Remediation of Abandoned Mines Using Coal Combustion By-products

Abstract

Acid mine drainage (AMD) is a phenomenon that occurs when pyrite that is present in abandoned coal mines comes in contact with oxygen and water, forming acidic water rich in dissolved metals. Grout injection into mines is a popular technique that provides a permanent solution to control AMD. The main objective of this study was to investigate the effectiveness of coal combustion by-products (CCBs) in encapsulation of pyrite to remediate AMD. To meet this objective, CCB-based grouts were tested for spread, slump, bleed, and strength. Pyrite was coated with grouts and laboratory tests were performed to evaluate the encapsulation potential. Hydraulic conductivity was measured, and the leachate was analyzed for AMD- related parameters. Results indicated that flowability and strength of grout are related to the fly ash and free lime contents. High pH, calcium and sulfate concentrations, and low concentrations of iron and aluminum in the leachate indicate that effective encapsulation has taken place.