Effects Of Curing Temperature And Time On The Geopolymerisation Processes And Properties Of Alkali-Activated Metakaolin-Based Geopolymer

The initial geopolymerisation processes and properties of alkali-activated metakaolin-based geopolymer are directly impacted not only by the composition of initial raw material metakaolin, the specific surface and the composition or relative amount and concentration of alkali activator used but also depend on the curing conditions during the initial period of geopolymerisation reaction. This study aims to analyze the effects of curing temperature (20℃,40℃,60℃,80℃and100℃) and time on the geopolymerisation processes and properties of alkali-activated metakaolin-based geopolymer.The variations in the kinetics of geopolymerisation in terms of geopolymer formation at different curing temperatures (from20℃to100℃) were systematically investigated by the Impedance Analyzer. Isothermal differential scanning calorimetry (DSC) measurement was employed to measure the effect of curing temperature on geopolymerisation processes from the perspective of the variations in response to the reaction heat as well. The variations of setting time of geopolymer pastes at different curing temperatures were conducted by Vicat needle. It was established that the elevation in curing temperature accelerates the dissolution of metakaolin particles, the polymerization of precusors and the solidification of the geopolymer pastes in the initial geopolymerisation reaction.The effects of curing temperature and time on the mechanical properties of geopolymers have also been analyzed. The study reveals that prolonging curing time improve the formation of hard structure of geopolymers especially in the early-stage (in12h) of geopolymerisation. The optimum curing temperature of geopolymer is60℃at which the samples present the compressive strength of97.95MPa when cured for7d.The microstructure and morphology of geopolymer were also investigated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and Scanning electron microscope (SEM). It was indicated that the hardening process of geopolymer should not only be attributed to the physical changes but also to the chemical reactions. The mechanical properties of geopolymer are mainly determined by the amorphous gel phase which formed in the geoplymerisation.