Abstract
In this study, several cement paste specimens were immersed in high concentrated calcium chloride solution to investigate the influence of cement type, water cement ratio, and immersion conditions on deterioration by CaCl2 attack. Portland cement pastes seriously deteriorated after 1 year exposure to CaCl2 solution. On the other hand, 40％ blast-furnace slag and 15％ silica fume cement pastes showed a good resistance to calcium chloride attack. The deteriorated parts on ordinary Portland cement paste were composed of multiple layers of thin cement pastes, and surface relief and spalling occurred near the surface of specimens. It was found that a large amount of a complex salt of 3CaO・CaCl2・15H2O are formed on this deteriorated parts by X-ray Diffraction. In addition, the deteriorated parts were analyzed by electron probe X-ray micro analyzer. As the results of the Cl/Ca mapping, a large amount of 3CaO・CaCl2・15H2O dispersed near the thin layer far from the surface crack. It was presumed that cracks along the exposed surface were induced by the volume change of 3CaO・CaCl2・15H2O formation. It has been shown that the amount of 3CaO・CaCl2・15H2O depends on the amount of Ca（OH）2 and the occurring of cracks is largely determined by the amount of 3CaO・CaCl2・15H2O and total pore volume of hardened cement pastes.
