Immobilization of Petroleum Sludge Incorporating Portland Cement and Rice Husk Ash

Portland cement and rice husk ash were incorporated to stabilize and solidify the contaminant in petroleum sludge. Stabilization and solidification technique was chosen as an alternative treatment to reduce toxicity of the sludge prior to final disposal of the waste. The sludge has significant amount of organic material which normally interfere with the cement hydration process. A way to improve is by incorporation of cement replacement material. Mixture proportioning was conducted to find optimum water to cement ratio, sludge to cement ratio and cement replacement percentage. The solidified sludge performance was measured by compressive strength and permeable porosity. The optimum ratio of water to cement was found at 0.45 and cement to sludge of 8. Rice husk ash (RHA) was added at 5, 10 and 15 % cement replacement. 5 % RHA exhibited the best performance with regards to unconfined compressive of 24.9 N/mm2. The strength was better than the sludge cement of 19.2 N/mm2. Permeable porosity has inverse relationship with strength at water to cement ratio of 0.4. However at water to cement ratio of 0.45, the relationship showed different trend where increase in porosity cause increase in strength. Porosity was found to increase with increasing RHA content. The surface morphology of solidified cement with voids was found to be in the range of 10 to 15 mm for 15 % RHA.