ABSTRACT
ABSTRACT Japan is facing the sea on every side. It has been reported that there are many deteriorated concrete structures due to salt damage. In recent years, in order to improve the resistance to salt-damage, materials have been research and developed using calcium aluminate. In this research, we focus on the aggregate (CaO · Al2O3 aggregate) and admixture (CaO · 2Al2O3) for making the specimens for improving resistance of salt damages. Compressive strength test, permeability of chloride ion and observation of aggregate interface on SEM were carried out, using concrete on different replacement of calcium aluminate materials. In order to confirm the composition of the product, a cement paste specimen using the calcium aluminate material was prepared and the hydration product was clarified using XRD. As a result of XRD test, it was found that the calcium aluminate materials react with water and calcium hydrate (Ca(OH)2) which is a cement hydration product. And the calcium aluminate materials (especially CA aggregate) added with salt, it was found that chloride ion was immobilized as Friedel's salt and hydration product was generated on the aggregate interface. We can see many hexagonal plate at the aggregate interface on observation of the aggregate interface by SEM. It was confirmed that the products are Friedel's salt and hydration products form calcium aluminate materials from previous studies. Although according to water permeability test, the interface of aggregate may be densified by these hydration products. It is suggested that the densification of the aggregate interface may decrease the permeability inside the concrete. Furthermore, the effect of shielding salt is expected under the severe salt environment on long term.
