Interaction effects of iron ash and steel fibers on concrete strength performance

This study examines the mechanical performance of concrete incorporating iron ash (IAC) as a partial cement replacement and steel fibers (SFC) as reinforcement, with particular emphasis on the individual and combined effects of these additions on compressive and flexural strength. Concrete mixtures were prepared using iron ash contents of 5%, 10%, and 20% by weight of cement, and steel fiber dosages of 0.25%, 0.50%, and 0.75% by volume, and were tested after 28 days of curing. The results indicate that the inclusion of iron ash leads to a moderate improvement in compressive strength, attributed to its pozzolanic reactivity and its role in enhancing matrix densification. The incorporation of steel fibers significantly enhances compressive strength and, more prominently, improves flexural strength through crack-bridging mechanisms and increased post-cracking energy absorption capacity. The results of the two-way ANOVA reveal that neither iron ash nor steel fibers individually exert a statistically significant effect on compressive strength, and no significant interaction effect between the two variables is observed. In contrast, steel fiber content exhibits a strong and statistically significant influence on flexural strength. Furthermore, a moderate interaction effect between iron ash and steel fibers suggests improved interfacial bonding between the fiber and matrix when both materials are used concurrently. Overall, these findings demonstrate that steel fibers play a dominant role in enhancing tensile-related performance, whereas iron ash provides supplementary benefits, particularly when used in combination with fiber reinforcement.