Recycled concrete is a form of low-carbon concrete with great importance. The explicit finite element method is an economical and feasible method for analyzing static concrete structures, such as those made of recycled concrete. The shear strength of regular concrete beams has size effects. In this study, a group of physical tests on the size effect of the shear strength of recycled concrete beams without web reinforcement was carried out under the condition of a constant shear span ratio. The research results show that the shear strength of the test beam generally decreases with the increase in beam section height, and a regression formula of the shear strength was obtained, which can formulate this effect. The rationale and feasibility of the explicit finite element method solving the ultimate load of concrete structures (which can derive the shear strength) were briefly demonstrated, and an explicit finite element simulation of test beams was carried out. Results showed an obvious and phenomenologically regular size effect of the shear strength of recycled concrete beams without web reinforcement, which can be simulated by the explicit finite element method. This research aims to promote the study of low-carbon recycled concrete structures to a certain extent and encourage the application of economic explicit finite element methods for the static analysis of concrete structures.

This study explores the use of recycled brick powder (P_RB), derived from waste bricks, and calcined recycled slurry powder (P_CRS), sourced from waste cement blocks, as partial replacements for cement and fly ash in concrete. These materials can be utilized to produce concrete with favorable engineering properties. Five concrete mixtures with varying P_RB/P_CRS proportions were prepared. Uniaxial monotonic compression tests were conducted to generate stress-strain curves for each mixture. Corresponding physical superposed slabs were fabricated, and finite element (FE) models were developed for each slab. Both physical testing and explicit FE simulations were performed to evaluate the flexural performance of the slabs. The results demonstrated that the flexural performance of the P_RB/P_CRS recycled micro-powder concrete slabs was comparable to that of conventional concrete slabs. Notably, the slab incorporating a 1:1 mixture of P_RB and P_CRS instead of fly ash exhibited the highest yield and ultimate bearing capacities, reaching 99.3% and 98.4% of those of the conventional concrete slab, respectively. The FE simulations accurately predicted the flexural performance, with maximum deviations of 8.9% for the yield load and 6.5% for the ultimate load. Additionally, the simulation-based energy time-history curve provides valuable insights into the progression of slab cracking. This study contributes to the advancement of research on the engineering and mechanical performance of concrete members incorporated with P_RB/P_CRS.