Durability and Strength Improvement of Ambient-Cured Geopolymer Concrete using Polypropylene Fibers

This study investigated the effects of polypropylene fiber (PPF) reinforcement on the mechanical and durability properties of ambient-cured geopolymer concrete (GPC) composed of fly ash and ground granulated blast furnace slag (GGBS). While GPC offers a sustainable alternative to Portland cement due to its lower carbon footprint and elimination of heat curing, its inherent brittleness and low tensile strength limit structural applications. To address these challenges, PPF was incorporated at varying dosages (0%, 0.5%, 1%, and 1.5%) to assess its impact on workability, compressive strength, flexural strength, and durability. The results indicate that 1.0% PPF significantly improved flexural strength (3.35 MPa at 90 days) and overall toughness while maintaining compressive strength. However, higher PPF content reduced workability and increased porosity due to fiber agglomeration. Durability assessments showed that PPF reinforcement lowered oxygen permeability and chloride ingress, enhancing resistance to aggressive environments. X-ray diffraction (XRD) analysis confirmed the formation of sodium alumino-silicate hydrate (N-A-S-H) and calcium alumino-silicate hydrate (C-A-S-H) gels, contributing to matrix densification and reduced permeability. These findings suggest that PPF reinforcement enhances durability by refining the pore structure, as evidenced by reduced permeability and water absorption measurements. However, workability decreased at higher PPF contents due to fiber agglomeration. Despite challenges with fiber dispersion at higher dosages, statistical analysis revealed a strong correlation between compressive and flexural strength, underscoring the role of fiber content in mechanical performance. These findings demonstrate that PPF-reinforced GPC has strong potential for sustainable construction applications, particularly in environments requiring enhanced durability. Future research should focus on optimizing fiber dispersion techniques, refining mix designs, and evaluating long-term performance for large-scale implementation.