Effect of NO₂ sequestered recycled concrete aggregate (NRCA) on mechanical and durability performance of concrete

The utilization of recycled concrete as an adsorbent to sequester NO₂ without additives or catalysts is an innovative, cost-effective, and sustainable approach to capture NO₂ from targeted industrial facilities. This paper presents the mechanical and durability performance of ordinary portland cement (OPC) concrete containing NO₂ sequestered recycled concrete aggregate (NRCA). NRCA was used as a partial replacement for natural fine aggregate at 20% and 40% rates by volume. The incorporation of NRCA in concrete resulted in increased compressive strength, decreased water-permeable porosity, and reduced chloride ion migration. Moreover, test mixtures comprising 40% NRCA showed a significant chloride binding capacity compared to control concrete mixtures. Furthermore, high replacement rates of NRCA noticeably enhanced the resistance to chloride-induced corrosion of steel in concrete or at least was on par with the performance of a commercially available calcium nitrite-based corrosion inhibitor.