1143
CLINKERING O F PORTLAND CEMENT.
tion should be prepared by which to check the table for the individual using it. TABLEII.-sHOWING Illinois coal. I
z 3 4 5 6 7 8
PERCENTAGES O F SULPHUR. Residues from Parr calorimeter in photometer. (Per cent.)
Washings from Mahler bomb. (Per cent.)
.................. 2.30 ............ 1.55 ................ 4.03 ........... 2.16 .............. 4.00 ....... 2.57 .... 3.04 .................. 1.53
Odin, pea St. John’s lump Pana, slack Danville, lump.. Ridgely, pea. Bloomington, lump.. Spring Valley, washed.. Elmwood
2.17 1.65 4.04 2.31 4.01 2.68 3.20 1.61
Results from use of this method, as above outlined, in comgarison with thcse obtained under standard conditions, are shown i.n Table 11. UNIVERSITY OF ILLINOIS,
URBANA,ILL.
CONTRIBUTIONS FROM THE CHEMICAL LABORATORY O F THE UNIVERSITY O F MICHIGAN.]
FURTHER EXPERIMENTS ON THE CLINKERING OF PORTLAND CEMENT AND ON T H E TEMPERATURE O F FORITATION OF SOITE OF T H E CONSTITUENTS.‘ BY
EDWARD DEMILLE CAMPBELL.
THISwork is, in a way, a continuation of the results published by the author in this Journal (24, 248, 9%; 25, 1 1 0 3 ) and ~ the experiments have been largely suggested by the results of the work previously reported. In a paper entitled “An Experiment upon the Influence of the Fineness of Grinding upon the Clinkering of Portland Cement” 25, I I O ~ ) ,the author, with S. Ball, described the progress of linkering in a raw mixture used by a prominent eastern cement mill. This raw mixture was burned in the laboratory rotary 2ment kiln, employed for our previous experiments. Two experiments, 104 and 105, were made with this same raw maerial. I n Experiment 104 the raw mixture was burned without 1 The laboratory work in the experiments to be describedin this paper has been done d r i n g the present year by Messrs. E E Ware. D . H. Clary, and M G. Doll, to whom I ish here to acknowledge my indebtedness for the care with which the work has been one.
1144
EDWARD
Dei?lILLE CAMPBELL.
further grinding, while in Experiment 105 the material mas ground before burning, so that 9s per cent. woultl pass a ZOO mesh sieve. In Experiment 105 twentp-four samples of cliIiIie1i were collected at approximately equal temperature intervals over a range from 1022' C. to 1627" C. The progress o f clinkering \\.as indicated, first, b;v the gradual change in color of the cIinIicn from ivhite through various shades of yellow antl brown to nearl?. black when the temperature reached about 1475' C and above These samples of clinker were ground with 1.5 per cent. c calcium sulphate (tlehyc!rateti gypsum I and from the resultin cement pats \vere made. The per cent. of tvater required for normal consistei:cy, the initial antl final sets i v c r e tleterminetl, an the behavior of the pats oil submitting to t h c action of boiling water for twenty-four hours was noted. The extent to ivhic silica had conibinct! {vas shonn i i i a number o i cases hj- tiete i i i i n i n ~the proportion of silica soluble i n hot dilute hytlrochlor acid and i n I O per cent. sodium carbonate. I n Esperiment I( the results showed that the combination of the silica progresse ivith increasing temperature until about 1352' C. \vas reache when the amount of "untlecompose(1 silicatcs" was a minimum This temperature, r 3 j2' C., was that of n~asiniuiiitlisintegratie of the pats by bo'iling water. By the time the temperature 'has reachet! I 4 7 j " C. the constituents of the clinker had become rearranged. that the pats stood a perfect boiling test. I n the raw mixtures usually used in the pro8tluction of Po land cement, the silica, alumina antl ferric oxide almost alwa occur chemically combined i n the form of clay, shale o r ot'her silicates. In the theories now usually held in regard to the progress of clinkering, the calciiini o\;it!e is supposetl at one sta of the process to coiiibine directly \\-it11 the clay substance. tl is, the silicates as a whole; and the double silicates thus form are supposed to split up and form the final tricalciuni silica characteristic of a perfectly formed Portland cement. So far have but little data to show at what temperatures such dou silicates may be formed, or at what temperature they may be) to split up and trica!cium silicate be formed. If a comparis of the behavior during clinkering of a purely mechanical m ture of various oxides, acidic and basic, could be made with the of a natural rock mixture in whic!i the silica, alumina and fei
CLINKERING O F PORTLAND CEMENT.
1 I45
oxide are chemically combined, we might observe differences in behavior which would give same knowledge as to the probable temperatures of formation and rearrangement of the various consti tuents. Experiment Iio.-This experiment was undertaken far the purpose of comparing the behavior during clinkering of a purely mechanical mixture of the oxides entering in the formation of cement, with that of a natural rock mixture of the same ultimate composition, such as that used in Experiments 104 and 105. T h e raw materials used for Experiment I I O consisted of pure glass sand, a comparatively pure marl, chemically pure hydrated ferric oxide, chemically pure hydrated aluminum oxide, and chemically pure magnesium oxide, obtained by ignition of the carbonate. The composition of the materials used is given in Table I.
TABLEI. SIO?
L.W.marl...... 1.21 Glass sand.. ..... 99.60 Al( OH), ............. Fe(OH), MgO
~ 1 ~ 0 Fe203. % 0.25 0.25 0.2j
74.15
....
. . . . . . . . . . . . . . . . . 86.13 .........................
CaO
52.89
MgO
0.89
........ ........ ........ ....
Ioo.00
LOSS on ignition.
44.58
....
25.85 13.87
.....
These materials were first finely ground separately. T h e molecular ratio of the clinker in Experiment 105,calculated on the basis of 100 malecules of silica, was as follows : SiO,, 100; A1,0,, 24.9; Fe,@,, 4.5; CaO, 315.2; NgO, 19.1. In order t o attain the same molecular ratio from materials of the composition given as in the above table, we should have to use them in the following proportions : Sand, 566 grams ; A1 (OH) 3 , 329 grams ; F e ( O H ) ,, ;-) grams ; L. W. marl, 3343 grams ; R'lgO, 47 grams. T h e above amounts of the various materials were carefully mixed dry and subjected to a second grinding of six hours in the porcelain-lined mill used in Experiment 105. The finely ground material was then moistened with sufficient water to enable it to be rolled out and cut into cubes for burning, as in former practice. The furnace employed was that used in previous experiments, and the method of measuring the temperature attained by the clinker was the same as that used in Experimefit I O j . T h e thermocouples employed were carefully checked, from time to time,
I 146
EDWARD
DeMILLE
CAMPBELL.
to detect and correct for any change in electromotive force due to long heating in an atmosphere rich in carhon dioxide, with cccasioi?ally traces of carbon monoxide. From the prepared mixture of oxide eleven samples of clinker were collected from 12j7” C. to I j71° C. On cornparing the color of these various clinkers with those from Experiment I o j , made at corresponding temperatures, it was found that the colors agreed, as closely as could be detected, with each other in practically all cases. T h e samples of clinker were ground with 1.5 per cent. calcium sulphate (dehydrated gypsum) and from the resulting cement pats were made; the amount of water required for normal consistency, the initial and final sets, and the behavior under the boiling tests, were noted. The results of these tests are summarized in Table 11, together with those obtained from the clinkers i n Experiment I o j , produced at temperatures corresponding most closely ivith those of the present experiment. T h e completeness of chemical combination of the silica was determined as in Experiment 105, in the two samples produced at 1348” C. and 1480” C., by dissolying in dilute hydrochloric acid and treating the undissolved residue with IO per cent. sodium carbonate, thus obtaining a final insoluble residue of “undecomposed silicates.” T h e residue of “undecomposed silicates” on sample No. 9 was fused with sodium carbonate and thus resolved into its constituents, which were determined in the usual maimer. T h e amount of undecomposed silicates from sample No. 4 was only 0.41 per cent., while that of sample No. 9 was 1 . 4 j per cent., made up of 1.08 per cent. SiO,, 0.15 per cent. Fe,O, and A1,0,, 0.08 per cent. CaO, and 0.14 per cent. MgO. T h e complete analysis of sample So. g gave the following results: Total SiO,, 20.74 per cent. ; -A1202, 10.44 per cent; Fe,@,. ?.j6 per cent. ; CaO, 63.79 per cent. ; MgO, 2.29 per cent. ; total, 99.82 per cent. The physical tests on the cement from Experiment 110 compared with that of Experiment 105, made at the nearest corresponding temperature, are summarized in Table 11. As the experiments were performed by different men, and it was found by subsequent weighing that the average weight of clinker from Experiment I I O was about twice that in I o j we must expect that the reactions in I I O will apparently lag somewhat behind those of 105. This is best illustrated in the temperature at
CLINKERING OF PORTLAND CEMENT.
1147
which the first perfect pat is obtained, the difference in this case being 35" C. TABLE11. i
4i 0
c)
jl
I10
I
105
IO
I10
2
105
I1
IIO
1257
Very soft, mushy, loose from glass. Badly cracked, warped, very weak. Expanded, not warped, easily rubbed to sand. Badly warped and broken, Very easily rubbed to s a n d , cracked. Very badly warped, cracked, almost disintegrated. Disintegrated.
80
I247 62 1273 74
I281 54 3 1318 59
"
(' (1
'< 105 IIO
16 1401 33% 7 1432 25
105 17 1425 32 IIO 105
IIO 105
8 1457 26 18 1451 30 g 1480 26 19 1475 28
110 IO
105
20
(10
XI
105
23
r j I o 26 1501 27 1571 26 1582 24
.. .. .. ..
..
.. I .. .. ..
* *
18 6 IO 11
14 12
5 5 32
5 21
( 6 3 15 4 58 Badly warped, easily rubbed to sand. 2 22 Badly warped and cracked, almost disintegrated. 5 Badly warped and weak. 4 45 Slightly warped, cracked, loose from glass, but quite strong. 5 Badly warped, quite strong, 4 40 Perfect pat. " I 52 1' 4 22 " 2 37 I' 4 ..
..
..
The data obtained from Experiment 110,together with all the results from Experiment 105, as reported in our previous article, are represented graphically in Plate I. In this plate the abscissae represent the temperature at which the various samples of clinker were collected, and the ordinates the per cent. of water required for normal consistency, and the time for initial and final sets. Sample No. 21, Experiment 105, has been omitted from this cttrve, because, as was explained in the paper describing this work
I 148
EDWARD DeMILLE CAMPBELL.
in detail, at the time wher! this particular sample was collected, carbon monoxide ivas found in the products of combustion, which caused the clinker produced to gi1.e abnormal results. The rate of cooling and the conditions under which clinker cools has a marked influence on the time of both initial and final set. In both these experiments the hot clinkers falling from the rotary were caught in small metal trays so that they coolec! comparatively quickly in the a i r , probalil!. qiiicker than in most cases in coinmercial practice. This more rapid cooling teiicls to make the cement have a much quicker initial and final set, although tlie quantitative influence of this variable has not yet been determined. Tlie present experiment \vould have been more satisfactory had the collection of clinkers begun at as lo\\ :Lte171jlerattire as that einployed i n Experiment 105, because. in Experiimxt T I O the heavy lining of the furnace, ivith ivhich the clinker is constantl!. in co:itact, woultl probably not have had time to attain the same teinperature as tlie thermocouple and \:.oultl prolnli1.1 exert a more or less cooling effect on the clinker collected in tlie first hour or so. T h e result of this is to tliron- some tloubt on the similarity of the Idiavior of a mechanical inistiire of the oxides and that of a cement mixture n-hen heated to temperatures belon. 1350' C. However, by the time the temperature has reached almtt 1350' C. we have the most nearly complete combination of tlie silica at least, 110 matter in what form the constituents esisted in the original mixture ; that is, i f tlie material is finel!- enoygh tlivideil. the same compounds or solitl solutions ]vi11 b e formed at about 13jo" C. in all cases, irrespective of the contlitiomnin which the constituents existed in tlie original mixture. . i s the teiiiperature is raised above that at \vhich maximum disintegration take6 place tlie basic silicates, probaldy tricalciuni silicate. begin to separate out. leaving a more acid magnia, as is slio\vn by the larger proportion of "uiideccmposed silicates" Eound in clinlier burned at very high temperatures than in that burned at the temperature oi tnaximuiii disintegration. The results io~uitlin Experiment I I C confirm' 011this point those described under Experiment 10;. The complete separation of the hasic silicate, characteristic of Portland cement, which apparently was complete in Experiment 103 at 147j" C.,did not take place i n the present instance until I 510' C was reached, probably on accotiiit of the larger pieces of clinliel in Experiment I I O : hut. as has also been ,slio\vn in (nir pre-
CLINKERING O F PORTLAND CEMENT.
1 I49
liniinary experiments, this reaction, indicated by the formation of a pat capable of standing a perfect boiling test, may vary between 1400' C. and I57j" C. In case an excessive amount of calcium oxide is employed, no perfect boi!ing test will be obtained at all. Experiwwt 107.-This experiment was undertaken to show the behavior of dicalcium ferrite in clinkering. The raw materials used were chemically pure ferric hydroxide and L.W. marl, previously described, as used in Experiment 110. T h e finely divided material was first mixed and then subjected to prolonged grinding to insure fineness and a perfect mixture. The materials were carefully proportioned so as to give the molecular ratio zCaO.Fe,O,. The material thus prepared was moistened with sufficient water to enable it to be rolled out and cut into cubes for burning, as in the previously described experiments. From this material eleven samples were collected, from 976" C. to 1307' C., at which temperature the material began to fuse and stick to the sides of the rotary, showing that the overburning temperature! had been reached. These clinkers varied in color from dull brown to) nearly black as the temperature at which they were made increased. T h e various samples were ground with 1.5 per cent. of calcium sulphate (dehydrated gypsum), and from the resulting material pats were made to determine the amount of water required for normal consistency, the initial and final sets and the behavior under the boiling test. The results obtained on these samples are summarized in Table 111. TABLE111. 0
d 2 0 I.
e" 51 45 43 42 37 32 28
23 22 22 21
a
Y 2.j
2
Pui
-2
&.
z 20 3 .- .-; I g ds! B E E94 -E
'-
.. .. .. .. .. .. .. ..
.... ..
7 6 8 IO
I4 I1
9 I1
8 8 3
3 2 2 2 2
I I
.. .. .. ..
2 .
$2 -B I.E, EE 27 8 16 6 48
23 7 23
32 35 31
Y
0
4d
4
Slightly warped, weak. Warped badly, stronger. Warped slightly, fairly strong. Warped considerably, quite strong. Warped a little, quite strong. Warped very little, stronger. Same as No. 6. Same as No. 6. Not warped, very strong. Same as No. 9. Warped, very strong.
1150
EDWARD
DeMILLE
CAXPBELL.
Experiment Io8.-This was undertaken to study the behavior of dicalcium aluminate in clinkering. The materials used were finely ground, chemically pure aluminum hydroxide and L. by. marl. These were mixed in proportion to give the molecular ratio zCaO.Al,O,, and after mixing, were subjected to thorough grinding, as in the preparation of dicalcium ferrite, in order to insure fineness and perfect mixtiire. Fourteen samples of clinker were collected between 871' C. and 1305" C., which latter was the overburning temperature, as was indicated by the clinkers beginning to fuse and stick to the sides of the rotary. All the clinkers from this experiment were very light, almost white in color. The tests obtained from the clinkers after grinding with 1 . 5 per cent. calcium sulphate (dehydrated g\,psum) are summarized in Table IV. TABLEIV.
I1
871 905 942 976 1013 1038 1065 1107 1132 1161 1191
I2
I222
I 2
3 4
5 6 7 8 9 IO
13 1256 I305
14
I ' a
14 47
None
Pats
I
to 7 inclusive were very soft after boiling.
over 6 .. 4 52 4 37 ' I * * 47 i' 2 41 27 over 8 Perfect pat. .. 40 6 57 26 2 18 Free from glass, not warped. .. 6 2 5 Warped very slightly, some cracks. considerably, c r a c k e d 4 I I O Warped badly. 12 2 I Warped, cracked and broken. 3 2 19 Disintegrated. ( (
69 60
.. .. .. ..
..
..
Experiment Iog.--This was intended to show the behavior of monocalcium aluminate on clinkering. The materials used mere the same as those in Experiment 108. I t was intended to proportion the aluminum hydroxide and marl so that the inisture should have the molecular ratio CaO.Al,O,. The check analysis made on a sample of the clinker to verify the accu-
CLINKERING OF PORTLAND CEMENT.
1151
racy of the mixture showed that the ratio of CaO to Also, was 0.85 to 1.00 instead of 1.00 to 1.00, as originally intended. O n reviewing the figures it was found that an arithmetical mistake had caused this error. The analysis of a number of samples of clinker, however, revealed an interesting point, due to this very error. Nine samples of clinker were collected between 1156"C. and the overburning temperature, which did not occur until 150j" C., or 200' above that of the dicalcium aluminate. T h e clinkers obtained were ground without addition of calcium sulphate and made into pats, which were tested in the usual way. The results of these tests are summarized in Table V. TABLEV
+
I
..
2
I
1156 1215 3 I254 4 1280 5 13x5 6
I349
80
73 54
9 1505
45
..
3 i
Nos. I, 2, and 3 very soft, disinte18 over 24 grated, getting harder in order of 13 I 56 numbers. I 4 1 4 1 58 1 45 Harder than No. 3, easily pulverized with fingers. Harder than No. 4, less easily pulverized, weak. 54 2 I2 Difficultly pulverized with fingers, stronger than No. 5 . I 41 2 40 Could not pulverize with fingers, quite strong and hard. 1 47 3 49 Stronger than No. 7, harder and quite brittle, 2 0 0 2 30 Very strong, hard and brittle, warped.
..
Analyses of samples Nos. I , 5 and 8 were made to determine the proportion of calcium and aluminum oxides, readily soluble in hot, dilute hydrochloric acid. This was done by first boiling a 0.5 gram sample of the finely ground material with 50 cc. of water and then adding 5 cc. of hydrochloric acid (sp. gr. I ,201,stirring for two or three minutes and then filtering to determine the amount of insoluble residue. The calcium and aluminum oxides in the filtrate were determined in the usual manner, and the molecular
E D W A R D D e M I L L E CAMPBELL.
I 152
proportions in n.hich they \\ere ic;~uidn-ere calculated. The results of these anal!,ses are given in Table 1-1. TABLEVI. Sample. TemperNo. ature. j
11j6 131j
8
1407
I
Insoluble residue.
42.48 28.7j 16.98
CaO .41.03 i n solution. i n soiution.
29.81 29.2j 28.94
Aloleculsr ratio.
__A__-
CaO.
22.71
I
39.10
I
52.76
I
AI9O8.
o.4rS 0.736 1.006
.A study of the figures given in the last two co'lunins of Table \'I brings out the significant fact that when CaO is heated with Xl,O:, probably the tlicalciuni almiinatt is first formed, this formation being completed at about 1200' C. Further, that dicalcium aluminate, which ma!. lie cotii!iletely t'ornietl a little above 1 2 m O C., then begins to combine ivith more alumina, if present, as the teniperature incl-cases i i i i c i l t l i r mciiiocalcium aluminate has been io.rmec1 a t about 1400' C. The tlicalciuni aluminate when completely iornied, as is shown in sample S o . 12, Experiment I&, has a quick initial and a comIm-ativel!. quick final set, \:.bile the mo~iocalciumaluminate has a slon. initial and comparatively slo~vfinal set, even when tlie material has been partially fused, as is shown i n sample S o . 9, Esperiment 10g. T h e results found i n Experiments 107, 10s and 19 are shown graphically in Plate I1 in which, as in Plate I fo'r Experiments 105 and 110,the ordinates represent the per cents. of water required for normal consistency, the initial and final sets and the abscissae shoiv the temperatures at ivhich :lie various samples were collected . -111 tlie results so far obtained in this laboratory must, in a IiraJ-,be considered as fragmentary, nevertheless they seem to point to a number of clearly marked changes which, taken together with a tentative hypothesis, may serve as a foundation for a complete series of experiments, which will demonstrate all the reactions which take place in the clinkering of Portland cement. In natural rock cements which are burned at temperatures below most of those with which w e have been dealing, it is generally supposed that the hydraulic properties are due to some compound o'f calcium oxide with tlie clay substance as a whole, and not to a number of new bodies resulting from the splitting up of these double compounds, and rearrangement at the high
CLINKERING OF PORTLAND CEMENT.
1153
1154
E D W A R D DeJIILLE CABIPBELL.
CLINKERING OF PORTLAKD CEMENT.
I155
temperature employed in the manufacture of Portland cement. It is the temperature of formation and behavior of these latter compounds which we will consider in the present discussion. I n order to form a reliable judgment as to the equilibrium, which will exist in any mixture at a given temperature, and hence the properties of clinker produced from a given mixture burned at a definite temperature, we should know the properties of all the separate constituents which may be present; that is, if we regard clinker as a more or less complete solid solution containing a number of constituents, we must know the properties of all the constituents separately before we can judge the properties of the mixture or solid solution as a whole. -4lthough we have no data in regard to the behavior of pure tricalcium silicate, made at carefully Controlled temperatures, we know from the experiments of Newberry and others that the tricalcium silicate is generally considered slow-setting. \Ire have no data, either, in regard to the behavior of pure dicalcium silicate produced at definite temperatures. From the behavior of certain slags, however, and from the data given under Experiment 103 of our previously published work,l it would appear that dicalcium silicate formed above 1450' C. has probably a rather quick initial, as well as final set. In regard to the aluminates of calcium, Experiments 108and 19 probably give the first data in regard to the initial and final sets of these compounds from clinker produced at carefully controlled temperatures. A study of the curves in Plate 11, Experiment 108, on the dicalcium aluminate shows that the amount of water required for normal consistency increased with increasing dissociation of calcium carbonate until it reached its maximum of 125 per cent. when a temperature a little over 1000' C. had been reached. From this temperature the amount of water required fbr normal consistency decreases with almost perfect uniformity, reaching its minimum of Go per cent. for that sample produced at the overburning temperature. -4 study of the curves for initial and final sets would apparently indicate the increasing combination of aluminum oxide with calcium oxide as the temperature increased until by the time 1222' had been reached nearly all of the oxides were combined as dicalcium aluminate, 1
This Jouroal, 04, 969.
I
156
EDWARD DeMILLE CAMPBELL.
as indicated by the initial antl final sets reaching their minimum at this point. -As tlie temperature rises above this point, 1222' C.! the slight slowing up of the initial set, together with the marlmi slowing lip of tlie final set. would indicate prolmbly more or less dissociation of tlicalcium aluiniiiatc iiitcl the more slmv-setting monocalcium aluminate ant1 free calcium oxide. The ciirves for Esperinimt 109, monocalcium aluminate, show a steady decrease in the amount of water required for normal consistency witl: increase of temperature. This decrease, ho\vever, apparently takes place more rapidly after about 1255' C. is reached. -1wort1 here may account possibly, or very probably, for the someivhat almilit change iii thc \\-ater requiremeat, as well as some of the other properties. In this experiment the first clinker was collected ivitliin about an hour after lighting the furnace and it is not improbable that in this comparatively short time tlie heavy furnace lining had not become thoroughly heated through so that the pieces of clinker in contact ivitli the furnace lining had not reachetl ciiiitc as high a teniperatiirt. as \\-oultl lie indicated by the reatliiigs observed at tlie thermocouple. T h e curves for the initial antl final sets of Experiment 109.ho\vever, studied i n conjunction n i t h tlie analyses obtained upon the three samples of cliiilier, ~voultlapparentl\- indicate pretty c1eal-l:- that tlicalcium almiinate \vas first foriiietl until nearly all of the calcium ositle hat1 talccn this form antl then ns the tmiperature increasetl the tlicalciuiii alumiiiatc began ti? clissociate into nioiincalcium aluniinaie ant1 calciiiin oxide. which calcium oxide. ho\vcver. w o ~ ~ l at tl once combine with the excess of alumina present, until at about i 400"C. nothing hut mnnocalcicin Ftluminate is fouiitl, togsethvr wit!i the excess of uncombinetl alumina. The proportion of tli. . calcium aluminate ant1 inoiiosalciium aluminate. rxisting at an!. given temperature, ivil13 of course. be largely infiuencetl liy the re1atii.e masses of the tu-o ositles. From the cilr\'e for the final set. ho\vever, i n Esperiiiieiit ~qit ~ o u l t lseem as though the dissociation of tlicalciiim ali1,niiiiatc. 1. 111 ti; tF.!iI: ~>!:Icc)r:ipi(ll>., s001i after T 300' C. has heen passetl. S[onocalciiuii aluminate has apparently quite a slon. initial and final set. Had samples been collected iii Experiment rog in the interval heti\-een 1407' C. and r-06" C i t is probable the ciirvc' i\~oiiI(l1ia~:e Iiatl :I sonic\\-hat tliffcreiit forin. the filial set especia!l!- slc>\\-iiig i i p for a loiigcr
C L I N K E R I N G O F PORTLAND CEMENT.
11.57
period before dropping off,thus approximating more nearly the curves for the final sets of Experiments I I Oand 105. The curves for the dicalcium ferrite, Experiment 107, show, as for the dicalcium aluminate, a regular diminution in the amount of water required for normal consistency with increase of temperature. T h e quick initial sets a t 1000' C., or below, show that some dicalcium ferrite is probably formed even at this temperature; but the fact that the final set dces not reach its minimum until nearly 1200' C., o r a b u t the same temperature as that for the same condition as for dicalcium aluminate, 'would indicate that ferric oxide behaves almost like aluminum oxide, which would be further confirmed by the fact that the overburning temperatures of dicalcium ferrite and dicalcium aluminate practically coincide .Again, this distinct, although somewhat slight, slowing up of the final set of dicalcium aluminate alwve I ~ O ' C. would be suggestive at least of dissociation of part of the dicalcium into more slow-setting monocalcium ferrite ; however, me have at present no data in regard t o monocalcium ferrite. This last must be taken as merely suggested by the analogous behavior of the aluminates. A study of the curves for Experiment IO; shows that the amount of water required for normal consistency falls off regularly with increase of temperature after the point necessary for complete dissociation for calcium carbonate has been passed, in this case about I 1 2j oC. If we compare the curve for the initial and final sets in Experiment I O j with those from dicalcium aluminate and dicalcium ferrite, we will note that in all three cases we find the final sets reaching a minimuni at a temperature very near 1200' C. and that the initial set is rapid in all three cases a t this same temperature. This would indicate that in cement mixtures dicalcium aluminate and dicalcium ferrite were probably the most reactive constituents formed at this temperature. The very marked slowing up of the final set in Experiment To;, between 1200' C. and 1300' C., is probably due t o some silicate formation, since this marked rise in the curve is absent from the curves for pure aluminates and ferrites. The samples of clinker collected a t 1352' C. showed, as has been previously explained, maximum disintegration under the boiling test, together with a minimum amount of undecomposed silicates. Thus we would find this second valley,
I
158
THONAS EVANS AND WILLIAN C. FETSCH.
so to speak. in the curve of final set representing that period in the process of clinkering where we have most complete combination of the silica, but where the tricalcium silicate, characteristic of Portland cement, has not a < yet formed. or. at least, separated from solid solution. The rise in the curve betireell 1 3 j 2 O C. and 1475' C. is not improbably due to the gradual separation or formation of tricalciuin silicate. perhaps accoinpanied by progressive dissociation of dicalcium aluminate and ferrite. 147jo C'. is that temperatv.re at which the first perfect boiling test is obtained. \\-hether the gradual falling off in the time of final set with rise of temperature above I d 7 j o C. is due to dissociation of tricalciiim silicate and formation of the more quick-setting dicalcium silicate we are not prepared at this time to venture an opinion, since our work has not as !et reached a point which ~\-ouldjustify a positive opinion in regard to the behavior of the silicates themselves. Experiment I I Owould have been much more satisfactory had the collection of samples begun at as low a temperature aswas employed in Experiment 105. Xevertheless, if correct allowance is made for the first few samples of clinker probably not being quite as hot as is indicated by the thermocouple, we find that the curves are of ver?- much the same nature and indicate that probably the same reactions took place in both cases. Jn forming this jud,ment due allowance must be made for the fact that in Experiment I I O the individual pieces of clinker weighed twice as much as those in Experiment Ioj, and that the furnace lining during the collection of the first two or three samples had probably not had time to approach the temperature of the thermocouple as in Experiment 10;. ASN ARBOR~ I I C H I G A S
June z j ,
19~4.
CONTRIBUTIONS FROM THE CHEMICAL LABORATORY O F THE CNIVERSITY OF CINCINNATI, NO 62.1
IlAGNESIUM AMALGAM A S A REDUCING AGENT. BY 'PHOMAS EVANS A N D W I L L I A M c. FETSCIT Received IUl) 9 1904
~ I - H I Lmagnesium E amalgam has been lcnown for some time, having been prepared by TVanltlyn and Chapman in 1866, its use as a reducing agent in organic chemistry has hitherto been neglected.
