3CaO・Al₂O₃組成溶融物の物性と水和

抄録

The melt of 3CaO⋅Al₂O₃ (G-C₃A) composition in the presence of a small amount of SiO₂ was synthesized by rapid quenching after fusion. Furthermore, the physical properties and the hydration behavior of G-C₃A were investigated. G-C₃A results in a lowering of lattice constant, a decrease of specific gravity and an increase of free CaO compared with C₃A. The hydration was not completed even on 10 days curing, and 3CaO⋅Al₂O₃⋅6H₂O hydrate grew very slowly. It is thought that Al(OH)₄^- eluted from G-C₃A is remarkably depressed against Ca²⁺. The molar ratio (CaO/Al₂O₃) in case of G-C₃A was given 2.7 after 10 days curing but closely approached to 1.0 after 6 hours curing in case of C₃A. Namely, as glass phase is formed on G-C₃A surface, the strain occurs in inner layer. Therefore, it is difficult to elute Al(OH)₄^- by breaking -Al-O-Al- bonds. Although the elution of Al(OH)₄^- by NaOH is considerable, the growth of the hydrate cannot be expected because of depression of the elution of Ca²⁺. The results of surface analysis by ESCA showed that the binding energy of inner shell electron of Ca, Al, and Si combined with O (oxygen) in G-C₃A is 0.7-0.8eV higher than C₃A. Consequently, as the elution of Ca²⁺ and Al(OH)₄^- is depressed, the hydration reaction becomes inactive.