Cone penetration measurements in oil-contaminated sand stabilized by lateritic soil and potential usage in concrete mix

Abstract

Oil-contaminated soils are generally considered inadequate for structural concrete and highway construction. However, soils continue to be contaminated by oil and various methods of stabilization have been attempted. This paper documents a series of experiments carried out using the electronic cone penetration test (CPTu) to investigate the strength behaviour of a poorly graded sand (SP) when contaminated by oil and subsequently stabilized by a lateritic soil (LS). When contaminated with oil, the sand lost some of its strengths as indicated by the decreased cone resistance (qc) and sleeve friction (fs) values, which reduced further when the oil content (OC) was increased. When subsequently stabilized with the LS, the lost strengths recovered and continued to enhance with additional LS used. Based on the evaluation of results associated with qc, for a contaminated sand with up to 8% OC, the stabilization that would return the original uncontaminated sand’s strength was one with 20% LS content. Moreover, the stabilization was more efficient for sand with lesser OC than with more OC. Similar results as those associated with qc were found when the bases for evaluation were the internal friction angle (ϕ), standard penetration number (SPTN), and Young’s modulus (Es), since these parameters were all derived from qc. Based on the evaluation of results associated with fs, unlike in the case of qc, a blanket LS content of 15% was capable of returning the original uncontaminated sands’ value even for a sample with 10% OC. The morphologies of contaminated and stabilized sands have shown revealing results of breakdown and rejuvenation through scanning electron microscopy (SEM). Moreover, based on compressive and flexure concrete tests it was observed that the oil-contaminated sand, after stabilizing it with lateritic soil, should be useable as a fine aggregate in rural infrastructures and low strength concrete applications such as Sandcrete block and sidewalks, rather than being neglected.