Use of coal tar contaminated soil in road paving asphalt

The use of coal tar contaminated soil to replace reclaimable asphalt pavement (RAP) in the hot asphalt mix production was studied as an economical alternative to incineration and stabilization in landfill. Coal tar contaminated soil is classified as a 'characteristic waste'. Performing toxic characteristic leaching procedure using zero head space extraction (TCLP/ZHE) on coal tar contaminated soil prior to feasibility studies indicated that volatile organic compounds (VOCs) were below the regulatory levels. Trace metals in the contaminated soil were also found to be lower than regulatory levels. A bench-scale experiment was performed to monitor the emissions from the coal tar contaminated soil heated to the hot asphalt mix production operating temperature. Pilot-scale studies were performed to represent the worst case scenario of the full-scale operation's air to mass ratio. In the process of producing hot asphalt mix, air emissions were monitored during the mixing of coal tar contaminated soil with fresh aggregate and asphalt cement. Five runs were performed using different ratios of coal tar contaminated soil, asphalt cement, and fresh aggregate. The host asphalt mixtures obtained from the five runs were tested for the leachability of the contaminants. Test results showed acceptable levels of stability and flow for the resultant asphalts. The use of coal tar contaminated soil (CTCS) in road paving asphalt can highly alleviate disposal and remediation costs of CTCSs.