Accelerated Carbonation Techniques of Recycled Concrete Aggregates: A Systematic Review of Methods, Effects, and Optimal Conditions

The construction industry is experiencing significant difficulties connected to construction and demolition waste management and its carbon footprint reduction. In reaction to this, a systematic literature review was conducted, which summarized information on 124 peer-reviewed studies measuring the accelerated carbonation of recycled concrete aggregates (RCAs). The aim of the review was to enhance the performance of RCA by sequestration of CO2, as well as to measure the resulting effects on the properties of recycled aggregate concrete (RAC), such as micro-crack healing and improvement of mechanical strength, durability and sustainability. Peer-reviewed articles were chosen according to their relevance to RCA carbonation and independence, and an independent screening and critical evaluation were used to reduce bias, and the synthesis of the extracted data was conducted in the narrative, which illuminated existing trends and comparisons between studies. The review examined four carbonation modalities including standard, pressurized, flow-through, and wet carbonation and assessed the effect of the most significant parameters on the results of the strengths and durability including relative humidity, temperature, CO2 concentration, and carbonation duration. Relative humidity was defined as 50–70%, a temperature between 20 and 30 °C and a concentration of CO2 of 20–50%, which together had the best carbonation rate and overall performance. The analyses reveal that carbonation enhances significantly the micro-crack healing, mechanical properties, and durability of RCA, and consequently, the quality of RAC is improved with respect to compressive strength, water absorption, and density. The best benefits were accrued by smaller RCA particles, which can be explained by a larger reactive surface area.