Utilization of sludge from power plant as cement substitution

Abstract

The feasibility of wastewater treatment sludge from the power plant was studied as cement substituted material. The sludge were used as the air dried sample and the oven dried sludge at 300o C. Their properties, then the optimum ratio of cement substituted portion for cement block were determined. In the control set; cement, sand and water ratio were 1, 2.75 and 0.825 (w/w) respectively, while the treatment set, sludge replacing were varied at 10, 20 and 30 %. The blocks were produced and cured in tap water for 7, 14 and 28 days, and tested their compressive strength. The leaching ability of heavy metals, namely, Cd, Cr, Cu and Pb were determined by Waste Extraction Test or WET (according to the standard from the Notification of Ministry of Industry, A.D. 2005) and Toxicity Characteristic Leaching Procedure; TCLP (US EPA method 1311). The results showed that the solution from cement block curing, both of control set, treatment block had basicidic pH range 11 – 12 and caused reduction of the heavy metal solubility. The solution conductivity range 5 - 7 mS/cm. The 10% dried sludge cement blocks were the suitable ratio compared with the control set which the maximum compressive strength at 28th day was 253.81 Kg/cm2 and 4.73 % moisture. All metal leaching abilities were less than those Notification and US EPA standard. Those optimum ratios, 10 % can be applied to produce cement pot.