Recycling aluminum dross as a mineral admixture in CaO-activated superfine slag

Abstract

To reduce the environmental hazards caused by aluminum dross (AD), this paper aims to investigate the potential application of AD in CaO-activated superfine slag. The hydration heat, hydration evolution, and leaching behavior of blended binders with different calcined AD (CAD) dosages were evaluated experimentally. Additionally, the mechanical strength and pore size distribution of hardened backfill with different blended binders were measured. The results showed that the activity of AD was promoted by calcination, which increased the number of disordered network structures. The exothermic peak of blended binders was retarded by the increased dosage of CAD, and the peak value decreased from 2.86 mW/g to 2.52 mW/g with a reduction of 0.34 mW/g. At 3 d hydration, all blended binders containing CAD had lower chemically bound water (CBW) than control sample, while at 28 d hydration, the blended binder with 5% CAD had a relative higher CBW (24.89%) than control sample (24.7%). Increased addition of CAD decreased the formation of hydration products but contributed to the incorporation of Al into C–S–H, which enhanced the Al/Ca and Si/Ca atomic ratio. In addition, increasing the addition of CAD, the mechanical strength of hardened backfill dropped because of less formation of hydration products and larger porosity. These experimental findings will be beneficial to the practical utilization of AD in backfill technology.