Evaluation of Coal Ash as a Supplementary Cementitious Material for Application in Full-Depth Reclamation of Asphalt Pavements

摘要

Full Depth Reclamation (FDR) is a rapid means to rehabilitate existing pavement by blending the reclaimed asphalt and base materials with ordinary portland cement (OPC). Compacting the blend provides a stable base upon which a new layer of asphalt pavement can be constructed. The South Carolina Department of Transportation has employed FDR as a standard rehabilitation operation in maintaining the state’s large network of roads. However, the huge demand for OPC in the FDR projects, coupled with the relatively tight supply of OPC, is forcing the construction industry to explore the use of industrial by-products as supplementary cementitious materials (SCMs). In this study, four different coal-combustion residues (coal ashes) from four Duke Energy power plants were evaluated for use in FDR projects. The fly ash (FA) portion of each coal ash was used as pozzolan to replace up to 40% of cement by mass. For this purpose, the chosen SCMs were analyzed for their chemical and mineralogical composition and physical properties. The pozzolanic reactivity, relevant mechanical and durability aspects of the blended cementitious materials, at selected dosage levels, were investigated. The results show that all FAs can be used, with relative performance, as pozzolans to partially replace cement for base stabilization; however, the FA produced at power plant B, due to its low LOI, high fineness, and amorphous structure, performed better in stabilizing the base materials. This project highlights the beneficial utilization of industrial by-products as valuable construction materials that otherwise would be landfilled as solid wastes.