Long-Term Strength and Durability of Cement-Treated Coal Mine Overburden Materials in Subbase and Base Layers of Low-Volume Roads

Abstract

Coal is the most abundant fossil fuel and the main source of energy for the production of electricity all over the globe. Excessive utilization of coal results in the production of huge quantities of coal mining wastes called overburden (OB). In addition to occupying precious land, the disposal of these wastes poses major environmental and health risks to local communities. To establish the efficacy of locally available coal mine OB materials in the subbase and base layers of low-volume roads, a laboratory study has been conducted in the present research assessing its effectiveness in terms of mechanical and durability characteristics after stabilizing with various percentages of cement. The mechanical strength of cement-treated OB (CTOB) mixes has been evaluated through destructive tests and validated through nondestructive tests and microstructural analysis. Additionally, the durability characteristics of CTOB mixes have been investigated through the wet-dry (W-D) weathering cycle test, capillary rise (CR) test, and drying shrinkage test. The W-D weathering cycles positively impacted the mechanical strength of CTOB mixes up to 12 cycles; after that, deterioration has been observed. The microstructural study also confirmed the long-term strength development in CTOB blends after exposure to adverse weathering conditions. The CR in CTOB mixes with a cement content of 6% or more was less than 25% of the height sample within 24 h of soaking, and even after 72 h of soaking, these samples did not exhibit 100% of CR. Because 80% of final shrinkage occurs within the first 3 days of drying, a minimum of 3 days of curing is recommended to control the development of shrinkage cracks in the CTOB layers.