Optimizing fiber type and content in geopolymer–oil composites: A multi-criteria performance analysis

This study explores the effects of different fiber types and volume fractions on the performance of vegetable oil-modified geopolymer composites, with a specific focus on crack control, mechanical properties, environmental impact, and cost-effectiveness. The influence of various types of fibers, namely three types of basalt fibers (dispersible, alkali-resistant, and uncoated), polypropylene, glass, hemp, and cellulose fibers, was evaluated at 0.5 %, 1 %, 1.5 %, and 2 % volume fractions. The assessment covered spread flow, compressive and splitting tensile strength, crack formation, environmental impact, and costs. Among all fiber types, uncoated basalt (UCB) fibers demonstrated the most significant mechanical enhancement, increasing compressive strength by up to 17 % and splitting tensile strength by approximately 30 % compared to the reference mix, while reducing drying shrinkage crack width by nearly 80 %. Cellulose fibers effectively minimized crack number and exhibited the lowest global warming potential (0.06 kg CO₂-eq/kg). A multi-criteria decision analysis identified cellulose fibers at 1.5 % volume fraction as the optimal choice, closely followed by UCB fibers. These findings provide practical insights for designing sustainable, durable, and low-carbon repair mortars and sewer system linings, particularly in aggressive environments where crack resistance and environmental performance are critical.