Strength and Durability Performance of Fly Ash-Based Process-Modified Geopolymer Concrete

Most recent research has focused on the mechanical strength and durability of geopolymer concrete with heat activation (at different temperatures) and has indicated a limitation for its application in precast industries only. This limitation can be overcome by changing when the ingredients for geopolymer concrete are mixed so that curing can be made at ambient temperature. With this process modification (heat activation of fly ash and alkaline fluid), the modified geopolymer concrete shows a significant enhancement in mechanical strength (compressive, split tensile, flexural, and bond strength) and durability (water absorption, acid attack resistance, and rapid chloride permeability test) compared with conventional geopolymer concrete (heat activation after casting) and the control concrete. The microstructural properties analyzed through a field emission scanning electron microscope (FESEM) with energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) techniques show a better interaction of fly ash and activator solution at early ages for such process-modified geopolymer concrete. This accelerates the formation of a crystalline phase from the amorphous phase of fly ash.