Evaluating Compressive and Tensile Strength and Water Absorption of Geopolymer Mortar Containing Slag (GGBFS) in Comparison with Pozzolan Metakaolin

Geopolymers are aluminosilicate materials that can be a good alternative to various types of concrete, because they help protect the environment by removing pollutants such as CO2 resulting from cement manufacturing process and significantly increase concrete durability by reducing concrete permeability. This study aims to investigate the mechanical properties and durability of geopolymer mortar cured at different temperatures. Therefore, metakaolin and ground-granulated blast-furnace slag (GGBFS) were used as the raw materials for making geopolymer mortar. Sodium hydroxide (caustic soda) with the concentration of 12 M and sodium silicate (water glass) were employed as the activator. In total, 12 curing regimes including three temperatures of 60, 75, and 90 °C and four durations of 8, 12, 18, and 24 h were applied to the samples and its impact on compressive and tensile strength and water absorption of geopolymer mortars was examined. Compressive and tensile strength and water absorption of geopolymer samples were determined after 3, 7, and 14 days. The results indicated the compressive and tensile strength of the samples increased and water absorption of the samples decreased with increasing the curing temperature and duration. Compressive strength of the samples cured at 90 °C for 24 h was at the highest level (62.4 MPa).