Corrosion of Steel Bars in Autoclaved Concrete Pile Containing γ-2CaO·SiO2 with an Accelerated Carbonation Curing Submerged in the Real Marine Environment

Abstract

This paper presents a set of the investigation of corrosion of steel bars in autoclaved concrete pile containing γ -2CaO ·SiO2 (γ -C2S) with carbonation curing. OPC, γ -C2S, and fine silica powder were used as the binders; the replacement ratio of OPC by γ -C2S was 0%, 40%, and 80% by mass. Autoclaved concrete pile after carbonation was submerged in real marine environment at Kurihama Bay for two years. After immersion, visual observation of steel bars was conducted to confirm the corrosion state of steel inside the concrete pile. Furthermore, to evaluate the corrosion of steel bars -weight loss, corrosion current density, and anodic polarization curve were measured ; various corrosion substances also were measured to evaluate the permeability of corrosion factors. In addition, cement past sample with same mixed proportion and curing condition was made for explaining the permeable characteristics of corrosion substances. As the results, the steel bars in the 80% γ -C2S replacement ratio did not corrode while steel bars in the other mixed proportions had corroded. The weight loss of steel bar in the 80% γ -C2S replacement ratio after carbonation reduced by 39% and corrosion current density reduced more than 95% compared with the 0% γ -C2S replacement ratio. Furthermore, the corrosion substances in concrete pile -carbonation depth, total chloride ion content, and oxygen diffusion rate, reduced significantly at the 80% replacement ratio of γ -C2S. Based on the overall results of this study, we suggest that, when using γ -C2S with an autoclave curing, accelerated carbonation curing is able to do to densify the concrete surface preventing the steel from corrosion for the long-term exposure.Key words : γ-2CaO ·SiO2

Improvement in Carbonation Resistance of Portland Cement Mortar Incorporating γ-Dicalcium Silicate

“…Unlike conventional methods, the approach proposed in this study attempts to inhibit the diffusion of CO 2 by introducing a highly active CO 2 -capturable material, c-C 2 S, into concrete to fix up CO 2 present in the concrete, which could reduce CO 2 diffusion rate. During the reaction between CO 2 and c-C 2 S, carbonation products with large molecular weights are formed [10,11], which could block the capillary pores.…”