Furthermore, under the same scan conditions, this hump is more pronounced for the lower RM/FA ratio geopolymers, indicating that the geopolymer content is higher. As such, the geopolymer made with higher fly ash content possesses higher strength and stiffness, which is consistent with the mechanical testing results. Duxson et al. (2007) also reported that higher concentration of reactive Si in geopolymerization process typically leads to higher compressive strength.