Mesh mapping-based mesoscale modeling and shear performance analysis of recycled aggregate concrete beams

This article proposes a three-dimensional mesoscale modeling framework based on mesh mapping technology. Going beyond the traditional three-phase simplification, recycled aggregate is resolved into a multilayered “old natural aggregate—old interfacial transition zone (ITZ)—attached old mortar” system. By integrating random aggregate placement with automated rebar generation algorithms, efficient collaborative modeling of aggregates, mortars, multiple ITZs, and reinforcement is achieved within a uniform hexahedral background mesh. Material phases are automatically identified and assigned based on node-to-aggregate spatial inclusion criteria. The modeling process is highly efficient under typical mesh sizes, completing within seconds to tens of seconds. The framework is validated against four-point bending tests on beams without stirrups, followed by systematic parametric analyses on replacement ratio and mesocomponent properties. Results reveal that: first, ITZ properties—particularly the internal old ITZ (ITZ3)—are the dominant factor governing shear behavior. Second, strengthening the attached old mortar significantly enhances both load-bearing and deformation capacities, but the improvement saturates once its strength exceeds that of the new mortar. Third, the elastic modulus of natural aggregate exerts only marginal influence on macroscopic shear performance. The proposed method achieves a favorable balance among modeling efficiency, geometric fidelity, and reinforcement compatibility, offering an extensible and practical tool for mesoscale analysis of recycled aggregate concrete members.