Publication: Evaluation of the properties of light non-aqueous phase liquids contaminated sands after stabilization with laterite soil and potential usage in various constructions
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Date
2023-06-01
Authors
Reda Ali Abdelhalim Mohamed
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Abstract
Oil-contaminated soils are generally considered inadequate for structural concrete and highway construction. In this study, inexpensive laterite or lateritic soil (LS) was used as the stabilization additive. Clean sands were blended with heavy oil at 3, 5, 8, and 10% oil content (OC) to simulate contamination, where losses in geotechnical strength and permeability were observed. Subsequent stabilization by the laterite soil (LS) recovered the strengths. The LS amounts used were 5, 10, 15, 20%. Adding 15% LS to sands with 3-10% OC increases friction angles by 9.5-14.4%. For sands with 5% OC, treatment with 15% and 20% LS increases CBR by 27% and 36%, respectively, compared with the uncontaminated. Scanning electron microscopy (SEM) images show the morphologies of soil grains drenched in oil and the subsequent rejuvenation brought about by the stabilization. Also, a series of cone penetration test (CPT) tests were conducted to investigate the strength of oil-contaminated SP sand and subsequently stabilized by LS. Based on qc results, for contaminated sand with up to 8% OC, the stabilization that would restore the initial uncontaminated sand strength was 20% LS content. For the results of fs, a blanket LS content of 15% would return the initial uncontaminated sand value even for a sample with 10% OC. For practical applications, two concrete mixes: M1 = 1:1.26:2.52 (cement: fine aggregate: gravel) and M2 = 1:1.5:3 (cement: fine aggregate: gravel), were designed with water/cement ratios (w/c) of 0.476 and 0.50, respectively. The goal is to examine the properties of hardened concrete after casting, followed by curing for 28 and 750 days by submerging it in water. The results of the compressive strengths of M1 were approximately 40% and 43%, as averages for two curing times, which were higher than those of the unstabilized oil-contaminated fine aggregates due to the stabilization with 15% LS for the 5% and 10 % OC, respectively. A similar trend was observed for the second mix (M2). Results conclude that the chemical composition of the LS consists of three main compounds: SiO2, Al2O3, and Fe2O3, indicating that the LS contains a considerable amount of pozzolans that could encourage the formation of secondary cementitious materials, thus increasing concrete strengths. According to Marshall test outcomes, adding 15% LS to the oil-contaminated with 3% OC caused stability to increase by 40% while adding 15% LS to the oil-contaminated sand with 5% OC increased the stability by 16% compared to untreated specimens in both cases. The stability and flow values fall within a range of acceptable categories as stipulated by the Asphalt Institute. In conclusion, rather than neglected, oil-contaminated sands, after stabilization by LS, are now feasible for use as subgrade or subbase material or fine aggregates of both hot-mixed asphalt and concrete applications such as Sandcrete block and sidewalks.