Enhanced seawater corrosion resistance of reinforcement in nanophase modified fly ash concrete

This paper presents a method for enhancing the corrosion resistance of reinforcements through nano-phase modification of fly ash concrete. A combination of natural and accelerated corrosion tests were performed to evaluate the corrosion resistance of reinforcements. The tests were conducted on four types of fly ash concrete specimens with and without nanoparticles designated as fly ash concrete with 40 wt% fly ash (FA), fly ash concrete with 2 wt% nano-CaCO3 (FAC), fly ash concrete with 2 wt% nano-TiO2 (FAT) and fly ash concrete with 1 wt% nano-CaCO3 and 1 wt% nano-TiO2 (FATC). Electrochemical measurements showed that reinforcements in nano-CaCO3 modified fly ash concrete (FAC) exhibited noble potential value, high polarization resistance and lower corrosion rate. Impressed voltage test also corroborate the enhanced corrosion resistance of FAC specimens, which was evident from the longer crack initiation time with minimum anodic current as compared to fly ash concrete without nano additives. Corrosion products of cover concrete showed a comparatively lesser amount of detrimental phases like lepidocrocite and goethite which was in agreement with the corrosion results. The least depth of chloride ion penetration indicated the effective plugging of pores by nano CaCO3 particles that prevent diffusion and movement of chloride ions to surface of the rebar and thereby maintaining the passivity of the thin iron oxide layer around the steel rebar. (C) 2019 Elsevier Ltd. All rights reserved.