Utilization of Wyoming bottom ash in asphalt mixes

Coal ash is the portion of ash rejected by the stack and collected at the base as a waste product. Coal ash comprises of bottom ash and fly ash, fly ash accounts for 70 to 80% of total coal ash and the rest being bottom ash. Only 39% of bottom ash is utilized with the rest being disposed of in mined out areas of coal mines. This represents a significant volume of waste material. There would be considerable benefit to finding a use for this material. So, it is the intent of this project to look into the effect of pavements performance when bottom ashes from three power plant sources in Wyoming (Laramie River, Dave Johnston, and Jim Bridger) are added into asphalt mixes. The performance of these mixes were evaluated by conducting a laboratory evaluation and field evaluation. The laboratory evaluation consisted of preparing samples and then testing them for rutting, low temperature cracking and stripping. The field evaluation was done using experimental test sections in Gillette, Wyoming. These experimental test sections were tested with the Falling Weight Deflectometer (FWD). In addition the Pavement Condition Index (PCI) values were also determined for all of the sections. The statistical analyses showed that the field performance of all bottom ash mixes were comparable to the control mix, while the laboratory evaluation showed that all the ash mixes performance exceeded control mix performance.