Mesoscale-based mechanical parameters determination and compressive properties of fully recycled coarse aggregate concrete

The use of recycled coarse aggregate (RCA) to prepare concrete can reduce the depletion of natural resources, such as sand and stone, and solve the issue of environmental pollution resulting from waste concrete materials. To promote the popularization of the RCA application, a study has been carried out on fully recycled coarse aggregate concrete (FRCAC), which is 100% RCA replacement. The random convex polygon aggregate model was established using a self-compiled program. Then, A five-phase numerical model of FRCAC was proposed through the finite element software further developed, to realize the numerical simulation of uniaxial compression of FRCAC. The discount factor R between the mechanical parameters of the FRCAC mesoscopic components was determined by comparing the 8 groups of compressive strengths from the physical experiments with the 96 groups of compressive strengths from the numerical simulations. Meanwhile, the effects of RCA volume fraction, water-to-cement ratio (W/C) and mesoscopic composition on the compression performance of FRCAC were analyzed based on experimental and simulation methods. The result shows: 1) Simulation results exhibited good agreement with experimental results when the interface discount factor RITZ and the old mortar discount factor RM fell within the ranges of 0.45∼0.55 and 0.8∼0.85, respectively. 2) The compressive strength of FRCAC tends to decrease when W/C and the volume fraction of RCA rise, but the trend of declines is not constant. 3) The compressive properties of FRCAC were found to decrease with increased thickness of the old mortar and the interfacial transition zone, highlighting the necessity for pretreatment of RCA before its use. The findings of this research provide valuable insights and methodological references for the application and promotion of FRCAC and its mesoscopic models.