Effect of curing type on microstructure and compressive strength of geopolymer mortars

In this study, the compressive strength and microstructure of pumice, perlite, burnt clay and fly ash geopolymer mortars were investigated. Activator solutions with 1.0, 1.2, 1.6 and 2.0 Ms (silica/sodium oxide) ratios as well as 4, 8 and 12% sodium oxide ratios by weight of aluminosilicate material were used. Both oven curing and microwave curing were applied. According to the results, compressive strengths of microwave-cured pumice-, perlite- and burnt clay-based geopolymer mortars were 5.7, 54.7 and 15.5% higher than those of the oven-cured counterparts. However, the strength of fly ash geopolymer reduced upon microwave curing. The energy consumption per unit compressive strength in the microwave-cured mortars was found to be between 77.1–87.0% lower than those of the oven-cured ones, depending on the aluminosilicate type. The changes caused by the curing type in the microstructure were investigated by SEM/EDS, XRD, FT-IR and thermogravimetric analysis.