Experimental Investigation of Rheological and Strength Development Characteristics of High Concentration Power Plant Ash Slurry for Underground Mine Backfilling Applications
摘要
Fly ash is a serious solid waste pollutant in India with more than 150 million tonnes produced every year. Mine backfilling using high concentration fly ash slurry is an eco-friendly and cheaper way to control subsidence while also dealing with problems like poor permeability, ground instability, and waste hazards. In this research work, attempt has been made to analyze rheological and strength development properties of the concentrated fly ash slurry from captive power plant of NALCO for hydraulic stowing. The critical parameters—maximum settled concentration, settled porosity, percolation rate, mixing efficiency and Unconfined Compressive strength were quantified via a series of bench-scale studies conducted with and without bottom ash and lime additions. The rheology data indicated that both the fly ash slurry and the combination of fly ash and bottom ash slurry exhibited pseudo-plastic behaviour in the studied range of shear rates of 0–200 s− 1. Addition of 10–15% (by weight of total solids) of bottom ash and 5% (by weight of total solids) of lime improved drainage and lowered settled porosity. Furthermore, the strength analysis revealed that the UCS values increased with curing age with the maximum stress of 315 kPa for 65 wt% solids mixture (70% fly ash + 30% bottom ash + 5 wt% lime) after 28 days. The results verify that the high concentration fly ash-bottom ash-lime slurry is a technically feasible, economical and sustainable fill material for underground mine back-filling, which provides both effective waste utilization and solid ground stabilization.