Determination of mechanical, flowability, and microstructural properties of cemented tailings backfill containing rice straw

Abstract

China is the world’s major producer of tailings and straw, and they lead to serious environmental and economic problems. This work was conducted to study sustainable rice straw (RS) and tailings utilization for cemented tailings backfill (CTB), and the effect of RS on the properties of CTB was evaluated. The RS fiber of the RS content (0.08, 0.16 and 0.24 wt%) and RS length (0.9, 2 and 4 cm) were used to prepare CTB. RS fibers show slight side effects of a decrease of 5% in the flowability of the fresh CTB slurry because the natural RS fibers with high water absorption cause viscous increases in the fresh CTB slurry. This decrease further decreases with increasing RS fiber content and length. The impact of the RS fibers on the unconfined compressive strength (UCS) and the elastic modulus of the CTB is significant. A UCS of more than 85% CTB and an elastic modulus of more than 74% CTB have been increased more than twice. The RS fiber reinforcement improves the ductility of the CTB and maintains the integrity of the CTB matrix when failure occurs. Scanning electron microscopy (SEM) observations analyses revealed that much hydration gel was generated in the RSCTB matrix, and these hydration gels became trapped on the surface of the RS fibers, which established a physical skeleton structure and enhanced the strength of the CTB. Additionally, the RSCTB method can reduce the backfill cost by 24.76% by reducing the consumption of cement, increasing the comprehensive utilization of the RS and tailings, and reducing the environmental pollution caused by industrial and agricultural waste.