Durability assessment methods of CO2-treated recycled concrete aggregate for transportation infrastructure

The construction sector generates substantial construction and demolition (C&D) waste, with concrete accounting for up to 67% by weight. While recycled concrete aggregate (RCA) offers a sustainable solution, traditional RCA exhibits inferior properties that limit widespread adoption. CO₂ treatment has emerged as an effective enhancement method, transforming hydration products into calcium carbonate and silica gel through controlled carbonation processes. However, a critical knowledge gap exists regarding comprehensive durability assessment of recycled aggregate concrete (RAC) incorporating CO₂ -treated RCA for transportation infrastructure applications. This research evaluates systematic methodologies for assessing the long-term durability of carbonated RCA concrete under various exposure conditions. Advanced analytical techniques, including Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD) methods were examined for microstructural characterization, alongside field-applicable tests such as the Super Air Meter (SAM) for freeze-thaw resistance assessment, Surface Resistivity Testing for transport property evaluation, Accelerated Concrete Prism Testing (ACPT) for alkali-silica reactivity, and Initial Surface Absorption Testing for permeability analysis. Literature results demonstrate that properly carbonated RCA achieves durability properties comparable to natural aggregates while providing CO₂ sequestration benefits, with improvements of up to 33, 12.1, and 28% in compressive, splitting, and flexural strengths, respectively. The carbonation process effectively reduces aggregate pH from approximately 12.0 to below 9.8, mitigating alkali-silica reaction risks and enhancing compatibility with fresh cementitious binders. This research provides practical guidance on standardized durability assessment protocols that enable confident adoption of CO₂ -treated RCA in transportation infrastructure, supporting sustainable development through reduced environmental impact and enhanced material performance.