Original Paper(Vol.60 No.4 pp.332-338)

Permeability of Sulfate Ions in Cementitous Materials with Autoclave Curing and Accelerated Carbonation Curing Using -2CaOESiO2

Tsuyoshi SAITO, Nobuaki OTSUKI, Tatsuya YUMOTO and Saphouvong KHAMHOU

Abstract:Nowadays, in the middle east region where sulfate is abundantly found in soil, the sulfate attack on concrete structures is one of the serious problem. For this purpose, a material design of cementitous material is expected to obtain high sulfate resistance, leading to the research on the high durability of the cementitous material using -2CaOESiO2 (hereafterh-C2Sh). The authors have proposed the material design as follows: the cementitous material mixed with -C2S and conducted with autoclave and accelerated carbonation curing to obtain high durability performance due to the generation of tobermorite in the hardened body by autoclave curing, and densification at the surface of hardened body by accelerated carbonation curing. However, its sulfate resistance has not been investigated yet. Therefore, the purpose of this research is to evaluate the effect of using -C2S, autoclave curing and accelerated carbonation curing to permeability of sulfate ions related to the sulfate resistance, and clarify the mechanism of sulfate resistance from the view point of the reaction product and sulfate ion penetration. As a result, in the case of 80% -C2S substitution ratio with autoclave and carbonation curing, the sulfate ion penetration was the smallest due to the generation of vaterite. In addition, dissolution of tobermorite in the hardened body could be inhibited. Also, low-Ca/Si C-S-H at the surface of hardened body could possibly contribute to the resistance of sulfate ion penetration.

Key Words:-C2S, Autoclave curing, Carbonation curing, Tobermorite, Vaterite, Low-Ca/Si C-S-H, Sulfate attack