Concrete with CO 2 -treated coarse recycled concrete aggregates: mechanical, durability and environmental performance

This study investigates the performance of concrete produced with coarse recycled concrete aggregates (RCA) from two types (w/c 0.55 and 0.65), pretreated with CO2 under accelerated conditions for 24 h using 15% CO2. Five mixtures were evaluated: a reference (100% natural coarse aggregate), and four compositions with 100% replacement of each RCA, treated and untreated. Analysis included mechanical properties, durability, and environmental indicators. The concrete with CO2-treated RCA with w/c 0.55 showed the best overall performance. At 63 days, the compressive strength increased by 23.7% compared to the untreated counterpart and was statistically similar to the reference concrete, while the carbonation depth was 41.9% lower. Due to lower cement consumption, this mixture achieved superior environmental performance than the reference, with a carbon index of 9.23. Carbon capture, utilization, and storage (CCUS) technology for treating recycled aggregates has the potential to enhance both circularity and the carbon market in civil construction.