The use of brown coal fly ash to make geopolymer concrete

The use of industrial by-products to partly or totally substitute Ordinary Portland Cement (OPC) has become a topical research area due to both economic pressures and environmental impact as the production of OPC has greatly contributed to the production of CO2 to the atmosphere. The use of industrial by-products as partial replacements for OPC has now become well established, with class F Fly Ash (FA) and Ground Granulated Blastfurnace Slag (GGBS) being the most widely used. Recent research has also shown that concrete with similar strengths to both OP and blended cements can be achieved using class F FA as a 100% replacement material with a suitable alkali activator. This material is known as geopolymer concrete, with several commercial products recently coming on to the market. however, much of the FA produced in Australia is brown coal or class C FA, which can not be used as a replacement material for OPC, due to the chemical composition adversely affecting the properties of the concrete produced. However, the reaction to form geopolymer concrete is different to that when the FA is used as a partial replacement material. As such the possibility exists to use brown coal/class C FA to make geopolymer concrete. This paper reports on a research project investingating the use of brown coal FA from the La Trobe Valley in Australia for geopolymer concrete and the properties of the material produced.