Environmental behavior of construction and demolition waste as recycled aggregates for backfilling in mines: Leaching toxicity and surface subsidence studies

Abstract Environmental behavior of construction and demolition waste in cemented backfilling mining technology (CW-CBMT) is studied, with the aim of expanding the scope of construction and demolition waste (CDW) utilization, as well as developing strategies to release coal resources. Toxicity leaching, scanning electron microscopy (SEM), and mechanical properties testing about on-site sampling are carried out, and surface subsidence is surveyed. The results reveal that the maximum leaching concentration (0.00113 mg/L) of arsenic from cemented backfilling body with construction and demolition waste (CBCW) is small, the leaching solution is alkaline, and the leaching of heavy metals is influenced by aggregate particle size and by acidity and alkalinity. The results also show that the average compressive strength of CBCW is 2.4 MPa. The distribution of aggregates and elemental content influence the spatial distribution of compressive strength. The variation of internal distribution of elemental content of the CBCW can be interpreted by multifractal parameters. The maximum surface subsidence value is 245 mm, with the fastest sinking speed occurring in the mining stage and a return of surface subsidence stability after halting of mining. A comprehensive analysis of the test results shows that, from an environmental viewpoint, the application of CW-CBMT is successful.