Effects of cyclic carbonation and chloride ingress on durability properties of mortars containing Trass and Pumice natural pozzolans

Abstract

AbstractWith an increase in CO2 emission, corrosion of reinforcement as a result of carbonation has become more significant to researchers besides corrosion due to chloride ion ingress. Many structures are exposed to coupled effects of carbonation and chloride attack; therefore, investigating the effect of this combined attack on the durability of concrete is a vital subject. Also, the use of supplementary cementitious materials (SCMs) has become more common due to their contribution to concrete's properties. In this study, the combined effect of chloride attack and carbonation on the durability of mortars containing SCMs was studied. Two natural pozzolans (Pumice and Trass) were used as cement replacements in mortar mixtures with three w/b ratios of 0.485, 0.44, and 0.4. Four exposure conditions, namely normal (immersed in lime‐saturated water), chloride attack, carbonation, and cyclic carbonation and chloride attack were considered. Compressive strength, carbonation and chloride penetration depth, capillary water absorption, surface electrical resistivity, and chloride diffusion tests were performed. The results indicate that while carbonation depth is reduced in the combined attack environment, it imposed a more severe corrosive condition in comparison to pure immersion in saline water by increasing the diffusion coefficient up to 500%. Also, addition of pozzolans showed the potential to reduce the diffusion coefficient of the mortars as much as 76% pointing out that mortars without pozzolans were more vulnerable to this combined attack environment. Furthermore, cement replacement with Trass and reduction of w/b showed to be beneficial in reducing the destructive effects of the combined environment.