Experimental Studies on Fly Ash-Sand-Lime Bricks with Gypsum Addition

Coal fly ash, a burnt residue of pulverized coal, is hazardous and its disposal is a problem. In Bangladesh, the annual generation of this waste is approximately 0.6 million tons. On a global basis, less than 20 percent of coal fly ash (CFA) is used in the concrete related applications while the remainder is disposed of in landfills leading to various environmental problems such as polluting soils and groundwater. In this study, production of light weight structural bricks using fly ash, generated at Barapukuria Thermal Power Plant, as the major ingredient has been investigated. Optimum mix of fly ash, sand, hydrated lime and gypsum has been identified and the brick forming pressure was also optimized. 55% fly ash, 30% sand and 15% hydrated lime with 14% gypsum was found to be the optimum mix. The compressive strength, microstructure, shrinkage property, unit volume weight, Initial rate of absorption, absorption capacity, apparent porosity, open pore and impervious pore of the fly ash–sand–lime-gypsum bricks produced with optimized composition under various brick forming pressures were determined. Efflorescence and radio activity of the bricks formed under optimized conditions were also investigated. Later on effect of various curing process and variation of curing period were studied. The results of this study suggested that it was possible to produce good quality light weight non-fired structural bricks from coal fly ash generated at Barapukuria Thermal Power Plant.