Fly ash concrete containing petroleum contaminated soils

With more than three million underground storage tanks located throughout the United States and mass oil drilling, production, and transportation, leaking problems generate large quantities of petroleum contaminated soils (PCS). With the limited availability of solid waste disposal facilities, research is needed to investigate viable re-use options for PCS. This paper presents an attempt to apply stabilization/solidification techniques to PCS to bind the hydrocarbons in a structure formed by cement, fly ash, and aggregates to produce a construction material suitable for bulk applications. An experimental program was developed to examine the potential for using PCS as a fine aggregate replacement in concrete. Two PCS types with different levels of heating oil contamination were investigated (0.11% and 0.66% contamination concentration by weight). For each soil type, nine mixtures were obtained by replacing sand with PCS (PCS/sand ratio of 10%, 20%, and 40% by weight) and class C fly ash with cement (fly ash/cement ratio of 10% and 20% by weight). Compressive and flexural strengths, permeability (hydraulic conductivity), and leachability of benzene to water tests were conducted. The results indicate that the addition of PCS reduces both the compressive and flexural strengths of concrete. However, the obtained strength is adequate for structural applications. Concrete containing higher PCS/sand replacement ratio develops lower strength. That strength loss increases with higher contamination concentration. Given longer curing time, the fly ash presence can reduce such loss. The permeability coefficient of PCS concrete is slightly higher than control. Fly ash addition yields a more impermeable PCS concrete. For both soil types, at 40% PCS/Sand replacement ratio, the leachability of benzene was non-detectable after 24 hours and 10 days of casting.