Effects of carbonation and sponge wetting solution on diffusion potential of carbonated concrete with supplementary cementitious materials

Potential measurement of reinforced concrete is critical for identifying the corrosion state of rebar and monitoring the pH value and chloride concentration of concrete pore solution but remains a challenging task due to the many uncertainties involved. This study aims to investigate the effects of concrete carbonation and the sponge wetting solution on the diffusion potential of partially carbonated concrete blended with supplementary cementitious materials (SCMs). Portland cement is replaced by silica fume (SF), pulverized fly ash (PFA) and ground granulated blast -furnace slag (GGBS) at different replacement levels. Other experimental variables include the degree of concrete carbonation, the wetting solution of the sponge (tap water and 0.3 M NaOH) and the degree of saturation. The results indicate that concrete carbonation -induced diffusion potential would lead to significant errors on the monitoring of the pH value and chloride concentration by measuring the potential between the embedded sensors and external reference electrode. During the pH value and chloride concentration monitoring, 0.3 M NaOH should be used as the wetting solution of sponge for non -carbonated concrete and partially carbonated concrete while tap water should be used for fully carbonated concrete. To some extent, the decline in the degree of concrete saturation can reduce the diffusion potential.