Resilient Characteristics of Bottom Ash and Bottom Ash-Soil Mixtures

Abstract

Abstract Bottom ash, a byproduct of the coal combustion process to generate electricity by power plants, is generally underutilized and ends up in landfills or ponds. This paper aims at evaluating the characteristics of the coal combustion bottom ash for potential utilization in pavement construction materials. To achieve this objective, a comprehensive laboratory testing program was undertaken to evaluate the physical properties, compaction characteristics, and resilient modulus of bottom ash, subgrade soils, and bottom ash-soil mixtures. The investigated bottom ash was obtained from power plants in Wisconsin and Michigan. Test results showed that there is a wide spectrum of bottom ash properties pertaining to specific gravity and unit weight, while the investigated bottom ash samples were classified as granular material. Repeated load triaxial testing was performed to determine the resilient modulus of the bottom ash, subgrade soil, and bottom ash-soil mixtures. Specimens were tested at the maximum dry unit weight and optimum moisture content. Test results demonstrated that the resilient modulus values of bottom ash vary depending on the physical properties and unit weight of the bottom ash. For four bottom ash-soil mixtures, the resilient modulus values were low compared with the resilient modulus of subgrade soils, while for one type the resilient modulus was comparable/higher than that of subgrade soil. Therefore, mixing the bottom ash with subgrade soil showed increased resilient modulus values of the mixture for the bottom ash sample from Oak Creek Power Plan (OCPP). Mixing 50% of the bottom ash with subgrade soil, by dry weight, was considered an optimum amount to improve the resilient modulus of the bottom ash soil mixture for OCPP bottom ash.