Sustainable use of recycled cement concrete with gradation carbonation in artificial stone: Preparation and characterization

The utilization of recycled cement concrete (RCC) will be helpful to achieve the goal of carbon peak and carbon neutrality, especially the treatment of RCC by carbonation, which will improve the RCC’s properties. In this article, RCC was crushed and sieved into 6 grades of aggregate and powder according to the particle size. Each size of aggregate and powder was carbonized separately by CO2. The apparent relative density, specific surface area and cementitious activity were tested before and after the carbon sequestration. The effect of these materials, which included graded substituting cement and quartz sand, were investigated on the strength of artificial stone. The experimental results indicate that the carbon sequestration efficiency increases gradually with the decrease of particle size of RCC. The physical properties of the aggregates are better after carbon sequestration. In terms of apparent relative density, the maximum increasing rate is 2.59 %, and simultaneously the water absorption is reduced by at least 2.18 %. The preparation parameters of artificial stone are that the constant pressure time is 30 s and the forming pressure is 30 MPa. The increase in the content of recycled aggregate and powder will lead to a decrease in the compressive strength of artificial stone, but compared with the recycled material before carbonation, the compressive strength of artificial stone with the same content is significantly improved, with a maximum increase of 36.53 %. Moreover, the nano-indentation depth of artificial stone decreases using carbonation RCC, which indicates that the interface strength of cement pastes and carbonized aggregates is improved. This research demonstrates that the physical properties and interfacial strength of RCC through gradation carbonation are improved, which provides a valuable method for the graded utilization of RCC and the sustainable development of artificial stone.