INDUSTRIAL A N D ENGINEERING CHEMISTRY
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Vol. 19, N o . 11
The Combination of Lime in Portland Cement Compounds' Preliminary Investigation By W. C. Hansen and R. H. Bogue PORTLAND CEMENT h S S O C I A T 1 O N FELLOWSHIP, BUREAU OF
ST.ANDAROS, \ v A S H I N G T O N ,
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In the process of Partland cement manufacture, H E researches of Ranh e a t i n g c h a m b e r , AB, is lime and other basic oxides combine with silica and kin,2BatesJ3and others made of an alundum tube 36 other acidic oxides. The completeness with which have indicated that it by 1.5 inches (91 by 3.8 cm.) lime enters into combination can be measured. In is desirable to have in Portwith 0.25-inch (0.6-cm.) walls. this study there is noted the influence of replacements land cement as large a perThe central 24 inches (61 cm.) of magnesia, soda, and potash for lime, and of ferric centage of lime as is economof this tube are wound with oxide for alumina, on the temperature required for ically possible to bring into 0.8-mm. platinum-10 per cent burning and the completeness of combination of the combination with the acidic rhodium wire, the rhodium lime. Only one base composition is employed here; constituents. The presence being introduced to raise the others will be reported later. of uncombined lime, however, melting point of the wire. A continuously operating electric resistance furnace is generally regarded as unThe windings are in three was designed especially for this investigation. Temdesirable, as it is believed by units of 8 inches (20 cm.) each, peratures up to 1550" C. are readily obtained under some to be in part responsithe first having six to eight conditions which permit of a control to 10" C., satisble for excessive expansion turns per inch, the second and factory duplication of results, freedom from contamiof mortars and concretes. It third units from eight to ten nation of materials, and an output of about 2 pounds is generally believed that the turns per inch. The wire is of product per day. oxides, such as ferric oxide, cemented onto the tube with The completion of this program will result in an magnesia, and the alkalies, alundum cement and this core understanding of the influence of the several minor are not themselves important is p l a c e d i n s i d e a n o t h e r components of Portland cement on the phases proin forming hydraulic products alundum tube 36 by 3 inches duced, the burning temperature required, the extent in Portland ~ e m e n tbut , ~ that ( 9 1 b y 7.6 c m . ) . T h i s i s of combination, and on the cement properties of the they make it possible to proplaced inside a fire-clay cylproducts, under a wide range of compositions. duce the hydraulic combinainder 30 bv 11 inches (76 tions of lime, alumina, and by 28 cm.) kpported by magsilica in less time and a t lower temperatures than would nesite brick. The ends of the fire-clay cylinder are sealed by obtain if they were absent. The extent of their usefulness disks of transite cemented in with alundum cement. The is not known except in a qualitative way based upon the space between the fire-clay cylinder and the outer alundum experience of operators in burning various cement mixes. tube is filled with low-burned magnesia. Each of the three A series of investigations has accordingly been undertaken units is connected, through a 16-ohm rheostat, with a 110to determine quantitatively the influence of small amounts volt current. of magnesia, ferric oxide, alkalies, and other minor compoHoles are drilled through the core, a t 12, 18, 21.5, and nents on the combination of lime attained in various mix- 24 inches (30, 46, 55, and 61 cm.) from end A . Porcelain tures a t various temperatures. The present report de- tubes 6 inches by 0.25 inch (15 by 0.6 cm.) are cemented scribes the furnace and materials used, the procedure adopted, into these holes with alundum cement. These openings and the data obtained on one base composition. permit the insertion of platinum-platinum rhodium thermocouples into the heating chamber. They are numbered The Furnace 1 , 2 , 3, and 4 in Figure 2. It was first necessary to design and build a furnace which All the platinum used in the furnace was rendered free would meet the particular requirements of this study. from iridium, since White6 has shown that a t high temperaI n the rotary kiln, which is the standard equipment for tures iridium distils out of platinum-iridium alloys and that commercial cement manufacture today, the materials ad- it diffuses into platinum. The diffusion of iridium into a vance through the kiln and in so doing are gradually heated platinum-platinum rhodium thermocouple brings about a to a maximum temperature and then cooled rather rapidly. continuous change in the e. m. f. developed by the couple, It was desired to heat mixtures in a similar manner and t o rendering the couple unreliable unless very frequent calicontrol the time and rate of heating, as well as the maximum brations are made. temperature to which they were heated. The studies were OPER.4TION-BOatS of 0.125-mm. sheet platinum are to be made upon pure materials, and it was therefore neces- employed as containers for the charge. These fit loosely sary to avoid contamination during the heating process. into alundum boats 6 by 1.25 inches (15 by 3.6 cm.) and Also, a capacity of from 1 to 2 pounds of product per day 0.5 inch (1.3 cm.) deep. The alundum boats are used as was required, supports for the platinum t o avoid unnecessary wearing DESCRIPTION-A photograph of the furnace in operation away of the platinum by abrasion as the boats are passed is shown in Figure 1, and a cross section in Figure 2. The through the furnace. The boats hold from 25 to 35 grams I Received May 25, 1927. Published by permission of the Director of mixtures of calcium carbonate, silica, and alumina, and of the National Bureau of Standards. Paper 10 of the Portland Cement so yield 15 to 20 grams of product per boat. They are Association Fellowship at the Bureau of Standards. entered a t A and advanced in steps of 1 inch (2.5 cm.) every 2 THIS JOURNAL, 7, 466 (1915).
T
'
D.
4
Concrete-Cement Age, 3, 3 (1913). Klein and Phillips, Bur. Standards, Tech. Paper 4S (1914).
5
Phys. Rev., 23, 449 (1906).
INDUSTRIAL A N D ENGINEERING CHEMISTRY
1262
mixture such as these studied. These factors were controlled definitely in this investigation by the use of the specially constructed furnace described above. Compositions of Raw Materials (Figures in per cent) MgC0r.RAW MgMATERIALCaCOP Alz03" SiOz" FezOP (0H)z" KzC01b NarCOae Si02 Nil 0.01 99.37 0.09 0.0031 0.003 AlzOa 0.08 98.48 0.0346 0.07 0.0026 FezOa 0.01 0.002 0.018 99:i5 Fe. 0:Ob FeO Nil ...... CaO 55:+3 kii O:i5 0.06 Ca, o.'OO7 MgO 0.01 ...... ... 36.19 M g , 0.004 Alkalies 0.04 . . . . . . . . . ...... HsS metals . . . . . . Xi1 SOa T k e ...... Nil Xi1 Cl Trace ...... Table I-Partial
...
...
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Loss on ig-
... ......... .... .. 0.93 63.99 . . .
... ......
... ... ...
...
nition 1.42 0.21 ... Hz0 a t 1000 c. 0.02 By H. C. Stecker. b Taken from label on sample a s purchased from Baker and Adamson. o Taken from label on sample a s purchased from Powers-WeightmanRosengarten.
.........
...
Table 11-Influence of Temperature on Combination of CaO (Composition: CaO 67, AlrOa 10, Si02 23 per cent) TEMPERATURE OF HEATING THERMOCOUPLES No. 4n No. 3b No. 2b No. 1 b FREECaO c. e c. c. O C. Ptr cent 1160 1360 1330 1320 8.2 1140 1380 1380 1320 7.6 1160 1410 1410 1360 5.8 1160 1420 1420 1360 3.9 1330 1500 1475 1450 0.0 * 2 0 ° C . b j=lO°C.
Figures 4 to 13, inclusive, show the effects on the combination, as revealed by the free-lime content, resulting from the replacement of magnesia, soda, or potash for calcium oxide, and ferric oxide for alumina, in amounts up to 5 per cent. These effects are shown both singly and in combination. The initial composition is given in each case, so that the exact composition of any point on the curves may easily be ascertained. The maximum temperatures also are given, and the temperatures at each thermocouple for all samples are listed in Table 111. Table 111-Temperatures Measured a t Four Thermocouples of All Samples Illustrated in Figures 4 to 13 TEMPERATURE OF HEATINGTHERMOCOUPLES FIGURE KO.4" KO.3b No. 2b No. 1 b
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Figure &Representative Curve of Heating Process Obtained by Maintaining Points 2 and 3 a t a Constant Temperature
Experimental Data
The average composition of Portland cement today is close to the following: CaO, MgO, Na20, and K20, 67 per cent; AlZOs and Fe203, 10 per cent; and SiOa, 23 per cent. The following composition was chosen accordingly as the base composition in this preliminary study: CaO 67, AlzOs 10, and Si02 23 per cent. Various mixtures were then investigated in which a part of the calcium oxide was replaced by magnesia, soda, or potash, and a part of the alumina was replaced by ferric oxide. As previously pointed out, the values obtained in this study with respect to temperatures and degrees of combination cannot be considered as absolute because of uncontrollable factors, but those of each series are comparable and the different series are to a considerable degree comparable with each other. This is shorn to be true by the following examples: Two charges of the same composition-CaO 67,A1203 10, and Si02 23 per cent-were heated during the same run but with two boats between them. The first charge was found, after heating, t o contain 6.0 per cent free calcium oxide and the second 5.9 per cent. Two charges of another composition-CaO 63, MgO 3, NazO 1, A1203 10, Si02 23 per cent-were run on different days. 10" C., and the perThe temperatures were the same within centages of free calcium oxide found were 5.3 and 5.0,respectively.
*
The increase in combination, as shown by the decrease in free-lime content which results through an increase in the temperature of burning, is shown in Table 11. A maximum temperature of about 1500' C. is required to effect complete combination of lime, alumina, and silica, in the composition given, and under the manner of heating used in the present study.
Vol. 19, No. 11
4 5 6 and 7 8 9 10 11 12 13A 13B
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1160 1160 1200 1160 1200 1000 1080 1090 1160 1140 *io0
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1330 1410 1425 1315 1400 1270 1290 1300 1410 1400
c.
Eject of replacing calcium oxide by magnesia (Figure 4) and alumiitn by ferric oxide (Figure 5). A decrease in free lime is noted. The samples containing magnesia were burned at a lower temperature than those containing ferric oxide. The curves show t h a t small percentages of ferric oxide replacing alumina, and of magnesia replacing lime, aid materially in effecting combination of the lime. cidedly more effective than the ferric oxide in
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will be observed t h a t e about 4 per cent of magnesia replacing lime brings about complete combination a t 0 / 2 3 4 5 temperature of 1350 Arcvri c+ flfl raplaring CaO. c . 3 while 4 per cent of Figure 4-Effectlon Combination of CaO ferric oxide replacing Due t o Replacement of CaO by MgO up alumina brings about t o 5 Per Cent comdete combination only'at the higher temperature of 1410' C. Hence it is shown that 4 per cent of ferric oxide caused complete combination of lime at a temperature 100' C. .. lower than was reFigure-&Effect on Combination of CaO quired for the Due t o Replacement of A1208 by Fez03 up without ferric oxide, t o 4 Per Cent and 4 per cent magnesia effected complete combination a t a temperature 150' C. lower than was required for the sample without magnesia. Effects of small amounts of polassium oxide (Figure 6 ) and sod i u m oxide (Figure 7). It is apparent that these oxides have no especial value in increasing the combination of lime in this composition.8 They do, however, increase the amount of liquid present during burning to a very marked degree, as was shown by a n examination of the resulting products. There was distinctly increased fusion with increased potash or soda content. The potash and soda contents'of the samples, as given on the abscissas, were the amountsrof'potash or soda contained in t h e original samples. Some of this is undoubtedly volatilized during
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8 A similar conclusion with respect t o the:influence of alkalies was reached by S. B. and W. B. Newberry, J . SOC.Chem. I n d . , 16, 887 (1897).
November, 1927
INDUSTRIAL AND ENGINEERING CHEMISTRY
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temperature 40' C. lower than those containing 3 per cent magnesia. The 5 per cent samples contain a greater amount of free lime and would require for complete combination about the same temperature as was used with the 3 per cent samples. It will be observed that the percentage of free lime in both series decreases rapidly as ferric oxide is added, up to about 3 per cent ferric oxide. There is little change beyond that point. E f e c t of ferric oxide when sample contains 3 per cent magnesia and no soda (Figure 12). A comparison of this curve with Figure 11 shows that soda has very little influence in increasing the combination of the lime in the presence of magnesia. Figure 13 shows that soda aids slightly in the combinaPwcenr cf Ns,O +my 00 tion of lime in the absence of magnesia when small amounts Of ferric oxide are added. Figure 7-Effect on Combination of CaO Due t o Replacement of CaO Figure 14 shows the effect of increasing temperature upon b y NazO u p t o 2 Per Cent the combination of the lime in three different compositions.
the burning. It is observed t h a t up to 0.5-1.5 per cent, increasing potash and soda, respectively, favor combination of the lime, but above 0.5-1.5 per cent a reversal occurs, indicating that additional alkali above this amount decreases the combination. The validity of the data on the effect of soda and potash is indicated by work previously reported by Lerch and Bogue.6
Percent of KeO reploch9 C.0
Figure 6-Effect on Combination of CaO Due t o Replacement of CaO by K 2 0 u p to 2 Per Cent
I
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r-Figure %Effect o n Combination of CaO Due to Replacement of AlzOa by Fez08 in Presenceiof Nag0
Figure 8-Effect on Cornbination of CaO Due t o Replacement of CaO by MgO in the Presence of NazO
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Ah4 Figure 10-Effect on Combination ot'CaO Due.to Replacement of All03 by Fez&,in t h e g r e s e n c e of MgO and Nan0 pcmnt fi$, replacmy
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Figure 11-Effect on Combination of CaO Due to Replacement of AlzOa by Fez08 In Presence of MgO and NarO
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Percent f e r 4 repbring Alt 4 FpFigure 12-Effect on Combination of CaO Due t o Replacement of Ah01 b y Fez08 in the Presence of MgO
They showed that the presence of soda in a-synthetic laboratory cement in the amount of 2.29 per cent after burning gave a negative test with the ammonium acetate method for free lime, and also that commercial cements known to contain combined alkalies, but no free lime, reacted negatively. This may be regarded as evidence that the values for free lime obtained and reported herewith are actually a measure of this component, and are not vitiated by the presence of the alkalies combined in the material. However, because of the unusual reversal in direction of these alkali curves, a further test was made. A sample containing 2 per cent soda was prepared, burned, and titrated for free lime in the usual way. The free lime content was found by this method to be 3.1 per cent. The solution was then filtered off and the total calcium oxide in the filtrate determined gravimetrically by precipitation with ammonium oxalate. The content of lime by this method was found to be 3.0 per cent. Since the tn-o values are essentially the same, it is shown that the values obtained by the titration method are essentially correct even in the presence of combined alkalies in the product. The explanation of the reversal is not clear, but it seems probable t h a t the soda may combine with silica or alumina in a different ratio than does lime. For example, a given weight of soda may combine with a larger amount of silica or alumina than does the same weight of lime. Then, on replacing lime with soda, gram for gram, as was done in these experiments, the material (silica or alumina) available for combination with the lime would be decreased with each portion of soda added and the result would be analogous to the addition of more and more lime to the mixture. E f e c t of magnesia when sample has 1 per cent lime replaced by 1 per cent soda (Figure 8 ) and of ferric oxide on same composition (Figure 9 ) . It is evident again that magnesia is more effective than ferric oxide in this composition. The samples containing magnesia were burned at a temperature 70' C. lower than those containing ferric oxide. By a comparison of Figures 4 and 8 it would appear that, if we wish to maintain the percentage of lime as high as possible, the presence of soda offers no advantage as the influence of magnesia and ferric oxide appears to be as great alone as in the presence of soda. Effect of ferric oxide when samples contain 5 and 3 per cent, respectively, of magnesia and 1 per cent of soda (Figures 10 and 11). The samples containing 5 per cent magnesia were burned a t a
Figure 13-Effect on Combination of CaO Due t o Replacement of AlnOa by Fez08 "A" i n the Absence and "B" in the Presence of NazO
Conclusions The following conclusions may be drawn from these studies, but may be construed to apply only to the one base composition investigated-Ca0 67, AlzOa 10, Si02 23 per cent. 1-The replacement of lime by small amounts of soda or potash produces very little increase in the combination of lime with silica and alumina. 2-The replacement of alumina by small amounts of ferric oxide or the replacement of lime by small amounts of magnesia aids materially in promoting the combination of lime. The influence of magnesia is greater than that of the ferric oxide. 3-Replacements by ferric oxide and soda or magnesia and soda are not appreciably more effective than are replacements by ferric oxide or magnesia.
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INDUSTRIAL AND ENGINEERI-VG CHEMISTRY
Vol. 19, No . l l
6-A composition of CaO 67, A1203 10, and Si02 23 per cent It is not the aim of the paper to show that ferric oxide, requires, under the conditions of this study, a temPeratVe of magnesia, or the alkali oddes are desirable or undesirable 1500' C. to effect complete combination. 7 - 4 composition of CaO 63, MgO 3, NazO 1, +?037, pezo8 in Portland cement except in that they lower the temperature 3, sioz23 per cent, which approaches the composition of com- a t which a certain base composition can be burned to commercial Portland cement, requires a temperature of about plete combination. This base composition (CaO 67, &OI 1325 c. for complete combination under the conditions of these 10,s i o z 23 per cent) approaches the average composition of experiments. This is a decrease of 175" C. below the temperaPortland cement when the several components are referred to ture required for the base composition. 8-The common belief that any material that will cause an the oxides of lime, alumina, and silica. Furthermore, these increase in the amount of liquid formed in such a system, at a data indicate nothing a t all with respect to any other base given temperature, will likewise cause an increase in the combina- composition, and it is not permissible to assume similar tion of lime is true in this composition for magnesia and ferric oxide, but to a very limited extent for soda or potash, The effects for other compositions. The entire field of Portland charges containing these latter oxides were distinctly more fused cement is now being explored and the data are being correlated than the ones without them, but no great increase in combination with the properties of the products in service. was effected by their presence. A possible explanation is given.
Influence of Neutral Salts on the Plumping of Hides' By R. 0. Page and A. W. Page ~ ' O o L s T O ST A Y N E R I E s , R'OOLSTON,
Data showing the influence on the plumping of cowhide of the chloride and sulfate of sodium and of calcium chloride in concentrations u p to 4 normal, and a t the four pH values of 2,5,8, and 11, are given in detail. The pH of the solutions employed greatly affects the result of the addition of neutral salts. I n acid solutions, addition of the three salts studied reduces the plumping t o a minimum value of 0.8 a t a concentration of 0.75 normal. A t greater concentrations t h a n this t h e plumping increases again, this increase being most marked with calcium chloride, sodium sulfate giving results similar to those given by sodium chloride. A t t h e pH values 5 and 8, the three salts give widely differing results. Sodium sulfate gives in both cases a rather flat plumping curve with .a minimum a t a concentration of 0.75 normal, while sodium chloride gives a maximum a t about t h e same concentration, this maximum being less pronounced a t pH 8 t h a n a t pH 5. Increasing concentration of calcium chloride increases the plumping a t both these pH values, rapidly a t first, then more slowly a t concentrations between 1 and 3 normal, and finally more rapidly u p t o 4 normal. The plumping is more marked a t pH 8 t h a n a t pH 5. Hide pieces plumped in the more
N E W ZEALAND
concentrated solutions lose calcium chloride rapidly and completely on washing, but lose their plumping much more slowly, hide plumped in a 4-normal solution retaining its plumping even after soaking for a week in distilled water. In alkaline solutions increasing concentration of sodium chloride depresses t h e plumping, but much less t h a n in acid solution. The least plumping (1.27) occurs a t t h e maximum concentration studied. Sodium sulfate, on t h e other hand, depresses the plumping much more rapidly to a minimum of 0.84 a t 1.5-normal concentration, the plumping increasing again slightly in more concentrated solutions. Hide plumped in sodium hydroxide solutions of pH 12.5 reaches apparent equilibrium a t the end of a week, b u t in a calcium hydroxide solution of the same pH the plumping increases in t h e second week. I n neither case does the hide fall t o its initial thickness on restoring t o its original pH value, but on bating in both cases it falls further but not to its original substance. There appears to be a close connection between the nitrogen dissolved from cowhide by solutions of neutral salts and the plumping in such solutions.
.............. ECENT researches have indicated that as far as collagen and gelatin are concerned specific-ion effects, corresponding to the Hofmeister series, have real significance and cannot always be attributed, as LoebZhas done, to error of experimental method arising from neglect to control the p H values of the salt solutions employed. Stiasny* and his collaborators found that, in regard to the influence of salts upon both the dispersity of gelatin and the action of enzymes on hide substance, while the Donnan equilibrium is not applicable, the anion action is in accordance with the Hofmeister series. Ostwald, Kuhn, and Bohme4 found that the swelling of gelatin a t constant p H reveals the
R
1 Received June 16, 1927. Presented before the Division of Leather and Gelatin Chemistry at the 74th Meeting of the American Chemical Society, Detroit, Mich., September 5 to 10, 1927. 9 "Proteins and the Theory of Colloidal Behavior," 1st ed., Chap. V. 8 Collegium, 1S26, 13, 23, 67. 1 Kolloidchem. Beihefte, PO, 412 (1926).
existence of a specific-ion series; while Thomas and Fosters showed that in the destructive action of neutral salts on hide powder over a narrow pH range around the isoelectric point of collagen, once more a specific-ion effect is apparent corresponding to the Hofmeister series. Gustavson6 reviewed the literature, a t the same time suggesting an explanation of the action in question, and later' showed the important influence of previous treatment with neutral salts on the behavior of hide powder during tanning. McLaughlin and Theis,8 on the other hand, while confirming the finding of Thomas and Foster that sodium chloride dissolves hide powder more readily than does sodium sulfate, discovered that in the case of untreated hide the sulfate dissolves as much as the chloride. T m s JOURNAL, 17, 1162 (1925). e J . A m . Leather Chem. Assocn., 21, 206 (1926). 7 I b i d . , 21, 366 (1926). 8
a Cdtegium, 481 (1926).
