Optimizing Alkaline Activation of Natural Volcanic Pozzolan for Eco-Friendly Materials Production: An Investigation of NaOH Molarity and Na2SiO3-to-NaOH Ratio

Abstract

The production of Portland cement is energy-intensive and polluting. As a result, the search for ecological and economical alternatives has become a global priority. Geopolymers are among the most promising ecological alternatives to Portland cement. Their properties depend on the nature and concentration of the activators. This study investigates the effect of Na2SiO3/NaOH ratio and NaOH molarity on the alkaline activation of natural volcanic pozzolan. The physico-mechanical and microstructural properties of the investigated geopolymer were evaluated using compressive strength, density, porosity, water absorption, X-ray diffraction, infrared spectroscopy, and scanning electron microscopy. The results indicate that the optimal parameters for activation are a NaOH molarity of 8 mol/L and Na2SiO3/NaOH ratio of 1.2. These parameters enhance the dissolution of the volcanic pozzolan and the formation of a N-A-S-H geopolymer gel, resulting in a dense, less porous matrix with good resistance.