Using acetic acid as a preconditioner to optimize rheology of alkali-activated coal gasification slag based backfill pastes

The workability of alkali-activated coal gasification slag (CGS) based backfill materials is critical parameter in transportation processes, while the high water demand of CGS hinders its application due to its high specific surface area. This study utilizes acetic acid (AA) as a preconditioner to modify the surface characteristics of CGS, aiming to optimize the rheology of alkali-activated CGS backfill pastes (AAC). The shear stress, viscosity, thixotropic property, and zeta potential of AAC, and mineral composition and surface morphology of AA-modified CGS at various AA dosages were systematically investigated. It is found that the yield stress, plastic viscosity, and hysteresis loop area of AAC reaches the lowest value at 4 wt% AA dosage on the basis of the CGS, owing to AA reacts with the minerals on the surface of CGS particles, and then the AA is adsorbed on the CGS particles and acts as a surfactant, which increases the static electricity between CGS particles. However, the yield stress of AAC increases significantly when the AA dosage exceeds 4 wt%, attributing to the smaller particle size resulting from AA modification, which raises water demand. This investigation proposes a novel approach for optimizing the rheology of CGS based AAC and provides theoretical guidance for employing modified CGS as backfill materials.