Corrosion Mitigation in Mature Reinforced Concrete Using Nanoscale Pozzolan Deposition

Abstract

Electrokinetic nanoparticle (EN) treatments were employed to mitigate corrosion in reinforced concrete. In this approach an electric field was used to drive pozzolanic nanoparticles through the capillary pores of concrete and directly to the reinforcement. The intent was to use the nanoparticles as pore-blocking agents to prevent the ingress of chlorides. Treatment effectiveness was examined for both freshly batched and relatively mature concrete. Cylindrical reinforced concrete specimens were subjected to EN treatment immediately after batching and then exposed to chlorides for a period of two years. The EN-treated specimens exhibited a reduction in corrosion rates by a factor of 74 as compared to the untreated controls. Another set of specimens was subjected to chlorides for a period of two years prior to EN treatment application. Electrochemical chloride extraction and EN treatments were performed on these mature specimens for one week. These specimens were placed back into saltwater exposure for an additional year. The mature controls exhibited severe corrosion cracking as compared with the mature treated specimens after 1 year of saltwater exposure. The corrosion rates were 8 times that of the treated specimens. Microstructural and chemical analysis was conducted using scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. This study demonstrated that microstructural changes attributable to treatment were effective in mitigating reinforcement corrosion in both young and mature concrete.