Environmental factors affecting accelerated carbonation of recycled concrete aggregates using response surface methodology

To further enhance CO₂ capture and sequestration in concrete waste, this study investigates the interaction of four environmental factors, i.e., temperature, relative humidity (RH), CO₂ concentration and pressure on the accelerated carbonation of recycled concrete aggregates. 29 groups of accelerated carbonation tests are performed based on the Box-Behnken design. The effects of four factors on the carbonation percentage of recycled concrete aggregates (RCAs) are analyzed using a response surface methodology. A response surface model is obtained to characterize the experimental results. Additionally, three single-factor scenarios and three multi-factor coupled scenarios are employed to show the mechanisms affecting RCA carbonation and carbonation environments. Single factor analysis indicate that RH and CO₂ concentration can significantly affect the carbonation of the RCA and the significance of the interactions follows the order of temperature - RH, RH - CO₂ concentration and temperature - CO₂ concentration. The microstructure of RCAs during carbonation is further studied and presented.