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REFERENCES (1) XSSARSSON, G: Sveriges Geol. Undersbkn., Lrsbok, Ser. C 30 (6), S o . 399 (1936). BACCAREDDA, LI.,A Z D BCATI,E . ’ h t t i Socongr. intern. chim. 2, 09 (1933).
(2) (3) (4) (5) (6) (7)
BESSEY, G . E. : Private communication. FRICKE, R.: Z . anorg. Chem. 176, 2-19 (1925); 179, 257 (1929). FRICKE, R., BND SEVERINH. : Z. anorg. Chem. 206, 287 (1932). GOUDRIAAN, F . : Proc. Acad. Sci. Amsterdam 23, 129 (1921). GUGGESHEIM, E. A . : dlodern Thermodynanzzcs b y the Method of Willard Gibbs. hlethuen I%Co., London (1933). (8) JONES, F. E.: Trans. Faraday Soc. 36, 1454 (1939). (9) LEA,F. M.,A N D BESSEY,G. E.: Private communication. (10) LERCH,W., ASHTON, F. W., AND BOGUE,R.H.: J. Res. S a t l . Bur. Standards 2, 715 (1929). (11) MARSH,J. S.: Principles of Phase Diagrams. McGraw-Hill Book Company, New York (1935). (12) MYLIUS,C.: Acta &ad. Aboensis 7, 3 (1933), “The calcium aluminate hydrates and their double salts.” (13) ROOKSBY, H. P.: Trans. Ceram. Soc. 28, 399 (1928). (14) WEISER,H . B., AND MILLIGAN, W. 0.: J. Phys. Chem. 38, 1175-82 (1934). (15) WEISER,H . B., A N D MILLIGAN, W. 0 . : J. Phys. Chem. 44, 1081-94 (1940).
T H E QL-IXARY SYSTEM CaO-Alz03-CaS0~-I~20-H20 (1 PER CEIiT KOH) AT 25°C. F. E. JONES Building Research Station, Garston, Watford, Herts, England Received M a y 27, 19.44
The present work is a further contribution to the study of the reactions occurring in the setting and hardening of Portland cements, and the disintegration of such cements on exposure to sulfate waters. Attention has previously been confined to the quaternarysystem Ca0-~11z03-CaS04-Hz0(8,9). Since the liquid phase in a setting cement contains much alkali (1, 4, 5 , 6, 12, 13), it is necessary to consider how the equilibria found for the quaternary system may be modified in the presence of the additional alkali component. In working out the equilibria in the alkali systems, attention has been confined to concentrations of alkali equivalent to 1 per cent KOH and 1 per cent NaOH. respectively. Since the alkali present in British Portland cements is mainly K 2 0 , attention has been given first to the KZOsystem. The application of the results to the chemistry of cement will be considered in the discussion section. The experimental methods were similar to those previously used. Stainless-steel tubes of 200-ml. capacity were employed for shaking purposes. The potassium sulfate and potassium hydroxide used were of Xnalar purity. X o separate analyses were made for &O in the various solutions. Throughout the work there was no evidence of any change in the optical properties of the CaS04.2Hz0,Ca(OH)z,Ca=1.6Hz0, or
THE QVIXARI- SYSTEM
Ca0-Al~03-CaS04-I~20-H20AT 25OC.
357
C3A.3CaS04.32H20 solid phases to suggest the taking u p of alkali by these compounds. Specific analyses for alkali on 0.05-g. to 0.2-g. samples of these solid phases from certain of the equilibrium mixes s h o w d only 0.1 or 0.2 per cent d ~ 0 . 0 per 5 cent &O. In the case of aluininn gel, a 0.03-g. sample obtained from a mi.; containing relatiyely much IiOH gave 0 8 per cent 1 0 . 2 per cent L O , and a qimilar 0.1-g. sanipie of cryqtalline hydrated alumina gave 0.25 per cent 1 0 . 0 5 per cent IGO. The small amounts of L O found are probably to be ascribed t o some surface adsorption and retention of mother liquor in filtration. I n the study of the quaternary system C'a0-111203-CaS04-H20 (8, 9), the system wa. considered as a reciprocal ssalt-pair. The method of representation
frc i'
A
(La s04)3
(caoh
FIG.1. Quinary system Ca0-.11~0~-CaSO~-K~O-H?O (1 per cent KOH) a t 25°C.
adopted for the quinary system is the logical extension of this due to Jlinecke though, since the system non- shown is a restricted one, there is considerable modification in interpretation. The qpacc figure (figure 1),in which the quinary and quaternary boundary curves are shovn, consists of a prism built up of three reciprocal salt-pair systems and tn-o other quaternary $?stems represented on the triangular end-faces. Only the compositions of the salt mixtures in solution can be expressed by wch a figure, the water content not being shown. This may, however, be done by using a projection on t o the base (Ca0)3-,11203-(CaS04)aX12(S04)sfrom the edge (&0)3-(&S04)3 by lines through this edge and parallel t o the end triangles (figure 8). The water content may thus be represented in the usual ;i-aj- nithin a pyramidal ,qiace figure. The composition of the salt
3 58
F. E. J O S E S
mixture is determinable Tyith the knowledge that the alkali content is always equivalent to 1 per cent K O H . Thus, from the space figure the total content in moles of salt mixture in solution is obtained. This content, lew the fixed content of ( & 0 ) 3 , gives the molar content of ( C E ~ Oand ) ~ -11203 together; hence, from the projection (figure 8) giving the relative percentage contents of (CaO)3and (*%l2O3), the actual molar contents of iCaO)s and & 0 3 separately map be calculated. The projection also gives the mole percentage of 803 in the total content of salt mixture. In figure 1, however, as stated, the water content is not shown, though it may be calculated. Moreover, since the alkali concentration is maintained constant in solution and no alkali appears in any solid phase, the figure is essentially a cross section through the complete system for the alkali concentration equivalent t o 1 per cent KOH. This involves important differences in interpretation as compared with the same method of representation used for the complete system. Only two solid phases are required to define boundary curves in this restricted quinary system, and stability fields are surfaces, not volumes as in the complete system. The corners of the prism represent pure salt compositions as in the case of the complete system, but the further interpretation differs. While in the complete system the corners are associated with saturated solutions of the respective salts, this is not so in the restricted system. The base corners (CaS04j3, (CaO)s, &Os, and &(S04)3 are to be associated with pure solid phases CaS04. 2H20, Ca(OHj2, etc., in equilibrium with appropriate solution compositions, while the (&SO& and (&O)3 corners represent concentrations of sulfate or hydroxide equivalent to 1 per cent KOH. The point h represents a saturated solution of CaS04.2H20 in a &So4 solution (equivalent to 1 per cent KOH). Points along the edge (CaS04)3-(I
