The effect of acid mine drainage on the properties of an all-solid waste paste backfill body based on oil shale residue

Abstract

The complex environment of mine water is closely linked to the effect of the backfill body. The goal of this study was to establish a method with which to reduce carbon emissions from cementitious materials while addressing the large amount of unutilized solid waste, such as oil shale residue, which lies on the surface of the planet, and pollutes the environment. Oil shale residue, fly ash, slag and coal gangue were used to produce an oil shale residue-based all-solid waste paste backfill (OSGPB) to study the changes in strength and environmental impact with corrosion time under acid mine drainage conditions. The development of cracks was monitored using digital image correlation (DIC) technology. The corrosion mechanism of OSGPB was analysed using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). This study revealed that in an acid mine drainage environment, the unconfined compressive strength (UCS) decreased by 38.58% and 15.66% after 24 d of wetdry cycling and complete immersion corrosion, respectively. A significant quantity of corrosive gypsum was produced in the OSGPB, which expanded the internal micropores and gradually formed cracks. This led to more severe internal structural damage during wetdry cycles. Changes in the UCS of the OSGPB over 60 d were predicted using established grey models. The leached concentrations of heavy metal ions met the groundwater quality standard (class III) after the OSGPB was completely immersed in acid mine drainage and subjected to wetdry corrosion cycles. OSGPB showed great potential as a green backfilling material for mines.