Impact of Basalt Powder on the Physical, Fresh, Hardened and Microstructural Characteristics of Granulated Blast Furnace Slag-Based Alkali-Activated Mortars

In this study, the workability, mechanical and physical aspects of alkali-activated mortar (AAM) containing basalt powder (BP) and granulated blast furnace slag (GBFS) were investigated. For the experimental study, alkali-activated mortars (AAM) containing BP at 8%, 16%, 24%, 32% and 40% substitution rates for GBFS were developed. Mortars were synthesized with a sodium silicate/sodium hydroxide ratio of 3.0 for the binder materials and a 0.45 alkali activator-to-binder ratio. The flow diameters of the fresh mortars prepared using 40x40x160 mm molds were determined according to the European Federation of Experts in Construction Chemicals and Concrete Systems (EFNARC) standard. The fresh AAMs were wrapped in stretch film to prevent evaporation and then kept in an oven at 60°C for 48 hours. The cured samples were evaluated for their mechanical strengths at 3 and 28 days, freeze-thaw effects after 33 and 100 cycles, and microstructures after 100 cycles. According to the results, using 40% BP instead of GBFS caused a decrease of approximately 15.08% in 28-day compressive strength compared to the reference sample (100% GBFS). G100 showed a minimum porosity of 15.81% and a water absorption rate of approximately 7.3%. The G60B40 mixture had the highest sorptivity capacity with 5.29x10-3 cm/s0.5, while the G100 mixture showed the lowest capacity with 3.88x10-3 cm/s0.5. After 100 freeze-thaw cycles, the G60B40 sample had the largest strength loss of 61.61%, while the G100 sample showed the lowest strength loss of 9.89%.