Development of geopolymer with coal fired boiler ash

Abstract

Geopolymer is cement-less concrete system expected to minimize the detrimental effects of Ordinary Portland Cement (OPC) production to the environment, while facilitating the eco-friendly utilization of coal by-products. This research aims to investigate in to the development of Coal Fired Boiler Ash (Bottom Ash) based geopolymer in terms of optimizing its methods of synthesis, leading to an economically viable and sustainable end product. In this regard, strength and durability properties of the geopolymer have been explored and Bottom Ash based geopolymer was identified to possess excellent compressive strength characteristics on curing for a period of 6 hours or longer at 75°C curing temperature, with satisfactory flexural strengths varying in the range of 5.1-5.7N/mm2. The shrinkage characteristics of the geopolymer were 5-7 times the specified limits for OPC concrete, with the overall density values lying below the conventional concrete density at 1760-1930 kg/m3. This led to a specification being derived as per the requirements of SLS 855 standard, with Bottom Ash based geopolymer as a replacement for cement blocks.