Strength Investigation of Slag-Based Geopolymer Composites Incorporating Different Amounts of Colemanite Waste and Silica Fume Under Different Exposure Conditions

Abstract

In this study, it is aimed to investigate the strength performance of slag-based geopolymer mortar with different percentages of silica fume and colemanite waste by mixing Na₂SiO₃ and NaOH as the alkaline activator for the geopolymerization reaction, and cured at room temperature were prepared, in terms of compressive strength, flexural strength, ultrasonic pulse velocity and freeze-thaw resistance parameters. Five different mixtures were prepared by using different amounts of silica fume and colemanite waste by using the same amount of ground granulated blast furnace slag, sand and 8M sodium hydroxide for these five mixtures. The mixture, including a paste proportion of 20% slag, 40% colemanite waste, and 40% silica fume, was used as a control mix. The maximum compressive strength (21.24 MPa, 38.32 MPa) flexural strength (5.86 MPa, 6.98), weight loss caused by freeze-thaw effect (0.56%) and ultrasonic pulse wave test (3082 m/s) results were noted as for 7th and 28th day, respectively. After -60 cycles [1 cycle consists of (-18 oC) for 90 minutes and (+4 oC) for 30 minutes], the maximum compressive and flexural strength was observed as (40.18 MPa and 4.92 MPa, respectively). The results indicated that the strength results were consistently increased as silica fume increased. The addition of a certain amount of silica fume gave promising results both in terms of the strength and durability aspects. Overall, according to this experimental study, the utilization of 30% colemanite waste and 50% silica fume can be recommended so as to balance both sustainability and engineering aspects.