Abstract

Laboratory investigation on crude oil incinerated lateritic soil was undertaken to evaluate its geotechnical properties as connected to roadwork. The lateritic soil was thoroughly mixed with various percent 0, 8, 12, 16 and 20 % crude oil by dry weight of the soil. Each of the specimens were incinerated by allowing the crude contaminated soil to burn until the fire goes off. The rate of incineration is directly proportional to the quantity of crude oil content in the soil. Index properties of the crude oil incinerated (COI) soil was determine alongside the compaction characteristic and California bearing ratio test using British Standard light, BSL (or standard Proctor) and British Standard heavy, BSH (or modified Proctor) compaction energies. The result shows that the incineration shifted the aggregate size distribution curve from clayey soil A-7-6(16) to silty soil A-4(1). The liquid limits (LL) and plastic limit (PL) decreases with increased crude oil content and rate of incineration. The liquid limit of not more than 35% recorded, meets the requirement for sub-base material for road construction. The compaction trend showed an initial increase and gradual decrease in the dry density as the percentage incineration increased for BSH compaction level while the optimum moisture content decreases as the crude oil content and incineration rate (COI) increased for both efforts. The CBR (unsoaked) attained a peak value of 70% at 20% COI for BSH compaction energy, while the lower compaction energy (BSL) attained a peak value of 32% at 16% COI. Similarly, the CBR (soaked) attained a peak value of 45% at 12% COI for the higher compaction energy (BSH), while the lower compaction energy (BSL) attained its peak value of 28% at 8% COI. Base on the 30% CBR value recommended for sub-base of lightly trafficked roads by the Nigerian General Specification, 12% COI is recommended for use as a sub-base in road construction.