Optimized ceramic powder geopolymer mortar reinforced with basalt fibers for mechanical durability and environmental...

This research comprehensively investigates the influence of fiber content and the additional water to binder ratio (S/B) on the mechanical properties and durability of geopolymer concrete, including compressive strength, acid resistance, and flexural strength, aiming to identify optimal compositions for different applications. The investigated variables include varying basalt fiber contents (0, 0.5, 0.8 and 1.0%), alkaline solution-to-binder (S/B) ratios (0.5, 0.6 and 0.7), and the durability of specimens when exposed to aggressive environmental conditions, namely acidic attack and freeze-thaw cycles. The study also explores the role of chemical additives in enhancing the workability and refining the microstructural characteristics of the geopolymer matrix. After mixing and casting, specimens were subjected to thermal curing at 100 °C for 24 h, followed by ambient curing for 28 days. Mechanical performance was assessed through compressive strength, flexural strength, and ultrasonic pulse velocity (UPV) testing. Durability was evaluated by immersing the specimens in acidic solutions for 15, 30 and 45 days, and by exposing them to freeze-thaw cycles (50, 75 and 100 cycles). The results showed that the optimized mix containing 0.8% basalt fiber exhibited a 26.4% increase in compressive strength and 35% reduction in mass loss during acid exposure compared to the control. Also, in the flexural test, the optimal mixture sample containing 1% fibers in S/B 0.7 showed a 53.4% increase. The inclusion of basalt fibers up to 0.8% by volume markedly improved flexural strengths, as well as UPV values. Additionally, the fibers were effective in minimizing surface cracking and erosion under aggressive conditions. SEM analyses revealed a denser, more cohesive matrix in fiber-reinforced specimens, corroborating the mechanical and UPV findings. Overall, the integration of basalt fibers and optimized mix parameters proved effective in developing a high-performance geopolymer system with superior mechanical integrity and environmental resilience.