Mechanical properties and damage evolution of cemented recycled aggregate backfill modified by solid waste-based grouts

To address the demand for backfilling mine goafs and realize the synergistic resource utilization of solid wastes such as iron tailings and construction waste, cemented recycled aggregate backfill (RAFB) was prepared by modifying cement-tailings grout (CTG) with microfines of manufactured sand (MMS). Through uniaxial compression tests and real-time monitoring using acoustic emission (AE) technology, the mechanical properties and damage evolution process of RAFB under different solid mass fractions and water-cement ratios (W/C) were systematically analyzed. The results show that the compressive strength of RAFB mainly depends on the mechanical properties and groutability of CTG. The AE parameters (ring count, energy, b-value, AF value, and RA value) exhibit an obvious time-varying response law to stress development, which can effectively characterize the damage evolution of RAFB. The failure process of RAFB can be divided into four stages: compaction, elasticity, plastic yielding, and failure. The evolution of its damage variable presents two-stage characteristics (slow growth and rapid growth) and finally converges to complete failure. Analysis based on AF and RA values indicates that the failure of the backfill is dominated by the tensile mode, and as the W/C increases, the proportion of tensile failure increases from 68.3% to 75.6%. The research results provide a theoretical basis for the engineering application and damage early warning of MMS-modified backfill.