Mechanical properties and energy evolution characteristics of magnesium slag-blast furnace slag-based backfill under different curing age and magnesium slag content

Abstract

Utilizing solid waste resources and lowering backfill costs are made possible by the preparation of cementitious materials as cement substitutes using magnesium slag (MS) and blast furnace slag (BFS). Uniaxial compression tests were carried out on MS-BFS-based backfill with different MS contents (20%, 30%, 40%, and 50%) and curing ages (3, 7, and 28 d) to investigate their effects on the mechanical properties and energy evolution characteristics of the MS-BFS-based backfill. The coupled effects of curing age and MS content on the compressive strength and elastic modulus of the MS-BFS-based backfill are discussed. The energy damage evolution characteristics, energy distribution characteristics, and energy indexes at the peak stress point of the MS-BFS-based backfill were examined, and an energy damage constitutive model was constructed based on energy dissipation. The results show that with increasing curing age, the brittleness of the MS-BFS-based backfill specimen itself is gradually enhanced. With increasing MS content, the post-peak brittle deformation capacity of the MS-BFS-based backfill at all curing ages is enhanced, while post-peak plasticity diminishes. A moderate amount of MS (30%) improves the strength properties of the backfill and provides similar enhancement at all curing ages. At 28 days, the strength and elastic modulus of the backfill with 30% MS content can reach 7.677 MPa and 1317.063 MPa, respectively. The established two-factor coupling function can better represent the coupled effect of curing age and MS content on the mechanical parameters and energy indexes of the MS-BFS-based backfill. After introducing the pre-peak compaction coefficient, the damage constitutive model based on energy dissipation effectively characterizes the stress-strain behavior of the MS-BFS-based backfill. The findings can provide support for the application and stability analysis of MS-BFS-based backfill.

Keywords

solid waste resource utilization / magnesium slag-blast furnace slag-based backfill / magnesium slag content / mechanical properties / energy damage evolution / coupled effects

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