Sulphate Resistance of Geopolymer Concrete Prepared from Blended Waste Fuel Ash

The aim of this study is to investigate the performance of geopolymer concrete prepared using blended ash of pulverized fuel ash and palm oil fuel ash from agroindustrial waste along with alkaline activators when exposed to a 5% sodium sulphate solution for up to 18 months. Ordinary portland cement (OPC) concrete was also prepared as the control concrete. The main parameters studied were the evaluation of mass change, compressive strength, products of degradation, and microstructural changes. The deterioration was examined using X-ray diffraction (XRD), a Fourier transform infrared spectroscopy (FTIR), a thermogravimetry analyzer (TGA), and a field emission scanning electron microscope (FESEM). The results of geopolymer and OPC concretes were compared and discussed. The compressive strength of geopolymer concrete, when exposed to a 5% sodium sulphate solution for more than 1 year, was superior to that of OPC concrete. These materials could be used for making sulphate-resistant concretes, attributable to a more stable cross-linked aluminosilicate polymer structure formed in the geopolymer concrete.