Utilization of Illinois PCC Dry Bottom Ash for Compacted Landfill Barriers

Compacted soil barriers are one of the most important components of municipal waste landfills. The material used to construct a landfill liner and/or cap must prevent the flow of fluids through them. Soils with low values of permeability (such as compacted clays) are often used to construct landfill barriers. Natural sands and other cohesionless materials are used to construct hydraulic barriers by adding admixtures to modify their properties. Several studies have been conducted that dealt with determining geotechnical engineering properties of sand-bentonite mixtures. Pulverized coal combustion (PCC) dry bottom ash is a coal combustion by-product of burning coal to produce electricity. Because of the increasing costs associated with the disposal of bottom ash and the environmental regulations in place, there is a need to develop alternate methods for profitable and environmentally safe uses of this waste material. Most scientists and researchers have concluded that bottom ash has geotechnical characteristics similar to those of sands. However, information on the use of bottom ash, with or without admixtures, in the construction of landfill barriers is limited. Most of the available literature on the engineering properties of bottom ash deals with its use as a fill material. The physical and chemical characteristics of bottom ash depend on several factors including type of coal used and type of boiler and collection system. This paper presents the results of an experimental study conducted to determine the possible use of Illinois PCC dry bottom ash amended with bentonite to construct landfill barriers. Test results presented show that the average value of hydraulic conductivity of Illinois PCC dry bottom ash with 15% bentonite content is close to the acceptable value required for its use as hydraulic barrier. Therefore, it was concluded that Illinois PCC dry bottom ash, modified with 15% or higher bentonite content, is likely to provide adequate hydraulic conductivity for its use to construct landfill barriers.