Potential use of petroleum-contaminated soil in hot mix asphalt concrete

Petroleum-Contaminated Soil (PCS) results from leaking underground storage tanks, oil spills on clean soils, or soils surrounding petroleum refineries and crude oil wells. In Oman, Petroleum Development Oman (PDO) generates more than 50,000 tons/year of petroleum-contaminated soil (PCS) and faces a real challenge to safely dispose of these quantities. PDO is currently practicing the bioremediation process with high cost and limited results. This paper presents the results of using PCS as an fine aggregate substitute in Hot Mix Asphalt concrete (HMA) with percentages up to 40%, by total aggregate weight. Environmental assessment was performed by analyzing the raw contaminated soil for heavy metals, and hydrocarbons. The Marshall mix design method was used to prepare and test the mixes. The results indicated a reduction in optimum asphalt content from 4.1% in the control mix to 3.5% in the PCS mixes. The increase in PCS content up to 40% resulted in a reduction in stability from 24. 3 to 4.7 kN and increase in air voids from 3.5 to 9.4%. The flow was within the limits of specifications. Leaching of heavy metals using the Toxicity Characteristic Leaching Procedure (TCLP) was also performed on selected mixes. The results indicated concentrations well below the TCLP regulatory limits except for Zn for the 40% PCS mixes. The results indicated potential use of up to 15% PCS in surface mixes, while higher percentages (up to 40%) can however be used for medium or light traffic surface or base course layers.