Evaluation of Coal Combustion Products in Hot-Mix Asphalt Mixture

Very fine coal combustion products (CCPs) are a by-product of burning coal when generating electricity. Fly ash has generally been used in portland cement concrete. However, some CCPs have been used in hot-mix asphalt (HMA) as mineral fillers. Due to current changes of Environmental Protection Agency (EPA) emission requirements, large volumes of fly ash containing sulfur cannot be used in traditional concrete. Therefore, this research was undertaken to investigate if some of the finer CCPs can be used beneficially in HMA. In this project, fly ash was blended with PG 58-28 asphalt binder at various percentages (5%, 10%, and 15%). A rotational viscosity test was performed on the blend to see what percentages of fly ash by mass of asphalt binder would be workable. All percentages were found to be viable. Hamburg wheel tracking tests were then conducted on these Superpave HMA mixtures. Based on the Hamburg test results, the best performing mixture with 15% of fly ash was selected to conduct further tests, such as, modified lottman, dynamic modulus, and S-VECD test, and compare with the control group (without fly ash). This paper presents these results.