Development and evaluation of coal mine waste materials for gainful utilization

Coal mine overburden and thick inseam parting materials found in the lower Gondwana basin are treated as mine wastes. Unused fly ash from coal-fired plants is another waste material. This investigation focused on using these wastes to develop better composite materials. Composite materials of varying compositions with coal mine wastes from 50 to 90% and fly ash from 10 to 50% with 2-6% cement additives were developed and evaluated. Their physical, chemical and geotechnical properties were determined. Ordinary Portland cement strongly influenced the geotechnical parameters. The fly ash content was optimized for unconfined compressive strength (UCS) and California bearing ratio for both mine wastes. Composite materials with 70% overburden, 30% fly ash and 6% cement showed a UCS of 4.01MPa at 56 days. Composites with 80% inseam parting, 20% fly ash and 6% cement produced 4.90MPa UCS at 56 days. Linear correlations were observed between fly ash percentage in the two composites and their UCS values. Pearson's and Spearman's coefficients produced a high correlation of -0.9 for the composite prepared with parting material. Microstructural analysis showed calcium silicate hydrate gel formation occurring at 28 days. The composites meet the strength criterion for the base and subbase of coal mine haul roads.

Automated summary

Coal mine overburden and thick inseam parting materials, as well as unused fly ash from coal-fired plants, are treated as mine wastes. This investigation focused on using these wastes to develop better composite materials. The physical, chemical, and geotechnical properties of the composite materials were evaluated, and the fly ash content was optimized for strength requirements.