Local Materials in Geopolymer Mortar: A Case Study on Metakaolin and Blast-Furnace Slag

The ubiquitous use of Portland cement in construction is accompanied by significant energy consumption and environmental impact.Geopolymeric cement has emerged as a sustainable alternative, boasting mechanical properties that are potentially favorable and a notably lower environmental footprint.This study evaluates the mechanical, physical, microstructural, and durability characteristics of geopolymer mortars synthesized from local aluminosilicate precursors-namely metakaolin (MK) and granulated blast-furnace slag (GBFS)-activated with sodium silicate solutions of varying molar ratios (1.2 to 2).Mechanical parameters assessed include compressive and flexural strengths and dynamic modulus, while physical properties encompass workability and porosity.Microstructural analysis was conducted, and durability was gauged through compressive strength reduction and alkalinity loss following sulfuric acid exposure.The performances of these geopolymer mortars were juxtaposed with those of conventional Portland cement mortar.It was revealed that an optimal geopolymer formulation incorporates 75% aluminosilicate material and 25% alkaline solution, with a liquid-to-solid ratio of 0.5 and a sodium silicate solution molar ratio (SiO₂/Na₂O) of 1.8.This specific formulation yielded a compressive strength that surpassed that of the Portland cement mortar and displayed comparable porosity and resistance to compressive strength reduction postacid exposure.