CdloI S^ool^ STATE OF ILLINOIS WILLIAM G. STRATTON, Governor DEPARTMENT OF REGISTRATION AND EDUCATION VERA M. BINKS, Director Some Plastic Properties of Pastes Made from Hydrated Dolomitic and High-Calcium Limes D. L. Deadmore J. S. Machin DIVISION OF THE ILLINOIS STATE GEOLOGICAL SURVEY JOHN C. FRYE, Chief URBANA CIRCULAR 261 1958 ILLINOIS GEOLOGICAL SURVEY LIBRARY JAN Z6 ,yb9 ILLINOIS STATE GEOLOGICAL SURVEY 3 3051 00003 8608 SOME PLASTIC PROPERTIES OF PASTES MADE FROM HYDRATED DOLOMITIC AND HIGH-CALCIUM LIMES D. L. Deadmore and J. S. Machin ABSTRACT Four commercial hydrated limes were studied . Two from north- western Ohio were partially hydrated dolomitic varieties that gave instantaneous Emley plasticity values of about 120. After soaking, the Emley values increased to about 310. One Illinois hydrate was a high-calcium hydrate and had a plasticity of about 100, both im- mediately before and after soaking. The other Illinois hydrate was a highly hydrated dolomitic type. Its immediate plasticity was 274 and,after soaking, the value rose to 340. A study of particle- size distribution data and X-ray diffrac- tion analysis show that the differences in the observed plasticities are correlated with high MgtOHjn content and high relative amounts of fine particles. INTRODUCTION In connection with a study of the plastic properties of lime hydrate derived from Illinois dolomites, some measurements of plasticity of pastes made from com- mercial hydrates marketed in Illinois are presented in this communication. Four commercially prepared dry hydrates were purchased in the open market and are referred to as hydrates H, G, R, and M. The hydrates were received in 50-pound paper bags. All samples used in the tests reported below were immediate- ly transferred to glass containers with tight screw-cap lids in order to preserve their as-received compositions. Samples R and G were dolomitic hydrates from Ohio, M a dolomitic hydrate from Illinois, and H, also from Illinois, was a high-calcium hydrate. The labels on the bags described H as "chemically pure" lime, M and R as "mason's lime, " and G as "finish lime. " EXPERIMENTAL PROCEDURES Plasticity Determinations The visco-plastic properties of the four hydrate pastes or suspensions were explored by two methods - the conventional Emley plasticimeter and a Stormer ro- tational viscometer. A number of measurements of torque versus rate of shear were made on each hydrate at various water contents using a calibrated Stormer viscometer. The pro- [1] 2 ILLINOIS STATE GEOLOGICAL SURVEY cedure used was as follows: 100 grams of hydrate was placed in a beaker, the de- sired amount of water was added, and the mixture was stirred mechanically for five minutes to insure a uniform paste. The paste was transferred to the viscometer cup and the torque was measured at various uniformly increasing rates of shear. No measurements were made at decreasing rates of shear. Because the Emley plasticimeter is so widely used in the lime industry, Emley plasticity figures were also determined for each hydrate. The apparatus was constructed at the Illinois Geological Survey after the A.S.T.M. (1949) specifica- tions. Porcelain base plates were used. They were made at the University of Illi- nois in the Ceramic Engineering Department to conform to the prescribed absorption rates specified by A.S.T.M. (1949). The plasticity determinations were made in accordance with the standard procedure described by the A.S.T.M. method C-110-49 The plasticity of each hydrate was measured immediately after tempering with water to the standard consistency and again after soaking for 24 hours. The water at standard consistency, as given in the text, is the weight percent of water in the total water-solid mixture necessary to produce a paste of standard penetration on the penetrometer (or standard consistency) . Duplicate runs were made and the reproducibility was within ±15 percent of the average value of the two runs. Drying of Soaked Hydrates In order to study the hydrates after they had been soaked to see what alter- ations had taken place during soaking, it was necessary to dry the samples in such a way as to minimize any alteration caused by the drying itself. The drying method used is similar to that given by Wells and Taylor (1937). Seventy-five grams of the soaked sample were placed in 150 milliliters of absolute ethanol and shaken for several minutes. The slurry was placed on a BUchner vacuum filter and the li- quid removed by suction. The cake was then washed with ethanol and ether. The nearly dry cake was placed in a vacuum desiccator.at room temperature, which was continuously pumped for a period of 24 to 48 hours to remove the last ethanol and ether. Ignition Loss The ignition loss was determined by heating weighed samples in platinum crucibles to 975° C. for two hours. X-ray Identification The components of the hydrates were identified from X-ray powder diffrac- tion patterns made on a G.E. XRD-3 recording spectrometer, using CuKc radiation. A shallow aluminum sample holder was used. Particle Size Analysis The size distribution of these hydrates was determined by the usual sedi- mentation method using n-butanol as the dispersing agent, as suggested by Bishop (1939). PLASTIC PROPERTIES OF HYDRATED LIME PASTES Electron Micrographs Table 1 . - Yield Points and Water Contents _, . , of Commercially Hydrated Limes (Stormer) The electron micrographs were J ' made by Dr. A. E. Vatter in the Chem- istry Department of the University of Illinois. The carbon replica technique as first described by Bradley (1954) was used . Surface Areas Surface areas were determined by low-temperature — low-pressure ad- sorption of nitrogen, using the method of Brunauer, Emmett, and Teller (1938) . The value of the surface area measured is reproducible to about ± 5 percent when the area is more than one square meter per gram. EXPERIMENTAL RESULTS Visco-Plastic Character The visco-plastic properties of the commercially prepared hydrates were investigated by means of two dif- ferent instruments, the Emley plastici- meter and the Stormer viscometer men- tioned previously. Figure 1 shows the rate of shear versus the shearing stress for hydrate G from Ohio as an illustration of the influence of water on the viscous properties of the lime slurry as determined by the Stormer viscometer. The yield points for each water content were found by extrapolating the linear portion of each curve until it intersected the zero rate of shear axis. The water content is expressed as the per- centage of the total weight of the water-solid slurry. The yield points and water contents of each hydrate are given in table 1 and shown graphically in figure 2 . Table 2. - Emley Plasticity Values for the Commercial Hydrates Water content Yield point (percent) (dynes/cm^) 56.5 Hydrate H 600 58.3 500 60.0 325 63.6 125 66.7 70 50.0 Hydrate M 710 53.5 380 56.5 225 58.3 180 60.0 140 48.7 Hydrate R 820 50.0 515 52.4 390 53.5 280 55.6 180 60.0 80 48.7 Hydrate G 840 50.0 665 53.5 320 55.6 210 60.0 80 Emley value Water at standard con sis (percent) tency Yield point at water of Hydrate Unsoaked Soaked standard consistency* (dynes/cm^) H 91. 103. 51.5 1900. M 274. 340. 47.0 1150. R 111. 320. 45.5 1350. G 120. 305. 46.0 1400. * Yield point is obtained from figure 2 by extrapolation to the content of water at standard consistency. ILLINOIS STATE GEOLOGICAL SURVEY ( suojdiuj ) jdtawDiQ api|JOd s C O o 4-* 2 ja u o T> n u ■*-» Ul C <0 ■■[: «£ X> o'S > O in c 0) O ■ a 05 a: cu u o 9 01 M > 0) m (J 05 W o CM (0 a. 0) f0 (0 y i fn -o x; j 1 c . o >, K (0 u T> QJ C 10 U> *- cc C -•-j « c c X o 01 fO o. 01 iTi a> o 5 2 "3 ■M (0 X) >H >. J. x: • c en oi ( z UJ0/ S»U

n £ «> S T> 01 £ B 01 >» x: V C" ^ o O 5> ■S o CT 10 V. ■^ oi (0 s x: oi o •c w x: en PLASTIC PROPERTIES OF HYDRATED LIME PASTES 5 Table 3. - Particle-Size Distribution of the Hydrates (as received) Particle diameter Weight percent finer than (microns) H M R G 60 98.7 82.1 89.5 87.6 40 96.0 75.4 84.1 82.0 20 88.5 63.1 72.6 70.1 10 82.0 57.4 60.4 58.5 6 76.0 - 4 64.0 49.7 37.8 35.6 2.2 37.0 42.6 24.1 21.8 1.2 14.3 31.0 13.6 11.8 0.86 6.8 22.7 8.5 7.0 0.70 - 19.2 6.7 5.8 0.46 - 9.1 Emley plasticity values for the four hydrates, before and after soaking in water, are given in table 2. The yield point given is that for a water content equal to the water at standard consistency used in the Emley measurement. From table 2 one can see that the Emley value of plasticity for hydrate H shows no significant increase after soaking. However, hydrates M, R, and G show significant increases on soaking, particularly R and G. Hydrates R and G have rather low Emley values in the unsoaked condition, but hydrate M has a very high Emley value in this state. If one compares the yield point values with the unsoaked Emley values it appears that the yield points tend to be smaller for the more plastic hydrates. Table 4. - Surface Areas of the Hydrates Size, Area, and Shape of Hydrate Particles , Hydrate Unsoaked Soaked The particle size distribution of the hydrates was determined by sedi- H mentation in n-butyl alcohol . The re- M suits are given in table 3 and shown graphically in figure 3 . The surface R areas of both the unsoaked and soaked hydrates were measured and the results are given in table 4. Electron micrographs of the unsoaked hydrates are shown in plates 1 and 2. Plate 1 shows, magnified 7, 000 times, the shape and relative size distribution of the hydrate particles of less than 2.2 microns separated by butanol sedimentation. Hydrate M appears to have a slightly greater proportion of very fine and rather flat particles. Hydrates R, H, and G, particularly H and G, seem to have more mas- sive, coke-like particles or aggregates. Plate 2 shows the shape of the particles of the unsoaked hydrates of less than 0.86 microns magnified 7, 000 times. Hydrate H shows many well formed hexagonal platelets. Hydrates M, R, and G show fewer particles with well formed hexagonal outlines. The surfaces of the particles in hydrates M, R, and G appear to be rather uneven or rough compared to those of hydrate H. G 18.46 30.21 17.91 17.81 14.14 14.85 11.59 15.16 6 ILLINOIS STATE GEOLOGICAL SURVEY By measuring the particles in plate 1, it was found that all of them are less than 2.2 microns, the maximum size that is supposed to be present from sedimen- tation calculations. This is a fairly good check that the sedimentation determina- tion of particle size is valid. A number of particles smaller than 0.1 micron are also present. Measurement of particles in plate 2 show that all of the particles are actually less than 0.86jx as required by the sedimentation calculations. This further substantiates the sedimentation determination of particle size. Composition of the Hydrates The composition of the hydrates in terms of Ca(OH) 2 , MgfOH),, and MgO was estimated from ignition-loss data on the assumption that all the CaO is hy- drated, that there is no carbonate present, and that the stone used in making the hydrate was pure dolomite. The results, given in table 5, must be accepted with caution, because during the time from their manufacture until they were purchased from a supply dealer, the hydrates were stored in paper bags and therefore had carbonated to some extent. No correction for this carbonation was made in calcu- lating the compositions. Also, the purity of the original stone is unknown. Table 5. - Composition of the Hydrates Estimated from Ignition Loss Ignition loss (percent) Cor reposition (percent ) Unsoaked Soaked Hydrate Unsoaked Soaked Ca (OH) 2 Mg(OH) 2 MgO Ca(OH) 2 Mg(OH) 2 MgO H 24.8 25.4 100 100 M 27.4 27.9 56.0 44.0 56.0 44.0 R 20.7 23.1 60.7 19.2 20.1 58.9 28.1 13.0 G 22.6 24.1 59.3 26.2 14.5 58.2 32.0 9.8 X-ray powder diffraction patterns of the unsoaked hydrates were made. Table 6 shows the composition of the hydrates based on the diffraction patterns of the dry hydrates as received. These results agree with those given in table 5 qualitatively. Table 6. - Composition of the Hydrates from X-Ray Patterns (as received) Hydrate Ca(OH) 2 Mg(OH) 2 MgO CaO CaC0 3 Dolomite H P N .P. N.P. N.P. N.P. N.P. M P P N.P. N.P. N.P. P R P P P N.P. P N.P. G P P P N.P. P N.P. P - component is present. N.P. = component is not present. Illinois State Geological Survey Circular 261, Plate 1 J ftp • * S>' if* * c . * *.. - .i&£ « A w> IV Electron micrographs of hydrates H, M, G, and R. Fractions less than 2.2 MICRONS. UNSOAKED (X7000). ^ ^ r; 5 ^ i€2 .*• IS * El-ECTRON MICROGRAPHS OF HYDRATES H, M, G, AND R. FRACTIONS LESS THAN 0.86 MICRONS. XJNSOAKED (X7000). PLASTIC PROPERTIES OF HYDRATED LIME PASTES 7 The validity of the results given in table 5, from ignition-loss data, for hydrate H is considered fairly reliable because no CaCOo was detected in the X-ray diffraction pattern. However, for hydrates M, R, and G a small amount of carbonate was detected in the X-ray pattern. The compositions calculated from the ignition- loss data are therefore in error, but it is believed that the amount of error is not more than a few percent. From the X-ray and ignition-loss data it is seen that hydrate H is a very high-calcium lime, whereas the other three hydrates are dolomitic. Hydrate M is a very highly hydrated dolomitic lime containing a small amount of residual dolomite, but hydrates R and G are only partially hydrated inasmuch as both show a consider- able amount of MgO. They do not show any residual dolomite. In an effort to learn something about the composition of the various size fractions collected during the course of measuring the particle-size distribution, X-ray patterns of some of the size fractions for hydrates M, R, and G were made. The results are given in table 7. The results given in table 7, in spite of considerable variation, indicate that the proportion of Mg(OH) 2 tends to increase in the finer fractions (less than 1 micron) and that the MgO, Ca(OH) ? , and dolomite (in hydrate M) show smaller concentrations in the fine fractions. One may infer that, of the components pres- ent in these dolomitic hydrates, Mg(OH) 2 tends to be the finest, and that the re- sidual dolomite, Ca(OH)~ and MgO, tend to be somewhat coarser. These results are more striking when the diffraction patterns are compared directly, but the above data adequately show the general trends . DISCUSSION OF RESULTS The results suggest a reason for the particle-size distribution curves of hydrates M, R, and G. Hydrate M contains a larger proportion of Mg(OH)2 than either R or G, and, inasmuch as Mg(OH) 2 tends to be quite fine, this may be the reason that hydrate M contains a considerably greater proportion of very fine parti- cles as compared to hydrates R and G. Hydrate H is essentially a pure Ca(OH) 2 , and as seen from table 2 both its soaked and unsoaked plasticities are low. Hydrate M is highly hydrated, and its unsoaked and soaked plasticities are high. Hydrates R and G both have only a fraction of their MgO converted to Mg(OH)2 during their manufacturing process, and they show a low unsoaked plasticity. However, on soaking, both show large increases in plasticity. Hydrate M contains a much higher proportion of Mg(OH)2 than R and G, and the Mg(OH) 2 tends to be finer than the other components in these hydrates; there- fore, the higher unsoaked plasticity of hydrate M, as compared to R and G, may be due to a greater proportion of fine particles in hydrate M. The surface area of un- soaked hydrate M is somewhat larger than that of hydrates R and G, again indicat- ing that M may have a higher proportion of particles of finer sizes. Plate 1 also shows that M may have a slightly greater proportion of very fine material than have R and G and that the shape of the particles in hydrate M differ from those of H, R, and G. The flat, sheet-like particles of M, as compared to the massive, coke-like pieces in H and G, may help give M a greater unsoaked plasticity. An explanation of the increase in plasticity on soaking hydrates R and G is not so clearly indicated. If we accept the compositions given in table 5 on the basis that during soaking very little additional carbonation takes place (which is known to be true from data to be reported at a later date), then, even though the ILLINOIS STATE GEOLOGICAL SURVEY c 0) c o a o (l) U -V -n n o U) c C o D U E -t-J Tl u r 01 (Tl o c BS o o 2 10 to (1) ID TJ b -n -rH [fl X PJ e Tl o c m 01 c a n u -^H -t-» +-» f) ia iri i > E Uh +-J 0) c N 0' •-H -o CO 1 ' [fl 5* 3 ffl O E 1 ti X > c -<-H {^ 0) — 1 XI ro H m o 00 oo' O ^ cm IIS c c .^O LO fjl CO X! CD c C 3 ;n o ' ' e >, CT E U I TJ X XI o £ ££ ■53 « c • «J 6 c 3 O w o ^ X ciO (0 O c CD o X) >. X CD LO OO N NCO O LO ^3" LO LO sr lo lo oo O CO N CM CO LO ^ ^r ^r lo lo oo oooo OOCDOOO o o o o o CO CO N N ^ O LOOOOOOO K U1 N N in lO N N N 00 S lO oonTcocdo h m m m oi n LocDcMcnoor^ m in r~» t"~ r-~ ro n n co n m cm n n cm ^ in oi o en ^r co in in id s io i— I CM CM ^3* COi — I O CD 00 LO ^r ro oo o o LO CM O O O co m 1 co m cm co co co m 1 in oooooo oooooo lO rs CO CD O Q) e m ro o 3. 3. o o 3. j_CD CM 00 3. • • ■^ CM O I I I CM r-J CM £ E E -^ *^ *'"* CM CM E C 00 ° Z, co CO rO CO CO r* E E E -XJ *^ *^ "^ Oo CO "O O Q CM CM ^J x x x oo rj tji oi 2 2 2 h cm co f m PLASTIC PROPERTIES OF HYDRATED LIME PASTES 9 absolute values may be in error, the soaked and unsoaked compositions may be compared. Both hydrates R and G show an increase in the amount of Mg(OH)o, which was also substantiated by comparing the X-ray patterns of the soaked and unsoaked hydrates. Since Mg(OH)2 tends to be fine, the increase in the plasticity of R and G after soaking may be due to an increased proportion of fine particles. Both R and G show somewhat larger surface areas after soaking, which indicates that the particles may be somewhat finer. The small increase in the plasticity of hydrate M after soaking may be due to the fact that there is but little free MgO available for conversion to Mg(OH)2 on soaking, therefore its maximum plasticity is nearly developed in a matter of minutes after tempering with water. CONCLUSIONS It may be concluded that the three dolomitic limes have similar plasticities when soaked. The highiy hydrated Illinois dolomitic lime developed nearly its maximum plasticity in a few minutes after tempering with water; the others required an extended soaking period before maximum plasticity developed. This is probably due to differences in the methods of manufacture. The data relating to high-calcium hydrate containing no Mg(OH)o indicate that pure Ca(OH) 2 has intrinsically low plasticity. However, when some Mg(OH)2 is present in the hydrate, the plasticity rises sharply. This may indicate that Mg(OH)2 is a high-plasticity material. The higher Emley plasticity imparted by the presence of Mg(OH) ? may be due, at least in part, to the tendency of this ma- terial to form a large proportion of fine particles. REFERENCES A.S.T.M., 1949, Standard methods of physical testing of quicklime and hydrated lime: A.S.T.M. Standards, Pt. 3, p. 254-262. Bishop, D. L., 1939, Particle size and plasticity of lime: Natl. Bur. Standards Jour. Research, v. 23, p. 285. Bradley, D. L., 1954, Evaporated carbon replica technique for use with the elec- tron microscope: British Jour. Appl . Physics, v. 5, p. 96. Brunauer, S., Emmett, P. H., and Teller, E., 1938, Adsorption of gases in multi- molecular layers: Am. Chem. Soc. Jour., v. 60, p. 309. Wells, L. S., and Taylor, K., 1937, Hydration of magnesia in dolomitic hydrated limes and putties: Natl. Bur. Standards Jour. Research, v. 19, p. 215. Illinois State Geological Survey Circular 261 9 p., 2 pis., 3 figs., 7 tables, 1958 CIRCULAR 261 ILLINOIS STATE GEOLOGICAL SURVEY URBANA