American Journal of Materials Engineering and Technology, 2013, Vol. 1, No. 3, 35-40 Available online at http://pubs.sciepub.com/materials/1/3/2 © Science and Education Publishing DOI:10.12691/materials-1-3-2 Experimental Studies on Fly Ash-Sand-Lime Bricks with Gypsum Addition Tahmina Banu, Md. Muktadir Billah, Fahmida Gulshan, ASW Kurny * Department of Materials and Metallurgical Engineering, Bangladesh University of Engineering and Technology, Dhaka, Bangladesh *Corresponding author: aswkurny@mme.buet.ac.bd Received August 14, 2013; Revised August 26, 2013; Accepted August 28, 2013 Abstract 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. Keywords: coal fly ash, structural bricks, sand, gypsum, microstructure, properties Cite This Article: Tahmina Banu, Md. Muktadir Billah, Fahmida Gulshan, and ASW Kurny, “Experimental Studies on Fly Ash-Sand-Lime Bricks with Gypsum Addition.” American Journal of Materials Engineering and Technology 1, no. 3 (2013): 35-40. doi: 10.12691/materials-1-3-2. 1. Introduction Pulverized fuel ash commonly known as fly ash is a useful by-product from thermal power stations using pulverized coal as fuel. The high temperature of burning coal turns the clay minerals present in the coal powder into fused fine particles mainly comprising aluminium silicate. Fly ash produced thus possesses both ceramic and pozzolanic properties. Fly ash is a hazardous waste. The problem with fly ash lies in the fact that not only does its disposal require large quantities of land, water, and energy, its fine particles, if not managed well, by virtue of their weightlessness, can become airborne. When not properly disposed, fly ash is known to pollute air and water, and causes respiratory problems when inhaled. Globally around 20% fly ash is used in concrete related applications. Mainly CaO–SiO 2 –H 2 O and CaO–Al 2 O 3 – SiO 2 –H 2 O phases contribute to hardening [1,2]. Fly ash is also utilized in many different areas like paints, plastics and in agriculture [3,4,5,6,7]. In Bangladesh about 0.6 million tons fly ash is produced annually and its production is likely to increase significantly because the future power plants in Bangladesh are likely to be coal fired. Use of fly-ash is, on the other hand, yet to be popular. A small quantity of imported fly-ash is reported to be used in the manufacture of cement in Bangladesh. A viable option for the bulk utilization of fly-ash could be in the production of structural bricks containing fly ash as a major ingredient. The manufacture of conventional clay bricks involves the consumption of large amounts of clay. This depletes topsoil and causes degradation of agricultural land. If fly ash bricks containing no clay can be manufactured then this would not only help preserve the topsoil but also reduce environmental problem by caused by dumped fly ash. In this study an attempt has been made to produce light weight bricks for structural applications using fly-ash generated at the Barapukuria Thermal Power Plant. 2. Materials and Methods Fly ash, sand and hydrated lime mixtures with gypsum as a binder were used to make bricks. Process variables like the composition of the mix, pressure, curing conditions, etc were optimized. Finally the properties of the bricks produced under the optimum conditions were determined. Fly ash used in this study was collected from Barapukuria Thermal Power Plant. The other ingredients hydrated lime, sand and gypsum were collected from the