Based on the results presented in this work, it can be concluded that: the silica obtained as a gel by chemical extraction was composed of high purity, nanometer-scale particles that had an amorphous structure. This result confirmed the elevated pozzolanic activity in the material. These characteristics were obtained without burning at high temperatures and after grinding the rice husk ash (the raw material) for only 30 min. Partially substituting Portland cement by silica gel, obtained through a hydrothermal process, in cement pastes provided significantly increased compressive strength over 28 days, with the increase being most expressive in the first few days.