Abstract
Backfilling is a technique employed to fill the voids left over from the extraction of minerals in underground mining. This approach is widely recognized as an environmentally acceptable means of waste disposal. The process of backfilling is of paramount importance in the comprehensive functioning of mining operations, as it provides appropriate support, minimizes the dilution of waste material, facilitates safe working conditions, and mitigates the potential risk of surface subsidence. The materials utilized in this technique are commonly referred to as backfilling material. The selection of these materials is influenced by various factors, including their accessibility, cost, stowing system, grain size distribution, permeability, strength, stability, consolidation, compressibility, deformation, and load-bearing properties.
Fly ash, a byproduct of coal combustion in thermal power plants, has proven to be a highly suitable alternative material for backfilling purposes, particularly in place of sand, otherwise a pollutant if stored in ash ponds. Its utilization in the mining industry has demonstrated significant benefits, particularly in terms of stowing applications. Additionally, the power sector stands to gain advantages from the use of fly ash as a means of waste disposal. The presence of a significant proportion of SiO2 contributes to enhanced strength, consolidation, and stability, while the presence of calcium oxide imparts cementing properties to the material. The spherical morphology of fly ash particles contributes to a frictionless flow, thereby minimizing the abrasion and erosion of pathways used for stowing. However, the delayed settling and escape of fines due to the light weight and fine particle nature of fly ash hinder the quick settling of particles, which is necessary for efficient stowing. While it is probable to effectively stow fly ash by employing appropriate techniques.
Conversely, plastic stands out as one of the most environmentally detrimental substances on the planet. The predominant factors contributing to the excessive utilization of plastic include its affordability, lightweight nature, robustness, resistance to corrosion, and its exceptional thermal and electrical insulation properties. As a result, there has been a significant increase in the production of plastics over the past 80 years; however, only half of this quantity is being appropriately recycled or disposed of.
The aim of the current research is to produce synthetic lightweight aggregates by combining two environmentally hazardous materials, particularly fly ash and plastic, in different proportions. The resulting aggregates will then be investigated as a feasible backfilling material in terms of its environmental acceptability, using the hydraulic stowing method.