The behaviour of iron in geopolymer under thermal shock

In this paper, alkali-activated fly ash (geopolymer) samples were microstructurally analysed after thermal shock. The prepared samples were heated at 1000 °C, and then quenched in water to room temperature. X-ray diffraction (XRD), and energy dispersive spectroscopy (EDS) were used to analyse the samples. The colour of the interior and exterior section of samples were different, where the former was darker than the latter. XRD results showed that hematite forms in small quantities in both interior and exterior sections. EDS analyses showed the presence of iron-rich points in both sections; however, there were many accumulated iron points in the interior section. It was concluded that, to reduce free energy of the system, dissoluble iron during geopolymerisation diffuses through molten channels when geopolymer is being heated and forms accumulated iron regions.