Mechanical and Durability Performance of Rice Husk Ash–Periwinkle Shell Ash Blended Concrete under Crude Oil Exposure

Abstract

This study evaluates the mechanical and durability of grade 25 concrete modified with Rice Husk Ash (RHA) and Periwinkle Shell Ash (PSA) under crude oil exposure. RHA and PSA were incorporated at 0–10% replacement of cement by weight, while maintaining a constant water-to-cement ratio of 0.55. Concrete specimens were subjected to two curing regimes: 28 days of pre-curing in water and then followed by 62 days post-curing in crude oil immersion (totaling 90 days), and continuous crude oil immersion for 90 days. Mechanical and Durability were assessed through compressive strength and moisture absorption tests at 90 days of curing in line with BS standards. Microstructural investigations using Scanning Electron Microscopy (SEM) were carried out to examine pore refinement, crack morphology, and hydration products. The results indicate that optimal blends of ≈5–6% RHA and 4–5% PSA produced the best performance. They achieved higher density (eg.C7=2730kg/mm3 and W7=2803 kg/mm3), lower moisture absorption (e.g. W7=0.1785% and C6-0.486%), and improved retention of mechanical strength (e.g. W7=20.5N/mm2 and C9=16.0N/mm2) compared to control samples. Water-cured specimens consistently outperformed those in crude oil by 7.87% in strength, yet RHA–PSA concretes exhibited slower strength loss and reduced microcracking under crude oil exposure. SEM images confirmed denser C–S–H gel networks and refined pore structures at optimal dosages, whereas higher ash contents increased porosity and susceptibility to deterioration. The findings demonstrate that moderate incorporation of RHA and PSA enhances both the mechanical and durability of concrete in crude oil environments (C7=15.0N/mm2), making these materials promising sustainable additives for infrastructure exposed to petroleum-polluted conditions.