Optimization of the Preparation Process of Fair-Faced Concrete Incorporating Recycled Aggregates

Recycling construction wastes as aggregates to replace natural sources to produce concrete has attracted the attention of many researchers and is necessary for sustainable development. The water content of recycled coarse aggregate (RCA) and the concrete mixing approach in preparing fair-faced concrete incorporating recycled aggregates (FCRA) were optimized in this study. The results showed that the slump flow of FCRA exceeds 600 mm and that the 28-d compressive strength reaches approximately 40 MPa, which can meet the requirements of Chinese standards. Compared with concrete prepared with absolute dry RCA and with saturated surface dry RCA, the concrete prepared with semidry RCA better maintains its workability. The adverse effect on the compressive strength of concrete is weakened, which helps improve the structural performance of the ITZ of recycled aggregate concrete (RC). The concrete mixing approach has a significant influence on the physical and mechanical properties of FCRA. Compared with the ordinary mixing method, the 28-d strength of the concrete obtained by the cement stone wrapping approach is increased by 13.33%, and the surface pore area is reduced by 42.6%. Cement stone wrapping in two-stage mixing greatly improves the concrete performance, effectively satisfying the requirements for FCRA.