Abstract
Industrial waste residues are increasingly reutilized in the preparation of cemented paste backfill for reducing the cost of mine filling. Therefore, to promote the utilization of the bulk industrial waste residues (IWRs), mechanical and microstructure properties of cemented ultrafine tailings backfill (CUFTB) manufactured by reutilizing 5–10 wt% steel slag (SS), 5–10 wt% fly ash (FA), 16–22 wt% carbide slag (CS), 0–3 wt% desulfuration gypsum (DG), and 40–74 wt% blast furnace slag (BFS) and ultrafine tailing (d50 = 10.84 μm) were investigated after curing of 1-, 3-, 7-, 14-, 28-, 56- days. Unconfined compressive strength (UCS) test was adopted to determine strength and the regression analysis was applied to establish UCS prediction model. XRD, SEM, and MIP were used to evaluate the evolution characteristics of CUFTB microstructure. The obtained results indicate that the cementitious material synthetized by IWRs can completely substitute Portland Cement (PC) for CUFTB. After curing of 28 days, CUFTB exhibit UCS values with increasing of 10.80% ∼ 44.89% than those made of PC. Logarithmic function UCS=α⋅lnt+β is constructed to characterize UCS development with curing time. By optimizing the hyperparameters of Gaussian process regression (GPR) using Genetic algorithm (GA), GA-GPR model is established with high accuracy for predicting UCS. Microscopic analysis reveals that under the alkaline environment, the hydration reaction of SS, FA, BFS occurred to generate calcite (CaCO3), ettringite (AFt) and hydrate calcium silicate gel with a low Ca/Si ratio. Microtopography formed with more refined pore distribution of 0.003- and 1- μm inside CUFTB. To substitute PC using the cementitious material synthesized by IWRs can reduce the mining cost and CO2 emission. The findings provide the guidance for the synthesis of sustainable filling material by reutilizing IWRs.
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