Chemical deterioration of hardened cement pastes immersed in calcium chloride solution

Abstract

In this study, several cement pastes were immersed in CaCl2 solutions and the most seriously damaged specimens were analyzed in detail using XRD and EPMA in order to consider the mechanisms of chemical deterioration due to CaCl2. Cement pastes damaged by CaCl2 attack showed lifting and cracking on the exposed surface and finally formed a layered crack. The damaged part was composed of multiple layers of thin cement pastes. Furthermore, it was found through XRD analysis that the damaged part included a large amount of complex salts of 3CaO･CaCl2･15H2O. The degree of the damage seems to be related with the amount of Ca(OH)2 in the cement pastes. It is considered that the occurring of horizontal cracks is determined by the amount of 3CaO･CaCl2･15H2O formed near the surface and the total porosity of hardened cement pastes which relieves the expansive pressure.