Rheological and CO2 sequestration properties of alkali-activated gangue-based backfill slurry: Effect of temperature

Wet carbon sequestration of alkali-activated gangue-based backfill slurry (AGS) is considered to be a promising approach for both the resource utilization of gangue solid waste and CO 2 sequestration. However, this process has an adverse impact on the rheological properties of AGS. In this study, the influence mechanism of temperature within the carbon sequestration reactor on the rheological properties and CO 2 sequestration of AGS were explored through a carbon sequestration reactor, rheometer, x-ray diffraction (XRD), thermogravimetric analyzer (TGA), nitrogen adsorption-desorption instrument (BET), and scanning electron microscopy (SEM). The results show that the rheological properties of fresh AGS adhere to the Herschel-Bulkley model. As the temperature increases, the yield stress, plastic viscosity, and thixotropic properties of AGS first increase and then decrease. When the temperature is 50 °C, the CO 2 sequestration reaches its peak at 2.55 %. The enhanced formation of carbonation products leads to a reduction in the specific surface area and pore volume, an increase in cluster structure, and a denser microstructure, resulting in a decrease in the rheological properties of AGS. Additionally, the life cycle assessment revealed that when the temperature rises to 50 °C, carbon emissions can be reduced by 48.64 kg of AGS compared to that of the reference group, helping mine industries to achieve the negative carbon object.