Abstract Cold weather conditions impose substantial constraints upon the performance and long‐term resilience of concrete materials. Alkali‐activated slag (AAS) presents itself as a promising substitute, exhibiting sustained hydraulic activity even when exposed to ambient conditions characterized by low temperatures. This research paper investigates the mechanical performance and acid resistance of cold‐cured hybrid alkali‐activated mortars containing granulated blast furnace slag (GBFS), partially substituted Portland cement (PC), and basalt fiber (BF) as reinforcement. Mortars were prepared with two alkali activator dosages (8% and 12%) and three BF contents (0%, 0.3%, and 0.6%). Compressive and flexural strengths and ultrasonic pulse velocity (UPV) tests were performed to understand the mechanical performance of 7‐, 28‐, and 90‐days samples. For chemical durability under the 5% sulfuric acid attack, mass loss data and SEM images were obtained in conjunction with mechanical tests. Key findings indicate that increasing the alkali dosage improved early strength but caused microstructural vulnerabilities without fiber reinforcement. The best performance was observed in the mix with 8% activator, 15% PC, and 0.6% BF, which achieved 61.72 MPa strength after 90 days. The highest post‐acid strength (69.33 MPa) was found in the mix with 8% activator, 100% GBFS, and 0.6% BF. Mixes without fiber and those containing PC showed greater strength loss. SEM analysis indicated secondary densification around fibers after acid exposure, while PC‐rich mixes exhibited localized degradation. Overall, cold curing combined with optimized activator dosage and fiber reinforcement improves the mechanical and durability performance of hybrid alkali‐activated mortars, provided that PC content is carefully limited.
Bahçeci et al. (2026) studied this question.