A critical challenge related to the mining industry is managing and disposing of a large amount of mines overburden (OB) waste produced and dumped as heaps of stockpiles. The steady increase in tonnage and extreme weather events further elevates the environmental burden of OB waste disposal. In an attempt to utilize the whole volume of OB waste, the first phase of this study was designed to understand the suitability of using OB waste as raw material for LWA manufacture. For this purpose of investigation, different types of processed and unprocessed OB representative samples were collected from nearby mines, and a detailed characterization was carried out. A pelletizer was used to convert OB soil into spherical-shaped aggregates. The pelletization parameters such as angle, speed, duration, and minimum moisture demand were arrived at for each sample. The fresh aggregates were hardened using thermal sintering. The aggregates were tested for their density, strength, water absorption, and microstructural properties.
The second phase of the study was framed to enhance the pelletization efficiency and aggregate properties by adding chemical binders and mineral admixtures to the raw material. A variety of sodium-based salt solutions were used as chemical binders. The waste glass and granite powders were used as mineral admixtures. The study further seeks to establish a combination of chemical binders and mineral admixtures on an individual and a mix of two different OB wastes. The aggregate properties were analyzed for varying binder/admixture dosages, pelletization parameters, and sintering temperatures. In the third phase, a comparison on the effect of different aggregate hardening methods such as thermal sintering, microwave sintering, and geopolymerization of the aggregates was made. In this talk, the results from the initial phases of the study will be discussed.