Admixture Effect on the Porosity, Permeability and Leachability of Immobilized Hydrocarbon Waste

This research studies the waste management of residual hydrocarbon waste that can be retrieved from the wastewater stream in a petroleum refinery complex by the application of a technique known as Solidification and Stabilization (S/S). The S/S technique applies a binder, commonly Ordinary Portland Cement, to immobilize and encapsulate the hydrocarbon waste to chemically stabilize it preventing from external chemical reaction with the environment. The objective is to optimize waste to cement and admixture effect (fly ash) ratio based on the unconfined compressive strength as the main criteria. The performance of the S/S is measured through leaching analysis to determine leachability of metal in the leachate, porosity and permeability properties of the stabilized waste with the unconfined compressive strength and its leaching behaviour. It was found that the lowest water to cement ratio, 0.35 gives out the largest unconfined compressive strength of 66.17 MPa. The presence of sludge and fly ash showed that the highest cement to sludge ratio of 60 with highest amount of fly ash of 15% produces the strongest cement matrix of strength of 39.75 MPa compared to the other lower cement to sludge ratio. Porosity was lowest at 12.09 when the C/Sd was at 40 and C/B at 5%, which however increases rapidly as C/B increases to 15%. A reversal was observed when C/Sd of 60 with increasing C/B ratio. The metals content and total oil grease content in the leachate were relatively low and below the regulated metals content and total oil grease content in wastewater as outlined in EQA 1974.