Durability and Mechanical Properties of Pumice-based Geopolymers: A Sustainable Material for Future

Abstract

Geopolymers are known as ecofriendly materials because of their low CO2 emissions and waste materials that could be used in their fabrication. In this paper, pumice is used as a raw material obtained from volcanic ashes to produce a sustainable mortar. For this purpose, the effects of sodium oxide concentration (Na2O%) and silica modulus (MS) on the durability and mechanical properties of geopolymer mortars based on pumice as a natural pozzolan were investigated. Sodium oxide at the concentrations of 8, 10, and 12% by the mass of the binder and silica modulus of 1, 1.5, and 2 were used for preparing the mortars. The properties of the geopolymer mortar were investigated through compressive, flexural, and tensile strengths, water absorption, rapid chloride migration (RCM), and the length change of mortars exposed to a sulfate solution. Additionally, scanning electron microscopy (SEM) and X-ray diffraction analyses were performed on the specimens. The results showed that the optimum value for the compressive and flexural strengths was achieved at 10% and 1.5 for sodium oxide and silica modulus, respectively. As the Na2O concentration and silica modulus increased, the porosity decreased, and a denser matrix formed, resulting in lower permeability. The microstructural analysis of the geopolymer specimens also described the higher durability of specimens with higher sodium oxide content and silica modulus. The results of the environmental impact of pumice-based geopolymer revealed that it had a lower CO2 index than the reference specimen and could be a sustainable material for future uses.