2011 Volume 65 Issue 1 Pages 427-434
When hydrated CaO・2Al2O3 was mixed to ordinary portland cement, High early strength portland cement and Low heat portland cement respectively, a large amount of two types of hydrocalumite（3CaO・Al2O3・Ca（OH）2・12H2O and 3CaO・Al2O3・Ca（SO）4・12H2O）has formed in hardened cement. It was considered that generated hydrate depended because Al2O3 and SO3 amount in cement differently. Amount of portlandite in hardened cement has decreased with increased additive amount of CaO・2Al2O3, because a large amount of hydrocalumite formed in hardened cement by the reaction of CaO・2Al2O3 and Portlandite. When hydrated CaO・2Al2O3 and NaCl was mixed to various portland cements respectively, amount of fixed chloride ion has increased and ratio of soluble chloride ion in total chloride ion has decreased in hardened cement with increased additive amount of CaO・2Al2O3. When the various cement mortars made to mix CaO・2Al2O3 were immersed in salt water, the chloride ion penetration depth decreased and the chloride ion concentration of the surface part became high. This reason was chemical effect of fixation of chloride ion by formation of Friedel’s salt（3CaO・Al2O3・CaCl2・12H2O）for the reaction of hydrocalumite and chloride ion. The effect was remarkable in particularly Low heat portland cement.
