Volume 24, Issue 3 (September 2001)
Properties and Behavior of Raw Sludge Mixed with Pulverized Fuel Ash and Lime
Raw sludge from a water treatment plant and pulverized fuel ash (PFA) from a coal-fired power plant are normally considered to be waste. The raw sludge is usually soft and weak, and takes a large area for storage if stockpiled on open ground, or requires a heavy dam/retaining structure if impounded. Strength and stiffness of the sludge are important parameters for the design and construction of facilities for sludge storage. This paper presents results from a series of tests on geotechnical properties and behavior of local raw sludge mixed with PFA and lime. The focus is on the improvement of the shear strength and stiffness of the sludge by mixing with different ratios of PFA and percentages of lime. Test results are presented and analyzed. Relationships between unconfined compression strength (UCS), PFA/Sludge (P/S) ratios, and lime contents are obtained. Relationships between the effective friction angle (and cohesion) and P/S ratios for 8% lime are also obtained from consolidated undrained (UC) triaxial tests. Correlation between secant Young's modulus E50 and the peak deviator stress qpeak is established.