Enhancing Mechanical Performance of Green Cementitious Composites Using Alkali-Resistant Glass and Polypropylene Fibers

This study evaluates the mechanical behavior and sustainability of cementitious composites reinforced with alkali-resistant glass (AR-G) and polypropylene (PP) fibers. Fibers were incorporated at 1.75 vol.% and 2.25 vol.% while maintaining a consistent base mixture design. To reduce reliance on Portland cement, the mixture design replaced 55% of cement content with supplementary cementitious materials, specifically fly ash and silica fume. Mechanical testing evaluated compressive and flexural behaviors under monotonic and cyclic loading across various loading rates. AR-G fiber-reinforced cementitious composites demonstrated substantial improvements in compressive and flexural strengths with enhancements of up to 37.3% and 182.5%, respectively, compared to the control mix. In contrast, PP fiber-reinforced cementitious composites did not exhibit strength enhancement but demonstrated superior ductility characteristics. Further analysis revealed that PP fiber-reinforced cementitious composites displayed lower first-crack toughness but exhibited substantially higher ultimate flexural toughness relative to AR-G fiber-reinforced cementitious composites. Digital image correlation revealed that PP fiber-reinforced cementitious composites demonstrated strain-hardening behavior exceeding 2.5% bending strain and developed multiple fine cracks. Conversely, AR-G fiber-reinforced cementitious composites formed a single crack with an average width of ~0.15 mm at 2.5 mm deflection, regardless of loading rate or fiber content. From a sustainability perspective, cradle-to-gate embodied carbon decreased by approximately 16%–30%, depending on fiber type and content, compared with the Portland cement-only reference mix (without SCMs or fibers).