Compressive strength variability of brown coal fly ash geopolymer concrete

The use of Fly Ash (FA) as an alternative binder material to Ordinary Portland Cement (OPC) is well established, with class F FA the most commonly used in the synthesis of this alkali-activated binder at present. ASTM C618 classifies FA as class F produced from anthracite and bituminous and class C from lignite and sub-bituminous coals. In Australia, Victoria FA is produced from lignite known as Brown Coal (BC), but due to the chemical composition cannot categorize as class C. Recent studies have shown the viability of using 100% BC FA as the binder to create alkali activated geopolymer concrete. A previous study using Victoria BC FA for geopolymer concrete provided strength of more than 40MPa which is comparable to class F geopolymer and OPC specimens. The activation process of geopolymer concrete varies remarkably from PC concrete, due to the activation of the aluminosilicate by high concentration alkali. Therefore, the durability of geopolymer concrete may possibly be different to OPC concrete. This paper reports on a research project investigating compressive strength variability that could, in turn, affect the durability characteristic of the BC FA geopolymer concrete for use in the construction industry.