Synthesis and characterization of hydrogarnet Ca3(AlXFe1- X)2(SiO4)y(OH)4(3-y)

C(3)AH(6) is a stable phase in the CaO-Al2O3-H2O system at temperatures 20 degrees C and above. The presence of SiO2 results in the formation of C(3)AH(6) and C-S-H phases at room temperature. At 110 degrees C crystalline C(3)ASyH(2(3 - y)) phases form. Two solid solutions: C(3)AH(6)-C(3)AS(0.4)H(5.18) and C(3)AS(0.84)H(4.32)-C(3)AS(3) are found with log K-s0 = -20.50, -25.35, -26.70 and -39.7 at 20 degrees C, respectively. In the CaO-Fe2O3-H2O system, only traces of C3FH6 and C4FH13 phases are formed due to the high stability of FH phase. The presence of silica leads between 20 and 110 degrees C to the formation of C3FS0.84H4.32 and C3FS1.34H3.32 phases with log K-s0 = -32.50 and -34.20 at 25 degrees C. No significant solid solution formation occurred between C(3)AH(6) and C3FH6 end members, but between C(3)AS(0.84)H(4.32) and C3FS0.84E4.32 solid solution formation is observed. The determined solubility products indicate that C3FS0.84H4.32 is the most stable iron-containing phase in hydrated Portland cements. (C) 2014 Elsevier Ltd. All rights reserved.