Abstract
In this study, fly ash was utilized to synthesize geopolymer by activating with 4 M sodium hydroxide. Samples were cured at 120 °C for 6, 15 and 24 h, and they were aged for 7, 28 and 90 days. The degree of reaction was determined, and leaching tests were performed on all geopolymer samples according to US EPA TCLP method. The microstructural properties of samples were investigated by Fourier transform infrared spectroscopy (FTIR), X-ray diffractometry (XRD) and scanning electron microscope (SEM) techniques. Increase in both curing and aging durations resulted in higher compressive strength values. The results of leaching tests indicated that the metals were successfully immobilized. The major bonds of geopolymers were observed in FTIR spectrum. The intensity of the Al–O and Si–O asymmetric bonds increased with increase in curing duration. In XRD diffractograms, it was observed that all of the geopolymer samples had amorphous structure containing mainly two crystal phases. FTIR, XRD and SEM results revealed that geopolymerization was achieved in these synthesis conditions despite low molarity.
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