Summarizing, we attribute the comparatively high compressive strength of the rice husk ash-based one-part geopolymers mainly to the absence of significant amounts of crystalline byproducts, and the almost complete reaction of the rice husk ash, which resulted in a higher SiO2/Al2O3 ratio and a denser microstructure of the N-A-S(-H) gel in one-part geopolymers produced from other silica sources.