Enhancing mechanical and durability properties of recycled concrete aggregates (RCA) through large-scale CO2 carbonation treatment

This study investigates the mechanical and durability performance of recycled concrete aggregates (RCA) after large-scale carbonation treatment using carbon dioxide (CO 2 ). RCA obtained from a local producer in Nebraska, USA, was subjected to controlled carbonation in a 1-ton capacity carbonation chamber under varying conditions of initial CO 2 pressure, treatment duration, aggregate volume, and relative humidity. Mechanical and physical properties were evaluated through specific gravity, water absorption, aggregate crushing value (ACV), Los Angeles (LA) abrasion, and freeze-thaw (F-T) resistance tests. Results show that carbonation did not significantly alter bulk properties such as specific gravity and water absorption but substantially improved mechanical and durability performance. Carbonation reduced ACV by up to 20 %, LA abrasion mass loss by ∼17 %, and F-T mass loss by comparable margins, confirming enhanced resistance to crushing, wear, and freeze-thaw cycles. The improvements were most strongly correlated with CO 2 consumption per RCA mass and treatment duration, while optimal efficiency was observed at 50–60 % of relative humidity. Statistical analysis further identified CO 2 consumption per RCA mass and treatment duration as the most influential parameters across all tests. These findings highlight the dual benefit of carbonation in strengthening RCA while sequestering CO 2 and suggest practical guidelines for optimizing treatment conditions to achieve both mechanical and durability enhancement and environmental sustainability. • Large-scale CO 2 carbonation (1-ton chamber) was applied to recycled concrete aggregates (RCA). • Carbonation significantly improved RCA durability: ACV, LA abrasion, and F-T mass loss by 15–20 %. • CO 2 consumption per RCA mass and treatment time were the most influential factors. • Optimal carbonation efficiency and mechanical enhancement occurred at 50–60 % RH. • Short treatments (6–8 h) achieved > 60 % of total improvements, reducing time and energy demands.