Mechanical Properties of Fly Ash–Slag Based Alkali-Activated Materials under the Low-Energy Consummation-Sealed Curing Condition

Abstract

The effect of curing conditions (sealed and standard) on the mechanical properties of fly ash (FA) and ground-granulated blast-furnace slag (GGBFS)–based alkali-activated materials with NaOH and waterglass alkali activators are investigated in this study. The results show the highest 28-day compressive strength of samples was obtained in the A-3 samples and researched to 59.8 MPa under sealed curing conditions. Using scanning electron microscopy (SEM), it was found that samples with sealed curing condition have higher mechanical properties associating to the denser microstructure and low crack width. Under the sealed curing condition, lower carbonation degree of samples has higher content of ${\mathrm{Na}}^{+}$ to form the Si-O-Na bond resulting in the higher content of amorphous gel and geopolymerization degree based on the experiments results of electron paramagnetic resonance (EPR), Fourier transform infrared (FTIR) spectrometer, X-ray photoelectron spectroscopy (XPS), chemical bond water, and selective dissolution.