Rheological and mechanical properties of cemented foam backfill: Effect of mineral admixture type and dosage

In this work, the effect of mineral admixture type and dosage on the rheological and mechanical behaviors of a newly developed backfilling material, cemented foam backfill (CFB), is comprehensively investigated. Fly ash (FA), ground granulated blast-furnace slag (GGBS) and quicklime are selected as mineral admixtures, while H₂O₂ and CaCO₃ whisker are used as foaming agent and foaming stabilizer respectively. CFB samples are prepared with solid content between 70% and 76%, replacement rates of cement with FA or GGBS between 0% and 30% and cured at 7, 14 and 28 days. In addition, 5 wt % of FA or GGBS is replaced by an equal amount of quicklime to accelerate pozzolanic reaction in a portion of CFB samples. Then, fresh CFB is subjected to the rheological property (i.e., apparent viscosity and equivalent Bingham yield stress) test, while hardened CFB is subjected to porosity and mechanical tests. Additionally, thermogravimetric and X-ray diffractogram analyses are conducted on 7- and 28-day hydrated binder pastes (pure cement, cement + FA/GGBS, cement + FA/GGBS + quicklime) to reveal the influence of mineral admixture type and dosage on the hydration product of CFB.