Mechanical performance enhancement mechanism of recycled micro‐powder concrete: Physico‐chemical synergistic activation and damage constitutive modeling

To address the low cementitious activity of recycled micro‐powder (RMP) in concrete, this study proposes a synergistic activation method combining physical grinding with NaOH alkali excitation. The effects of water‐binder ratio, RMP dosage, and NaOH concentration on the mechanical properties of recycled micro‐powder concrete (RMPC) were systematically investigated, alongside the development of a Weibull‐based axial compression damage constitutive model. Results indicate a strong negative correlation between water‐binder ratio and mechanical performance; increasing the ratio from 0.4 to 0.6 reduced 28‐day compressive, tensile, flexural, and axial strengths by 53%, 19%, 34%, and 40%, respectively. Optimal performance was achieved at 10%–20% RMP dosage, where synergistic filling and pozzolanic effects improved flexural strength by 9% and compressive strength by 2%. Dosages ≥30% caused strength declines exceeding 20%. Furthermore, 2% NaOH excitation enhanced compressive strengths by 10%, while concentrations ≥3% inhibited hydration and deteriorated performance. The developed four‐point bending load‐deflection model ( R 2 ≥ 0.99) and axial compression damage constitutive model ( R 2 ≥ 0.97) demonstrated excellent agreement with experimental data, accurately capturing the full stress–strain response. These findings provide critical theoretical guidance for the high‐value utilization of construction solid waste and the structural design of eco‐friendly concrete.