Geopolymer Mortars: A Comparative Study of Fly Ash, Ground Granulated Blast-Furnace Slag, and Silica Fume–Based Binders for Sustainable Construction

The pressing demand for sustainable construction materials has spurred significant research into eco-friendly alternatives to traditional portland cement–based products. Geopolymer mortars, composed of aluminosilicate materials, have emerged as promising substitutes, boasting enhanced mechanical properties, durability, and a reduced carbon footprint. We conducted a comprehensive comparative study on water absorption and various aspects of geopolymer mortars formulated with ground granulated blast-furnace slag, fly ash, and silica fume. The investigation delved into their chemical composition, physical characteristics, and mechanical and durability performance, focusing on the influence of alkaline activator content on activation processes and binder formation. With compressive strengths ranging from 36 to 41 MPa at 56 days, the M10 mix had the highest strength. Assessments for durability against chemical attacks and moisture ingress showed promising results, with water absorption of geopolymer mortar below 12% and other parameters meeting acceptable limits. The incorporation of silica fume in the mortar mix resulted in an evaporation parameter (gel and capillary porosity) of less than 10%. Although the inclusion of ground granulated blast-furnace slag had a slight detrimental effect on the mortar due to its calcium content, mass loss under acid attack was approximately 1.2%. The compressive strength of the mortar reached 35 MPa (M10) after 56 days of exposure to acid in the samples. This article includes a comprehensive discussion on the potential applications and limitations of fly ash, ground granulated blast-furnace slag, and silica fume–based geopolymer mortars. The study contributes significantly to advancing eco-friendly construction materials and promoting a more environmentally conscious built environment.