Fire Performance of Fly Ash-Based Geopolymer Concrete: Effect of Burning Temperature

Geopolymer concrete (GEO) is a cementless concrete produced from the reaction of an aluminosilica-rich material, in particular, fly ash, with an alkaline solution, which can either be sodium or potassium-based. In light of the potential of fly ash-based GPC as an alternative to Ordinary Portland Cement (OPC)-based concrete as a green building material, an investigation on the fire performance of GEO, in comparison to OPC-based concrete, is essential. The results of an experimental study on the fire performance of fly ash-based GEO that was subjected to a flame test using a methane burner torch, after 28 days of curing, to simulate a real fire event, are presented. Concrete specimens were exposed to a fire flame at 500 °C and 1200 °C for two hours and subsequently cooled to the ambient temperature, prior to testing. Visual inspection was performed on the specimens to observe for any cracking, spalling and change in colour. Losses of mass and residual compressive strength were measured. The results were compared with those of OPC-based reference specimens. The findings revealed that, in contrast to OPC-based concrete, the strength of GPC increased when exposed to fire at 500 °C. GEO also suffered a smaller loss of mass as compared to OPC-based concrete due to the smaller amount of loss in moisture from burning. It was also observed that no spalling had occurred on the GEO, with less cracking on the exposed surface in relation to OPC-based concrete, hence indicating that the structural integrity of GEO was successfully maintained.