A model for dissolution of CaO-SiO{sub 2}-H{sub 2}O gel at Ca/Si<1 by considering disordered structure

A model for dissolution of CaO-SiO{sub 2}-H{sub 2}O (C-S-H) gel is proposed by considering a Margules type of non-ideal mixture of binary solid solutions at Ca/Si (C/S)<1. The Guggenheim and Prausnitz equations are used to represent the activities of model solids as a function of mole fractions. The Gibbs-Duhem equation, together with the activities of model solids, is applied to express the conditional solubility products of model solids as a function of C/S ratio. The determination of Guggenheim's empirical parameters is performed with the geochemical code PHREEQE on experimental data. The dissolution model is developed by considering the effect of disorder in the structure of C-S-H gel at C/S<1. The solubility results predicted by the proposed model are comparable with experimental data. The study predicts some structural information of C-S-H gel at C/S<1.

[1]  Elaine Anderson,et al.  INVESTIGATION OF COLLOIDAL HYDRATED CALCIUM SILICATES. I. SOLUBILITY PRODUCTS , 1960 .

[2]  P. Glynn.  MBSSAS: a code for the computation of Margules parameters and equilibrium relations in binary solid-solution aqueous-solution systems , 1991 .

[3]  T. N. Chang,et al.  Investigation of the Colloidal Hydrated Calcium Silicates. II. Solubility Relationships in the Calcium Oxide-Silica-Water System at 25° , 1965 .

[4]  Wakichi Kondo,et al.  Heterogeneous equilibrium of calcium silicate hydrate in water at 30 °C , 1981 .

[5]  F. Adenot,et al.  Study of the structural properties of the CSH(I) BY molecular dynamics simulation , 1997 .

[6]  Christian Ekberg,et al.  A thermodynamic model for the calcium silicate hydrate gel, modelled as a non-ideal binary solid solution , 1997 .

[7]  E. Reardon.  Problems and approaches to the prediction of the chemical composition in cement/water systems , 1992 .

[8]  S. Brunauer,et al.  DEVELOPMENT OF SURFACE IN THE HYDRATION OF CALCIUM SILICATES. II. EXTENSION OF INVESTIGATIONS TO EARLIER AND LATER STAGES OF HYDRATION , 1962 .

[9]  P. Roller,et al.  The System Calcium Oxide-Silica-Water at 30°. The Association of Silicate* Ion in Dilute Alkaline Solution , 1940 .

[10]  H. Stade,et al.  On the coordination of Al in ill-crystallized C-S-H phases formed by hydration of tricalcium silicate and by precipitation reactions at ambient temperature , 1987 .

[11]  X. Cong,et al.  29Si MAS NMR study of the structure of calcium silicate hydrate , 1996 .