Effect of limestone powder addition on corrosion initiation time of reinforced concrete

This work aimed to evaluate the effects of limestone powder (LP) replacement fraction (8-24 wt %) on chloride diffusion and chloride threshold (Cth) for corrosion initiation. Depassivation of steel was diagnosed by monitoring the self-corrosion potential and corrosion current density using open circuit potential and AC impedance tests, respectively. Corrosion initiation time (T-ini) was estimated based on the measured Cth coupled with a dual time-varying diffusion model. The results indicate that the chloride diffusion coefficient decreases with 8 wt% LP addition, though further increase in LP content reverses the trend. With increasing exposure duration, both the surface chloride concentration and diffusion coefficient vary remarkably at first and eventually tend to be stable. As the cover depth decreases from 55 mm to 45 mm, T-ini is found to decrease by 30.0%-42.9%. Incorporation of LP appreciably decreases Cth regardless of its replacement frac-tion, consequently leading to a decreased T-ini, despite a low chloride diffusivity can be obtained with appropriate LP addition.