESSIVE ), 0.01 in/in 
 
 FIGURE 35. - Gunite compressive strength plot 
 showing gradual failure. 
 
 Table 9 presents the compressive 
 strength analyses of all specimens 
 tested. It should be noted that three 
 product manufacturers involved in the 
 gunite demonstrations elected to have 
 samples of their products (collected 
 during the demonstration) tested at pri- 
 vate testing laboratories. The validated 
 analyses are included in this paper to 
 provide comparative references . The 
 higher strength readings recorded by the 
 private laboratories are due to the fact 
 the samples were cured in meticulously 
 controlled (temperature and humidity) fog 
 rooms, end capped, and tested in cube 
 rather than cylinder form. The Bureau's 
 testing results, though perhaps lower in 
 overall value, were obtained from test- 
 ing procedures that were carefully dupli- 
 cated for all specimens . Owing to the 
 presence of laminations in most of the 
 gunite products tested by the Bureau, 
 considerable latitude occurred in the 
 test results. To offset this, the lowest 
 compressive strength values were elimi- 
 nated and the highest values were aver- 
 aged and recorded. 
 
 FLEXURAL STRENGTH ANALYSIS 
 
 The fibrous gunite products were 
 tested for flexural strength using the 
 simple beam-third point loading methods. 
 Bearing blocks were used to insure that 
 the forces applied to the beams were ver- 
 tical and without eccentricity. As near- 
 ly as practicable, the test specimens had 
 a span three times their depth plus a 
 
 minimum of 1 in on each end. The Bureau- 
 tested specimens measured 4 by 4 by 14 
 in. Samples 11-17 were tested by a pri- 
 vate testing laboratory and measured 3 by 
 3 by 12 in. Samples 1-3, 6, and 7 were 
 also tested at another private testing 
 laboratory using a specimen size of 3 by 
 3 by 12 in. 
 
36 
 
 
 
 t^ vO 
 
 CM 
 
 H 
 
 H 
 
 H 
 
 »* CO 
 
 cy> 
 
 E-i 
 
 f-< i-i i-i 
 
 H 
 
 >. JJ 
 
 4J 
 
 4-1 
 
 4J 
 
 1 c (u 
 
 1 t 
 
 
 p-« 
 
 CM ro 
 
 CO 
 
 Z 
 
 Z 
 
 z 
 
 -3- CO 
 
 00 
 
 ^ 
 
 z z z 
 
 Z 
 
 C O 
 
 O 
 
 u 
 
 o 
 
 CO -H ^ 
 
 a c 
 
 
 ,-H 
 
 O CM 
 
 ^H 
 
 
 
 
 -* CO 
 
 00 
 
 
 
 
 CO 3 
 
 3 
 
 3 
 
 3 
 
 4-1 1 4J 
 
 O CO 
 
 
 r-t 
 
 #« «> 
 
 #K 
 
 
 
 
 ^ tfK 
 
 •. 
 
 
 
 
 a-TS 
 
 •O 
 
 TJ 
 
 T3 
 
 4-1 CM 
 
 tJ w 
 
 
 
 ro fO 
 
 CO 
 
 
 
 
 <)■ CO 
 
 CO 
 
 
 
 
 e o 
 o u 
 
 O 
 
 u 
 
 O 
 U 
 
 o 
 l-l 
 
 PL( ^ O 
 
 Crt 
 
 
 
 
 
 
 
 
 
 
 
 
 
 l-l 
 
 
 
 CM r- 
 
 in 
 
 H 
 
 H 
 
 Ch 
 
 so O 
 
 00 
 
 H 
 
 H H H 
 
 H 
 
 o a 
 
 a. 
 
 a 
 
 a 
 
 1 
 
 cu M 
 
 
 ^^ 
 
 fO in 
 
 <r 
 
 Z 
 
 Z 
 
 fe 
 
 vO -H 
 
 CO 
 
 2: 
 
 Z Z Z 
 
 Z 
 
 
 
 
 
 <u f^ CO 
 
 T) CJ 
 
 
 f— 4 
 
 -* <!■ 
 
 <r 
 
 
 
 
 \D »a- 
 
 m 
 
 
 
 
 M 
 
 
 
 
 X Q) 
 
 c <: 
 
 
 ^ 
 
 #« #1 
 
 #> 
 
 
 
 
 #t fs 
 
 •■ 
 
 
 
 
 (U (U 
 
 <u 
 
 (1) 
 
 0) 
 
 4-1 a a 
 
 •i-t 
 
 
 
 <r -^r 
 
 •<j- 
 
 
 
 
 vO vO 
 
 so 
 
 
 
 
 fl5 
 
 1-1 
 
 4-1 
 
 42 
 
 4J 
 
 O -H 
 4-1 M 4-1 
 CO IM 
 
 rH C 
 >^•H 
 CJ 
 
 
 
 •<r o 
 
 CM 
 
 H 
 
 H 
 
 H 
 
 vo in 
 
 -H 
 
 ^ 
 
 H H H 
 
 H 
 
 
 LTl 
 
 p~. in 
 
 \o 
 
 Z 
 
 Z 
 
 Z 
 
 r-- vD 
 
 r^ 
 
 53 
 
 z z z 
 
 Z 
 
 o >, 
 
 
 
 
 4J 
 
 -o 
 
 
 ^^ 
 
 vO C30 
 
 r«. 
 
 
 
 
 in r-» 
 
 i-H 
 
 
 
 
 CuXi 
 
 >^ 
 
 s>% 
 
 >% 
 
 •o c 
 
 M (U 
 
 
 ^ 
 
 9. *. 
 
 CO 
 
 
 
 
 vo in 
 
 SO 
 
 
 
 
 0) T3 
 
 ^ 
 
 ^ 
 
 X 
 
 4-1 4-1 l-l 
 
 CO bo a) 
 
 O CO 
 i»-4 CO 
 
 3 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 CO ^ 
 
 CM 
 
 H 
 
 H 
 
 H 
 
 O o 
 
 o 
 
 9—1 
 
 H H H 
 
 H 
 
 W <U 
 
 T3 
 
 -C3 
 
 T3 
 
 (1) C UH 
 
 •O O 
 
 
 <!' 
 
 vO -* 
 
 in 
 
 Z 
 
 Z 
 
 Z 
 
 o\ in 
 
 CM 
 
 2 
 
 z z z 
 
 Z 
 
 <0 -O 
 
 0) 
 
 (U 
 
 0) 
 
 4-1 0) M-l 
 
 Q) CD 
 
 x 
 
 i-H 
 
 rH -1 
 
 ^H 
 
 
 
 
 in o 
 
 CO 
 
 
 
 
 iH C 
 
 T3 
 
 •a 
 
 t3 
 
 M -H 
 
 4-1 -H 
 
 o 
 
 (— t 
 
 #t ^ 
 
 «> 
 
 
 
 
 #^ •\ 
 
 ^ 
 
 
 
 
 3 
 
 C 
 
 c 
 
 C 
 
 T3 4J -O 
 
 l-l -o 
 
 
 
 vO ^D 
 
 vO 
 
 
 
 
 so 00 
 
 r~~. 
 
 
 
 
 CO y-i 
 
 3 
 
 14-1 
 
 3 
 i*-i 
 
 3 
 iw 
 
 C CO 
 
 CO CM 
 
 O 
 
 Ou CO 
 
 
 
 
 
 
 
 
 
 
 
 
 ^^^ 
 
 
 
 O r~ 
 
 ^ 
 
 H 
 
 H 
 
 H 
 
 -H CM 
 
 r«. 
 
 H 
 
 H H H 
 
 H 
 
 •o 
 
 
 
 
 (U 
 
 0) CO 
 
 OJ 
 
 CO 
 
 CM vD 
 
 CJN 
 
 Z 
 
 Z 
 
 Z 
 
 CO <r 
 
 CO 
 
 Z 
 
 ^: iz: z 
 
 Z 
 
 c 
 
 
 
 
 > 4-1 
 
 l-l 
 
 M 
 
 <— 1 
 
 r~~ vO 
 
 ^ 
 
 
 
 
 00 «3- 
 
 so 
 
 
 
 
 CO >» 
 
 bO 
 
 bO 
 
 bO 
 
 - iH CO 
 
 0) 
 
 to 
 
 i-H 
 
 ^ #» 
 
 - 
 
 
 
 
 •t *> 
 
 ^ 
 
 
 
 
 U 
 
 C 
 
 C 
 
 C 
 
 M CO 
 
 CO iH 
 
 3 
 
 
 in vD 
 
 ^ 
 
 
 
 
 so 00 
 
 r~~ 
 
 
 
 
 O 
 
 1-1 
 
 4-) 
 
 •H 
 4J 
 
 •r-l 
 4J 
 
 O CO 4J 
 X 0) O 
 
 4-1 & 
 
 CO a 
 
 
 
 
 
 
 
 
 
 
 
 
 CO 
 
 
 vD —1 
 
 ON 
 
 H 
 
 H 
 
 H 
 
 —1 sD 
 
 (Js 
 
 H 
 
 H H H 
 
 H 
 
 O CO 
 
 CO 
 
 CO 
 
 CO 
 
 4J (J X 
 
 O CO 
 
 
 CvJ 
 
 in o 
 
 CM 
 
 Z 
 
 Z 
 
 Z 
 
 so CO 
 
 a\ 
 
 Z 
 
 z z z 
 
 Z 
 
 X M 
 
 0) 
 
 cu 
 
 0) 
 
 3 a. CO 
 
 CO 
 
 u 
 
 ^-1 
 
 —1 in 
 
 00 
 
 
 
 
 o in 
 
 CM 
 
 
 
 
 4J O 
 
 4-1 
 
 4J 
 
 u 
 
 CO e 
 
 
 1) 
 
 ^H 
 
 ^ #^ 
 
 
 
 
 
 •t as 
 
 •t 
 
 
 
 
 3 ^ 
 
 ^^ 
 
 v-' 
 
 ■^x 
 
 o 
 
 • (U 
 
 a, 
 
 
 vo in 
 
 in 
 
 
 
 
 00 so 
 
 p~. 
 
 
 
 
 CO CO 
 
 
 
 
 (1) u a> 
 
 ^ X 
 C 3 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 CO 
 
 
 00 ro 
 
 v£> 
 
 P— 1 
 
 H 
 
 H 
 
 CM <• 
 
 00 
 
 H 
 
 H H H 
 
 H 
 
 (U 
 
 CO 
 
 >> 
 
 >^ 
 
 4J 0) 
 
 •H O 
 
 T3 
 
 ^^ 
 
 r^ r^ 
 
 CM 
 
 ^ 
 
 Z 
 
 Z 
 
 CO o 
 
 so 
 
 Z 
 
 z z z 
 
 Z 
 
 X bO 
 
 (U 
 
 M 
 
 M 
 
 >^ S 
 
 
 c 
 
 •-H 
 
 CM r^ 
 
 o 
 
 
 
 
 in 00 
 
 so 
 
 
 
 
 ■u C 
 
 •H 
 
 o 
 
 o 
 
 t^ CO 
 
 -H fH 
 
 3 
 
 .— t 
 
 •> f^ 
 
 
 
 
 
 •• 0s 
 
 
 
 
 
 1-1 
 
 h 
 
 4J 
 
 4-1 
 
 /5 t3 4J 
 
 • CO 
 
 O 
 
 
 \D in 
 
 vO 
 
 
 
 
 0\ <T< 
 
 0^ 
 
 
 . 
 
 
 .Q CO 
 
 o 
 
 4J 
 
 CO 
 
 CO 
 u 
 
 1 CO 
 TS 00 X 
 
 CM O 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 o o 
 
 in 
 
 in 
 
 O 
 
 00 
 
 -* O 
 
 CM 
 
 H 
 
 H H H 
 
 H 
 
 (1) 
 
 CO 
 
 o 
 
 o 
 
 0) CM W 
 
 4J 
 
 * 
 
 
 -H ^ 
 
 r-^ 
 
 CM 
 
 CO 
 
 CM 
 
 -^ 00 
 
 so 
 
 Z 
 
 Z Z Z 
 
 Z 
 
 •O H 
 
 u 
 
 XI 
 
 ^ 
 
 4J 
 
 Q) C 
 
 CO 
 
 o 
 
 a> CM 
 
 in 
 
 m 
 
 CO 
 
 >a- 
 
 C^ CO 
 
 I-H 
 
 
 
 
 <u 
 
 o 
 
 CO 
 
 CO 
 
 CO U 4J 
 
 l-l CU 
 
 C 
 
 —1 
 
 •K f« 
 
 •K 
 
 f. 
 
 «t 
 
 
 ^ ^ 
 
 •K 
 
 
 
 
 JJ 
 
 ^ 
 
 hJ 
 
 hJ 
 
 •H O O 
 
 O T5 
 
 a 
 
 
 fO CO 
 
 CO 
 
 -* 
 
 <■ 
 
 <j- 
 
 <f CO 
 
 <1- 
 
 
 
 
 CO C 
 
 •--1 o 
 
 CO 
 
 
 
 CO U-l 3 
 CO T) 
 
 O -H 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 •H 
 
 
 vO sD 
 
 ^H 
 
 CO 
 
 o 
 
 r-~ 
 
 -;j- 00 
 
 SO 
 
 H 
 
 H H H 
 
 H 
 
 CO CO 
 
 
 bO 
 
 bO 
 
 CO O 
 
 CU 
 
 U 
 
 
 CM in 
 
 ON 
 
 00 
 
 
 -* 
 
 S3- sD 
 
 O 
 
 Z 
 
 z z z 
 
 Z 
 
 CO *J 
 
 
 c 
 
 c 
 
 (U U 
 
 N C 
 
 (U 
 
 CT^ 
 
 r~. O 
 
 CO 
 
 o 
 
 00 
 
 <r 
 
 00 -H 
 
 O 
 
 
 
 
 CO M 
 
 bO 
 
 •H 
 
 •H 
 
 U Q. 
 
 •H CO 
 
 a 
 
 
 ^ m. 
 
 #» 
 
 ^ 
 
 » 
 
 •\ 
 
 » rt 
 
 *• 
 
 
 
 
 0) 
 
 c 
 
 4-> 
 
 U 
 
 - CO 
 
 CO 
 
 CO 
 
 
 in in 
 
 in 
 
 in 
 
 in 
 
 in 
 
 SO in 
 
 sO 
 
 
 .^_-___-_^^_,^^^_ 
 
 
 
 •H 
 4J 
 
 CO 
 
 (3) 
 
 CO 
 (U 
 
 CO (U 
 
 (u CO a 
 
 1 U 
 
 >< o 
 
 
 
 
 
 
 
 
 
 
 
 
 
 0) 
 
 
 H H 
 
 H 
 
 H 
 
 H 
 
 H 
 
 r-. i-~. 
 
 1 — 
 
 H 
 
 H H H 
 
 9—1 
 
 CO Ki 
 
 CO 
 
 H 
 
 H 
 
 •H 4-1 CO 
 
 Z >4-l 
 
 4J 
 
 
 2 Z 
 
 z 
 
 Z 
 
 Z 
 
 Z 
 
 r^ o^ 
 
 00 
 
 Z 
 
 z z z 
 
 S3 
 
 a) 
 
 dJ 
 
 
 
 4-1 CO CO 
 
 
 •H 
 
 
 Cvl CM 
 
 CM 
 
 Cvl 
 
 CM 
 
 Csl 
 
 r-~ CO 
 
 in 
 
 
 
 
 •H <^ 
 
 H 
 
 
 
 •H Q 
 
 Q) -O 
 
 c 
 
 00 
 
 
 
 
 
 
 » •« 
 
 «^ 
 
 
 
 
 4J 
 
 
 JS 
 
 J= 
 
 iH <U 
 
 l-l CU 
 
 3 
 
 
 
 
 
 
 
 '-vj- -* 
 
 -3- 
 
 
 
 
 •H bO 
 
 X 
 
 bO 
 
 bO 
 
 CJ • 4J 
 
 
 bO 
 
 
 
 
 
 
 
 
 
 
 
 
 S-< 
 
 1 
 
 
 00 CO 
 
 vO 
 
 00 
 
 in 
 
 CM 
 
 r~ r-~ 
 
 CM 
 
 H 
 
 o o o 
 
 O 
 
 •H -H 
 
 bO 
 
 3 
 
 3 
 
 CO /~\ 
 
 o 
 
 T3 
 
 
 ^ in 
 
 00 
 
 ^ 
 
 .—1 
 
 <J^ 
 
 O in 
 
 CO 
 
 Z 
 
 r^ r-» <r 
 
 ^O 
 
 CJ iH 
 
 M 
 
 ^ 
 
 ^ 
 
 <4-l l-l 14-1 
 
 CO Cu 
 
 tu 
 
 
 00 in 
 
 vD 
 
 ,—1 
 
 vD 
 
 CO 
 
 CO CO 
 
 CO 
 
 
 CT^ in r-~ 
 
 r>- 
 
 CO X 
 
 3 
 
 CO 
 
 CO 
 
 0) O 
 
 (U (U 
 
 l-i 
 
 t-«. 
 
 * * 
 
 •K 
 
 ^ 
 
 * 
 
 •« 
 
 •K ^ 
 
 •K 
 
 
 »« •K * 
 
 *> 
 
 U-l Q) 
 
 ^ 
 
 4J 
 
 4-1 
 
 - l-l 
 
 .-H M 
 
 0) 
 
 
 ■<!• -vi- 
 
 -^ 
 
 in 
 
 in 
 
 in 
 
 so so 
 
 so 
 
 
 SO SO sO 
 
 so 
 
 O 
 
 CO 
 
 4J 
 
 4J 
 
 CO 3 
 
 & 
 
 T-t 
 
 
 
 
 
 
 
 
 
 
 tD U> so 
 
 lO 
 
 - ^1 
 CO fn 
 
 4-) 
 4-1 
 
 •H 
 
 •H 
 PU 
 
 l-l 4-) CO 
 <U CJ ^ 
 
 a (u 
 CO CO 
 
 
 
 
 
 
 
 
 
 
 
 
 >4-l 
 
 
 
 
 
 
 
 
 
 
 O O O 
 C3N O ^ 
 
 o 
 
 CO 
 
 U 
 0) 
 
 •H 
 
 P-i 
 
 
 
 P CO o 
 3 <4-i O 
 
 CO o 
 
 y-i 
 
 
 
 
 
 
 
 
 
 
 CM in o- 
 
 r^ 
 
 U >, 
 
 
 >% 
 
 >, 
 
 4-1 3 >H 
 
 U 4J 
 
 o 
 
 
 
 
 
 
 
 
 
 
 #. 0^ ffK 
 
 «v 
 
 3 Si 
 
 
 ^ 
 
 ^ 
 
 O C U3 
 
 <u 
 
 
 
 vo O 
 
 CO 
 
 00 
 
 in 
 
 csl 
 
 so 00 
 
 CM 
 
 H 
 
 r- so ^ 
 
 sO 
 
 U 
 
 >^ 
 
 
 
 CO rt 
 
 ,£ c 
 
 CO 
 
 vO 
 
 0\ r^ 
 
 CM -H 
 
 CO 
 CM 
 
 in 
 
 in 
 
 00 
 
 o 
 
 -vf ^ 
 
 CM CM 
 
 CO 
 
 Z 
 
 i^ so a> 
 
 lO 
 
 O t3 
 CO (U 
 
 ^ 
 
 CO 
 
 C 
 
 CO 
 
 M-l a CU 
 
 3 rH 
 
 4J CO 
 O X 
 
 r^ 
 
 
 
 
 
 •u 
 
 
 *• ^ 
 
 •K 
 
 «K 
 
 «• 
 
 ^ 
 
 * ^ 
 
 #1 
 
 
 o o o 
 
 O 
 
 M-i a 
 
 CO 
 
 (U 
 
 c 
 
 c 4J a 
 
 4J 
 
 bO 
 
 
 CO CO 
 
 CO 
 
 CO 
 
 CO 
 
 CO 
 
 in >a- 
 
 ■<f 
 
 
 in — < o 
 
 in 
 
 3 5 
 
 C 
 
 a 
 
 (U 
 
 CO o a 
 
 l-l 
 
 C 
 
 
 
 
 
 
 
 
 
 
 CO CM -* 
 
 so 
 
 c o 
 
 Q) 
 
 •H 
 
 a 
 
 e 3 CO 
 
 < (U 
 
 Q) 
 
 
 
 
 
 
 
 
 
 
 «s tfs tf^ 
 
 •* 
 
 CO 14-1 
 
 a 
 
 CJ 
 
 •H 
 
 13 CO 
 
 M 
 
 
 
 
 
 
 
 
 
 
 •<}• in -* 
 
 -3- 
 
 a u 
 
 •H 
 
 0) 
 
 CJ 
 
 <U O 
 
 & 
 
 4J 
 
 
 
 
 
 
 
 
 
 
 so so sD 
 
 lO 
 
 0) 
 
 O 
 
 a 
 
 (1) 
 
 J2 l-l CM 
 
 o 
 
 CO 
 
 
 
 
 
 
 
 
 
 
 
 
 tu a. 
 
 • <U 
 
 CO 
 
 a 
 
 4-1 a. 
 
 . iH 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 »— t .-H 
 
 vO 
 
 ~a- 
 
 in 
 
 o 
 
 o in 
 
 00 
 
 H 
 
 H H H 
 
 H 
 
 j= 
 
 i-i a 
 
 
 CO 
 
 a 
 
 CO 
 
 <u 
 
 
 -t 00 
 
 ON 
 
 vO 
 
 r^ 
 
 CM 
 
 rH <r 
 
 p- 
 
 Z 
 
 Z Z Z 
 
 Z 
 
 ■U CO 
 
 1) CO 
 
 
 
 4-1 O 
 
 cu 4J 
 
 > 
 
 u-1 
 
 o in 
 
 r-^ 
 
 <J- 
 
 in 
 
 in 
 
 a> CM 
 
 o 
 
 
 
 
 CO 
 
 M 
 
 c 
 
 
 CO 0) l-l 
 
 XS CJ 
 
 •H 
 
 
 » ^ 
 
 «K 
 
 •K 
 
 t^ 
 
 •s 
 
 •K VK 
 
 #1 
 
 
 
 
 JJ S 
 
 3 
 
 c 
 
 C 
 
 X <4-l 
 
 3 O. 
 
 CO 
 
 
 CO CM 
 
 CM 
 
 CO 
 
 CO 
 
 CO 
 
 CO -vj- 
 
 <3- 
 
 
 
 
 CO 
 
 4J C 
 
 o c 
 
 
 
 T3 0) 
 
 CJ 
 
 in 
 
 CO 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Q) 
 
 
 p^ <t 
 
 vO 
 
 r-v 
 
 CM 
 
 o 
 
 00 CM 
 
 in 
 
 H 
 
 H H H 
 
 H 
 
 bO 
 
 CO >, 
 
 
 hJ 
 
 <U >% M 
 
 0) .-1 
 
 l-i 
 
 
 o o 
 
 O 
 
 \o 
 
 O^ 
 
 CO 
 
 in ON 
 
 CM 
 
 Z 
 
 z z z 
 
 Z 
 
 •O C 
 
 •4-1 hJ 
 
 
 
 4J ^ CO 
 
 l-l 
 
 D. 
 
 <J- 
 
 CO r^ 
 
 m 
 
 o 
 
 in 
 
 00 
 
 <r in 
 
 o 
 
 
 
 
 OJ -H 
 
 3 
 
 CU 
 
 
 CO 
 
 <U 0) 
 
 Q 
 
 
 w> #« 
 
 *t 
 
 ^ 
 
 •K 
 
 •K 
 
 «K as 
 
 *^ 
 
 
 
 
 4J 4J 
 
 C 
 
 ^ 
 
 0) 
 
 u •« 
 
 s XI 
 
 o 
 
 
 vO vO 
 
 vO 
 
 r-. 
 
 ^ 
 
 vX3 
 
 r-s so 
 
 r~ 
 
 
 
 
 CO CO 
 
 CO <u 
 
 CO 
 
 J^ 
 
 4J cu \o 
 
 
 U 
 
 
 
 
 
 
 
 
 
 
 
 
 t-i (U 
 
 e ^ 
 
 hJ 
 
 CO 
 
 CO -o 
 
 VO >^ 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 r~. r-< 
 
 CJN 
 
 H 
 
 H 
 
 9—1 
 
 O -H 
 
 ^H 
 
 o 
 
 o o o 
 
 o 
 
 4-1 4-1 
 
 CO 
 
 
 i-J 
 
 c c 0) 
 
 1 CO 
 
 1 
 
 
 <r r^ 
 
 o 
 
 Z 
 
 Z 
 
 ^ 
 
 —1 CTn 
 
 o 
 
 ■4- 
 
 CM CM CM 
 
 in 
 
 CO 
 
 >%kJ 
 
 
 
 O 3 rH 
 
 CM a 
 
 
 
 in CM 
 
 a^ 
 
 
 
 
 00 <j> 
 
 <JN 
 
 CM 
 
 o vo in 
 
 o 
 
 C bO 
 
 J3 
 
 <4^ 
 
 
 a '4-1 a 
 
 
 • 
 
 ro 
 
 f ^ 
 
 «^ 
 
 
 
 
 ^ »» 
 
 #1 
 
 •• 
 
 ^ ^ #v 
 
 «> 
 
 o c 
 
 
 o 
 
 14-4 
 
 <u s.' a 
 
 r^ ^-s 
 
 CT\ 
 
 
 r~~ 00 
 
 r— 
 
 
 
 
 ^H ^H 
 
 ^H 
 
 O 
 
 in in <r 
 
 in 
 
 a -H 
 
 T) <W 
 
 
 o 
 
 T) CO 
 
 Q) 3 
 
 
 
 
 
 
 
 
 r-i >—* 
 
 1-H 
 
 -H 
 
 t— I t— t f-H 
 
 rH 
 
 <i> u 
 
 (U o 
 
 
 
 CO 
 
 4J CO 
 
 W 
 
 
 
 
 
 
 
 
 
 
 I/) in in 
 
 J1 
 
 "O (U 
 
 4-1 
 
 CO 
 
 
 (U >. 
 
 o <u 
 
 hJ 
 
 
 
 
 
 
 
 
 
 
 
 
 <u 
 
 CO 
 
 4-1 
 
 CO 
 
 l-l U t-i 
 
 C M 
 
 
 
 
 
 
 
 
 
 
 
 
 5 
 
 
 00 r-v 
 
 00 
 
 H 
 
 ^ 
 
 H 
 
 r^ o 
 
 -* 
 
 o 
 
 O O O 
 
 o 
 
 (U (3 
 
 (U CO 
 
 iH 
 
 4-) 
 
 cu o o 
 
 3 
 
 
 vO 00 
 
 CM 
 
 Z 
 
 ^ 
 
 Z 
 
 CM 00 
 
 m 
 
 f-H 
 
 00 -H r^ 
 
 CM 
 
 M -H 
 
 3 4J 
 
 3 
 
 iH 
 
 !3 4-1 <4-l 
 
 4-1 pq 
 
 H 
 
 
 vD a^ 
 
 CO 
 
 
 
 
 C3^ r^ 
 
 00 
 
 -* 
 
 in ^ CM 
 
 CO 
 
 4) bO 
 
 CTiH 
 
 CO 
 
 3 
 
 CO 
 
 O ^^ 
 
 
 csi 
 
 «^ ^ 
 
 •^ 
 
 
 
 
 ^ ^ 
 
 •k 
 
 «t 
 
 ^ ^ *. 
 
 *« 
 
 > C 
 
 Q) 3 
 
 (1) 
 
 CO 
 
 t-^ U CO 
 
 o 
 
 
 
 CO <d- 
 
 -* 
 
 
 
 
 r-- r- 
 
 r^ 
 
 CJ\ 
 
 CM CM CM 
 
 J- J- J- 
 
 CM 
 
 I-H 
 . i 
 
 H CO 
 
 CO 1-1 
 
 CO 
 
 4J 
 CO 
 
 (U 
 
 )-l 
 
 4J 
 
 and 
 
 Labo 
 
 suit 
 
 H-l CO 
 
 CO 4J • 
 Q) bO vO 
 
 
 
 
 
 
 
 
 
 
 
 
 
 • 1 • • 
 
 
 
 in CO 
 
 -* 
 
 H 
 
 H 
 
 H 
 
 O 0^ 
 
 o 
 
 o 
 
 o o o 
 
 O 
 
 •^ -H <U ^~» 
 
 4J • 
 
 <u • 
 
 CO • 
 
 (U 
 
 iH C vO 
 
 
 
 CT. -H 
 
 in 
 
 Z 
 
 Z 
 
 Z 
 
 in CM 
 
 ON 
 
 CM 
 
 CO CO CM 
 
 sO 
 
 0) -H > to 
 
 T) CO ^-s 
 
 4J /-s 
 
 (U ^-s 
 
 so bO l-l 
 
 a (U t 
 
 
 -^ 
 
 vO 00 
 
 r^ 
 
 
 
 
 CO o 
 
 1—4 
 
 -* 
 
 in r^ -H 
 
 ■<r 
 
 4J -H M 
 
 0) (U (-1 
 
 M 
 
 4J M 
 
 c 
 
 a l-l vo 
 
 
 
 •K A 
 
 •» 
 
 
 
 
 ^ * 
 
 »k 
 
 * 
 
 «^ #^ #^ 
 
 •^ 
 
 CO CO 4-1 a> 
 
 4.1 4.) 0) 
 
 OJ 
 
 (U 
 
 CO -H (U 
 
 CO 4J O 
 
 
 
 -* -* 
 
 •^ 
 
 
 
 
 sO so 
 
 so 
 
 SO 
 
 p-> r* r-~ 
 J- J- J- 
 
 -T 
 
 0) 4-1 (0 l-l 
 
 4-1 O +J 3 
 
 CO M 
 
 (U 3 
 
 t-i 
 >^ 3 
 
 >-l 
 
 >. 3 
 
 4J 4-1 ^ 
 
 O CO H • 
 
 c« M in 
 1 
 
 
 
 
 
 
 
 
 
 3 rt 4-1 
 
 •U P"-, 4J 
 
 CO 4J 
 
 CO 4-1 
 
 3 CU >. 
 
 1 <U M 
 
 
 
 • • • 
 
 CO 
 
 • • 
 
 CO • • 
 
 CO 
 
 • • • • 
 
 4J T3 (U CJ 
 
 CO o 
 
 T3 CJ 
 
 T3 O 
 
 •OH CO 
 
 • > CJ 
 
 
 (U 
 
 CO • • 
 
 Ss 
 
 • • 
 
 >^ • • 
 
 CO 
 
 CO . . > 
 
 O O CO (0 
 
 4J TS CO 
 
 1 CO 
 
 1 CO 
 
 O • T3 
 
 W -H <3 
 
 
 iH 
 
 >% • > 
 
 (0 
 
 • > 
 
 ct) . > 
 
 >% 
 
 V-i 4J O o ■< 
 
 Z 1-1 oj y-i 
 
 O 1 <*-! 
 
 ~3- 14-4 
 
 in in 
 
 l-l J3 CO 
 
 H CO 
 
 
 a. 
 
 n o < 
 
 T3 
 
 o < 
 
 'V O < 
 
 CO 
 
 <U CO Q Q 
 
 a< u 3 
 
 Z 00 3 
 
 -3- 3 
 
 -3- 3 
 
 Pj bo QJ a) 
 
 O CO T3 
 
 
 a 
 
 T3 a 
 
 
 a 
 
 a 
 
 •a 
 
 X 0) 
 
 -H D. CcvJ oo C 
 
 J- c 
 
 IT) C 
 
 3 3 rt 
 
 Z (U M 
 
 
 (« 
 
 
 •* 
 
 
 00 
 
 
 4J W 
 
 H 0) CO 
 
 CO 
 
 CO 
 
 CO 
 
 M CO 
 
 
 M 
 
 r* 
 
 
 •— 1 
 
 
 
 CM 
 
 
 00 
 
 O 
 
 
 z Ma 
 
 a 
 
 a 
 
 a 
 
 ja o CO 
 
 a-T3 
 
37 
 
 Where specimen fracture occurred within 
 the middle third of the span length, the 
 flexural strength or modulus of rupture 
 (R) was calculated as follows: 
 
 Pi? 
 bd^ 
 
 where R = modulus of rupture, psi, 
 
 P = maximum applied load, lb, 
 
 i = span length, in, 
 
 b = average width of specimen, 
 in, 
 
 and d = average depth of specimen, 
 in. 
 
 in the mine, and removed from the forms 
 the following day. All of the samples 
 analyzed by the private testing labora- 
 tories were sawn. Initially only 28-day 
 tests were to be performed; however, some 
 measure of the early flexural capacity 
 
 was considered necessary. Table 10 pro- 
 vides the analysis results of the flex- 
 ural strength testing. Since many of the 
 test specimens were somewhat laminated, 
 the lowest values were deleted and the 
 highest two values are presented and 
 averaged. Owing to the high incidence of 
 laminations and the absence of any speci- 
 men capping or grinding (shims were used 
 as discussed in ASTM C 42-77), the over- 
 all Bureau analyses results were lower 
 than those obtained from private testing 
 laboratories. 
 
 The most serious problem encounterd in 
 the testing was in obtaining a competent 
 specimen. Laminations were present in 
 the bulk, of the specimens. 
 
 The initial Bureau-tested specimens 
 were sawn out of large blocks with a 
 diamond-tipped blade (fig. 36). Cutting 
 time for the numerous specimens became 
 excessive, however, and shot panels with 
 suitable dimensions were later used. The 
 gunite was shot directly into the pre- 
 oiled forms and then trowelled to a 
 smooth surface on top. The specimens 
 were covered with plastic, left overnight 
 
 FIGURE 36. - Diamond-tipped saw used to cut 
 steel-fibered gunite specimens. 
 
 Three different 24- by 24-in steel- 
 fibered-gunite test panels of the same 
 prebagged mix shot by the same nozzle man 
 using the same gun on the same day and 
 tested by the same independent testing 
 laboratory gave flexural strength results 
 that varied by as much as 640 psi (lowest 
 to highest). As shown in table 10, for 
 sample 6 the value for two of the sawn 
 beams was almost 70 pet lower than the 
 highest value. Out of a group of three 
 beams sawn and tested from each of three 
 shot sample blocks , one group had a mean 
 of 1,006 psi, a second had 1,023 psi, and 
 a third had 1,541 psi. This wide con- 
 trast in flexural strengths of the sam- 
 ples becomes even more cogent when it 
 is realized that many of the products 
 achieved lower flexural strengths (maxi- 
 mum) than the observed variance of this 
 product (even though their compositions 
 were distinctly similar). 
 
 This extreme range of analysis vari- 
 ability is difficult to explain and can 
 only be attributed to nozzle and gun crew 
 operation and gun operation. Although an 
 extremely high quality prebagged gunite 
 mix can be purchased to remedy a spe- 
 cific underground problem, one of the 
 predominant factors in obtaining the 
 high-strength finished product rests with 
 the application of the product by the 
 gunning crew. 
 
38 
 
 
 
 «NJ \0 
 
 a^ 
 
 H 
 
 H 
 
 H 
 
 v£> CM 
 
 <r 
 
 ir* iri tr^ 
 
 H 
 
 1 
 
 0) 
 
 
 4-1 
 
 4-1 
 
 4-1 1 (U •> 
 
 
 r~^ 
 
 CO vO 
 
 ON 
 
 z 
 
 Z 
 
 Z 
 
 in CO 
 
 <f 
 
 z z z 
 
 Z 
 
 a j= 
 
 
 U 
 
 O 
 
 to 43 V( O 
 
 
 r—t 
 
 CO O 
 
 1—) 
 
 
 
 
 ^ CO 
 
 CM 
 
 
 
 o 
 
 4-> 
 
 
 3 
 
 3 
 
 O CU CT^ 
 
 
 i—t 
 
 •> r. 
 
 •> 
 
 
 
 
 ^ ^ 
 
 9^ 
 
 
 
 o 
 
 
 
 13 
 
 -3 
 
 13 !5 O 
 
 
 
 ^-< i-H 
 
 ^H 
 
 
 
 
 1—1 i-H 
 
 1-H 
 
 
 
 IH 
 
 ,£3 
 
 
 O 
 
 O 
 
 CU 43 
 
 
 
 
 
 
 
 
 
 
 
 
 
 4J 4-1 4-1 I-H 
 
 
 
 CVJ O 
 
 1— 1 
 
 H 
 
 H 
 
 H 
 
 in r^ 
 
 1-H 
 
 H i-^ f-f 
 
 H 
 
 (U 
 
 
 
 CX 
 
 CX 
 
 CD bO CO 
 
 
 vO 
 
 r^ CO 
 
 in 
 
 z 
 
 Z 
 
 Z 
 
 CO CM 
 
 CO 
 
 Z Z Z 
 
 Z 
 
 S 
 
 •O 
 
 
 
 
 <U 3 43 
 
 
 .—1 
 
 i-H i-H 
 
 f— 1 
 
 
 
 
 CO r^ 
 
 in 
 
 
 
 >. 
 
 0) 
 
 
 
 
 4J cu 4J •• 
 
 
 ^H 
 
 •V *s 
 
 «^ 
 
 
 
 
 «S «K 
 
 ^ 
 
 
 
 .H 
 
 t3 
 
 
 <U 
 
 CU 
 
 P CO 
 
 
 
 ^H 1—1 
 
 ^H 
 
 
 
 
 1-H 1-H 
 
 ^H 
 
 
 
 O 
 
 C 
 
 
 43 
 
 43 
 
 13 4-1 4-1 15 
 3 CO O O 
 
 
 
 
 
 
 
 
 
 
 
 
 O^ 
 
 3 
 
 
 4-t 
 
 4-1 
 
 
 
 Cvj O 
 
 i-H 
 
 H 
 
 H 
 
 H 
 
 in vt 
 
 o 
 
 ir> fr* i-t 
 
 H 
 
 
 MH 
 
 
 
 
 «0 3 tH 
 
 
 m 
 
 CTi CO 
 
 v£) 
 
 Z 
 
 Z 
 
 Z 
 
 r^ O 
 
 CJN 
 
 z z z 
 
 Z 
 
 X 
 
 s.^ 
 
 
 >. 
 
 >. 
 
 iH 13 iH 
 
 
 r-H 
 
 ^ C^ 
 
 O 
 
 
 
 
 O -H 
 
 o 
 
 
 
 cu 
 
 
 
 ^ 
 
 ,Q 
 
 CO O O 
 
 
 ^H 
 
 ^ 
 
 ^ 
 
 
 
 
 #1 #t 
 
 ^ 
 
 
 
 4-) 
 
 
 
 
 
 •- M (J 14-1 
 
 
 
 i-H 
 
 1—1 
 
 
 
 
 1-H 1-H 
 
 1-H 
 
 
 
 CO 
 
 
 
 13 
 
 13 
 
 M 3 CX 
 O i< CO 
 
 
 
 
 
 
 
 
 
 
 
 
 
 ^ 
 
 
 r-^ in 
 
 ^D 
 
 H 
 
 H 
 
 H 
 
 r^ v£) 
 
 CM 
 
 trt i-^ h^ 
 
 H 
 
 
 O 
 
 
 CU 
 
 CU 
 
 43 CU <U CO 
 
 o 
 
 -Cf 
 
 i-H CO 
 
 CNI 
 
 Z 
 
 Z 
 
 Z 
 
 vo in 
 
 vT) 
 
 z z z 
 
 Z 
 
 CO 
 
 4-1 
 
 
 13 
 
 T3 
 
 4J iH 
 
 fi 
 
 1—1 
 
 o o 
 
 o 
 
 
 
 
 1 — 1 1-H 
 
 1-H 
 
 
 
 
 CO 
 
 
 3 
 
 3 
 
 3 iw CO •> 
 
 •H 
 
 .-H 
 
 ». ^ 
 
 " 
 
 
 
 
 •^ ^ 
 
 •- 
 
 
 
 tJ 
 
 M 
 
 
 3 
 
 3 
 
 CO CO ^O 
 
 
 
 f— t i-H 
 
 1-H 
 
 
 
 
 1-H 1-H 
 
 1-H 
 
 
 
 d 
 
 O 
 
 
 14H 
 
 IH 
 
 >". 
 
 0) 
 
 
 
 
 
 
 
 
 
 
 
 CO 
 
 43 
 CO 
 
 
 bO 
 
 bO 
 
 cu CO cu (U 
 
 J-i 
 
 
 
 
 
 
 
 
 
 
 
 43 -3 43 r-t 
 
 CO 
 
 
 V^ i-H 
 
 ■<r 
 
 H 
 
 H 
 
 H 
 
 00 -H 
 
 in 
 
 i-* irf H 
 
 H 
 
 >H 
 
 hJ 
 
 
 3 
 
 3 
 
 4-1 1 4-t CX 
 
 3 
 
 CO 
 
 CM <!■ 
 
 CO 
 
 Z 
 
 Z 
 
 Z 
 
 00 O 
 
 <3- 
 
 Z Z Z 
 
 Z 
 
 o 
 
 
 
 •rl 
 
 •H 
 
 00 g^ 
 
 cr 
 
 1—1 
 
 <r cvj 
 
 CO 
 
 
 
 
 in r^ 
 
 v£) 
 
 
 
 ^ 
 
 bO 
 
 
 ^ 
 
 4-1 
 
 >,CM UH CO 
 
 CO 
 
 ^H 
 
 .. •> 
 
 •> 
 
 
 
 
 •s .S 
 
 ^ 
 
 
 
 4-> 
 
 (3 
 
 
 CO 
 
 CD 
 
 ,Q O CO 
 
 u 
 
 
 1—1 ^H 
 
 -H 
 
 
 
 
 1-H 1-H 
 
 1-H 
 
 
 
 3 
 CO 
 
 •H 
 4-1 
 
 
 CU 
 4J 
 
 CU 
 4J 
 
 -3 VJ CO p 
 
 
 
 
 
 
 
 
 
 
 
 
 Q) 
 
 
 cNi r^ 
 
 o 
 
 H 
 
 H 
 
 H 
 
 ON -* 
 
 1^ 
 
 H H H 
 
 H 
 
 
 CO 
 
 
 ^^ 
 
 •^-^ 
 
 CU O 4«! O 
 
 a. 
 
 
 r^ cx) 
 
 CTi 
 
 Z 
 
 Z 
 
 Z 
 
 
 00 
 00 
 
 z z z 
 
 Z 
 
 CU 
 
 ,i2 
 
 0) 
 
 
 
 
 4J l+H O <4H 
 CO O 
 
 CO 
 
 r-H 
 
 
 
 
 
 
 ^ 
 
 
 
 
 *-> 
 
 
 
 >. 
 
 >^ 
 
 •H CU iH -3 
 
 t3 
 
 
 
 
 
 
 
 1-H 
 
 
 
 
 >. 
 
 (3 
 
 
 iH 
 
 o 
 
 u 
 o 
 
 CD JJ 43 CU 
 
 c 
 
 
 
 
 
 
 
 
 
 
 
 CD CO 3 
 
 3 
 
 
 ON — ^ 
 
 in 
 
 H 
 
 H 
 
 H 
 
 ON r->. 
 
 00 
 
 H H H 
 
 H 
 
 iC 
 
 o 
 
 
 4J 
 
 4-t 
 
 CO 0) 'H 
 
 O 
 
 1—1 
 
 CO i-H 
 
 CM 
 
 Z 
 
 Z 
 
 Z 
 
 00 00 
 
 00 
 
 z z z 
 
 Z 
 
 
 CD 
 
 
 to 
 
 CO 
 
 to iH to 
 
 Ou 
 
 i-H 
 
 CM (NJ 
 
 CM 
 
 
 
 
 CO CO 
 
 CO 
 
 
 
 13 
 
 4-1 
 
 
 u 
 
 U 
 
 4-1 {X 4-1 
 
 
 r— 1 
 
 .. •> 
 
 •> 
 
 
 
 
 ^ ». 
 
 •- 
 
 
 
 CU 
 
 M 
 
 
 o 
 
 ^ 
 
 - CO 43 
 
 »■ 
 
 
 1-H I-H 
 
 f— 1 
 
 
 
 
 I-H .-H 
 
 1-H 
 
 
 
 4-) 
 
 0) 
 
 
 43 
 
 o 
 
 CD Q CO O 
 
 CO 
 
 
 
 
 
 
 
 
 
 
 
 CD 
 
 •H 
 
 43 
 
 q 
 
 
 to 
 
 h-3 
 
 to 
 
 <U CD 
 
 C 
 
 
 
 
 
 
 
 
 
 
 
 •H O 
 
 cu 
 
 
 m v£> 
 
 o 
 
 <f 
 
 ^H 
 
 CO 
 
 CM r^ 
 
 o 
 
 H H H 
 
 H 
 
 CD 
 
 Pi 
 
 
 
 
 4J • CM CO 
 
 
 
 o 
 
 00 00 
 
 00 
 
 00 
 
 ■<f 
 
 vO 
 
 r-- <l- 
 
 1-H 
 
 z z z 
 
 Z 
 
 CO 
 
 
 
 bO 
 
 bO 
 
 •H r-N r-l 
 
 •H 
 
 1— ( 
 
 in in 
 
 in 
 
 ■o- 
 
 O 
 
 in 
 
 o in 
 
 vD 
 
 
 
 to 
 
 c« 
 
 
 d 
 
 3 
 
 rH ^1 CO 
 
 o 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 •H 
 
 •H 
 
 •H CU O 
 
 
 
 
 
 
 
 
 
 
 
 cu 
 
 
 -H ^H 
 
 i-H 
 
 CM 
 
 CO 
 
 00 
 
 CM rH 
 
 CM 
 
 H H H 
 
 H 
 
 r. 
 
 bO 
 
 
 4J 
 
 4-t 
 
 U M M cu 
 
 a- 
 
 c^ 
 
 -H i-H 
 
 ^ 
 
 r^ 
 
 00 
 
 C^J 
 
 Csl O 
 
 1-H 
 
 z z z 
 
 Z 
 
 CO 
 
 C 
 
 
 CO 
 
 CO 
 
 CO 3 MH JH 
 
 CO 
 
 
 vo in 
 
 in 
 
 <r 
 
 in 
 
 in 
 
 vO ^O 
 
 ^ 
 
 
 
 (U 
 
 •H 
 
 
 (U 
 H 
 
 ^ 
 
 MH 4-1 (U 
 O (U !3 
 
 
 
 
 
 
 
 
 
 
 
 
 
 cu 
 
 
 H H 
 
 H 
 
 H 
 
 H 
 
 H 
 
 H H 
 
 H 
 
 H H H 
 
 H 
 
 4-) 
 
 43 
 
 
 
 
 - CO »H 
 
 4-1 
 
 00 
 
 2: iz 
 
 3 
 
 z 
 
 Z 
 
 Z 
 
 Z Z 
 
 Z 
 
 \z z :z 
 
 Z 
 
 •H 
 
 (U 
 
 
 
 
 CO IH CO CO 
 
 •H 
 
 
 CM Csl 
 
 CM 
 
 CT) 
 
 CO 
 
 oo 
 
 tr) CO 
 
 CO 
 
 
 
 rH 
 
 o 
 
 
 ^ 
 
 42 
 
 M 3 cu 
 
 c 
 
 
 
 
 
 
 
 
 
 
 
 •H 
 O 
 
 
 
 bO 
 U 
 
 bO 
 
 cu 3 ^ CO 
 
 3 
 
 
 
 
 
 
 
 ~^ 
 
 
 
 
 »^ eg >, 
 
 bO 
 
 
 
 9- 
 
 CJN 
 
 r^ 
 
 CO 
 
 00 C3N 
 
 ON 
 
 o o o 
 
 CO 
 
 CO 
 
 
 
 3 
 
 3 
 
 3 cu ^ 
 
 
 
 ^-s /-s 
 
 <l 
 
 ON 
 
 <f 
 
 CM 
 
 <3N in 
 
 r^ 
 
 St VO -H 
 
 o 
 
 M-l 
 
 >. 
 
 
 X> 
 
 43 
 
 4J iH CO 
 
 -d 
 
 r-^ 
 
 CM Csl 
 
 Z 
 
 -* 
 
 CO 
 
 <r 
 
 in in 
 
 in 
 
 C3N 00 CT. 
 
 ON 
 
 
 43 
 
 
 CO 
 
 CD 
 
 o 4-1 a 3 
 
 cu 
 
 
 ^^ v-^ 
 
 
 
 
 
 
 
 U) O) 1^ 
 
 1^ 
 
 CD 
 
 13 
 
 
 4-> 
 4-» 
 
 4-t 
 4J 
 
 to O to 
 MH 3 to 
 
 
 
 
 
 
 
 
 
 
 
 
 0) 
 
 
 
 
 
 
 
 
 
 in o o 
 
 1-H 
 
 JH 
 
 9i 
 
 
 •H 
 
 •H 
 
 3 13 CD M 
 
 ^ 
 
 
 
 
 
 
 
 
 
 o in r^ 
 
 -* 
 
 (U 
 
 e 
 
 
 Ph 
 
 Ci^ 
 
 3 O CU 
 
 •H 
 
 
 
 
 
 
 
 
 
 in in in 
 
 in 
 
 >H 
 
 >H 
 
 • 
 
 
 
 5 >H M 43 
 
 M-l 
 
 
 
 
 
 
 
 
 
 ,— 1 ^H 1-H 
 
 1-H 
 
 3 
 
 4J 
 
 O 
 
 M 
 CU 
 
 43 
 
 ^ 
 
 CX O 4-1 
 
 14H O 
 
 1+-I 
 
 
 /-\ /-^ 
 
 cx 
 
 o 
 
 p^ 
 
 <y\ 
 
 in CM 
 
 C3N 
 
 l£) l^ to 
 
 li> 
 
 O 
 
 »H 
 
 ^J 
 
 
 
 cu cu 
 
 O 
 
 vD 
 
 Csl Osl 
 
 <c 
 
 in 
 
 o 
 
 r^ 
 
 ON <r 
 
 1-H 
 
 
 
 to 
 
 <U 
 
 3 
 
 
 
 43 43 CO (U 
 
 
 
 
 
 v-^ x.^ 
 
 » 
 
 ■^ 
 
 in 
 
 <f 
 
 <f in 
 
 in 
 
 in in o 
 
 vO 
 
 <4H 
 
 CX 
 
 4-) 
 
 CO 
 
 CD 
 
 4-1 4-1 4-1 (1) 
 
 ^ 
 
 
 
 
 
 
 
 
 
 CO in CO 
 
 O 
 
 3 
 
 
 o 
 
 3 
 
 3 
 
 rH H 
 
 4-1 
 
 
 
 
 
 
 
 
 
 O O C3N 
 
 o 
 
 C 
 
 CO 
 
 CO 
 
 9i 
 
 9i 
 
 4-1 3 jC 
 
 CO >% CO H 
 
 tkO 
 
 
 
 
 
 
 
 
 
 ^ «s 
 
 ^ 
 
 
 to 
 
 KH 
 
 
 
 
 
 c 
 
 
 
 
 
 
 
 
 
 ^H r-H 
 
 1-H 
 
 ^ 
 
 I? 
 
 3 
 
 •H 
 
 •H 
 
 43 (U 
 
 (U 
 
 
 
 
 
 
 
 
 
 U3 LO U> 
 
 ID 
 
 
 
 3 
 
 O 
 
 O 
 
 p 
 
 u 
 
 
 
 
 
 
 
 
 
 
 
 CU 
 
 bO 
 
 1 
 
 CU 
 
 CX 
 
 CU 
 
 CX 
 
 13 -3 • 
 
 4J 
 
 
 
 
 
 
 
 
 
 
 
 (U 0) CU >% 
 
 CO 
 
 
 00 O 
 
 vj- 
 
 o 
 
 t^ 
 
 ON 
 
 00 CO 
 
 v£> 
 
 H H H 
 
 H 
 
 . 4-) 
 
 C 
 
 
 CD 
 
 CD 
 
 4-t xt ,3 to 
 CO 3 H -3 
 
 
 
 <!• O 
 
 r-^ 
 
 ^H 
 
 ^ 
 
 CO 
 
 00 CM 
 
 o 
 
 z z z 
 
 Z 
 
 X) 
 
 •H 
 
 >. 
 
 
 
 rH 
 
 in 
 
 r-^ o 
 
 vO 
 
 00 
 
 vD 
 
 r^ 
 
 t^ o 
 
 ON 
 
 
 
 CU 4-> 
 
 4-) 
 
 ^ 
 
 3 
 
 3 
 
 Vj 3 
 
 to 
 
 
 
 
 
 
 
 ^ 
 
 
 
 
 4J CO 
 
 CD 
 
 
 3 
 
 3 
 
 4-1 MH cu 
 
 
 
 
 
 
 
 
 1-H 
 
 
 
 
 CD 
 
 CU T3 
 
 CU 
 4.) 
 
 T3 
 0) 
 
 
 
 CD ^^ • 
 3 CD CO 
 
 P 
 
 
 
 
 
 
 
 
 
 
 
 53 
 
 
 0\ 00 
 
 -* 
 
 ^o 
 
 CTi 
 
 00 
 
 C3N \Ci 
 
 00 
 
 ^ ^ ^ 
 
 H 
 
 4J <U 
 
 
 4-) 
 
 
 
 O >^ CD 
 
 CU 
 
 <r 
 
 in CM 
 
 <y\ 
 
 CM 
 
 v£) 
 
 -* 
 
 r-. r^ 
 
 CM 
 
 z z z 
 
 Z 
 
 4J 
 
 bO 
 
 CD 
 
 (U 
 
 CU 
 
 M CO 
 
 iH 
 
 
 in -vT 
 
 <d- 
 
 ■vJ- 
 
 <f 
 
 vt 
 
 in -vi- 
 
 in 
 
 
 
 4-) CO 
 
 (3 
 
 CU 
 
 ^ 
 
 4«5 
 
 <u o (U cu 
 
 fe 
 
 
 
 
 
 
 
 
 
 
 
 O U 
 
 •H 
 
 3 
 
 CO 
 
 to 
 
 13 4-1 JD ^ 
 
 
 
 
 
 
 
 
 
 
 
 
 
 in a, 
 
 a. 
 
 
 
 
 <t ON 
 
 CM 
 
 o o o 
 
 o 
 
 Z 4J 
 
 M 
 
 cr hJ 
 
 )J 
 
 CO 4-1 
 
 1 
 
 
 vi- <: 
 
 <ti 
 
 H 
 
 H 
 
 H 
 
 CO <t 
 
 <f 
 
 i-H ^O CO 
 
 CO 
 
 CD 
 
 CU 
 
 cu 
 
 
 
 O 5h 3 
 
 
 
 C3^ Z 
 
 2 
 
 z 
 
 Z 
 
 Z 
 
 o o 
 
 O 
 
 CM 00 O 
 
 o 
 
 c 
 
 CU 
 
 M 
 
 
 
 CD O 'H MH 
 
 • 
 
 CO 
 
 
 
 
 
 
 #v r^ 
 
 ^ 
 
 *^ #« ^ 
 
 ^ 
 
 H O 
 
 (3 
 
 
 <4H 
 
 MH 
 
 rH 43 1 O 
 
 o 
 
 
 
 
 
 
 
 I-H 1-H 
 
 1-H 
 
 CM ^ CM 
 
 CM 
 
 Z 6 
 
 •H 
 
 CO 
 
 O 
 
 O 
 
 CO CO CM 
 
 .— 1 
 
 
 
 
 
 
 
 
 
 in un un 
 
 LO 
 
 cu 
 
 13 
 
 bO 
 
 CO 
 
 CO 
 4-t 
 
 CD 
 4-t 
 
 1-3 —1 CD 
 CU CU 
 
 w 
 
 
 
 
 
 
 
 
 
 
 
 M bO >> 
 
 ^ 
 
 
 ^ a 
 
 a 
 
 H 
 
 H 
 
 H 
 
 r^ CO 
 
 in 
 
 O O O 
 
 o 
 
 . (U 
 
 ^■*\ 
 
 cu 
 
 iH 
 
 iH 
 
 <U 3 43 .rH 
 
 ^ 
 
 
 <!■ < 
 
 <J 
 
 Z 
 
 Z 
 
 Z 
 
 00 CM 
 
 in 
 
 ^ m in 
 
 CM 
 
 (U V-i 
 
 CD 
 
 4-) 
 
 3 
 
 3 
 
 ;? 'H 4-t 
 
 fvj 
 
 r~- Z 
 
 z 
 
 
 
 
 vO 00 
 
 r^ 
 
 r^ r^ v£) 
 
 r^ 
 
 rH CU 
 
 • U 
 
 CD 
 
 CO 
 
 CD 
 
 4-1 1 
 
 H 
 
 
 
 
 
 
 
 
 
 1-H 1-H 1-H 
 J- J- J- 
 
 1-H 
 J- 
 
 CO 
 •H —1 
 
 tlve 
 ture 
 
 (U 
 4-) 
 
 4-1 
 
 cu 
 
 (U 
 
 r^ CD CO 4-1 
 
 cu 3 
 13 H >. cu 
 3 X> U 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 ON a, 
 
 a 
 
 H 
 
 H 
 
 H 
 
 eg O 
 
 I-H 
 
 o o o 
 
 o 
 
 .H 1 
 
 to o 
 
 O 
 
 ■p 
 
 4-1 
 
 CO cu • 
 
 
 
 CN <J 
 
 <d 
 
 Z 
 
 Z 
 
 Z 
 
 ^ o 
 
 00 
 
 00 CO CM 
 
 1-H 
 
 D^ "— ' 
 
 4-t to . 
 
 3 
 
 CD • 
 
 CD • 
 
 43 1 MH O 
 
 
 -H 
 
 m z 
 
 z 
 
 
 
 
 o r>. 
 
 vO 
 
 •^ -St CO 
 
 «v ^ ^ 
 
 ^H I-H ^H 
 
 1-H 
 
 CX -H 
 
 to 
 
 CO 
 
 3 iw cu 
 
 CU 3 rH 
 
 CD 3 Pu 
 
 CD 
 
 3 
 
 CU /-v 
 
 4-1 h 
 
 CU 
 
 4-1 M 
 
 o bo CO MH in 
 
 P -HO 
 
 CD 3 -3 " 
 
 
 
 
 
 
 
 
 
 J- ^ J- 
 
 J- 
 
 4.) 4J 
 
 o o 
 
 Z 3 
 
 <u 2 d 
 M a CO 
 
 CX CO 
 
 •H 
 
 (H 
 
 >. 3 
 
 CO 4-1 
 
 >^ 3 
 
 CO 4-1 
 
 4-J 43 O — • 
 O CD >-l CM 
 
 
 
 
 
 
 
 
 3 4J MH -3 
 
 
 
 CO • • 
 
 CO 
 
 • • 
 
 CO • • 
 
 • • • • 
 
 13 
 
 (U 4-) 
 
 CJ 
 
 -3 O 
 
 t3 O 
 
 13 4-1 4-13 
 
 
 0) 
 
 >^ • > 
 
 >. 
 
 • > 
 
 >N • > 
 
 CO • • > 
 
 O 
 
 M o ts 
 
 CU 
 
 1 CO 
 
 I to 
 
 O -H -3 CO CO 
 
 
 rH 
 
 CO . <d 
 
 CO 
 
 • <« 
 
 CO • <: 
 
 )H 4J • • < 
 
 CX (H 
 
 3 CO 
 
 a-<r ^w 
 
 in <4H 
 
 (H Ph (U 
 
 
 D. 
 
 TS O 
 
 -r* 
 
 O 
 
 •tS O 
 
 0) CD O O 
 
 < Oj 
 
 >. TJ P3 
 
 zn 
 
 •<t 3 
 
 <r 3 
 
 CL, 3 4J •> 
 
 
 d 
 
 Q 
 
 
 Q 
 
 Q 
 
 42 <U Q Q 
 
 z- 
 
 3 OcM 
 
 -o J- 3 
 
 ^ 3 
 
 ^ <U -H O O 
 
 
 CO 
 
 r^ 
 
 <d- 
 
 
 00 
 
 4-t -U 
 
 CO M 
 
 
 tO 
 
 cO 
 
 43 CO 43 CO 
 
 
 C/3 
 
 
 
 --H 
 
 
 
 CM 
 
 
 O 
 
 1 
 
 
 CX CX 
 
 
 
 
 
 
 4-1 4-t CO ON 
 
39 
 
 Although the flexural strength test, as 
 used in this paper, can be used with 
 considerable success in determining the 
 quality of fibered gunite, the Flexural 
 Toughness Index may soon supplement the 
 flexure test and take its place in the 
 quality control and testing of fibered 
 gunite and concrete. This engineering 
 property is essentially a measure of the 
 specimen's ability to sustain additional 
 loading after the first crack occurs 
 (when the matrix of the gunite or con- 
 crete has failed) , when the stress-strain 
 curve moves through the ultimate strength 
 and continued additional loading is sup- 
 ported by the interlocking nature of 
 the cemented fibers only. Although re- 
 searchers have attemped to quantify this 
 load-bearing capability, the parameter 
 is not at present usable in any design 
 procedure. 
 
 The toughness index was calculated for 
 some fibered specimens in this study. As 
 shown in figure 37 for one of the tested 
 specimens, the (proposed) toughness in- 
 dex is calculated as the area under the 
 
 3,500 
 
 1 
 
 1 1 1 
 
 
 
 First-crack 
 
 f^ — Ultimate strength 
 
 
 3,000 
 
 - strength / 
 
 \ 
 
 - 
 
 2,500 
 
 / 
 
 \ 0.075- in 
 
 - 
 
 ^ 2,000 
 
 / 
 
 \ deflection 
 
 - 
 
 o 1,500 
 
 - / 
 
 V 
 
 - 
 
 1,000 
 
 - / 
 
 \i 
 
 - 
 
 500 
 n 
 
 ' 1 
 
 1 1 ! 1 1 
 
 ^ 
 
 0.02 0.04 0.06 0.08 0.10 0.12 
 DEFLECTION (FLEXURAL), 0.02 in/in 
 
 FIGURE 37. - Flexural strength curve of a 
 steel-fibered gunite sample. 
 
 load-deflection (L-D) curve out to 0.075 
 in, divided by the area under the load 
 deflection curve of the fibrous beam up 
 to the first-crack strength (proportional 
 limit defined as the first deviation from 
 linear) (29) : 
 
 Toughness index = 
 
 area under L-D curve to 0.075 in deflection , 
 area under L-D curve to first crack 
 
 The toughness index, however, is not 
 standardized as it should be. One source 
 defines the term as "the area under 
 the load deflection curve out to 0.10 in 
 (2.54 mm), divided by the area under 
 the load-deflection curve of the fi- 
 brous beam up to the first crack strength 
 (30)." When more precisely defined, the 
 
 parameter will measure the amount of work 
 required to strip the fibers in the fail- 
 ure crack plane from the concrete ( 31 ) . 
 Owing to the controversy involving this 
 engineering parameter (see appendix F) , 
 the toughness index data are not herein 
 presented. 
 
 POROSITY AND PERMEABILITY ANALYSES 
 
 Fibered-gunite products are subjected 
 to relatively harsh moisture conditions 
 when applied in deep coal mine environ- 
 ments. The exposed gunite surface is in 
 constant contact with mine ventilation 
 air that in some instances exhibits rela- 
 tive humidity conditions that may ap- 
 proach 100 pet. Unless mine ventilation 
 air is dehumidified, primarily during 
 the hot summer months , the mine atmos- 
 phere can resemble a dense fog. Addi- 
 tionally, when fibered gunite is used for 
 roof and rib support in deep mines (metal 
 
 or nonmetal) containing high-sulfur ores 
 or in high-sulfur coal seams (sulfur con- 
 tent exceeding 1,5 pet), the gunite may 
 be subjected to seepage or drainage that 
 is moderately to highly acidic. The 
 drainage contacts the outer and inner 
 surfaces of the gunite (where the gunite 
 contacts the coal or rock surface) and 
 causes deterioration of the alkaline ce- 
 ment structure. This causes loss of ad- 
 hesion, strength, and sealant protection 
 of the host rock surface. 
 
40 
 
 The hydraulic conductivity (permeabil- 
 ity) and porosity of the fibered gunite 
 determine the rate of seepage migration 
 through the material from the rock-gunite 
 contact surface outward, and are also 
 directly related to the propensity for 
 absorption of acidic drainage or vapor 
 inwardly. Gunite permeability and/or po- 
 rosity, therefore, may be one of the 
 primary factors in determining the dura- 
 bility of the material, which involves 
 primarily its alkali-acid reactivity, 
 leaching characteristics, resistance to 
 chloride or sulfate attack (and the sub- 
 sequent expansion and cracking) , rein- 
 forcement steel corrosion, and freeze- 
 thaw characteristics. 
 
 For the above reasons, it was consid- 
 ered pertinent that this investigation 
 include porosity and/or permeability 
 analyses of the tested gunite samples. 
 The analyses were performed by the author 
 at the Department of Energy's Bartles- 
 ville Energy Technology Center in Bar- 
 tlesville, OK. Owing to the suspected 
 presence of extremely low permeability 
 readings (in the 1 x 10~^ darcy range) , a 
 special research apparatus and technique 
 were developed for the permeability anal- 
 ysis phase of this investigation. 
 
 The gunite samples were cored with pre- 
 cision equipment to an outside diameter 
 of 1.5 in and a length of 2.75 in. Both 
 ends of the cores were trimmed with a 
 precision laboratory diamond- tipped core 
 saw. Although great care was used in 
 coring and trimming the gunite samples , 
 the laminated zones (especially in the 
 
 steel-f ibered samples) caused some core 
 dimension irregularities. Some specimens 
 had to be shortened somewhat to remove 
 laminated zones. 
 
 The gunite porosity analyses were de- 
 rived by the following procedure: 
 
 1, The cores were dried in a constant 
 temperature oven at 115° for 24 h. 
 
 2, Core dry weight and length dimen- 
 sions were recorded. 
 
 3, Bulk volume was caluclated using 
 the formula 
 
 bulk volume = irr^j^, 
 
 where r = radius of core 
 
 and 
 
 I = core length. 
 
 4. The cores were then placed in a 
 vacuum cell, which was evacuated and then 
 submerged in water under a high vac- 
 uum for a minimum of 4 h. Figure 38 
 shows the laboratory setup for sample 
 evacuation. 
 
 5. The cores were then removed from 
 the water, blotted, and weighed. The 
 weight of the saturated water (saturated 
 core weight minus dry core weight) and 
 volume of the saturated water (weight of 
 the saturated water divided by density of 
 the water) were then calculated. 
 
 6. Porosity of the samples was then 
 determined by the formula 
 
 Porosity i<^) = 
 
 weight of the saturated water 
 density of the water 
 
 irr^Jl 
 
41 
 
 This method of extracting a sample po- 
 rosity value is an offshoot of the true 
 formula: 
 
 (<!)) pet = ^ • 100 
 
 or (j) pet = ^^j ^s . 100, 
 
 where 
 
 and 
 
 Vt 
 Vp = pore volume, 
 
 Vt = total volume, 
 
 Vc = solid volume. 
 
 The porosity value obtained by this meth- 
 odology may be more appropriately known 
 as the effective porosity in that it re- 
 lates directly to the volume of intercon- 
 nected pores and their ability to uptake 
 water under vacuum. 
 
 Table 11 summarizes the porosity data 
 acquired for the samples. The complete 
 data file is presented in appendix C. 
 Porosity measurements are, at best, dif- 
 ficult to acquire and prone to error. 
 Although error in porosity analyses is 
 inversely proportional to the total sam- 
 ple volume (thus the sample should be 
 
 FIGURE 38. - Gunite core air evacuation sys- 
 tem for porosity analysis. 
 
 large) , the samples were considered to be 
 large enough to permit reasonably short 
 evacuation times without inducing skin- 
 effect aberrations in the porosity data, 
 caused by incomplete filling of the in- 
 nermost pores by the brine (water). The 
 absorption of water along the length of 
 the fiberglass strands (in those samples 
 containing fiberglass) may have induced 
 error that increased effective porosity. 
 
 TABLE 11, - Gunite density and porosity 
 
 Sample 
 
 Core density, 
 
 Core porosity, 
 
 Sample 
 
 Core density. 
 
 Core porosity. 
 
 
 g/cm^ 
 
 pet 
 
 
 g/cm^ 
 
 pet 
 
 1 
 
 2.01 
 
 25.59 
 
 10 
 
 2.18 
 
 18.62 
 
 2 
 
 2.10 
 
 20.41 
 
 11 
 
 2.16 
 
 19.25 
 
 3 
 
 2,11 
 
 17.45 
 
 12 
 
 2.16 
 
 19.56 
 
 4 
 
 2.12 
 
 19.98 
 
 13 
 
 2.13 
 
 20.62 
 
 5 
 
 1.69 
 
 34.95 
 
 14 
 
 0) 
 
 0) 
 
 6 
 
 2.00 
 
 25.09 
 
 15 
 
 1.96 
 
 29.78 
 
 7 
 
 2.01 
 
 24.49 
 
 16 
 
 2.06 
 
 21.60 
 
 8 
 
 1.81 
 
 29.67 
 
 17 
 
 1.96 
 
 210.10 
 
 9 
 
 2.10 
 
 20.90 
 
 
 
 
 ^Defective sample. 
 
 2a major portion of this 
 
 lamination zones. These samples con- 
 
 porosity is in the 
 tained styrene butadiene latex polymer. 
 NOTES. ~ 
 
 1. Although steel-f ibered specimens are normally considered to have a homogeneous 
 distribution of the fibers, concentrations were found in lamination zones, possibly 
 inducing density errors. 
 
 2, Samples 5 and 8 are f ibered surface bonding mortars (cements) and therefore 
 contain larger pore volumes and interconnected pores. 
 
42 
 
 It should be noted that samples 15-17 
 contained sytrene butadiene latex poly- 
 mer. Although they exhibited low compar- 
 ative porosity readings, they would have 
 had even lower porosity values had they 
 not contained minor lamination zones. 
 
 Fibered-gunite permeability analyses 
 were conducted using the laboratory setup 
 diagrammed in figure 39 and shown in fig- 
 ure 40. The procedure involved the con- 
 finement of a previously evacuated, satu- 
 rated section of core in a precisely fit- 
 ting rubber sleeve within a stainless 
 steel Hassler tube. The core was flooded 
 under pressure with a metered amount of 
 fluid. As shown in figure 41, the core 
 is fitted with fluid gathering and in- 
 jecting Teflon endpieces of the same 
 diameter as the core; these have inlet 
 and outlet orifices. The endpieces are 
 
 locked in place by brass endcaps. The 
 rubber sleeve around the core is sealed 
 and heavily pressurized to a minimum of 
 100 psig above the metered flow pressure 
 of the core flooding pump to prevent lat- 
 eral skin flow along the core exterior 
 length. Any fluid collected at the out- 
 let end of the Hassler tube, therefore, 
 was measured and considered to have moved 
 through the core matrix. 
 
 Owing to the extremely low permeabili- 
 ties of the gunite core samples, a capil- 
 lary tube was used to collect the core 
 flood water at the outlet orifice. Water 
 column height increase over a monitored 
 period of time was used to calculate the 
 permeability characteristics. 
 
 The following conditions were main- 
 tained for the research: 
 
 Cheminert double-plunger 
 metering pump with variable 
 flow rate 
 
 Metering valve 
 Water delivery gauge 
 
 Methylene blue 
 indicator solution 
 
 Rubber tubing 
 
 Pump air valve 
 supply line 
 
 High-pressure fluid in 
 
 High-pressure .. ^ . 
 pump (180 psig) ^^J^"^ 
 
 yZn\ scale 
 
 l/16-in-l D 
 flowmeter tube 
 
 Metering 
 valve 
 
 {13 
 
 Fluid out 
 
 (atmospheric 
 
 pressure) 
 
 Teflon cap plug 
 
 Stainless steel 
 
 ^V^ Core confining ^ ,, , , . j 
 ^ ^ pressure (fluid) ^^^sler tube and caps 
 
 (in cross section) 
 
 High-pressure gauge 
 
 Bypass 
 
 Note= Not to scale. 
 Hassler tube expanded 
 to show detail 
 
 FIGURE 39. - Gunite permeability analysis system diagram. 
 
43 
 
 FIGURE 40t » Gunite permeability analysis equipment. 
 
 1. The laboratory and water temper- 
 ature was maintained constant at 22° 
 to 23°C. A water viscosity of 0.94 cP 
 (32) was used in all the permeability 
 calculations. 
 
 2. Hassler tube outer sleeve pressure 
 (for core confinement) was maintained at 
 a constant pressure of 180±5 psig. 
 
 3. Hassler tube core inlet pressure 
 was maintained at a precise 80±5 psig 
 setting, using a precision metering 
 value. 
 
 4. A precision Cheminert metering pump 
 with variable flow rates was used to in- 
 ject and flood the confined gunite cores 
 with water. A 100-yL/min flow rate (Q) 
 was selected and used throughout the re- 
 search effort. 
 
 5. Air pressure used to control the 
 Cheminert metering pump piston valves was 
 maintained at a constant 60 psig. 
 
 6. New methylene blue indicator solu- 
 tion was injected into the capillary out- 
 let riser tube to allow precise visual 
 readings . 
 
 FIGURE 41. - Hassler tube and associated core 
 permeability measuring apparatus. 
 
 The permeability of the somewhat porous 
 gunite medium is a measure of its ca- 
 pacity to transmit fluids or, more suc- 
 cinctly defined, a measure of the fluid 
 conductivity of the material. The perme- 
 ability represents the reciprocal of the 
 resistance the porous medium offers to 
 fluid flow (33) . The practical unit of 
 measure of permeability is the darcy and 
 its submultiples , the millidarcy (10~^ 
 darcy) and microdarcy (10~^ darcy). Dar- 
 cy 's law, expressed with fluid viscosity 
 parameters, made it possible to define 
 penffeability when it was determined that 
 a thin slice of material, in this in- 
 stance a core of gunite, with thickness 
 dx and cross section S, is traversed per- 
 pendicularly at its faces by a rate of 
 flow Q (counted in volume at the tempera- 
 ture and average pressure of the slice) 
 of a fluid with viscosity y, and is af- 
 fected by a pressure differential, dp. A 
 generalized form of Darcy 's law applies 
 here and is written as follows: 
 
 dp=Max 
 
 Sk dp 
 
 or Q = — • -r*^ 
 
 ^ M dx 
 
 7. Capillary cross-sectional area was 
 determined to be 0.0198 cm^ by using the 
 formula Tir^, where radius is 1/2 the in- 
 side capillary diameter (1/16 in). Cap- 
 illary length of water accumulated over a 
 unit time provided volume per unit time. 
 
 °^ ^ s • d? 
 
 with the coefficient K 
 permeability (34) . 
 
 being the 
 
44 
 
 TABLE 12. - Gunite mean permeability values 
 
 Sample 
 
 Permeability, 
 10"^ darcy 
 
 Std dev, 
 10"^ darcy 
 
 Sample 
 
 Permeability, 
 10"^ darcy 
 
 std dev, 
 10"^ darcy 
 
 1 
 
 4.14 
 
 29.75 
 
 2.12 
 
 15.02 
 
 168.89 
 
 122.27 
 
 62.87 
 
 8.34 
 
 15.74 
 
 0.86 
 
 1.42 
 
 .68 
 
 .54 
 
 2.88 
 
 1.78 
 
 3.74 
 
 .45 
 
 .60 
 
 10 
 
 11 
 
 12 
 
 13.92 
 11.61 
 3.31 
 5.36 
 0) 
 <1.0 
 <1.0 
 <1.0 
 
 0.20 
 
 2 
 
 3 
 
 .67 
 .64 
 
 4 
 
 13 
 
 .79 
 
 5 
 
 14 
 
 0) 
 
 6 
 
 7 
 
 15 
 
 16 
 
 NA 
 NA 
 
 8 
 
 17 
 
 NA 
 
 9 
 
 
 NA Not available. 
 ^Defective sample. 
 NOTES.— 
 
 1. Laminations effectively shortened the core length, making the permeability val- 
 ues larger than normal in cores with such laminations. 
 
 2. Samples 15-17 were styrene-butadiene-latex- impregnated gunite cores and were 
 determined to be essentially impermeable to fluid movement. 
 
 3. Although the compressibility of water may be a factor here and varies with 
 pressure, temperature, and dissolved gases, the factor was disregarded in the perme- 
 ability calculations. 
 
 For this investigation, the permeabil- 
 ity analyses were determined using a for- 
 mula that was extracted and simplified 
 from the Darcy 's law equation since Q, 
 dp, y, and S were maintained constant. 
 The extracted equation used to calculate 
 permeability in this research was as 
 follows: 
 
 Vt y 
 
 K = 
 
 A AP 
 
 Owing to the sensitivity of the system 
 and to the extremely low permeabilities, 
 at least six timed runs were performed on 
 each sample. The data accumulated are 
 presented in appendix D, Table 12 shows 
 the mean (arithmetic average) values and 
 standard deviations, calculated using the 
 formula 
 
 (Ix)2 
 
 I 
 
 x 
 
 2 _ 
 
 Sx = 
 
 n 
 
 n-1 
 
 where V = volume of fluid collected in 
 the capillary, cm^ , 
 
 t = time, s, 
 
 M = water viscosity, cP, 
 
 A = core cross-sectional area, 
 cm^, 
 
 AP = pressure differential across 
 the core (inlet-outlet) , 
 psia, 
 
 Since permeability and porosity are di- 
 rectly related in some types of materi- 
 als, an effort was made to determine the 
 relationship of the two factors for the 
 gunite samples. The porosity and perme- 
 ability data were compared using a linear 
 regression computer program to best fit a 
 straight line to the plotted data points. 
 Porosity values were plotted on the ab- 
 scissa (x axis), and permeability values 
 were plotted on the ordinate (y axis). 
 The general linear regression formula 
 used in the curve fit (straight line) 
 calculation was 
 
 and 
 
 L = core length, cm. 
 
45 
 
 b = 
 
 a = 
 
 r2 = 
 
 LxiYi 
 
 !.xi 
 
 ly, 
 
 n 
 
 2 _ 
 
 
 yi 
 
 - b 
 
 n 
 
 •Xi 
 
 LxiYi - 
 
 Ix, I 
 
 yi 
 
 (Ixi)2 , 
 Ix,^-— -—Ix.^- 
 
 dx,)^ 
 
 o 
 o 
 
 T3 
 CD 
 'O 
 
 UJ 
 
 160 
 
 120 
 
 80 - 
 
 CD 
 
 < 40 
 
 UJ 
 
 
 
 1 
 A 
 
 1 
 
 1 ' 1 ' 
 
 - 
 
 + 
 
 y^ 
 
 - 
 
 + >^ 
 
 ^ " 
 
 •X 
 
 1 
 
 . +, , , 
 
 n 
 
 20 
 
 24 
 
 28 
 
 32 
 
 36 
 
 Figure 42^4 is a curve fit of the 
 porosity-permeability data of gunite 
 specimens 3-10 plus 12 and 13. Figure 
 42B shows the same data minus specimen 8, 
 which was a surface-bonding cement and 
 caused an errant relationship and line 
 fitting. R-square, the correlation coef- 
 ficient of the two parameters, was 0,569 
 in plot A and 0.885 in plot S. Correla- 
 tion coefficients that approach 1.0 indi- 
 cate excellent data correlation. 
 
 The range scale of the x-axis was 
 shifted to the right in plot A to expand 
 the cluster of data that occurred to the 
 right of the abscissa-ordinate intersect 
 point. The right-lateral shift in poros- 
 ity data and consequent negative ordinate 
 intercept is an indication that a portion 
 of the porosity present (lamination 
 zones, air pockets, etc.) is not avail- 
 able for fluid flow (permeability). The 
 plots indicate a good correlation between 
 the gunite porosity and permeability data 
 for the samples compared. 
 
 The lowest observed permeabilities oc- 
 curred in the latex polymer gunite sam- 
 ples. The high-strength silica fume wet- 
 mix gunite was second with a permeability 
 of just over 2.0 x 10~^ darcy. One seal- 
 ant (surface bonding cement) material 
 (sample 5) exhibited an extremely high 
 penneability compared to the normal gun- 
 ite specimmens. 
 
 o 
 
 O 
 
 ■o 
 to 
 'O 
 
 >- 
 
 _J 
 
 m 
 < 
 
 LU 
 
 QL 
 LU 
 Q. 
 
 5 10 15 20 25 30 35 
 POROSITY, pet 
 
 FIGURE 42. - Linear regression curve fit of 
 porosity and permeability. 
 
 The gunite specimens exhibited a gen- 
 eral trend of increasing permeability 
 with decreasing compressive strength. 
 Permeability also tended to increase with 
 an increase in water-cement ratio, al- 
 though enough specific water-cement ratio 
 data were not available to confirm the 
 trend. Fiber type did not appear to 
 directly affect permeability. Sample 
 laminations, particularly in the steel- 
 fibered specimens, masked any potential 
 correlations of fiber type and content 
 with permeability. 
 
 DELIVERY HOSE STATIC DISCHARGE 
 
 During the application of two dry-mix 
 f iberglass-fibered-gunite products, con- 
 tinuous, strong, 1-1/2- to 2-in-long 
 
 blue-white static discharges were ob- 
 served along the delivery hose. Although 
 the discharges were primarily observed 
 
46 
 
 to take place between the hose and the 
 slightly damp concrete mine floor, one 
 nozzle operator stated that he sometimes 
 felt a shock. Although the occurrence of 
 the discharges in the Lake Lynn Exper- 
 imental Mine was not dangerous , in an 
 operating deep coal mine with methane and 
 coal dust in the mine air and blasting 
 materials in common use, such static dis- 
 charges may be extremely dangerous, par- 
 ticularly in return airways or nonven- 
 tilated areas. The minimum ignition 
 potential of methane-air mixtures occurs 
 at 0.9 of stoichiometric mix (which is 
 9.48 pet methane in air) and requires 
 less than 0.5 mj of energy (35) . The 
 discharge of 10 mJ capacitive energy 
 through a bridgewire is enough to fire an 
 electric blasting cap (36) . The concen- 
 trated discharge of static from the dry 
 mix delivery hose to a pointed conductive 
 metal object may, therefore, be suffi- 
 cient, under the right circumstances, to 
 ignite methane or to fire an electric 
 blasting cap. 
 
 The relative humidity in the mine at 
 the time of the static discharge observa- 
 tion was 44 pet, and the temperature of 
 
 the mine air was 49° F. The combination 
 of the dry, cold air with the relatively 
 dry concrete mine floor may seldom be 
 duplicated in an operating coal mine, but 
 the possibility does exist. The relative 
 humidity readings taken during the re- 
 mainder of the dry-mix-type gunite appli- 
 cations ranged from 48 to 57 pet, and 
 static discharges were not observed. The 
 wet-mix gunite application had no ob- 
 servable static discharges, as would be 
 expected. 
 
 The development and use of a sheathed 
 (metallic) mesh discharge grounding sys- 
 tem for delivery hoses would add consid- 
 erable bulk and weight to the hose and 
 would make it unwieldy and difficult to 
 clean. The solution to static bleed off, 
 therefore, may rest in the impregnation 
 of better conductive fiber or metallic 
 strands in the hose wall itself. Al- 
 though many delivery and placement hose 
 types are designed to be "static dissi- 
 pating," the observed static discharges 
 are proof enough that the hazard poten- 
 tial remains, particularly during dry, 
 cold (low relative humidity) seasons. 
 
 GUNITE OPERATION CREW REQUIREMENTS 
 
 One of the most important factors in 
 the application of fibered gunite is the 
 selection, training, and on-the-job ex- 
 perience of the gunning crew. Most crews 
 consist of three or four members: a 
 
 nozzle operator, a gun operator, and one 
 or two gun loaders . One of the crew 
 serves as the foreman and must be thor- 
 oughly familiar with all facets of the 
 operation including equipment setup and 
 
 
 TABLE 
 
 13. - Gunite crew requirements 
 
 
 
 Sample 
 
 Type of mix 
 
 Nozzle and hose 
 
 Gunite gun 
 
 Hopper 
 loaders 
 
 Other 
 
 Crew total 
 
 1-3 
 
 4-5 
 
 Wet 
 Dry 
 Dry 
 Dry 
 Dry 
 
 1 
 
 1 
 
 32 
 
 32 
 
 1 
 
 2 
 1 
 
 
 1 
 1 
 
 13 
 2 
 
 ^2 
 2 
 2 
 
 2l 
 
 
 
 
 
 
 63 
 
 7 
 4 
 
 6-8 
 
 4 
 
 9-10 
 
 11-17 
 
 55 
 7 
 
 ^The wet-mix method required a concrete-mortar mixer crew of 3. The manufacturer 
 had not established a prebag mix at the time of the application demonstration. 
 ^1 crew member sprayed curing compound on the freshly applied gunite. 
 3l crew member operated the nozzle and/or water valve and 1 assisted with the hose 
 
 movement. 
 
 4 
 
 The hopper loaders also performed gun adjustments. 
 ^A 6th person, identified as a sales representative, assisted to a limited degree. 
 ^Samples 11-17 were demonstrated at the manufacturer's facilites 
 
 the author. 3 additional crew members were present, 
 tlons, but mainly assisting in latex polymer pumping. 
 
 accompanied by 
 performing a variety of func- 
 
47 
 
 operation, water and air pressure and 
 volume adjustments for optimum gunning 
 conditions, and rock surface preparation, 
 scaling, and washdown requirements. Ta- 
 ble 13 provides a comparative breakdown 
 of the gunite crews used by the various 
 manufacturers of the products tested. 
 Each gunite manufacturer that partici- 
 pated in the comparative application re- 
 search was urged to bring its most exper- 
 ienced, seasoned gunite crew. 
 
 Gunite shot rate ranged from 1,350 
 Ib/h for a surface-bonding cement shot 
 with a special gun to 9,491 Ib/h for a 
 f iberglass-fibered dry-mix gunite (table 
 14) . Most of the gunning rates averaged 
 approximately 6,000 Ib/h (1.5 yd^/h as- 
 suming gunite weighs 4,000 Ib/yd^). The 
 in-place application rate, considering 
 water added, gun losses, etc., ranges 
 from 1.1 to 2.9 yd^/h for the dry-mix 
 gunite. Sealant and surface bonding ce- 
 ment rates were less. Shooting rate for 
 the wet-mix gunite was estimated at 0.38 
 yd^/h, but the wet-mix gun is rated at up 
 to 7.8 yd^/h. Owing to the crews' pre- 
 cise measuring of the ingredients and 
 
 additives, the wet-mix gun's capacity was 
 not remotely approached. 
 
 Some gunite manufacturers do not main- 
 tain a complete mobile crew to perform 
 gunite training and demonstrations for 
 their specific product. During the ap- 
 plication of one product, three different 
 men from one crew were permitted to run 
 the nozzle, two apparently for the first 
 time. One of the three operators had the 
 water valve setting so open the wet gun- 
 ite ran down the mine rib. A second 
 operator later sprayed dry dusty gunite 
 material on the top of the wet zone, ap- 
 parently to dry it up. 
 
 The company that applied products 9 and 
 10 maintains a trained crew for use in 
 teaching coal company crews the correct 
 method of applying their products. One 
 piece of equipment that permitted this 
 crew's close coordination and precise ad- 
 justment of the gunite gun and nozzle was 
 a voice-activated (permissible in coal 
 mines) communication headset-microphone 
 system, worn by the nozzleman and gun 
 operator. Air and water pressures. 
 
 TABLE 14. - Gunite shooting rate 
 
 Sample 
 
 Shot 
 duration. 
 
 mm 
 
 Bags 
 shot 
 
 Bag 
 
 weight, 
 
 lb 
 
 Total 
 
 gunite 
 
 weight , lb 
 
 Gunite shot 
 
 bags/min 
 
 Ib/h 
 
 1 
 
 ydVh' 
 
 3 (wet-mix) 
 
 4 
 
 4^^ 
 
 55 
 
 6 
 
 7 
 
 8 
 
 9 
 
 10 (roof)... 
 10 (rib) 
 
 167 
 83 
 
 125 
 60 
 70 
 38 
 40 
 55 
 50 
 52 
 
 NA 
 
 180 
 
 170 
 
 27 
 
 128 
 
 64 
 
 48 
 
 145 
 
 67 
 
 75 
 
 NA 
 50 
 50 
 50 
 60 
 60 
 50 
 60 
 80 
 80 
 
 34,200 
 9,000 
 8,500 
 1,350 
 7,680 
 3,840 
 2,400 
 8,700 
 5,360 
 6,000 
 
 NA 
 2.25 
 1.36 
 .45 
 1.83 
 1.68 
 1.20 
 2.64 
 1.34 
 1.44 
 
 1,509 
 6,506 
 4,080 
 1,350 
 6,583 
 6,063 
 3,600 
 9,491 
 6,432 
 6,923 
 
 0.38 
 1.73 
 1.10 
 
 .36 
 1.61 
 1.52 
 
 .83 
 2.95 
 1.73 
 1.87 
 
 NA Not available. 
 
 •"^For shot durations of less than 1 h, rate is shown assuming the same rate would 
 have continued for 1 h. 
 
 ^Assumes a cubic yard weighs 4,000 lb and contains 3,700 lb solids and 300 lb wa- 
 ter. This figure considers specimen collection and gun losses (not rebound) and rep- 
 resents cubic yards in place. 
 
 ^This is a rough estimate provided by the manufacturer. The low gunning rate was 
 due to the precise additive blending and gunite characteristics measuring before 
 shooting was allowed. 
 
 '^Sample 4 was shot during 2 monitored periods of time. 
 
 ^Surface bonding cement. 
 
48 
 
 gunite feed rate, rotor speed, and nozzle 
 distance were varied In synchronous tim- 
 ing as the nozzle operator moved from rib 
 to roof application areas and maintained 
 constant verbal contact with the gun 
 operator. The results of the verbally 
 communicated coordination of movement in- 
 clude a reduction in rebound waste (hence 
 lower costs) , better compaction of the 
 finished product (hence higher strength) , 
 and a more uniformly applied product. 
 
 Several points made by two of the par- 
 ticipating manufacturers who had given 
 training sessions to gunite equipment and 
 product purchasing clients in the mining 
 industry include — 
 
 1. Only the long-term, responsible 
 personnel of the company should be given 
 the gunite training and then only if 
 those personnel are to function as a gun- 
 ite crew on a regular basis. The manu- 
 facturers found that in many instances 
 
 when they returned to a mine (at the mine 
 superintendent's request) no more than 6 
 months after a full-scale training ses- 
 sion, the gunite crew contained none of 
 the originally trained personnel, 
 
 2. Equipment used to convey and pneu- 
 matically apply fibered gunite products 
 is subjected to severe internal abrasion 
 and must have the specified maintenance 
 performed if it is to function properly. 
 A gunite gun capable of applying gunite 
 with no more than 10 to 15 pet rebound is 
 quickly converted into a 50-pct waste 
 generator when poorly maintained and im- 
 properly operated. Inefficient gunning 
 techniques and the attendant high costs 
 cause mine management to forego the ob- 
 vious safety benefits obtainable from 
 f ibered-gunite products. An adhered-to 
 training policy and equipment maintenance 
 schedule will reduce a high percentage of 
 the gunite costs that are attributable to 
 waste rebound. 
 
 GUNITE COST ANALYSIS 
 
 The ultimate cost per cubic yard of in- 
 stalled fibered-gunite products depends 
 on a number of factors: 
 
 A, Cost of the gunite materials (prebag 
 
 or bulk) : 
 
 1. Cement content and type. 
 
 2. Fiber content and type. 
 
 3. Other ingredient proportions (ag- 
 
 gregates, sand, etc.). 
 
 4. Special additives in the mix 
 
 (e.g., silica fume, fly ash, 
 ground slag) . 
 
 B, Products required in applying the 
 
 gunite: 
 
 1. Accelerators. 
 
 2. Plasticizers and/or water re- 
 
 ducers (wet-mix) . 
 
 3. Superplasticizers (wet-mix). 
 
 4. Specialty additives (e.g., sty- 
 rene butadiene polymer), 
 
 6. Curing compounds. 
 
 C. Application crew requirements. 
 
 D. Application equipment. 
 
 E. Rebound percentage (waste) and gun 
 
 dust losses. 
 
 Tables 15-17 provide an analysis of the 
 generalized costs of some of the categor- 
 ized items. Materials costs vary geo- 
 graphically; therefore, the costs pre- 
 sented reflect a general Northeast U.S. 
 average. 
 
 The general price quoted for bulk gun- 
 ite sand and aggregate if of a river sand 
 variety is $13/ton to $15/ton, according 
 to a major producer. Gunite manufac- 
 turers with their own dredging operation 
 or located near one may pay as little as 
 $7/ ton to $8/ ton for river sand. Manu- 
 factured sand or sand-sized limestone 
 
49 
 
 TABLE 15. - Portland cement price data^ 
 
 Type cement 
 
 Bag price 
 (per 94 lb) 
 
 Bulk tanker price 
 (per 1,000 lb) 
 
 Cost per yd 3 
 (in gunite)^ 
 
 I 
 
 $4.22 
 4.36 
 4.52 
 
 $60.00 
 63.00 
 66.00 
 
 $45.00-$59.00 
 
 II 
 
 47.25- 61.43 
 
 Ill 
 
 49.50- 64.35 
 
 ^Prices were quoted for June 1983 by a major cement 
 producer. 
 
 ^Gunite cement content ranged from approximately 750 to 
 974 lb/yd3. 
 
 TABLE 16. - Gunite fiber price data 
 
 Fiber type 
 
 Cost per Ib^ 
 
 Concentration , ^ 
 lb/yd3 
 
 Cost per yd^ 
 (in gunite) 
 
 Steel 
 
 $0.30 
 
 1.80 
 
 .90 
 
 5.00 
 
 350-265 
 ^40 
 ^+40 
 M.6 
 
 $15.00-$79.50 
 
 AR-f iberglass 
 
 E— fiberglass 
 
 72.00 
 36.00 
 
 Polypropylene 
 
 8.00 
 
 ^Price data approximated for April 1983 by a gunite manufacturer. 
 
 ^These figures represent the concentration of fibers normally 
 used in gunite products. The figures do not imply that equivalent 
 performance will be achieved by the various fiber types at these 
 concentrations . 
 
 ^50 Ib/yd^ represents approximately 0.4 pet by volume, and 265 
 Ib/yd^ represents approximately 2 pet by volume (7^). The precise 
 volume percentage varies slightly with fiber configuration. 
 
 ^Average. 
 
 TABLE 17. - Wet-mix gunite admixture costs 
 
 Material 
 
 Drum price^ 
 per gal 
 
 Bulk price^ 
 per gal 
 
 Dosage, 
 oz/100 lb 
 cement 
 
 Cost per yd^ 
 (in gunite)"^ 
 
 Accelerator (liquid) 
 
 Accelerator (liquid) (nonchloride) 
 Plasticizer and/or water reducers: 
 
 Hydroxylated carboxylic acis,... 
 
 Lignosulf onates 
 
 Polymer admixture 
 
 Superplasticizers : 
 
 Sulfonated naphthalene formalde- 
 hyde condensate 
 
 Sulfonated melamine formaldehyde 
 condensate 
 
 $5.00 
 19.50 
 
 5.50 
 3.75 
 7.25 
 
 8.50 
 6.00 
 
 $2.50 
 17.50 
 
 NA 
 2.00 
 4.50 
 
 5.50 
 3.00 
 
 16-64 
 
 NA 
 
 2- 4 
 6-10 
 
 3- 9 
 
 10-20 
 24-40 
 
 $2.30-$12.18 
 
 NA 
 
 .64- 1.68 
 .70- 1.52 
 .79- 3.08 
 
 3.22- 8.37 
 4.21- 9.14 
 
 NA Not available. 
 
 ^The prices and additive rates were provided by a major concrete and cement product 
 supplier. 
 
 ^Drum price based on a 55-gal quantity. 
 
 3 Bulk price based on 5,000-gal quantity minimum. 
 
 '^Gunite cement content ranged from 750 to 975 Ib/yd^. The cost in gunite range is 
 based on the bulk price if available. 
 
50 
 
 aggregate, such as was contained in sev- 
 eral of the tested products, can also be 
 purchased for $7/ton to $8/ton or slight- 
 ly less if the manufacturing facility is 
 located near an operating quarry. 
 
 The cost of the styrene butadiene latex 
 polymer additive used in gunite samples 
 15-17 ranges from $6.35/gal in 1- to 10- 
 drum (55-gal) quantities to $4.18/gal in 
 a 3,000-gal tank car. At a nominal mix- 
 ture rate of 3-1/2 gal per bag of cement, 
 a 9-bag/yd^ gunite mix would require 31.5 
 gal at a cost of $132/yd3 to $200/yd3 
 of gunite (depending on the quantity of 
 chemical purchased) . This price informa- 
 tion was obtained from a major producer. 
 
 The prebagged, dry-mix fibered gunite 
 contains all of the necessary ingredients 
 for application except water. Curing 
 agents were not used for any dry-mix 
 product tested in this investigation. 
 Prices on a per-bag basis ranged from 
 $3.05 per 50-lb bag to $4.25 per 60-lb 
 bag for f iberglass-f ibered gunite. Sur- 
 face bonding mortars (containing high 
 concentrations of portland cement) cost 
 $4.69 to $6.95 per 50-lb bag. Steel- 
 fibered prebagged dry-mix gunite cost 
 from $3.49 per 60-lb bag to $3.80 per 
 80-lb bag. Cost per cubic yard through 
 the gun ranged from $226 to $262 for 
 f iberglass-fibered gunite (by weight) 
 and from $176 to $258 for steel-f ibered 
 gunite (by weight) . The f iberglass- 
 fibered surface bonding mortars (ce- 
 ments) , of which only two were tested, 
 cost $347/yd3 to 514/yd^ (by weight) . 
 The products were pneumatically applied 
 for demonstration purposes only. The 
 polypropylene-f ibered gunite (only one 
 tested) costs $157/yd^ through the gun. 
 Appendix E presents the complete cost 
 data for the dry-mix products involved in 
 this investigation. 
 
 The wet-mix gunite applied in the Lake 
 Lynn Laboratory Mine contained the con- 
 ventional cement, aggregate, fibers, and 
 water plus an accelerator, plasticizer, 
 water reducer, superplasticizer, and sil- 
 ica fume additives. A curing compound 
 was also used. Specific quantity amounts 
 of the various admixture ingredients used 
 
 in the three wet-mix products were not 
 revealed by the manufacturer. All par- 
 ticipating gunite manufacturers, however, 
 signed an agreement with the Bureau that 
 any contained additives would not be 
 flammable or impart gaseous vapors or by- 
 products that would be noxious or dele- 
 terious to human health upon exposure to 
 moist mine environments and/or explosive 
 research such as will be conducted in the 
 area where the gunite products were ap- 
 plied. Some of the additives were mea- 
 sured out precisely in graduated cylin- 
 ders and added to the gunite batch mix- 
 ture. The wet-mix admixture work for 
 specimens 1-3 was performed by a graduate 
 research engineer with the company that 
 manufactures the wet-mix gunite gun. 
 This particular wet-mix recipe, there- 
 fore, required highly specialized techni- 
 cal personnel. 
 
 The manufacturer of the wet-mix gunite 
 products provided a range of materials 
 content for the products. Documentation 
 provided by the company indicated that 
 plasticizer, superplastizer , and acceler- 
 ators were added, but volumes were not 
 specified. A cost estimate for the wet- 
 mix, steel-f ibered, silica fume gunite 
 was prepared in order to provide cost 
 comparison with the prebagged dry-mix 
 products. Table 18 presents the esti- 
 mated data derived for specimen type 3 
 from various sources. The estimated cost 
 of $235/yd3 to $323/yd3 through the gun 
 does not include curing compound cost, 
 equipment charges, or labor. The wet-mix 
 high-strength silica fume gunite is ex- 
 pected to cost $300/yd3 to 310/yd3. Cost 
 per cubic yard would be less for wet-mix 
 specimen types 1 and 2, which are of low- 
 er strength. 
 
 Table 19 presents a prebagged cost (es- 
 timate) comparison of dry-mix and wet-mix 
 gunites (as tested) . The estimated com- 
 parison is provided with the assumption 
 that some liquid additives (other than 
 water) may be required. Based on an ex- 
 pected cost of $300/yd3 to $310/yd3, the 
 type 3 steel-f ibered gunite could cost 
 $134/yd^ (through the gun) more than 
 the lower priced steel-f ibered dry-mix 
 gunite. The decreased rebound of the 
 
51 
 
 TABLE 18. - Cost estimate for prebagged, wet-mix, silica fume, steel-f ibered gunite 
 
 Material 
 
 Quantity 
 
 Cost (bulk) 
 
 Cost per yd- 
 
 Cement (Type III) 
 Sand (aggregates) 
 Fibers (imported) 
 Silica fume 
 
 Accelerator •'^ 
 
 Plasticizer^ 
 
 Superplasticizer^ . 
 
 Total materials. 
 Other cost items :^ 
 Sealable paper 
 bags. 
 Overhead costs^... 
 
 Total 
 
 Profit^ 
 
 Total cost (est) 
 
 through- the-gun . 
 Expected cost 
 
 890 to 950 Ib/yd^. 
 
 2,400 Ib/yd^ (est) 
 
 150 lb/yd3 (est). 
 
 15 to 18 pet (by 
 wt) of cement. 
 
 16 to 64 oz/100 lb 
 of cement . 
 
 4 to 8 oz/100 lb 
 
 of cement. 
 10 to 20 oz/100 lb 
 
 of cement . 
 NAp 
 
 46 to 74/yd3 
 
 $66/1000 lb 
 
 $13/ton to $15/ton. 
 
 $0.50/lb (est) 
 
 $50/ton to $75/ton. 
 
 NAp. 
 NAp, 
 NAp. 
 NAp. 
 
 NAp. 
 
 $5/gal 
 
 $2/gal to 3.75/gal 
 
 $3/gal to 5.50/gal 
 
 NAp 
 
 $0.15 to $ 0.20 each... 
 $0.50/bag to $ 0.70/bag 
 
 $59 -$63 (est) 
 16 - 18 
 
 75 (est) 
 3.50- 6.75 (est) 
 
 5.80- 11.90 (est) 
 
 1.01- 2.14 
 
 2.13- 8.36 
 
 NAp. 
 NAp. 
 
 NAp. 
 
 162 
 
 -185 
 
 6. 
 
 90- 14.80 
 
 23 
 
 - 52 
 
 191 
 
 -252 
 
 44 
 
 - 71 
 
 235 
 
 300 
 
 -323 
 
 -310 
 
 NAp Not applicable. 
 
 •'•Type or quantity of accelerator was not revealed by manufacturer. Cost estimate 
 derived by assuming dose rate of 16 to 64 oz per 100 lb cement, cement content of 890 
 to 950 Ib/yd^, and cost of $5/gal. 
 
 ^Type or quantity of plasticizer was not revealed by the participating manufac- 
 turer. Cost estimate was derived by assuming a dose rate of 4 to 8 oz per 100 lb ce- 
 ment, cement content of 890 to 950 Ib/yd^ , and cost of $3.75/gal. 
 
 ^Type or quantity of superplasticizer was not revealed by the participating manu- 
 facturer. Cost estimate was derived by assuming a dose rate of 10 to 20 oz per 100 
 lb of cement, cement content of 890 to 950 Ib/yd^ , and cost of $3/gal to $5/gal. 
 
 ^To compare prebagged wet-mix and dry-mix products, the bag cost, overhead cost and 
 profit must be estimated and included. 
 
 ^This range is provided based on information provided by one of the participating 
 dry-mix gunite manufacturers, using a profit range of 23 to 28 pet. 
 
 TABLE 19. - Prebagged gunite cost comparison 
 
 Type 
 
 Fiber 
 
 Compressive strength 
 as tested, psi 
 
 Cost per yd^ 
 (by weight) 
 
 Dry-mix. . . 
 Wet— mix. . . 
 
 Steel 
 
 ^9,668 
 ^,700 
 27,000 
 ^7,637 
 ^12,000 
 ^5,000 
 
 $176 
 
 258 
 
 226 
 
 157 
 
 ^$300-310 
 
 Fiberglass 
 
 Polypropylene. . 
 Steel 
 
 
 
 
 ^Private laboratory. ^Bureau of Mines. 
 
 ^Based on a statement from the manufacturer, the cost per 
 cubic yard for the silica fume high-strength wet-mix gunite may 
 approach $300 to $310. Note that some of the wet-mix additives 
 may not have dry (nonliquid) substitutes and, accordingly, 
 could not be prebagged. 
 
52 
 
 wet-mix gunlte, compared to that of the 
 dry-mix types, would reduce this cost 
 differential by up to 5 to 8 pet. The 
 increased strength of the tested wet-mix 
 
 gunite over that of dry-mix types may 
 also require less thickness (hence lower 
 volume) to provide the same structural 
 support on a given gunite job. 
 
 CONCLUSIONS AND RECOMMENDATIONS 
 
 Gunite Engineering 
 Parameter Relationships 
 
 Strength differences exhibited by fi- 
 bered and nonfibered gunites in com- 
 pression were obvious but not dramatic. 
 Strength differences between fibered and 
 nonfibered gunites in flexure, however, 
 were dramatic. The differences were sig- 
 nificant enough to conclude that for ap- 
 plications (e.g., mining) where prospec- 
 tive differential loading is possible and 
 flexural movement may occur, some type of 
 fiber must always be used when guniting. 
 
 The highest strength 
 contained steel fibers. 
 
 gunite products 
 
 Wet-mix, steel-f ibered gunite with sil- 
 ica fume and an array of admixtures 
 showed the highest compressive and flex- 
 ural strengths of the gunite products 
 tested. 
 
 When dry-mix steel-f ibered gunites are 
 sprayed in multiple-layered applications, 
 lenses of poorly cemented material (lami- 
 nations) develop. Uniaxial compressive 
 and flexural failure occurred at the lam- 
 ination lenses repeatedly. Laminations 
 were also found in the fiberglass-f ibered 
 products. 
 
 Polypropylene-fibered samples (specimen 
 13) had higher 7- and 28-day compres- 
 sive and flexural strengths than AR- 
 fiberglass-f ibered samples (specimen 14) 
 which were of similar composition, shot 
 through the same gun by the same noz- 
 zleman, and tested at the same private 
 laboratory. 
 
 Specimens gunned outside in daylight 
 had flexural and compressive strengths 
 of higher value than identical products 
 gunned in the diminished light of a min- 
 ing environment. The strength increases 
 obtained significantly exceeded the 
 
 15-pct difference between cored and cubed 
 sample strength (products demonstrated 
 outside were tested at private labora- 
 tories and cubed samples were taken) . 
 
 Gunite permeability tends to increase 
 as compressive strength decreases and as 
 the water-cement ratio increases. Gunite 
 fiber content did not appear to affect 
 the permeability of the material. 
 
 Splitting tensile strength analyses are 
 not an applicable test procedure for fi- 
 bered (especially steel-f ibered) gunite 
 poured cylinders , if specimen rodding is 
 performed in the test cylinder to induce 
 compaction. The isotropic orientation of 
 the fibers is disrupted, preferred lon- 
 gitudinal orientation occurs and a sub- 
 sequent reduction in splitting tensile 
 strength results. 
 
 Gunning Techniques and Rebound 
 
 Gunite sample blocks shot by the same 
 nozzleman using the same prebagged mix, 
 the same gun, the same day, and tested by 
 the same laboratory gave sawn beam flex- 
 ural strength variations of almost 70 
 pet, indicating that the gunning tech- 
 nique has a dominating effect on the 
 final product strength. 
 
 The application of wet-mix gunite, as 
 used and tested in this investigation, 
 required a highly trained technician to 
 perform admixture addition. Serious in- 
 teracting physicochemical reactions can 
 occur if the additives are not introduced 
 to the gunite in the correct amounts and 
 in consideration of their synergistic 
 effects. 
 
 Although only an estimated rebound was 
 obtainable for the wet-mix products in 
 this investigation, this rebound was the 
 lowest of all gunite types tested. 
 
53 
 
 The mean rebound (excluding the highest 
 and lowest values) for the dry-mix gunite 
 tested was over 20 pet. A rebound value 
 of less than 16 to 18 pet is extremely 
 difficult to achieve and can only be ob- 
 tained by the most proficient of gunning 
 crews . 
 
 A major portion of the rebound col- 
 lected for the steel-f ibered products was 
 steel fibers and larger sized aggregate 
 particles. Although other factors may 
 have more effect, the shorter f ibered 
 (steel) gunite had lower rebound. 
 
 The use of steel fibers, particularly 
 in the dry-mix equipment , appears to in- 
 duce pulsation activity in the gun, re- 
 sulting in a higher propensity for lami- 
 nations. Laminations were present in all 
 of the cores taken from dry-mix steel- 
 f ibered specimens. 
 
 The maintenance of dry-mix guns is cri- 
 tical in mines with high ventilation air- 
 flow rates; otherwise serious product 
 strength reduction may occur from cemen- 
 titious fines separation. 
 
 Air pressure fine tuning and nozzle- 
 rock surface distance adjustment are as 
 important as water flow rate adjustments 
 when moving from rib to roof application 
 with dry-mix gunites. 
 
 For dry-mix applications, reduced air 
 pressure with a closer (24 to 30 in) 
 nozzle-to-roof distance appeared to re- 
 duce nozzle spurting and loss from the 
 peripheral edges of the spray pat- 
 tern (hence reduced rebound) , The re- 
 duced air pressure also cuts dust, per- 
 haps at the expense of compaction (and 
 ultimate strength) . 
 
 After approximately an hour of constant 
 gunning, the nozzle operators were ob- 
 served to experience considerable arm 
 fatigue. The roof -nozzle angle of appli- 
 cation and distance began to change ac- 
 cordingly, resulting in higher rebound. 
 
 The gunning rate of the wet-mix gunite 
 applied in this investigation was slower 
 than that of any dry-mix type except one 
 
 surface-bonding cement. The slow appli- 
 cation rate was due primarily to the pre- 
 cise batch mixing of the ingredients and 
 admixtures . 
 
 Gunite Dust 
 
 The wet-mix high-strength gunite had 
 a higher total dust loading in milli- 
 grams per pound shot than four other 
 gunned dry-mix products. The dust was 
 primarily generated at the mixer. 
 
 Four out of eight of the dry-mix gunite 
 dust loadings would have exceeded the 
 standards for dust if the operation had 
 continued for a full shift or if the gun- 
 ning was being done near a working sec- 
 tion that was generating high dust 
 levels . 
 
 Gunite dust loading is almost entirely 
 a function of crew performance methods 
 and gun condition. 
 
 A direct correlation was observed be- 
 tween dust generated at the gun and re- 
 bound. In all but one case (gun malfunc- 
 tion) , high dust at the gun gave high 
 rebound. 
 
 Gunite Safety 
 
 Fiberglass fibers, as well as steel 
 fibers, can penetrate cloth gloves 
 and clothing and cause abrasions and 
 skin irritation when the gunned products 
 are handled. Fiberglass allergies are 
 documented and can cause minor 
 discomforts. 
 
 Steel fibers are dangerous when being 
 gunned, since they travel at high ve- 
 locity and have considerable penetra- 
 tion power. When gunning on hard rock 
 surfaces , the fibers have an initial high 
 rebound percentage and can inflict seri- 
 ous eye damage unless protective glasses, 
 or preferably goggles, are used. 
 
 Gunite Cost 
 
 Silica fume appears to be a more cost 
 effective way of obtaining lower perme- 
 ability, higher strength gunite than 
 
54 
 
 using latex polymers. Other, untested 
 characteristics, however, may justify the 
 use of polymer gunite in specialty appli- 
 cations underground, 
 
 Through-the-gun cost for steel-f ibered 
 dry-mix gunites tested is $176/yd^ to 
 $258/yd^ (by weight) compared with $300/ 
 yd^ to $310/yd^ (expected cost) for wet- 
 mix, high-strength, silica fume, steel- 
 f ibered gunite, excluding labor. Reduced 
 rebound and shot thickness requirements 
 for the wet-mix gunite may offset a por- 
 tion of the cost differential. The tech- 
 nical admixture staff requirements of the 
 wet-mix silica fume material may add to 
 the cumulative installation costs. 
 
 The cost comparison per cubic yard of 
 the various fibered products tested 
 revealed that the steel-f ibered dry- 
 mix prebagged gunite is the least expen- 
 sive and has the highest strength, 
 when compared with other fibered dry-mix 
 products. 
 
 General Conclusions 
 
 Bird-nest blockage of the gunite equip- 
 ment, which was a serious disadvantage 
 when attempting to hand -mix the fibers In 
 conventional mixers, has been virtually 
 eliminated by the prebagged mixes. The 
 use of fibers with larger diameter (or 
 equivalent diameter in the case of non- 
 round fibers) and shorter lengths has 
 reduced the problem even more. These 
 factors and the recent trend toward fiber 
 deformation (kinking, end enlargement, 
 corrugating, etc.) have reduced the prob- 
 lem to an insignificant level. 
 
 Aggregate size fraction distribution is 
 critically important in wet-mix gunites 
 that employ silica fume. 
 
 Recommendations 
 
 Strong static discharges were observed 
 along the gunite delivery hose during the 
 application of two dry-mix products. The 
 static discharges may be capable of ig- 
 niting methane concentrations or of deto- 
 nating blasting caps under ideal condi- 
 tions. Better static discharge grounding 
 
 or bleed-off is recommended for dry-mix 
 gunite delivery hose systems if used in 
 deep mine return airways and nonventi- 
 lated areas. 
 
 A nozzleman training and certification 
 program would be of considerable benefit 
 to the gunite industry and would help 
 standardize the quality of the gunned 
 material. 
 
 The flexural toughness index parameter 
 needs professional attention by the gun- 
 ite industry to resolve the issues re- 
 garding the influence of fiber length and 
 first-crack strength on the index value. 
 The engineering parameter would be useful 
 in preparing specifications as well as 
 in product quality control and strength 
 testing. 
 
 A gunite product-by-product standard 
 strength factor may be beneficial. The 
 factor could be prepared by obtain- 
 ing flexural strength or toughness in- 
 dex values from samples of material that 
 had been precisely mixed, poured into a 
 sized mold, vibration-compacted, cured to 
 specification, and tested using a stan- 
 dard procedure. The standard strength 
 factor would represent a target strength 
 for the gunning crew. Deviations from 
 the standard strength factor would repre- 
 sent the gun crew contribution to the 
 product strength. The gunite products 
 could be classified according to achiev- 
 able strength, making product selection 
 by the user less difficult when the mate- 
 rial was needed for a particular purpose, 
 
 Gunite application with a gun operated 
 on compressed air in an underground mine 
 is too loud to permit efficient verbal 
 communication between the gun and nozzle 
 operators. Low-rebound, high-quality ap- 
 plication can only be accomplished wherv 
 good communication is available — espe- 
 cially when the nozzle operator is mov- 
 ing from roof to rib. An MSHA-approved , 
 voice-activated headset is highly recom- 
 mended for use in mining gunite work. 
 
 Even the wet-mix equipment used in this 
 investigation with its sophisticated 
 nozzle-operator remote control system 
 
55 
 
 could have benefited from the use of a 
 communication system. 
 
 Careful observation of the operating 
 dry -mix nozzles in the mine revealed that 
 unless the nozzle end was held vertical 
 (in roof shooting) blockage occurred on 
 the tilted lower side, forming a roll of 
 wet gunite that converged inward on the 
 moving stream and then began pouring off 
 
 onto the floor to become waste. Nozzle 
 improvements , using a conical stream of 
 air around the periphery of the orifice, 
 may redirect the waste roll back into the 
 main stream of material. The design sug- 
 gested may require an additional hose and 
 fitting for high-pressure air but would 
 be beneficial, especially from a cost 
 standpoint. 
 
 REFEBIENCES 
 
 1. American Concrete Institute. ACI 
 Manual of Concrete Practice — 1980. Part 
 V. Recommended Practice for Shotcreting 
 (ACI 506-66). 1980, pp. 506-1 to 506-19. 
 
 2. American Concrete Institute Com- 
 mitte 506. State-of-the-Art Report on 
 Fiber Reinforced Concrete. Dec. 3, 1982, 
 pp. 1-43. 
 
 3. Lankard, D. R. An Overview of 
 Steel Fiber Reinforced Concrete (SFRC). 
 Paper 1, Steel Fiber Reinforced Con- 
 crete - A Review of the State-of-the-Art. 
 Batelle Development Corp., May 1982, 
 pp. 1-19. 
 
 4. Poad, M. E,, M. 0. Serbousek, and 
 J. Goris. Engineering Properties of 
 Fiber-Reinforced and Polymer-Impregnated 
 Shotcrete. BuMines RI 8001, 1975, 25 pp. 
 
 5. American Concrete Institute. 
 State-of-the-Art Report on Fiber Rein- 
 forced Concrete reported by ACI Commit- 
 tee 544. ACI Pub. 544.1R-82, May 1982, 
 pp. 9-29. 
 
 6. Prestressed Concrete Institute 
 Journal. Prestressed Concrete Institute 
 on Glass Fiber Reinforced Concrete Pan- 
 els. Recommended Practice for Glass Fi- 
 ber Reinforced Panels. V. 26, No. 1, 
 Jan. -Feb. 1981, pp. 1-33. 
 
 7. Woods, H. Corrosion of Embedded 
 Materials Other Than Reinforcing Steel. 
 Concrete and Concrete-Making Materi- 
 als. ASTM Spec. Tech. Pub. 169-A, 19 
 pp. 230-238. 
 
 8. Roller, A. Fiber Reinforced Con- 
 crete. Construction Specifier J., v. 35, 
 Dec. 1982, pp. 44-55. 
 
 9. Grutzcek, M. W. , S. Atkinson, and 
 D. M. Ray. Mechanism of Hydration of 
 Condensed Silica Fume in Calcium Hydrox- 
 ide Solutions. Fly Ash, Silica Fume, 
 Slag and Other Mineral By-Products in 
 Concrete, Am. Concrete Inst. SP-79, 
 1983, pp. 643-664. 
 
 10. Bernhardt, C. J. SiO Fume as Ce- 
 ment Addition. Betongen IDAG J, (Nor- 
 way), v. 17, Apr, 1952, pp, 29-53. 
 
 11. Jahren, P. Use of Silica Fume 
 in Concrete. Fly Ash, Silica Fume, Slag 
 and Other Mineral By-Products in Con- 
 crete. Am, Concrete Inst, Pub, SP-79, 
 1983, pp, 625-643, 
 
 12. Regourd, M, , B, Mortureux, P, C, 
 Aitcin, and P. Pinsonneault, Microstruc- 
 ture of Field Concretes Containing Silica 
 Fume. Paper in Proceedings of the 4th 
 International Conference on Cement Micro- 
 scopy, March 28-April 1, 1982, Las Vegas, 
 Nevada, ed, by G, R, Gouda, Int. Cement 
 Microscopy Assoc, Duncanville, TX, 1982, 
 pp. 1-12. 
 
 13. Fesil Silica. Tech. Bull., (Oslo, 
 Norway). A. S. Fesil & Co. June 1980, 
 1 p. 
 
 14. Cement and Concrete Association 
 Journal, A Report of a Joint Working 
 Party of the Cement Admixture Association 
 and the Cement and Concrete Association, 
 
56 
 
 Superplasticizlng Admixtures in Concrete. 
 1976, pp. 1-33. 
 
 15. Malhotra, V. M. Superplasticiz- 
 ers: Their Effect On Fresh and Hardened 
 Concrete. Concrete Int. J, v. 3, No. 5, 
 May 1981, pp. 66-81. 
 
 16. Concrete Construction Journal. 
 How Super Are Superplasticizers? V. 27, 
 May 1982, pp. 409-415. 
 
 17. Travis, R. B. Classification of 
 Rocks. Q, CO Sch. Mines, v. 50, No. 1, 
 Jan. 1955, p. 17. 
 
 18. Price, W. H. Concrete Aggre- 
 gates — Grading and Surface Area. Ch. in 
 Concrete and Concrete-Making Materials. 
 ASTM Spec. Tech. Publ. 169-A, 1966, 
 pp. 404-413. 
 
 19. Henager, C. H. The Technology and 
 Uses of Fiberous Shotcrete — A State-of- 
 the-Art Report. Battelle Development 
 Corp., 1977, pp. 1-59. 
 
 20. Ryan, T. F. Gunite, A Handbook 
 for Engineers. Cement and Concrete As- 
 soc, London, 1973, pp. 1-61. 
 
 21. Hendricks, R. S. Shotcrete Gives 
 Stronger Support at Lower Cost. Min. 
 Eng., V. 22, May 1970, pp. 69-73. 
 
 22. Breslin, J. A., and G. E. Niewia- 
 domski. Improving Dust Control Technol- 
 ogy for U.S. Mines. The Bureau of Mines 
 Respirable Dust Research Program 1969-82. 
 BuMines Impact Rept., 1982, 40 pp. 
 
 23. U.S. Code of Federal Regulations. 
 Title 30 — Mandatory Health Standards — 
 Underground Coal Mines, Subchapter 0, 
 Subpart B; Part 70 — Respirable Dust Stan- 
 dard When Quartz Is Present; Jan. 1980, 
 p. 423. 
 
 24. 
 
 Title 30 — Regulations and 
 
 Standards Applicable to Metal and Nonmet- 
 al Mining and Milling Operations. Sub- 
 chapter N; Part 57 — Air Quality, Ventila- 
 tion Radiation and Physical Agents; Jan. 
 1980, p. 124. 
 
 25. Liebhafsky, H. A., H. G. Pfeiffer, 
 E. H. Wins low, and P. D. Zemay. X-Ray 
 Absorption and Emission in Analytical 
 Chemistry, Wiley, 1960, 357 pp. 
 
 26. Malhotra, V. M. Contract Strength 
 Requirements — Cores Versus In-Situ Evalu- 
 ation. Am. Concrete Inst. J., Title 74- 
 16, Apr. 1977, p. 167. 
 
 27. American Society for Testing and 
 Materials. Standard Test Method for Com- 
 pressive Strength of Cylindrical Concrete 
 Specimens. C 39-72 in 1977 Annual Book 
 of ASTM Standards. Part 14: Concrete 
 and Mineral Aggregates ; Manual of Con- 
 crete Testing. Philadelphia, PA, 1977, 
 pp. 25-28. 
 
 28. Gonnerman, H. F. Effect of End 
 Condition of Cylinder on Compressive 
 Strength of Concrete. Proc. ASTM, v. 24, 
 pt 2, 1924, pp. 1036-1065. 
 
 29. American Concrete Institute Com- 
 mittee 544. Measurement of Properties 
 of Fiber Reinforced Concrete. Am. Con- 
 crete Inst. J., Title 75-30, July 1978, 
 pp. 283-289. 
 
 30. Ramakrishnan, V., W. V. Coyle, 
 L. J. Fowler, and E. K. Schrader. A Com- 
 parative Evaluation of Fiber Shotcretes. 
 Civil Eng. Dep. SD Sch. Mines and Tech- 
 nol. Rep. SDSM&T-CBS 7902, Aug. 1979, 
 p. 10. 
 
 31. Lankard, D. R. The Engineering 
 Properties of Steel Fiber Reinforced Con- 
 crete. Paper 2. Steel Fiber Reinforced 
 Concrete - A Review of the State-of-the- 
 Art. Batelle Development Corp., May 
 1982, pp. 1-31. 
 
 32. Perry, J. H. , C. H. Chilton, S. D. 
 Kirkpatrick, and D. Sidney. Chemical En- 
 gineers Handbook. McGraw-Hill, 4th ed., 
 1963, pp. 3-201. 
 
 33. Amyx, J. W. , D. M. Bass, Jr., and 
 R. L. Whiting. Petroleum Reservoir Engi- 
 neering - Physical Properties. McGraw- 
 Hill, 1960, pp. 64-129. 
 
57 
 
 34. Monlcard, R. P. Properties of 
 Reservoir Rocks; Core Analysis. Gulf 
 Publ. Co., 1980, pp. 43-84. 
 
 35. Litchfield, E, L. , T. A. Kuba- 
 la, T. Schellinger, F. J. Perzak, and 
 D. Burgess. Practical Ignition Problems 
 Related to Intrinsic Safety in Mine 
 Equipment. Four Short-Term Studies. Bu- 
 Mines RI 8464, 1980, p. 4. 
 
 36. Prugh, R. W. , and K. G. Rucker. 
 Static Electricity Hazards in the Pneu- 
 matic Loading of Blasting Agents. Paper 
 in Proceedings 5th Symposium on Rock 
 Mechanics (Univ. MN, May 1962), ed. by 
 C. Fairhurst. Pergamon, 1963, pp. 419- 
 438. 
 

 
 
 PQ 
 
 
 
 
 
 
 
 
 
 Xi 
 
 1-1 
 
 
 
 
 CO d 
 o 
 
 
 
 (0 
 
 
 
 
 
 
 
 
 
 
 
 CO 1-1 
 
 
 
 r-< 
 
 ■< t-~ <! -* CM 
 
 o> 
 
 00 vO CM VO 
 
 o 
 
 
 
 
 CO u 
 
 
 w 
 
 3 
 
 Z ro a - 
 
 "1 cs 
 
 -* 
 
 .-H ,-H CO ^H 
 
 o 
 
 
 
 • 
 
 T-t 
 
 
 tj 
 
 S 
 
 
 
 
 ii> 
 
 
 
 CO 
 
 
 
 4.1 
 
 ^-^ CO 
 
 
 a 
 
 P 
 
 
 
 
 
 
 
 •o 
 
 
 
 CJ 
 
 d d 
 
 O CO 
 
 
 •* 
 
 Pt, 
 
 
 
 
 
 
 
 c 
 
 
 
 
 •rl U 
 
 
 •a 
 
 
 
 
 
 
 
 
 CO 
 
 
 
 o 
 
 u u 
 
 
 
 
 
 
 
 
 
 
 d 
 
 <: 
 
 
 
 
 
 
 
 
 
 
 CM 
 
 CO 1 
 
 
 3 
 
 
 
 
 
 
 
 
 
 
 
 
 u u 
 
 
 O 
 
 Cfl 
 
 <! vo < -<r — t 
 
 CO 
 
 00 m CM VD 
 
 CO 
 
 
 
 ^ 
 
 •H tu 
 
 
 XI 
 
 i-H 
 
 !S CO Z - 
 
 -t CNJ 
 
 -* 
 
 .-1 .-I CO — 1 
 
 "O 
 
 
 
 o 
 
 r-l t4H 
 
 
 1J 
 
 3 
 
 
 
 
 113 
 
 
 
 •H 
 
 
 
 CO 
 
 CX 14H 
 
 
 pi 
 
 g 
 
 in ro 
 en ■-I 
 
 
 
 
 r-t 
 
 o 
 
 
 
 O 
 
 CX 3 
 CO ,Q 
 
 
 
 O 
 
 
 J- 
 
 
 
 
 
 CO 
 
 
 
 Ot 
 
 
 
 
 fc 
 
 
 
 
 
 
 
 f\ 
 
 
 
 CO 
 
 CO (U 
 4-1 . ^ 
 •H CO 4J 
 
 
 -o 
 
 
 
 
 
 
 
 
 
 
 
 
 c 
 
 XI 
 
 <! o < o O 
 
 o 
 
 o o o o 
 
 
 
 
 >s 
 
 CO 
 
 
 3 
 
 1-1 
 
 Z in z in m 
 
 0^ 
 
 O O 00 CM 
 
 o 
 
 
 
 S 
 
 d <u d 
 
 
 o 
 
 
 in o c» 
 
 O 
 
 m c^ 00 o 
 
 o 
 
 
 
 6 
 
 •H r-l •H 
 
 
 ,i2 
 
 #> 
 
 
 ». 
 
 #s 
 
 #> 
 
 
 ^ ^ » ^ 
 
 1^ 
 
 
 
 
 bO 
 
 
 01 
 
 4-1 
 
 fO -H 
 
 .-H 
 
 r-H f— 4 1-H f— t 
 
 ■s 
 
 
 
 *> 
 
 T5 d 
 
 
 « 
 
 S 
 
 
 
 
 
 
 
 CO 
 
 
 
 u 
 
 CU •H -O 
 
 CO d (U 
 
 
 
 
 
 
 
 
 
 
 
 
 
 < r~ < <r 00 
 
 in 
 
 o -* in 00 
 
 CO 
 
 
 
 o 
 
 3 CO W 
 
 
 
 m 
 
 Z ^ Z ^O 00 
 
 vO 
 
 — 1 0^ CO vO 
 
 c 
 
 
 
 <4H 
 
 (U u 
 
 
 
 Xi 
 
 r^ in CM 
 
 ^H 
 
 00 -H <t -* 
 
 1-1 
 
 
 
 0) 
 
 >i B <u 
 
 
 
 r-t 
 
 
 
 
 
 
 •■ 
 
 CO 
 
 
 
 IH 
 
 r-l r-l 
 
 
 4-) 
 
 
 
 
 
 
 
 ^H 
 
 4-1 
 
 
 
 <u 
 
 rH - rH 
 
 
 O 
 
 
 
 
 
 
 
 
 c 
 
 
 
 ^ 
 
 CO CU O 
 
 
 
 
 
 
 
 
 
 
 X! 
 
 
 < o < — 1 en 
 
 o 
 
 00 <3" 00 ^ 
 
 o 
 
 
 
 *J 
 
 U O 
 
 
 CO 
 
 
 Z 00 Z C3N m 
 ^ 00 <r 
 
 m 
 
 O 00 <5^ <d- 
 
 o <■ m vD 
 
 o 
 
 
 
 #> 
 
 u o 
 
 O 14H 4-1 
 
 
 p 
 
 
 
 ». 
 
 
 LO 
 
 
 ^ fK 
 
 •a 
 
 
 
 •T3 
 
 d tu o 
 
 
 (U 
 
 CvJ 
 
 t-H 
 
 
 
 <-t rH 
 
 C 
 
 
 
 d 
 
 u d 
 
 
 4-1 
 
 XI 
 
 1 
 
 
 
 
 
 
 CO 
 
 
 
 s 
 
 4J OJ 
 
 
 cfl 
 
 1-t 
 
 m 
 
 
 
 
 
 
 
 
 o 
 
 o ,d CO 
 
 
 3 
 
 
 ^ 
 
 
 
 
 
 X3 
 
 1-1 
 
 
 
 XI 
 0) 
 
 d w rt 
 v.^ 3 
 
 
 
 
 
 « 
 
 
 
 
 
 
 
 
 p 
 
 •* 
 
 
 
 
 t-H 
 
 
 
 
 
 O 
 
 
 
 
 (u -a 
 
 
 
 
 
 
 
 
 
 
 O 
 
 
 
 <u 
 
 *j iH d 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 <1 0\ vO 00 v£) 
 
 in 
 
 O 00 -* CM 
 
 O 
 
 
 
 3 
 
 d CO 3 
 
 
 u 
 
 >> 
 
 >— ' 
 
 Z fO CO 00 CJ> 
 
 in 
 
 r-. CT\ -* vO 
 
 
 
 
 u 
 
 tu o 
 
 
 2 
 
 PQ 
 
 4-1 
 
 
 • ■ 
 
 • • 
 
 • 
 
 
 • • • • 
 
 <r 
 
 
 
 H 
 
 S 00 x> 
 
 
 CO 
 
 
 s 
 
 CM ^ 
 
 
 CM CO ^ rt 
 
 
 
 
 
 p. (U 
 iH CU pi 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 < 00 O 00 -< 
 
 vO 
 
 00 ON CO vO 
 
 CO 
 
 
 
 • 
 
 3 rH 
 
 
 ro 
 
 
 <-H 
 
 Z CM m in CO 
 
 r-~ 
 
 t^ O vD r-- 
 
 x: 
 
 • 
 
 
 4-1 
 
 cr cu 
 
 
 T3 
 
 >. 
 
 1-1 
 
 
 • • 
 
 
 • 
 
 
 • • ■ • 
 
 bO 
 
 O 
 
 
 o 
 
 0) B 
 
 
 >-l 
 
 m 
 
 o 
 
 CO CM ^ 
 
 
 CM ~a- ^ -H 
 
 •H 
 
 -* 
 
 
 Cl- 
 
 CO u 
 
 < 
 
 
 
 > 
 
 
 
 
 
 
 
 0) 
 
 
 
 
 CJ tn . o 
 
 H 
 
 
 
 
 
 
 
 
 
 
 3 
 
 o 
 
 
 in 
 
 •H to 4-1 
 
 
 
 
 
 
 
 
 
 
 < 
 
 m 
 
 
 
 <C 
 
 CO CO 
 
 
 CO CO ■* vt 
 
 
 
 
 
 4-1 iH d o 
 
 a 
 
 •a 
 
 
 
 z 
 
 -*- 
 
 ^ "^^ 
 
 
 •^ 
 
 ^ *^^ ^^ ^^ 
 
 tr) 
 
 14H 
 
 
 o • 
 
 to O C5 tu 
 
 
 >^ 
 
 
 •—* 
 
 
 OJ CSJ 
 
 
 CM CM -H ^ 
 
 -d 
 
 O 
 
 
 4J XI 
 
 S >4H -rl CO 
 
 o 
 
 
 >. 
 
 4-1 
 
 
 1 
 
 1 
 
 
 1 
 
 1 1 1 
 
 >% 
 
 
 
 r-^ 
 
 3 4J 
 
 ^ 
 
 M 
 
 m 
 
 S 
 
 -* -* — 1 ^ 
 
 -* 
 
 .— » i—i ^Si \0 
 
 
 O 
 
 
 CO 
 
 tu to CO d 
 
 s 
 
 (U 
 
 
 
 1^ t^ \0 vO 
 
 i-~ 
 
 vo ^o ^r -* 
 
 t-H 
 
 •H 
 
 
 o 
 
 d 4J CJ o 
 
 o 
 
 a 
 
 
 
 
 
 
 
 
 
 CO 
 
 4-1 
 CO 
 
 4-1 
 
 ^- 
 
 a. to •H ti 
 
 pa 
 
 
 
 
 
 
 
 
 
 T3 rH 4J 
 
 g 
 
 to 
 
 
 ■-H 
 
 
 
 
 
 
 
 
 u 
 
 O 
 
 U 
 
 x: a CO 
 
 bO 
 
 >. 
 
 1-1 
 
 ■< -* ■-* m in 
 
 <r 
 
 m m -H -H 
 
 « 
 
 
 x: 
 
 3 <U 
 
 4-1 Tj a. p 
 
 
 CO 
 
 [33 
 
 o 
 
 Z in in ~* -* 
 
 in 
 
 ^ >*<*-* 
 
 ^ 
 
 ^-\ 
 
 CO 
 
 O D. -H d CO 4-1 
 
 w 
 
 fO 
 
 
 > 
 
 
 
 
 
 
 
 to 
 
 u 
 
 
 rH 
 
 3 3 CO 
 
 H 
 
 
 
 
 
 
 
 
 
 
 CO 
 
 x: 
 
 T3 
 
 rH 
 
 o bo d 
 
 
 
 
 
 
 
 
 
 M 
 
 
 
 o o u <f <r 
 
 CM 
 
 r^ r~. t~~ r^ 
 
 (0 
 
 bO 
 
 U 
 
 tu to 
 
 ,Q d o 
 
 a 
 
 4-1 
 
 
 o^ O U vD o 
 
 r^ 
 
 O o -H ^ 
 
 
 •H 
 
 CO 
 
 ,a bOT3 (U -H S 
 
 & 
 
 C P 
 
 * 
 
 OO 0^ /-N 00 00 
 
 C3^ 
 
 0^ ^ ^\ ^ 
 
 : 
 
 CU 
 
 >. 
 
 
 tu Pi d tu 
 
 o 
 
 a; 0) 
 
 CO ^ 
 
 A 1 
 
 4-1 
 
 
 
 
 
 4J 
 
 S 
 
 
 o in 
 
 •H d T3 
 
 1 
 
 e a 
 
 -a r-l 
 
 O CO 
 
 
 
 
 
 x: 
 
 
 U 
 
 4-1 • 
 
 a • M tu 
 
 1 
 
 cS 
 
 >> 
 
 m oj 
 
 
 
 
 
 bO 
 
 >^-rl 
 
 f-~i 
 
 • 
 
 
 00 
 
 
 
 
 
 •H 
 
 Xi 
 
 X3 
 
 13 
 
 ex d x: 
 
 <! 
 
 
 
 
 
 
 
 
 
 (U 
 
 
 3 
 
 tu 14H 
 
 to O tu 4J 
 
 
 
 
 
 
 
 
 
 
 >. 
 
 
 
 
 
 
 
 
 3 
 
 
 O 
 
 4J O 
 
 •rl 4J 
 
 X 
 
 n 
 
 
 
 
 
 
 
 
 
 4-1 
 
 
 CO 
 
 CO 4-1 CO (X 
 
 M 
 
 T3 0) 
 
 f 
 
 < o o o o 
 
 O 
 
 o o o o 
 
 >. 
 
 d 
 
 p 
 
 a 0) 
 
 CO CO IH 3 
 
 Q 
 
 4-1 
 
 4J 
 
 Z in in o <:»■ 
 
 in 
 
 O >* vO vD 
 
 M 
 
 (1) 
 
 <u 
 
 •rl 4J 
 
 3 CJ CO 
 
 § 
 
 r-4 -H 
 
 O XI 
 
 00 en o\ in 
 
 o 
 
 m o CO r~ 
 
 
 B 
 
 o. 
 
 4J CO 
 
 •H & 
 
 u 
 
 CO C 
 
 x: --1 
 
 
 *. as 
 
 •> *s 
 
 
 
 - - - 
 
 
 tU 
 
 
 CO IH 
 
 00 rH tu 0) 
 
 0^ 
 
 4-> 3 
 
 CO 
 
 00 ^ vO CO 
 
 CM 
 
 r- -H in in 
 
 
 o 
 
 M 
 
 CU 
 
 CX t» IH 
 
 Pi 
 
 O bO 
 
 
 
 
 
 
 
 r-H 
 
 • 
 
 1 
 
 (U 
 
 73 
 
 (U CX CO 
 
 ■3 
 
 H 
 
 
 
 
 
 
 
 
 bO 
 
 to 
 
 (H 
 (L) 
 
 4J 
 
 <» tu 
 
 rH to CM 3 
 
 CX cr 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 ► /^N 
 
 
 • ^^ • 
 
 ^^ • 
 
 /->. 
 
 ^^ • • /'^ 
 
 XI 
 
 4-1 
 
 3 
 
 d 
 
 B rH bo to 
 
 
 T3 
 
 
 
 > CO 
 
 
 • en • 
 
 CO • 
 
 CO 
 
 CO • • CO 
 
 
 J? 
 
 
 0) a; 
 
 CO CU d 
 
 
 C 
 
 
 
 c 
 
 
 • c • 
 
 e • 
 
 C 
 
 C • • C! 
 
 c 
 
 3 
 
 X2 
 
 ^ 1 
 
 C« 3 iH O 
 
 
 CO ' 
 
 
 
 0) 
 
 
 . (U . 
 
 OJ • 
 
 (U 
 
 (U . . 0) 
 
 o 
 
 
 rH 
 
 3 B 
 
 O M 4-1 
 
 
 CO 
 
 
 
 
 
 
 • B • 
 
 e • 
 
 B M S • • S 
 
 
 (U 
 
 
 bO O 
 
 U 3 
 
 
 C CO 
 
 CO 
 
 
 •H 
 
 
 • T-t • 
 
 n-l • 
 
 •H tt) • t-l • • -H 
 
 c 
 
 boo 
 
 •rl O 
 
 . 4J -TJ 4J 
 
 
 CU O 
 
 60 
 
 
 y 
 
 > ^v U /-s 
 
 O -^ 
 
 O 14-100 U • • O 
 
 
 to 
 
 O 
 
 14H 0) 
 
 CO o 
 
 
 S iH 
 
 CO 
 
 
 OJ 
 
 • C (U c 
 
 0) C 
 
 tU M-l ^-\ 0) • • OJ 
 
 • o 
 
 U 
 
 CO 
 
 IH 
 
 4J to -o .c 
 
 
 •H 
 
 XI 
 
 
 a 
 
 • 3 O- 3 
 
 O. 3 
 
 o< 3 OJ a. • • D, 
 
 0) x: 
 
 0) 
 
 
 to 
 
 d T3 OJ to 
 
 
 O C 
 
 
 
 CO 
 
 • bO CO bO 
 
 CO bO 
 
 CO .a C CO • 'CO 
 
 iH CO 
 
 > 
 
 bO -H CO 
 
 to d w 
 
 
 <U 3 
 
 
 
 *v-^ 
 
 » — / ^-/ s»^ 
 
 ^— / N--/ 
 
 ^^ N—' O ^-^ • • ^ 
 
 X3 
 
 10 
 
 d 
 
 ,d r 
 
 rH tu CJ to 
 
 
 O, 00 
 
 
 
 
 
 
 
 
 
 N • • 
 
 CO 4-1 
 
 
 •H 
 
 4J U 
 
 CO 1 tu CO 
 
 
 CO 
 
 
 < CO O C3^ CO CM 
 
 CO vO 
 
 — 1 r^ CO < < CO 
 
 r-l d 
 
 d 
 
 B 
 
 a) 
 
 tu a rH 3 
 
 
 
 
 Z 
 
 
 
 
 —1 Z Z 
 
 •H 0) 
 
 CO 
 
 3 
 
 - u 
 
 CO O rH 
 
 
 
 
 
 
 
 
 
 
 CO 4J 
 
 > d 
 
 
 CO 
 CO 
 
 4J 3 
 CO 4J 
 
 CJ o 
 
 -a <u CJ HI 
 
 
 
 . 
 
 
 
 
 
 
 
 4-1 
 
 
 rH (U 
 
 4J 
 
 o o o o 
 
 O 
 
 o o o o 
 
 to o 
 
 CO 
 
 to 
 
 3 O 
 
 d) u d 
 
 
 Cd 4-1 
 
 J= 
 
 o in 00 -* 
 
 o 
 
 o <r vo o 
 
 o 
 
 
 
 "O to 
 
 M CO O 
 
 
 4-1 •!-( 
 
 bOXi 
 
 O CO vO 00 
 
 o- 
 
 P~ O CO o 
 
 u 
 
 •o 
 
 •a 
 
 14H 
 
 OJ (H U N 
 
 
 O C 
 
 •H .-1 
 
 
 *« •. 
 
 n » 
 
 •> 
 
 
 - ' ►: 
 
 O 0) 
 
 (U 
 
 <u 
 
 d 3 
 
 Xi 0) CO 
 
 
 ^ a 
 
 <U 
 
 <y\ — 1 r^ CO 
 
 CM 
 
 00 -H in vol 
 
 z e 
 
 4-1 
 
 4J 
 
 a| 
 
 •rl p T3 d 
 
 
 s 
 
 
 
 
 
 
 f—t 
 
 3 
 
 to 
 
 to 
 
 HH 3 O 
 
 
 
 
 
 
 
 
 
 
 rH 
 
 y~^ 
 
 ,-H 
 
 
 •u -a •H 
 
 tu CJ d 4-1 
 
 
 ». 
 
 
 
 
 
 
 
 
 < o 
 
 3 
 
 3 
 
 x: 
 
 
 u 
 
 
 
 
 
 
 
 
 z > 
 
 o 
 
 O 
 
 bO bO 
 
 M CO 3 -H 
 
 
 box: 
 
 
 
 
 
 
 
 
 
 r-l 
 
 rH 
 
 •H d 
 
 CO MH O CO 
 
 
 CO M 
 
 XI 
 
 < O O O O 
 
 O 
 
 o o o Ol 
 
 CU 
 
 to 
 
 CO 
 
 X! -rl 
 
 3 .fi d 
 
 
 m -H 
 
 i-i 
 
 Z m in vo vD 
 
 in 
 
 vO vD 00 OOl 
 
 X! 
 
 o 
 
 O 
 
 to 
 
 00 d 0) CO 
 
 
 0) 
 
 
 
 
 
 
 
 
 • 4-1 
 
 
 
 >^ 3 
 
 eg (H p 
 
 TJ g 4J 
 
 
 3 
 
 
 
 
 
 
 
 
 1-1 
 
 tu 
 
 (U 
 
 r-l 
 
 
 
 
 
 
 
 
 
 
 CO CO 
 
 Vj 
 
 u 
 
 (U T3 
 
 d -d 1 
 
 
 
 
 
 
 
 
 
 
 
 to 
 
 4J 
 
 < o r^ 00 <a- 
 
 00 
 
 in ~a- r~ in 
 
 •H 0) 
 
 ^ 
 
 ^ 
 
 B <U 
 
 CO CO M 
 
 
 bO 
 
 O 
 
 Z 00 CM CM vO 
 
 <r 
 
 -* 00 vo r^ 
 
 4J N 
 
 3 
 
 3 
 
 (U 4J 
 
 . j3 a) 
 
 
 (0 
 
 x: 
 
 .-H ^H 
 
 
 ^H .-H 
 
 d -H 
 
 
 
 u to 
 
 m iH i4H 
 
 
 PQ 
 
 CO 
 
 
 
 
 
 
 
 (U r-l 
 
 to 
 tu 
 
 CO 
 
 tu 
 
 4-1 r-l 
 
 X 3 
 
 0) O 14H 
 
 CO P rH 3 
 
 
 
 
 
 
 
 
 
 
 
 1 
 
 » 
 
 
 
 
 
 
 
 •H 4J 
 
 iH 
 
 •H 
 
 tu CJ 
 
 4J 3 .43 
 
 
 U CO 
 
 C C 
 
 
 
 
 
 
 
 MH 3 
 
 4-1 
 
 4J 
 
 rH 
 
 CJ *J -d 
 
 
 o u 
 
 O -H 
 
 < CO O O 00 
 
 o 
 
 in o CM] 
 
 d 
 
 •H 
 
 •H 
 
 (U to 
 
 3 O d 0) 
 
 
 Xi 3 
 
 •H 
 
 Z oc 
 
 vO r~ 
 
 CO 
 
 -* 
 
 m 1 in in| 
 
 O : 
 
 4J 
 
 4-1 
 
 X! CJ 
 
 •d CO to 'd 
 
 
 en -O 
 
 4J 
 
 
 
 
 
 
 
 O (U 
 
 d 
 to 
 
 d 
 to 
 
 4J 
 
 to 
 
 O <4H •H 
 
 
 
 
 /— «^ 
 
 
 
 
 • 
 
 
 i • • • 
 
 M 3 CJN 3 
 
 
 
 
 X 
 
 
 
 
 
 
 » • • • 
 
 >> 3 
 
 3 
 
 3 
 
 O CO 
 
 a d 1 
 
 
 
 
 •H 
 
 
 
 
 
 
 . .t~v • 
 
 d 1-1 
 
 cr 
 
 ir 
 
 4-1 3 
 
 S CO -u 
 
 (U B <U <4H 
 
 
 (U 
 
 
 f 
 
 
 
 
 
 
 • • .--nC-^ 
 
 CO O 
 
 
 
 
 
 r-l 
 
 
 
 
 
 
 
 « • H-l /-N 
 
 (X > 
 
 M 
 
 M 
 
 bO u 
 
 T-i r-i 1 
 
 
 a. 
 
 
 4-1 
 
 
 
 
 
 
 • O X3 
 
 B 
 
 tu 
 
 tu 
 
 d <u 
 
 CX >, cxo 
 
 
 e 
 
 
 OJ 
 
 
 
 
 
 
 • -H 
 
 o >^ • 
 
 4J 
 
 u 
 
 •H 4-1 
 
 ^ e rH 
 
 
 CO 
 
 
 3 
 
 
 
 
 
 
 • u u 
 
 O PQ U 
 
 CO 
 
 CO 
 
 is 
 
 cO CO ^ • 
 
 
 !/) 
 
 
 
 
 
 
 
 
 
 : tU 
 
 :s 
 
 s 
 
 en 4-1 w <! (U 
 
 
 
 
 
 
 
 
 
 t^ 
 
 r^ 
 
 <~i 4-lcsJ no Jt- LD LD COt^ CO C 
 
 
 
 
 CO -^ 
 
 in vc 
 
 l-~ 
 
 00 
 
 <y 
 
 cr. o O 
 
 O CO 
 
 
 
 
 0) o 
 
 
 
 
 
 
 
 
 
 
 
 
 ^H ^H 
 
 U 3 
 
 
 
 
 4-1 N 
 
59 
 
 < 
 
 I 
 
 H 
 Q 
 
 W 
 
 M 
 
 <! 
 I 
 I 
 
 • 
 
 pa 
 
 X 
 
 H 
 Q 
 Z 
 Cd 
 
 o 
 o 
 
 y-i bO 
 
 •H @ 
 
 u 
 -a • 
 
 3 w 
 
 C 
 
 CO 0) 
 
 •H 
 
 ^ 
 CO 
 
 4-1 ^^ 
 03 
 
 3 m 
 
 13 U 
 0) 
 
 iH iH 
 
 to & 
 
 u a 
 o rt 
 
 > 
 H CO 
 
 o -u 
 
 H 05 
 
 a 
 
 o ex 
 ^§ 
 
 4-1 0) 
 03 
 
 3 4J 
 
 T3 M-l 
 
 0) K 
 
 CO S 
 
 M O 
 
 •H T3 
 
 03 C^l 
 
 oi >, 
 
 J3 
 
 bO 
 >. 
 
 ■C CO 
 (U M 
 U 0) 
 
 O rH 
 
 (U o, 
 
 r-l B 
 
 i-H CO 
 
 o 0) 
 o 
 
 4J 
 
 4-1 y-i 
 
 03 -H 
 S M 
 t3 73 
 
 CO O 
 
 4J ta 
 o 
 
 H 
 
 CO M 
 <U 4-> JS 
 
 '4-1 
 CO 
 W3 
 
 bO 
 
 en v£> CO 
 in r-. cvi 
 vO vo O 
 
 o 00 00 
 r^ r^ o 
 r- r^ o 
 
 • • • 
 o o 
 
 O r-- r-. 
 o^ <n o 
 r^ r^ o 
 
 <3 O < 
 Z Z Z 
 
 Z Z Z 
 
 <3 < <j 
 Z Z Z 
 
 CO ro O 
 00 \i3 c^) 
 lO uo O 
 
 ■< <; << 
 Z Z Z 
 
 <3 <d < 
 Z Z Z 
 
 u~l \D --1 
 CM CO — < 
 O O O 
 
 <r CM o 
 
 vo r^ ON 
 
 • • • 
 
 <r CO I 
 
 CO cfl CO 
 
 z z z 
 
 O CM CM 
 
 <r «;j- o 
 00 00 o 
 
 CT\ r-~ 00 
 
 CO UO --I 
 
 I— I .— * o 
 
 ^ CM 0^ 
 CO vO vO 
 
 -* CO o 
 
 r~. -si- CO 
 O o o 
 t-^ p-~ o 
 
 vO vD O 
 ^^ 00 CO 
 CO CM O 
 
 1—1 CM —I 
 CM CM O 
 -* <t O 
 
 <r ■<}• 
 
 CM 00 -a- 
 
 CO --I -H 
 CM CM O 
 
 CO 00 m 
 
 CO CO O 
 
 r^ r^ o 
 
 CO CO CO 
 
 z z z 
 
 r^ m CM 
 >* ~* O 
 ^ -vl- O 
 
 00 in CO 
 
 CJ> 0^ O 
 
 r^ r^ o 
 
 -vT -4- o 
 ~a- r«- CO 
 
 ■<f -* O 
 
 O vD -^f 
 ■* CO o 
 
 CT^ r-- CM 
 
 o o o 
 
 -3- >:f O 
 
 -J- CM CM 
 
 r^ .-H v£> 
 
 .-H ^H O 
 
 <t -^ 
 
 vO CM sD 
 Cvl CO O 
 \0 \D O 
 
 O ->J- v£) 
 vO CO cs) 
 vD VD O 
 
 CO CO CO 
 
 z z z 
 
 r--. .-I vO 
 
 vO vO O 
 
 in in o 
 
 ON 00 ^ 
 f— I 1— t o 
 00 00 O 
 
 00 CO in 
 o o o 
 in in o 
 
 vD vO o 
 
 r~ <■ CO 
 o o o 
 
 (NJ NJD V£> 
 
 .-I 00 CM 
 CO CM O 
 
 CTN —I CM 
 \D r~ O 
 
 <yi ON o 
 
 <}• -vT I 
 
 &. D-CM 
 
 <; <c CM 
 
 z z • 
 
 o 
 
 +1 
 
 in 
 
 (1> Q,\D 
 
 <J <! m 
 
 z z • 
 
 +1 
 
 CO 
 O 
 
 • 
 
 00 
 
 <j <; <3N 
 
 z z • 
 
 i-H 
 +1 
 
 P- CXCvJ 
 
 <! -^ o 
 Z Z • 
 
 +1 
 
 CO 
 
 9- a.m 
 
 <! -"Sj in 
 
 Z Z • 
 
 >* 
 
 +1 
 
 CO 
 
 in 
 
 &< 0< ON 
 
 <! <; CM 
 z z ♦ 
 
 +1 
 
 in 
 
 z z 
 
 +1 
 in 
 
 <j <; ^ 
 z z • 
 
 +1 
 
 CO 
 
 P, d CM 
 
 <3 <J CO 
 Z Z • 
 
 +1 
 o 
 
 00 >3- vO 
 in 00 CM 
 1— I in -* 
 
 o vj -* 
 
 !->. -H ~j 
 
 in vo o 
 
 o o o 
 CM ON r^ 
 CJN r--- 00 
 
 vo CO r~ 
 
 O CO vO /^^ >^> 
 
 in in ON CO ro 
 
 O Cvj CM 
 
 vD r^ --H 
 
 CO vO CO 
 
 O r-. CO 
 
 -* CO o 
 
 -^ •<)• O 
 
 ON in v^ 
 
 ON vo ^ 
 f-H CM o 
 
 CO O vD 
 -H CM 
 
 00 O CM 
 CM O CM 
 
 -H in CO 
 
 vO O -3- 
 CM ON ON 
 
 r-» CO vo 
 
 CO in CM 
 o in in 
 in CM r-^ 
 
 ON in \D 
 
 vO O CO 
 o -H o 
 
 00 O CM 
 CM ON vO 
 cvj v£> <t 
 
 on tT) CO 
 
 CO vO CO 
 
 CM 1-H ON 
 
 CO CM 00 
 
 r~ in 00 
 
 O '^ CO 
 O O O 
 
 p- 00 ^ 
 
 CO 00 in 
 
 vO vO O 
 
 ^D in ON 
 
 vD CO \0 
 
 in CM so 
 
 -<r ^ o 
 
 ^ CO CM 
 ON O -H 
 
 r~. O CO 
 
 •^ --H VO 
 
 00 r^ 00 
 
 CO CO o 
 
 ON CO -a- 
 in -H in 
 
 •<f CM 00 
 
 CO r^ CO 
 in -;r <JN 
 
 r-. r-. o 
 00 ON --I 
 in <j- On 
 
 ON ■<}• r-~ 
 r>. CM -* 
 
 in <JN -* 
 in o in 
 CO 00 -d- 
 
 O o O 
 
 ON -H CM 
 \0 .-H -vT 
 
 ~a- r-- CO 
 in 00 CO 
 
 CO vO CO 
 
 CO o P-- 
 
 ^ m CO 
 
 in \£) r-l 
 
 O r^ r^ 
 
 --H On 00 
 
 ON CO r-. 
 
 nD CM vO 
 
 <r r^ CM 
 
 ON <JN o 
 
 in 00 CO 
 
 On in NO 
 
 in CO p~ 
 
 00 00 o 
 CM in CO 
 in -^ vo 
 
 NO vO o 
 
 o o o 
 r~ O CO 
 
 -^ CO CJN 
 
 vO -* r^ 
 
 ^ CM O 
 
 <r -3- o 
 
 — I CM 1—1 
 
 CO CM 00 
 ^ CM 
 
 -* CM 00 
 -H CM 
 
 CO 00 in 
 
 ■^ vD CM 
 -4- CM 00 
 
 -* NO CNJ 
 
 CM CM O 
 
 CO in CM 
 
 • • • 
 
 •<r o NO 
 
 ^ Csl 
 
 in CO 00 
 
 ^ vO -^ 
 
 NO 00 CM 
 
 • • • 
 
 CO CM ON 
 
 r-l CM 
 
 <! CO <1 
 
 Z r^ Z 
 
 p~ 
 
 in (3N -vT 
 
 CM vO -^ 
 
 r^ in 00 
 
 O -^ -* 
 
 O CM CM 
 CO p^ -* 
 
 in CM r-» 
 
 O ON 00 
 
 i-H CM rH 
 
 CM O 00 
 CNj CO o 
 
 in r^ csl 
 
 O <3- •<(■ 
 
 in CM P-. 
 00 in NO 
 
 -3- ^ NO 
 -H CM 
 
 CM CNl O 
 
 <r <JN m 
 St 00 -d- 
 
 -4- cjN in 
 00 ~a- NO 
 
 ^ 00 nO 
 
 CO in CM 
 
 o o o 
 
 CO CO O 
 
 mom 
 
 ON ON ON 
 
 r^ ON i-H 
 
 c^ <J- m 
 00 o •-• 
 00 ^ CO 
 
 m p~ CM 
 00 NO 00 
 
 00 ^ CM 
 
 CO p^ ~* 
 CO m CM 
 ^H p^ m 
 
 O CM CM 
 
 no m ON 
 <r 00 CO 
 
 CM 00 NO 
 
 00 ON r-l 
 
 -H CO CM 
 
 •<!• rH vO 
 
 • 4-1 
 4J ^ 
 
 X3 bo 
 bO -H 
 •H 0) 
 
 • •• 4J J3 
 
 • /— \ j3 bO 
 
 • CO bO -H 
 
 • 00 -H 0) 
 
 4J 00 
 
 0) 03 03 
 U O 
 
 ac: 
 
 (U » 
 0) 03 
 
 u o 
 
 . •• 4J J2 
 
 • ^ X! bO 
 
 • CO bO -H 
 
 • 00 -H 0) 
 
 • ~^ 0) & 
 4J C7N S 4-) 
 03 • — 0) 03 
 3 rH M O 
 
 J3 bO 
 bO -H 
 •H <U 
 
 N.-' Dh Pu Q s_/ pn p^ 
 
 (U 03 
 1-1 O 
 
 CU CM 
 
 • CO 
 
 • 00 
 
 ■W CO 
 0) ^ 
 3 CO 
 Q ^ 
 
 4-) X 
 
 J= bO 
 bO-H 
 
 •H (U 
 <U IS 
 S 4-) 
 01 03 
 M O 
 
 Pm Cl, 
 
 • CO 
 
 • 00 
 
 4J <!■ 
 
 03 -^ 
 
 3 CO 
 
 Q --^ 
 
 • 4-1 
 
 4-> J3 
 
 JC bO 
 
 bO-r-t 
 
 •H 0) 
 
 0) > 
 
 0) 03 
 
 M O 
 
 Cm cm 
 
 4J 4-> <f 
 03 ~^ 
 3 CO 
 
 CO bO 
 
 bO 
 
 4-1 
 03 
 
 o 
 
 p^ ( 
 
 J3 bO 
 bO-H 
 •H OJ 
 
 » 4-t 
 (U 03 03 
 M O 
 
 • CO 
 
 • 00 
 
 • o 
 
 Oi CM Q 
 
 3 CO 
 
 4-1 J2 
 
 J2 bO 
 bO-H 
 
 d) ts 
 
 0) 03 03 
 
 M O 3 
 
 Pm CM Q 
 
 rH S -U 4-1 
 
 CO 
 
 m 
 
 NO 
 
 bO 
 C 
 
 •H 
 Wl 
 
 3 
 •T3 
 
 0> 
 4J 
 
 o 
 
 <U 
 
 O 
 O 
 
 CO 
 O 
 
 4-1 
 
 03 
 
 3 
 
 03 
 
 •i-t 
 
 03 
 
 3 
 t3 
 
 bO 
 0) 
 
 •O '4H 
 
 QJ 
 H 03 
 
 
 
 4J bO 
 O -H 
 Z Q) 
 
 4J 
 CO 03 
 
 z o 
 
 •H <u 
 
 rH U 
 
 a, o 
 a.i4H 
 
 CO 0) 
 
 4J 
 
 O 4J 
 
 z xi 
 
 bO 
 
 •H 
 
 <! S 
 Z 
 
 M 
 0) 
 
 CO 03 
 
 H -H 
 •H 
 
 CO : 
 
 > -Ul 
 
 CO JS 
 bO 
 
 li. 
 
 J3 
 
 C 
 
 bO 
 
 3 
 
 •H 
 
 m 
 
 0) 
 
 H 
 
 
 ^ 
 
 IHCO 
 
 (X 
 
 
 en 
 
 
 3 
 
 • 
 
 C 
 
 C 
 
 1 
 
 o 
 
 •rl 
 
 
 4-) 
 
 •u 
 
 CJ 
 
 J3 
 
 3 
 
 bO 
 
 3 
 
 •H 
 
 14H 
 
 0) 
 
 ^ 
 
 4-> 
 
 1 
 
 03 
 
 
 O 
 
 o. 
 
 O. 
 
 s-x 
 
 3 
 
 
 CM 
 
 dcM 
 
 3 
 
 
 M 
 
 
60 
 
 APPENDIX C.~GUNITE PORE VOLUME, DENSITY, AND POROSITY DATA 
 
 
 Dry 
 
 Satu- 
 
 Length 
 
 Radius 
 
 Bulk 
 
 Wt of 
 
 Core 
 
 Vol of 
 
 Poros- 
 
 Core 
 
 wt. 
 
 rated 
 
 of core. 
 
 of core. 
 
 volume , 
 
 sat sol. 
 
 density. 
 
 sol, cm^ 
 
 ity, 
 
 
 g 
 
 wt, g 
 
 cm 
 
 cm 
 
 cm^ 
 
 g 
 
 g/cm^ 
 
 (pore vol) 
 
 pet 
 
 1 
 
 163.80 
 
 184.70 
 
 7.20 
 
 1.9 
 
 81.66 
 
 20.90 
 
 2.01 
 
 20.90 
 
 25.59 
 
 2 
 
 190.78 
 
 209.30 
 
 8.00 
 
 1.9 
 
 90.73 
 
 18.52 
 
 2.10 
 
 18.52 
 
 20.41 
 
 3 
 
 172.31 
 
 186.15 
 
 6.99 
 
 1.90 
 
 79.274 
 
 13.84 
 
 2.11 
 
 13.84 
 
 17.45 
 
 4 
 
 168.39 
 
 184.23 
 
 6.99 
 
 1.90 
 
 79.274 
 
 15.84 
 
 2.12 
 
 15.84 
 
 19.98 
 
 5 
 
 134.11 
 
 161.74 
 
 6.97 
 
 1.90 
 
 79.047 
 
 27.63 
 
 1.69 
 
 27.63 
 
 34.95 
 
 6 
 
 158.45 
 
 178.26 
 
 6.96 
 
 1.90 
 
 78.93 
 
 19.81 
 
 2.00 
 
 19.81 
 
 25.09 
 
 7 
 
 159.27 
 
 178.63 
 
 6.97 
 
 1.90 
 
 79.047 
 
 19.36 
 
 2.01 
 
 19.36 
 
 24.49 
 
 8 
 
 143.65 
 
 167.14 
 
 6.98 
 
 1.90 
 
 79.161 
 
 23.49 
 
 1.81 
 
 23.49 
 
 29.67 
 
 9 
 
 164.35 
 
 180.71 
 
 6.90 
 
 1.90 
 
 78.25 
 
 16.36 
 
 2.10 
 
 16.36 
 
 20.90 
 
 10 
 
 172.37 
 
 187.07 
 
 6.96 
 
 1.90 
 
 78.93 
 
 14.70 
 
 2.18 
 
 14.70 
 
 18.62 
 
 11 
 
 171.53 
 
 186.77 
 
 6.98 
 
 1.90 
 
 79.161 
 
 15.24 
 
 2.16 
 
 15.24 
 
 19.25 
 
 12 
 
 172.96 
 
 188.56 
 
 7.03 
 
 1.90 
 
 79.72 
 
 15.60 
 
 2.16 
 
 15.60 
 
 19.56 
 
 13 
 
 168.95 
 
 185.28 
 
 6.98 
 
 1.90 
 
 79.161 
 
 16.33 
 
 2.13 
 
 16.33 
 
 20.62 
 
 14 
 
 0) 
 
 0) 
 
 0) 
 
 0) 
 
 0) 
 
 0) 
 
 0) 
 
 0) 
 
 0) 
 
 15 
 
 121.78 
 
 127.84 
 
 5.46 
 
 1.90 
 
 61.92 
 
 6.06 
 
 1.96 
 
 6.06 
 
 9.78 
 
 16 
 
 94.75 
 
 95.49 
 
 4.05 
 
 1.90 
 
 45.93 
 
 .74 
 
 2.06 
 
 .74 
 
 1.6 
 
 17 
 
 157.20 
 
 165.30 
 
 7.06 
 
 1.90 
 
 80.06 
 
 8.1 
 
 1.96 
 
 8.1 
 
 10.1 
 
 ^Defective sample. 
 
APPENDIX D. —PERMEABILITY DATA 
 
 61 
 
 
 Sleeve 
 
 Time, 
 
 Inlet 
 
 Average 
 
 Height , 
 
 Volume , 
 
 Permeability, 
 
 Core 
 
 pressure, 
 psi 
 
 s 
 
 pressure, 
 psi 
 
 pressure, 
 psi 
 
 cm 
 
 cm^ 
 
 10"^ darcy 
 
 1 
 
 185 
 185 
 
 368 
 376 
 
 108-126 
 103- 84 
 
 117 
 93.5 
 
 0.7 
 .7 
 
 0.01386 
 .01386 
 
 3.45 
 
 
 4.23 
 
 
 185 
 
 306 
 
 84- 84 
 
 84 
 
 .7 
 
 .01386 
 
 5.78 
 
 
 185 
 
 360 
 
 104-114 
 
 109 
 
 .7 
 
 .01386 
 
 3.79 
 
 
 185 
 
 380 
 
 104-118 
 
 HI 
 
 .7 
 
 .01386 
 
 3.52 
 
 
 185 
 
 342 
 
 106-108 
 
 107 
 
 .7 
 
 .01386 
 
 4.07 
 
 
 Av... 4.14 
 
 
 180 
 
 151 
 
 90- 91 
 
 90.5 
 
 2 
 
 .0396 
 
 Std dev... .86 
 
 2 
 
 28.2 
 
 
 180 
 
 147 
 
 91- 89 
 
 90.0 
 
 2 
 
 .0396 
 
 29.2 
 
 
 180 
 
 145 
 
 88- 86 
 
 87.0 
 
 2 
 
 .0396 
 
 30.6 
 
 
 180 
 
 159 
 
 86- 88 
 
 87.0 
 
 2 
 
 .0396 
 
 27.9 
 
 
 180 
 
 138 
 
 86- 90 
 
 88.0 
 
 2 
 
 .0396 
 
 31.8 
 
 
 180 
 
 141 
 
 89- 89 
 
 89.0 
 
 2 
 
 .0396 
 
 30.8 
 
 
 Av 29.75 
 
 
 180 
 
 1,900 
 
 80 
 
 80 
 
 1 
 
 -0198 
 
 Std dev... 1.42 
 
 3 
 
 1 10 
 
 
 180 
 
 1,401 
 
 80 
 
 80 
 
 X 
 
 1 
 
 .0198 
 
 1.50 
 
 
 180 
 
 3,695 
 
 80 
 
 80 
 
 4 
 
 .0791 
 
 2.28 
 
 
 180 
 
 2,294 
 
 80 
 
 80 
 
 3 
 
 .0594 
 
 2.75 
 
 
 180 
 
 3,620 
 
 80 
 
 80 
 
 4 
 
 .0791 
 
 2.32 
 
 
 180 
 
 2,270 
 
 80 
 
 80 
 
 3 
 
 .0594 
 
 2.78 
 
 
 Av 2.12 
 
 
 180 
 
 451 
 
 80 
 
 80 
 
 -x 
 
 0S94 
 
 Std dev... .68 
 
 4 
 
 14.02 
 15.05 
 
 
 180 
 
 420 
 
 80 
 
 80 
 
 ■J 
 
 3 
 
 .0594 
 
 
 180 
 
 425 
 
 80 
 
 80 
 
 3 
 
 .0594 
 
 14.87 
 
 
 180 
 
 413 
 
 80 
 
 80 
 
 3 
 
 .0594 
 
 15.31 
 
 
 180 
 
 548 
 
 80 
 
 80 
 
 4 
 
 .0791 
 
 15.38 
 
 
 180 
 
 680 
 
 80 
 
 80 
 
 5 
 
 .099 
 
 15.49 
 
 
 Avg 15.02 
 
 
 180 
 
 62 
 
 78 
 
 80 
 
 S 
 
 099 
 
 Std dev... .054 
 
 5 
 
 169.50 
 173.09 
 
 
 180 
 
 85 
 
 78 
 
 80 
 
 7 
 
 .138 
 
 
 180 
 
 86 
 
 79 
 
 80 
 
 7 
 
 .138 
 
 171.07 
 
 
 180 
 
 89 
 
 79 
 
 80 
 
 7 
 
 .138 
 
 165.31 
 
 
 180 
 
 88 
 
 80 
 
 80 
 
 7 
 
 .138 
 
 167.18 
 
 
 180 
 
 88 
 
 80 
 
 80 
 
 7 
 
 .138 
 
 167.18 
 
 
 Av 168.89 
 
 
 180 
 
 1 17 
 
 80 
 
 fiO 
 
 7 
 7 
 
 .138 
 .138 
 
 Std dev.. 2.88 
 
 6 
 
 125.56 
 122.42 
 
 
 180 
 
 J. X / 
 
 120 
 
 79- 81 
 
 80 
 
 
 180 
 
 120 
 
 79- 81 
 
 80 
 
 7 
 
 .138 
 
 122.42 
 
 
 180 
 
 121 
 
 78- 82 
 
 80 
 
 7 
 
 .138 
 
 121.41 
 
 
 180 
 
 121 
 
 79- 81 
 
 80 
 
 7 
 
 .138 
 
 121.41 
 
 
 180 
 
 122 
 
 79- 81 
 
 80 
 
 7 
 
 .138 
 
 120.42 
 
 
 Av 122.27 
 
 
 180 
 
 215 
 
 80 
 
 80 
 
 7 
 
 .138 
 .138 
 
 Std dev... 1.78 
 
 7 
 
 68.43 
 66.87 
 
 
 180 
 
 im 1. J 
 
 220 
 
 80 
 
 \J\J 
 
 80 
 
 / 
 
 7 
 
 
 180 
 
 243 
 
 80 
 
 80 
 
 7 
 
 .138 
 
 60.54 
 
 
 180 
 
 243 
 
 80 
 
 80 
 
 7 
 
 .138 
 
 60.54 
 
 
 180 
 
 245 
 
 80 
 
 80 
 
 7 
 
 .138 
 
 60.05 
 
 
 180 
 
 242 
 
 80 
 
 80 
 
 7 
 
 .138 
 
 60.79 
 
 
 Av 62.87 
 
 
 
 
 
 
 
 
 Std dev... 3.74 
 
62 
 
 APPENDIX D. —PERMEABILITY DATA—Continued 
 
 
 Sleeve 
 
 Time, 
 
 Inlet 
 
 Average 
 
 Height , 
 
 Volume , 
 
 Permeability, 
 
 Core 
 
 pressure, 
 psi 
 
 s 
 
 pressure, 
 psi 
 
 pressure, 
 psi 
 
 cm 
 
 cm^ 
 
 10"^ darcy 
 
 8 
 
 180 
 180 
 
 507 
 727 
 
 80 
 80 
 
 80 
 80 
 
 2 
 3 
 
 0.039 
 .059 
 
 8.30 
 
 
 8.68 
 
 
 180 
 
 1,210 
 
 80 
 
 80 
 
 5 
 
 .099 
 
 8.69 
 
 
 180 
 
 1,676 
 
 80 
 
 80 
 
 7 
 
 .128 
 
 8.79 
 
 
 180 
 
 809 
 
 80 
 
 80 
 
 3 
 
 .059 
 
 7.80 
 
 
 180 
 
 1,888 
 
 80 
 
 80 
 
 7 
 
 .138 
 
 7.80 
 
 
 Av 8.34 
 
 
 180 
 
 860 
 
 80 
 
 80 
 
 7 
 
 .138 
 
 Std dev... .045 
 
 9 
 
 16.93 
 
 
 180 
 
 397 
 
 80 
 
 80 
 
 3 
 
 .059 
 
 15.72 
 
 
 180 
 
 936 
 
 80 
 
 80 
 
 7 
 
 .138 
 
 15.56 
 
 
 180 
 
 536 
 
 80 
 
 80 
 
 4 
 
 .079 
 
 15.52 
 
 
 180 
 
 941 
 
 80 
 
 80 
 
 7 
 
 .138 
 
 15.47 
 
 
 180 
 
 955 
 
 80 
 
 80 
 
 7 
 
 .138 
 
 15.25 
 
 
 Av 15.74 
 
 
 180 
 
 614 
 
 80 
 
 80 
 
 4 
 
 .079 
 
 Std dev... 0.60 
 
 10 
 
 13.67 
 
 
 180 
 
 1,048 
 
 80 
 
 80 
 
 7 
 
 .138 
 
 14.01 
 
 
 180 
 
 1,031 
 
 80 
 
 80 
 
 7 
 
 .138 
 
 14.24 
 
 
 180 
 
 457 
 
 80 
 
 80 
 
 3 
 
 .059 
 
 13.77 
 
 
 180 
 
 1,059 
 
 80 
 
 80 
 
 7 
 
 .138 
 
 13.87 
 
 
 180 
 
 1,051 
 
 80 
 
 80 
 
 7 
 
 .138 
 
 13.97 
 
 "^ 
 
 Av 13.92 
 
 
 180 
 180 
 
 1,174 
 ,537 
 
 80 
 80 
 
 80 
 80 
 
 7 
 3 
 
 .138 
 .0594 
 
 Std dev... .20 
 
 11 
 
 12.56 
 
 
 11.77 
 
 
 180 
 
 1,061 
 
 80 
 
 80 
 
 6 
 
 .118 
 
 11.91 
 
 
 180 
 
 1,255 
 
 80 
 
 80 
 
 7 
 
 .138 
 
 11.75 
 
 
 180 
 
 781 
 
 80 
 
 80 
 
 4 
 
 .079 
 
 10.79 
 
 
 180 
 
 1,353 
 
 80 
 
 80 
 
 7 
 
 .1386 
 
 10.90 
 
 
 Av 11.61 
 
 
 180 
 180 
 
 1,829 
 3,644 
 
 80 
 80 
 
 80 
 80 
 
 2 
 5 
 
 .039 
 .099 
 
 Std dev.. . .67 
 
 12 
 
 2.31 
 
 
 2.90 
 
 
 180 
 
 4,684 
 
 80 
 
 80 
 
 7 
 
 .138 
 
 3.16 
 
 
 180 
 
 1,131 
 
 80 
 
 80 
 
 2 
 
 .039 
 
 3.73 
 
 
 180 
 
 2,186 
 
 80 
 
 80 
 
 4 
 
 .079 
 
 3.87 
 
 
 180 
 
 2,722 
 
 80 
 
 80 
 
 5 
 
 .099 
 
 3.89 
 
 
 Av 3.31 
 
 
 180 
 180 
 
 1,273 
 2,404 
 
 80 
 80 
 
 80 
 80 
 
 4 
 
 7 
 
 .079 
 .138 
 
 Std dev... .064 
 
 13 
 
 6.6 
 
 
 6.12 
 
 
 180 
 
 1,312 
 
 80 
 
 80 
 
 3 
 
 .059 
 
 4.81 
 
 
 180 
 
 1,725 
 
 80 
 
 80 
 
 4 
 
 .079 
 
 4.88 
 
 
 180 
 
 436 
 
 80 
 
 80 
 
 1 
 
 .019 
 
 4.82 
 
 
 180 
 
 2,563 
 
 80 
 
 80 
 
 6 
 
 .118 
 
 4.92 
 
 
 Av 5.36 
 
 
 180 
 180 
 180 
 
 2,652 
 2,500 
 2,500 
 
 80 
 80 
 80 
 
 80 
 80 
 80 
 
 1 
 <1 
 <1 
 
 NA 
 NA 
 NA 
 
 Std dev... 0.79 
 
 15 
 
 <1.0 
 
 16 
 
 <1.0 
 
 17 
 
 <1.0 
 
 NA Not available. 
 
 NOTE. — There are no data for core 14, which was defective. 
 
APPENDIX E.— COST DATA 
 
 63 
 
 Sample 
 
 Fiber type 
 
 Mfg. 
 cost per 
 bag 
 
 Bag 
 wt, 
 lb 
 
 Bags per yd^ 
 
 By 
 vol 
 
 By 
 wt 
 
 Cost per yd^ 
 
 By 
 vol 
 
 By 
 wt- 
 
 Admixture 
 costs per yd^ 
 
 l2 
 
 2^ 
 
 32 
 
 4 
 
 5 
 
 6 
 
 /•••••• 
 
 8 
 
 9 
 
 10 
 
 U 
 
 12 
 
 13 
 
 14 
 
 15 
 
 16 
 
 17 
 
 Steel. 
 ...do. 
 
 .do. 
 
 AR-f iberglass .... 
 ...do 
 
 Steel^ 
 
 . . .do^ 
 
 E-f iberglass 
 
 AR-f iberglass .... 
 
 Steel 
 
 ...do 
 
 None 
 
 Polypropylene. . . . 
 AR-f iberglass .... 
 
 Steel 
 
 None 
 
 Polypropylene. . . . 
 
 NAp 
 NAp 
 NAp 
 $3.05 
 6.95 
 3.49 
 3.49 
 4.69 
 4.25 
 3.80 
 3.80 
 2.70 
 3.40 
 4.25 
 3.80 
 2.70 
 3.40 
 
 NAp 
 NAp 
 NAp 
 50 
 50 
 60 
 60 
 50 
 60 
 80 
 80 
 80 
 60 
 60 
 80 
 80 
 60 
 
 NAp 
 NAp 
 NAp 
 68 
 47 
 54 
 54 
 54 
 45 
 41 
 41 
 41 
 45 
 45 
 41 
 41 
 45 
 
 NAp 
 NAp 
 NAp 
 74 
 74 
 74 
 74 
 74 
 
 61-2/3 
 46-1/4 
 46-1/4 
 46-1/4 
 61-2/3 
 61-2/3 
 46-1/4 
 46-1/4 
 46-1/4 
 
 NAp 
 NAp 
 NAp 
 $206 
 330 
 188 
 188 
 253 
 191 
 156 
 156 
 111 
 153 
 191 
 156 
 HI 
 153 
 
 NAp 
 NAp 
 NAp 
 $226 
 514 
 258 
 258 
 347 
 262 
 176 
 176 
 125 
 210 
 262 
 176 
 125 
 157 
 
 NAp 
 NAp 
 NAp 
 NAp 
 NAp 
 NAp 
 NAp 
 NAp 
 NAp 
 NAp 
 NAp 
 NAp 
 NAp 
 NAp 
 ^$143 
 5l41 
 ^141 
 
 NAp Not applicable. 
 
 ^Assuming a cubic yard of applied gunite weighs approximately 4,000 lb and contains 
 3,700 lb of solids and 300 lb of liquid. 
 
 ^Types 1-3 contain silica fume, an accelerator, plasticizers , and a superplasti- 
 cizer and employ a curing agent. See table 18 for cost estimate. 
 
 ^ Price per bag is f.o.b. plant, purchased in volume. This price was quoted for 
 mining customers. Single-bag, over-the-counter price is $5.75/bag. 
 
 ^This cost derived by taking 917 lb cement/yd^ (manufacturer's specification) 
 gal/94 lb cement x $4.18/gal of styrene butadiene. 
 
 ^This cost derived by taking 907 lb cement/yd^ (manufacturer's specification) 
 gal/94 lb cement x $4.18/gal of styrene butadiene. 
 
 X 3.5 
 
 X 3.5 
 
64 
 
 APPENDIX F. —TOUGHNESS INDEX DISCUSSION 
 
 The proposed toughness index was in- 
 tended to be a dimensionless number 
 indicative of the fiber's contribution 
 to the flexural strength; however, the 
 selection of an appropriate denomina- 
 tor in the toughness index equation is 
 still in question, is sparking contro- 
 versy among fiber producers, and will 
 require careful resolution by the Ameri- 
 can Concrete Institute (Committee 544) 
 
 before the index can be meaningfully 
 used. 
 
 At present , the toughness index is 
 calculated as the area under the load- 
 deflection (L-D) curve out to 0.075 in or 
 0.10 in, depending on the author, divided 
 by the area under the load deflection 
 curve of the fibrous beam up to the 
 first-crack strength: 
 
 „ , .J area under L-D curve to 0.075-in deflection 
 
 Toughness index = ^ 7—=; — t- z \ ' 
 
 area under L-D curve to first crack 
 
 The toughness index is not standard- 
 ized as it should be. The difficulty is 
 caused by the disparity of index values 
 obtainable by the different fiber config- 
 urations. Short, straight fibers with 
 high surface areas (rectangular in cross 
 section) can be mixed in gunite in volume 
 percentages up to 2 pet (approximately 
 265 lb/yd ^) without impairing the work- 
 ability seriously. At these loading 
 rates, the fibers will increase first- 
 crack strength (the equation denominator) 
 to such a high value it reduces the prod- 
 uct toughness index seriously. 
 
 Long, deformed fibers, on the other 
 hand, can only be used in low volume 
 
 percentages, in the 0.4 pet range (ap- 
 proximately 50 lb/yd ^) if workability is 
 to be maintained. Accordingly, first- 
 crack strength would be somewhat lower 
 (making the equation denominator small) 
 and the post-first-crack strength higher 
 (making the equation numerator large) and 
 giving a very high comparison value. 
 
 The use of a denominator containing the 
 first-crack value of a plain, fiberless 
 mix of the same proportion used in the 
 fibered product would provide a better 
 measure of the fibers' contribution to 
 the matrix. 
 
 ^U.S. GPO: 1984-705-020/5040 
 
 INT.-BU.OF MIN ES,PGH.,PA. 27649 
 
4 
 
 4 
 
 H7b- 854 
 
^' J'^--. 
 
 
 
 ^'^^ *!m^^ -^^ ^°''-^;rr°^ ^■^'''.^i';z^'"\ o°".^%"°o ,^^ -• 
 
 
 
 
 o « ■> -^* 
 
 ■o5 ^ 
 
 
 ^0^ \5, *7*l^^4' A 
 
 
 • V*x A'' *'J^<1.^^<" .A. A »• R S • "p. ^^ fc 
 
 -^^^t^V ., "v^^\/ V**->'^°' %'^»":^'\^^ 
 
 A> 
 
 
 %\..^/^i'°- .A^>^^\ c,°^^^%>o /\c;^/\ 
 
 ,40 - - - - ' 
 
 
 
 J-"'*, 
 
 
 
 * 
 
 
 ^^^°^ 
 
 
 
 
 9' ,, '^^,^^:^'\#'' "o^*^-^/ >^,^^7^-y^ \.*^^'^%o'^ V 
 
 
 
 **'% 
 
 \^i 
 
 
 ^*. o 
 
 
 ^bV" 
 
 
 <^°^ 
 
 I < v« '^ 
 
 .^^°- 
 
 
 :^ >. c.-?^" *i 
 
 
 7, ^^'3 
 
 
 
 
 **'\ 
 
 
 .-^^ \!.^.#^*.^^ 
 
 V 
 
 .0' o"""*, "O. 
 
 .-5l" 
 
 vr , 
 
 

 
 
 
 '^^^ 
 
 "oV 
 
 
 
 /..i^>>o .,/Vi.;^^"'^.. .oo^^.^^^o ./\ci^/\. co 
 
 
 
 C,^*^^. 
 
 I* -^^ "^ 
 
 
 -.^^'V 
 V ^ 
 
 
 
 ^ ^ ^"loL' 
 
 
 
 ^ * o « •> .^ 
 
 
 >■ ' » « <?. (V - O N , 
 
 
 
 
 
 
 HECKMAN 
 
 BINDERY INC. 
 
 ,^^ JAN 85 
 
 N. MANCHESTER, 
 INDIANA 46962 
 
 
 ^^^^ 
 
 'bV"