Mechanistic evaluation of NO₂ sequestered recycled concrete aggregates as anodic corrosion inhibitors in chloride-exposed OPC concrete: insights from kinetics and performance assessment

This study evaluates a novel corrosion inhibitor derived from NO₂ sequestered recycled concrete aggregates (NRCAs) integrated as fine aggregates in new OPC concrete exposed to chlorides. It investigates the corrosion resistance of concrete with various NRCAs and the kinetics of passive film formation on rebar to elucidate the corrosion inhibition mechanism. The performance of NRCAs is compared to a commercially available calcium nitrite-based inhibitor (CI). Results show NRCAs act as effective anodic corrosion inhibitors, with 1 and 2-year-old NRCAs demonstrating similar long-term performance to CI. Additionally, NRCAs facilitate rapid formation of thin passive films on rebar, akin to CI. The efficacy of NRCAs is influenced by the properties of the parent concrete. These findings underscore the potential of NRCAs as sustainable alternatives in concrete construction, offering both environmental benefits and comparable performance to conventional inhibitors. Future research will focus on optimizing NRCA properties to enhance their inhibitory effects.