Calcite Precipitation at Cement–Bentonite Interface. Part 1: Effect of Carbonate Admixture in Bentonite

Calcium leaching from cementitious materials into bentonite is a key process for the long-term alteration of cement–clay interfaces engineered barrier systems. Strong chemical gradients between cement and clay drive precipitation minerals such as calcium silicate hydrate (C–S–H) calcite. To analyze mineralogical porosity evolution at interface, composite specimens consisting paste mixed with various amounts sodium carbonate were subjected to immersion chloride migrations tests investigated by electron probe micro-analysis (EPMA), thermogravimetry/differential thermal analysis (TG-DTA), X-ray diffraction (XRD) after 4–20 months immersion. The results show that adding enhanced formation calcite in form surface layer on paste. This suggests pore clogging interface implies existence threshold amount addition above which occurs. first two papers; accelerated samples presence an electrical field discussed second paper.