Towards understanding the hydration and hardening properties of the cemented paste backfill with a green steel-slag binder

Abstract

ABSTRACT Binder is the main cost burden in cemented paste backfill (CPB) and an obstacle towards fully green mining technologies. In this work, an improved, low-cost, efficient, and green binder with steel slag content up to 50 wt% was presented for mine backfill. The binder hydration and CPB hardening properties were experimentally investigated. Results show that the CPB with green SS binder (50 wt% steel slag, 35 wt% blast furnace slag, 15 wt% desulphurisation gypsum) has the highest 28-day strength of 2.21 MPa, which is 2 times higher than the Portland CPB control (0.98MPa). The green binder has less hydration heat and a slower and longer deceleration stage duration. The hydration products of the green binder are mainly ettringite and amorphous gel. The substantial gel-like products obtained from multiple activation processes are the mystery of the outstanding CPB strength. The hardening process of green binder CPB can be divided into fast hydrating stage, compacting stage, and potential refining stage. The findings can help better understand the steel slag CPB properties and improve solid waste valorisation and sustainable development of the mining, mineral processing, and iron and steel making industries.