Comparative Evaluation of High-Performance Mortars Incorporating Silica Fume, Fly Ash, and Polypropylene Fibers

Superior mechanical performance, durability, and resistance to crack propagation in high-performance mortars are increasingly being achieved with the optimization of supplementary cementitious materials combined with fiber reinforcement. However, quantification of combined effects due to the addition of silica fume, class F fly ash, and polypropylene fibers is rather limited. This paper compares the performance of mortar systems containing silica fume, class F fly ash, and polypropylene fibers at various dosages, controlled by low water-to-binder ratios. Ternary and quaternary mixes were prepared to isolate the effects of each constituent and their interactions on compressive strength, flexural behavior, and microstructural density at 1, 7, and 28 days. Test results showed that silica fume significantly enhanced early and 28-day strength through matrix densification, while class F fly ash contributed to workability and later-age strength development through pozzolanic activity. Low dosages of polypropylene fibers did not significantly affect compressive strength; however, they significantly enhanced crack resistance, toughness, and post-crack behavior, especially when combined with silica fume-rich matrices. Synergetic effects have been observed in mixes containing both silica fume and class F fly ash, in which improved packing density and balanced hydration kinetics resulted in superior mechanical and microstructural performance. The results emphasize the importance of optimized SCM-fiber combinations toward achieving high performance in mortars and provide guidelines for the design of durable and high-strength mortar systems for advanced construction applications.