Aug., 1913
THE JOURNAL OF INDUSTRIAL
to enter the services of are willing and content of the several large color factories, accepting a small pittance for the privilege of working under conditions which may eventually lead to something worth while. The cost of living is comparatively are willing to accept small, and these young men mere living expenses in exchange for the opportunity to “make good.” The trouble with the American chemists in this connection is that they want to draw large salaries before they have really demonstrated to the manufacturer the ability to give ample value in return for the money he pays them. American manufacturers are perhaps as keen as those in any other country in making use of the chemist to develop their business, but they are very shy in buying a “pig in a poke.” If the young chemist in this country would be satisfied to go into a manufacturing plant under conditions similar to those accepted by the young German chemist, there is no doubt but that large research laboratories could be organized; but, as a rule, the young man here in America can make a much better living under other conditions, and consequently he
who one
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627
pursues that line which demands the least sacrifice. In the dyestuff industry another condition also prevails which makes it rather unattractive to the American manufacturer. Dyestuffs embrace a large number of compounds, and though the aggregate used in this country is large in quantity, nevertheless the amounts of the individual compounds themselves are not very great. Therefore the manufacturer would have to engage in the preparation of a large number of substances in comparatively small amounts, and this is not in accord with the best American practice, for the market would be limited almost entirely to the home country. If under American conditions, there were good profit to be made in the dyestuff industry, we feel sure this industry would have received its proper development in this country; but the American chemist, manufacturer, and capitalist have found more profitable outlets in other fields of endeavor, and have naturally followed the lines of least resistance. So the answer to the question What's the Matter with the American Chemist?” is “Nothing.” “
J. M. Matthews
ORIGINAL PAPERS THE CONSTITUTION OF PORTLAND CEMENT CLINKER By Edward D. Campbell Received June 26, 1913
With the attention now being given to the problem of determining the actual constituents of Portland
cement, a description of an experimental method for the separation and analysis of alite and celite, formed at the ordinary clinkering temperature, may not be without interest. Tórnebohm and Le Chatelier, as early as 1897, described “alite” as the crystalline material separating Tórneout from an inter-crystalline magma, “celite.” bohm1 further lays stress on the fact that celite is fusible at the clinkering temperature and promotes the crystallization of the alite. No claim is made that celite is a definite chemical or mineralogical entity, and it is according to this interpretation of the terms that they are used in this article. In 1912, while attempting to study the equilibrium which would be established, at the clinkering temperature, in Portland cement clinker, E. G. Pierce, working in conjunction with the author, noticed that the pure magnesium oxide crucible, in which pieces of the clinker were being heated, was stained wherever these pieces were in contact with it and that this stain often spread over a considerable part of the crucible. This observation showed at once that some constituent of the clinker must be very fluid at the clinkering temperature so that under the proper conditions it might be separated from the main mass of the clinker by absorption in a manner exactly analogous to that employed when the mother liquor is withdrawn from crystals by means of a porous plate. This conception that, at the clinkering temperature, Portland cement 1
Tonindustrie Z., 21, 1148 (1897).
clinker consists of a mass of crystals bathed in the mother liquor from which they have crystallized and that this mother liquor may be drawn off from the crystals by means of a properly prepared porous plate, forms the basis for the work described in the present paper. Considerable preliminary work was done by Mr. Pierce, but, owing to lack of time, the results obtained were not sufficiently conclusive to warrant publication. During the last year the work has been carried on by P. K. Fletcher and . N. Taber, working under the direction of the author. Although there yet remains much to be done before the constitution of clinker will be thoroughly understood, the results given herein seem to be sufficiently significant to render their publication desirable. The furnace used in the work was a Méker high temperature furnace described as No. 36 in the catalogue of the Scientific Materials Co., Pittsburgh, slightly modified as the needs of our work demanded. In this furnace the material under treatment is supported on a tripod and is surrounded by the flame from a Méker blast lamp situated below the bottom on which the tripod rests. The tripod used was made of alundum cement and wrapped with platinum foil so that the material did not come in direct contact with it, the whole being surrounded by a cylinder of refractory ware through which the flame must ascend and around the outside of which the products of combustion must descend before being drawn off through the two chimneys located on opposite sides of the furnace near the This principle of construction enables a bottom. much higher temperature to be obtained than can usually be secured in small, gas-fired furnaces. The temperatures were of a measured by means
/
628
THE JOURNAL OF INDUSTRIAL
standard platinum -rhodium thermal couple, the bead oí a short piece oí oí which was protected by means The thermal was so placed couple tubing. Marquart that the bead was in the annular space between the and inner cylinder and the material under treatment within 2-3 mm. of this latter. Temperature readings not exceeding could be made with a reading error two degrees and the temperature could be held con stant for as long as desired with a variation of less than eight degrees. It is not thought that the temthan to5 from their peratures recorded are more value. encountered in determining Some difficulty was of method the best preparing suitable absorbent made in the form of discs were These finally plates. in diameter, 3-4 mm. in thickness, about 30 mm. and weighing about 12 grams. These plates were placed with the clinker on one side and larger, heavier, magnesium oxide discs on the other, which, by their added capillary action insured the complete saturation of the small plates and the more complete removal of These discs were prethe celite from the clinker. C. P. Merck's from magnesium oxide which pared was found on analysis to contain 0.01 per cent alumina, 1503, and 0.03 per cent silica, Si02, but was free from any trace of ferric oxide, Fe203, or calcium oxide, CaO. Lots of 50 grams each of this magnesium oxide were packed in pure magnesium oxide crucibles and burned in the furnace at a temperature of 1500 o C. for one hour. This preliminary burning shrinks the magnesium oxide to approximately one-half of its original volume. Four parts, by weight, of this burned magnesium oxide- were then intimately mixed with one part of unburned magnesium oxide and to the whole was added strong magnesium chloride solution till a proper consistency was obtained to enable the mass to be moulded into discs with the aid of glass forms. The magnesium chloride solution used contained 250 grams of Kahlbaum’s The discs, after C.P. MgCI2 to the liter. removal from the forms, were thoroughly dried in a drying oven and became quite hard, owing to the formation of magnesium oxychloride cement which served as a binder. then stacked on the These discs were which had been first placed a tripod, upon thin disc of magnesium oxide covered by a disc of sheet platinum, thus insuring freetrue
dom frompossiblecontamination, andburned temperature of 1500° for an hour and a quarter. This resulted in strong discs, the faces of which could be ground to a smooth finish thus insuring good contact with the faces of the discs of clinker which were similarly ground. The material for making the clinkers in all experiments designated by the letter “A" was the raw mixture used by one of the largest Eastern cement mills. Several kilos of this material were ground for four hours in a porcelain lined jar mill to insure homogeneity and fineness. The material used in the experiments designated "B" was prepared by adding 8.42 at a
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ENGINEERING
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Vol. 5, No. 8
of Kahlbaum’s C. P. calcium carbonate, a weighed portion of the “A” mixture, thus maintaining constancy of the molecular ratios except that of the calcium oxide, CaO. The analysis of the “A” mixture was as follows:
per cent
CaC03, to
SiOo....................................
14.33
AieOa.......................... KcsOg...................................
4.44
1.74 41.40
CaO....................................
MgO................................... Undetermined......................... Loss on ignition..........................
2.02 0.89 35.18
The discs of clinker made were prepared by taking the raw mixture, moistening with water and tamping firmly into cylindrical moulds 43 mm. in diameter and 22 mm. in height. After drying, these discs were burned in the same manner as the magnesium oxide discs. The temperature of burning of the “A” mixture 0 was held at 1475 C. while that of the “B” mixture was C. In all cases the clinker was allowed to cool 1550° slowly with the furnace. The discs of clinker resulting from these burnings were about 30 mm. in diameter, 18 mm. thick and weighed from 32-35 grams each. Before using for an absorption the faces of the clinker were
ground true.
In setting up an experiment to determine the percentage of celite absorbed in a given time and at a given temperature, two small and two large, hard burned, magnesium oxide discs were accurately ground and weighed. A disc of the clinker to be treated was similarly ground and weighed. These five were then stacked in the furnace as shown by Fig. 1 in the accompanying photograph. The temperature -was then gradually raised until the thermal couple indicated the required temperature, at which
Fig. I
Fig. 2
point it
-was held constant as long as desired. At the end of the burning the stack of material was allowed to cool slowly with the furnace. The appearance of a typical stack after the absorption is shown in Fig. 2. On removing a stack from the furnace the discs were usually found more or less firmly cemented together, but a complete separation of the magnesium oxide discs from the alite could be easily made. After this separation the discs were accurately weighed, the increase in weight of the magnesium oxide discs due:
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THE JOURNAL OF INDUSTRIAL
Aug., 1913
AND
Table
TemperF.x-neri
Time
ature C.
-
°
ment
Hours
Per
Weight of constituents
cent
from 3-gram sample
celite absorbed
Ai
1475
13
20,87
As
1500
9
22.66
Ag
1510
3
21 40
A4
1575
21/3
26.25
B4
1575
8
20.80
Si02
AI2O3
-fr'eaUa
0.0743
0,0320
[ 0.0433
0.0747
0.0323
0.0476
0.0637
0.0279
[ 0.0476
0.0632 0.0671 0.0669 0.0769 0.0766
0.0277
0.0432
Í -
(
0.0559
í -
{ 0.0555
0.0353 0.0350
[
0.0314 0.0317 0.0343 0.0347
Table
0
ment
C.
(clinker) (clinker)
AI2O3 Fe203
22.11 20.61
7.32 6.82
2.69 2.51
25 .89
2.58
26.07
2.56 2.96
1.04 1.04 1.23
26.04
2.91
1.29
25,65
3.67 3.66 1.76 1.74
1.39
A B
1475 1500
Ai
1475
A2
1500
3 + 3 +
A3
1510
3
21.40
A,
1575
2V3
26.25
j 25.71
B,
1575
8
20.80
|
CaO 64.02
66.46
11.21
0.1928 0.1932 0.2161
0.0173
0.3493
0.0173 0.0160
0.3490 0.3865
0.2157 0.2288
0.0160
0.0113
0.3858 0.3866
13.63 13.64 14.46 14.39
0.2282
0.0113
0.3858
MgO 3.13 2.91
Table
A1203 100.0
A3 A4
100.0 100.0 100.0
b4
IV— -Molecular
Experiment
22.66
sío2
A B
100.0 100.0
Al
100.0
a2 a4 b4
100.0
|
23.34 23.36
Ratios
III—Molecular
Experiment Ai
Table
3
| 25 .83
Fe203 27.6 28.0 30.1 28.7
in
Celite
2.77 2.71 2.91
526.5
69.7
127.2
554.4 587.4
69.0 60.6
Impure
2.64 2.62
2.93
MgO
548.9
Alite
37.3 and
Clinker
CaO
MgO
4.6 4.6
311.4 346.6
21.1
1.5 1.8 2.0
281.9 276.5
14.7 15.1
278.2
.2
327.7
15.9 18.7
Fe203 Al203 Clinkers
2.56
Absorbed
98.4
75.8
19.5
66.42 66.47 71.14 71.16
CaO
in
19.5
0.74 0.74
2.52
SÍ02
140.9
Ratios
1.29
67.78 67.31 67.00 66.96
21.1
Alites
100.0 100.0
5.9 6.6 8.4 4.4
1
The analyses of the clinker and of the alite w made by the methods usually employed for the acWhen attempts curate analysis of such materials. made to analyze the magnesium oxide saturated were with celite, accurate results could not be obtained on account of the interference from the high concentration of magnesium salts. In order to obtain large enough weights of Si02, A12Os, Fe203, and CaO derived from celite to be satisfactory, three-gram samples of the small magnesium oxide discs were used in all cases. The finely ground material was easily and completely decomposed on digestion with hot dilute hydrochloric acid. The silica was removed by two evaporations. In order to obtain an accurate separation of the aluminium and ferric hydroxides from the magnesium
629
Percentage composition of celite absorbed
0.3854 0.3858
Alites 20.87
13
wt. in
MgO
Percentage composition of impure alite and clinker
celite absorbed S1O2 Clinkers
Hours
Total
wt.
0.0205 0.0205
II
cent
TemperExperi- ature Time
Calculated CaO
the absorbed celite being calculated to per cent of the original -Weight of the clinker. In experiment A2, Table II, three successive absorptions of three hours each were made, the magThe nesium oxide discs being changed in each case. that of the celite show of these results absorptions withdrawn in the nine hours, 70 per cent was absorbed by the first set of discs, 25 per cent by the second, and only 5 per cent by the third.
CHEMISTRY
I
0.2154 0.2150
to
Per
ENGINEERING
salts it
3 gms.
Si02
11.22*
9.13 9.07
AI2O3 19.28 19.36
Fe203 8.30 8.37
CaO
MgO
55.89 55.73
5 .31
18.24
7.99 7.94
55.20 55.36
18.11 17 .36 17.34 19.89 19.86
8.12
55.91
8.22 8.87 8.99
55.91 59,18 59.15
5
.32
4.95 4.96 4.15 4.15
2.92 2.93
found necessary to make the first pre-
was
cipitation in the cold, allowing the precipitate to stand for three hours before filtering. By filtering and washing the precipitate thus obtained, redissolving and reprecipitating in the usual manner, a complete precipitation of the aluminium and ferric hydroxides free from magnesium compounds could be obtained. It was also found necessary to make the first precipitation of calcium oxalate in the cold by adding a moderate excess of ammonium oxalate to a solution rendered just alkaline with ammonia, a drop of methyl red being used as indicator. The first precipitate of calcium oxalate was allowed to settle about 20 hours, when it was washed two or three times by decantation, redissolved in a little hydrochloric acid and then reprecipitated in the usual manner. The results of the analyses are shown in Tables I and II. Since tests show that all of the iron in both alite and celite exists in the ferric condition, when the burning is conducted in an oxidizing atmosphere, the iron is reported as Fe203. The per cent of magnesium oxide in the celite is calculated by assuming that the magnesium oxide of the clinker not accounted for by the analysis of the alite has been absorbed as a constituent of the celite. The molecular ratios of the constituents in celite are given in Table III, while those of the clinker and of the impure alite are given in Table IV. In order to determine whether celite possessed cementing qualities and whether the alite showed the presence of free calcium oxide, pats were made which, after remaining in a damp atmosphere for twentyfour hours, were subjected to the action of steam for six hours. The behavior of the pats under this test is shown in Table V. Table Pat Pure MgO burned at 1500°....... Material
7
of
pts. 1500° MgO
4-
1
pt. cement.
MgO disc containing Ai celite..... MgO disc containing B4 celite..... alite........................ B4 alite........................
V
6 hrs. in Steam Condition after Expanded—loose from glass—moderately strong—slight cracks. Completely disintegrated and washed
Soft, like mud, Soft, like mud. Perfect—strong—hard. Warped—cracked—rather weak—partly adhered.
From Table V it will be seen that the A, sample The lack of of elite behaved like a sound cement. soundness in the B, alite shows the presence of some free calcium oxide. The mixtures of celite and MgO set like a normal cement, but the expansion of the MgO caused the pat to go to pieces on steaming. This is no proof of unsoundness in the celite, for a pat of normal Portland cement and hard-burned MgO behaved
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The question of the soundness of celite on bine with silica, Si02, up to almost the amount required to form tricalcic silicate, and this work was confirmed steaming is therefore unsettled. Some interesting facts seem to be brought out by by Shepherd and Rankin.1 The fact that in alite the amount of calcium oxide in excess of that required the tables of analyses and molecular ratios. First, that although the proportion Of ferric oxide, Fe303, to form orthocalcium silicate is a function of the total to the alumina, A1203, is a little higher in the celite basicity and that when alite reacts with water dicalcic than in the alite, the difference is not very marked silicate and calcium hydroxide are the first products and the assumption that ferric oxide is molecularly of reaction, would suggest the conception that the equivalent to alumina, so far as the formation of celite calcium oxide in excess of that required to form calcium orthosilicate is in solid solution rather than in goes, seems justifiable although the hydraulic properdirect combination with the silica. ties of the aluminates and ferrites differ in degree. The above conception of the constitution of celite Second, Unger’s contention1 “that the alite contains the bulk of the alumina, if not all of it, while the celite and alite would reduce the problem of the constitution contains all of the iron,” is not sustained. Third, of Portland cement clinker to a study of solubilities with a given basicity of the mass as a whole, and would offer a comparatively simple explanation the proportion of silica to alumina and ferric oxide in of the changes taking place at temperatures exceeding the celite increases with the temperature. Fourth, 1400°. A little above 1400° the calcium alumínate with a given temperature, the proportion of melts and simultaneously dissolves calcium oxide and As the transformation of the silica to the alumina and ferric oxide in the celite de- calcium orthosilicate. as the basicity of the mass as a whole increases. creases ß or possibly y orthosilicate into the a form progresses Fifth, while, with a given basicity of the mass as a at temperatures above 14100 the solution of the a orthosilicate in the calcium alumínate would soon whole, the proportion of alumina and ferric oxide to become supersaturated so that crystals of a orthothe silica in the alite seems to increase somewhat with silicate containing calcium oxide and calcium alumíthe temperature, this is open to some question, as the have been due to increase less apparent may complete nate in solid solution would begin to separate removal of the celite. It is worthy of note that the out. This process of transformation of the ß or y proportion of ferric oxide to alumina holds fairly into the a orthosilicate would go on until the constant. Sixth, with a given temperature, the pro- recrystallization of this latter into alite was complete. of alumina and ferric oxide to the silica in A certain minimum concentration of calcium oxide portion alite decreases as the basicity of the mass as a whole in solid solution in a orthosilicate seems to be necesincreases. Since the celite must have been quite sary to prevent the transformation of the a into the fluid at the temperature of absorption it would, like ß or y forms just as the presence of certain concentraordinary liquid solutions, be homogeneous at a given tions of nickel or some other elements in iron will temperature and with a given basicity of the mass as prevent the transformation of the y into the a form of that element. a whole. Although much work yet remains to be done it has As a result of consideration of the experimental been thought that the suggestion of a working hypothwork herein described, the following hypothesis of the 0 esis based upon the parallelism which seems to exist the above 1400 during clinkering changes taking place between fused solutions at high temperatures and process and the constitution of the final clinker is solutions at ordinary temperatures might be suggested. First, that celite consists essentially of aqueous of some service in the attempts which are being made to above 14000 and a calcium alumínate fusible a little of solve the difficult problem of the constitution calcium when orthosilicate of dissolving, liquid, capable and calcium oxide, this latter being the more readily Portland cement. Chemical Laboratory soluble and that the solubilities of the orthosilicate University of Michigan and the calcium oxide follow laws parallel to those Ann Arbor which govern the solubility of salts in liquid solution. No evidence is yet forthcoming to enable the chemical constitution of the pure, fusible alumínate to be given THE DRYING RATES OF RAW PAINT OILS—A COMPARISON Secso that no chemical formula is suggested for it. By L. V, Redman, A. J. Wbith and F. P. Brock of either a or that alite consists ond, essentially ß' Received June 3, 1913 calcium orthosilicate holding in solid solution calcium The object of this research is to compare the relative oxide with some calcium alumínate and ferrite. The drying qualities of a series of raw oils used in the paint concentration of the calcium oxide held in solid soluand varnish industry. Some of these oils, to the tion is dependent upon the basicity of the mass as a whole and the temperature; but the limit of solubility trade such as soya bean and fish oil, have been introduced in large quantities recently. apparently is when the proportions required to form The oils used in this research are linseed, fish, soya the usually accepted tricalcic silicate have been reached. bean and chinawood. Considerable work has been It has been shown by A. H. White, working in this done upon the drying of linseed oil, and very recently of of a small amount that in the presence laboratory,2 investigations have been made upon suitable driers alumina calcium oxide could be made to apparently comfor fish, soya bean and chinawood oil, but no compariCement and Engineering News, Aug., 1910, p. 328.
similarly.
1
2
This Journal,
1, 7 (1909).
1
This Journal,
3, 211 (1911).
