Kiyofumi Kurumisawa

Mechanical Properties of Deteriorated Hardened Cement Paste

The porosity of hardened cement paste changes when it is exposed to the actual environments, and it may be expected that the chemical structure of the C-S-H undergoes changes. The C-S-H is the main component, comprising 60% or more by volume of hardened cement paste, and this study focuses on changes in the chemical structure of C-S-H. Deterioration induced by ammonium nitrate solution was accompanied by changes in the pore structure as well as structural changes in the C-S-H in the hardened cement paste. It was ascertained that when evaluating the decreases in the elastic modulus of the hardened cement paste, both the pore structure and the structure of the C-S-H must be considered.

The Influence of Leaching on the Ion Adsorption Ability of Hardened Cement Paste

The durability of the concrete structure is determined by transport properties of concrete. The transport of chloride ions greatly changes by the amount of adsorption by hydrates. However, there are few studies on change of the amount of adsorption with the calcium leaching. In this study, the purpose is to investigate a change of the amount of adsorption of the chloride ion with the calcium leaching of hardened cement pastes. The amount of chloride ion adsorption increased with the increase of the replacement ratio of the blast furnace slag. The authors established an equation to predict the amount of chloride ion adsorption on C-S-H and Afm. It was clarified that the amount of chloride ion adsorption on C-S-H of leached hardened cement paste depends on Ca/Si and Al/Si.