Effect of phosphoric acid molarity on acid-based geopolymers
DOI:
https://doi.org/10.46421/entac.v20i1.5738Keywords:
Geopolymers, Acid-based geopolymers, Phosphoric Acid, Metacaulim.MolarityAbstract
Acid-activated geopolymeric matrices are innovative materials with properties as promising as those of alkaline geopolymers. Phosphoric acid is commonly employed in acid geopolymerization; however, its optimal molarity is not yet well established. This study investigates the effects of the liquid/solid ratio (0.2 - 0.4), the molar concentration of the acid activator (8 - 12 mol/L), and the curing temperature (25 / 60 °C) on the fabrication of geopolymer mortars made from metakaolin and natural sand. The pH was measured over time, and the compressive strength at 28 days was evaluated, with the highest observed strength being 10.56 MPa, corresponding to a pH of 2.98. The best strengths were found at intermediate molar concentrations, as an excess of acid negatively affected geopolymeric bonds. Thermal curing did not have a significant effect. These results suggest that phosphoric acid-activated geopolymeric matrices hold potential, but further studies on composition and mix design are needed to ensure competitive properties.
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