The disposal of oil sludge together with construction and demolition waste in Tanzania is still a challenge in both space and technology. In order to reduce the space requirement for oil sludge together with construction and demolition waste disposal, the recycling of these waste becomes a vital option. This paper is mainly concerned with the determination on the possibility of recycling the oil sludge together with construction and demolition waste into building material in Tanzania. The materials used were oil sludge from oil re-refining industry, construction and demolition (C&D) waste, cement and water. The amount of oil sludge produced annually is 20 tons at First Enviro-limited company which is located at Kahama, Tanzania. The quality of materials used were tested and analyzed in the laboratory. Results of sludge characterization showed that the amount of Mercury, Cadmium, and Lead were 0.277, 0.078, and 1.01 mg/l, respectively. This concentration is within the acceptable range of the amount required in the soil however; in future, the metal concentration in the soil is expected to accumulate, which will result into negative impacts in relation to the environment. In the recycling process, different mix ratios of cement, oil sludge and C&D waste were applied. The experiment was meant to determine the optimal mixing ratio. This study demonstrated that the oil re-refined sludge together with construction and demolition waste can be recycled into building material in Tanzania and hence reduce their adverse impacts to the environment.
Key words: Recycling, oil sludge, construction and demolition waste, building materials.