Thermodynamic study of cement/rock interactions using experimentally generated solubility data of zeolites

Abstract

Alteration of widespread interfaces between cements and clays in geological time scales is essential to the safety assessment of radioactive waste repositories but not well understood partly due to the low reliability of thermodynamic data for zeolites. Here, we collected and full-scale characterized Ca-based zeolites with six types of frameworks that could possibly form in the interfaces. Besides, chemical interactions between degraded cementitious phases and rock forming minerals after equilibrating for ~6 years were investigated. By using the currently generated thermodynamic data of selected zeolites, chemical interactions in the cement/rock systems were studied, showing that no equilibrium was reached after 6 years and zeolites favored in thermodynamics, such as chabazite and gismondine rather than faujasite, can be expected to form at even longer timescale. The experimentally derived thermodynamic data was verified preliminarily by establishing consistent predominance diagrams of cement-zeolite-clay minerals, helping to predict zeolite stability domains in large timescales.