Effect of curing temperature and SiO2/K2O molar ratio on the performance of metakaolin based geopolymers
Abstract In this study, the effect of curing temperature and SiO 2 /K 2 O molar ratio on the mechanical properties of metakaolin based geopolymers were investigated. Different curing temperatures (from 50deg to 90 degC) were used for curing process. A series of geopolymers with different SiO 2 /K 2 O molar ratio N were prepared, with N =2.4, 2.0, 1.6 and 1.2, respectively. The phase composition, microstructure and mechanical properties of the resulting geopolymers were studied. The results indicate that curing temperature and SiO 2 /K 2 O molar ratio impacts final microstructures and mechanical properties of the resulting geopolymers. Microstructures become denser with increases in curing temperature, which was beneficial to the improvement of geopolymer's mechanical properties. The optimum curing temperature was 80 degC giving the best mechanical properties with the compressive strength of 106.2 MPa and elastic modulus of 8.3 GPa, respectively. With increasing SiO 2 /K 2 O molar ratios, the microstructure was quite porous and contained unreacted metakaolin particles, and the corresponding mechanical properties declined sharply, attributed to low degrees of geopolymerization caused by high alkali content.