Experimental research on mechanical and microstructural characteristics of hybrid fiber reinforced concrete (HFRC)

This study investigates the mechanical and microstructural performance of hybrid fiber-reinforced concrete (HFRC) incorporating steel, glass, and polypropylene fibers in varying proportions to optimize crack control and structural durability. Experimental results indicate that the optimal HFRC mixes exhibit a significant enhancement in mechanical properties, with compressive strength increasing by approximately 20-25%, split tensile strength by around 30%, and flexural strength improvements reaching up to 35% compared to plain concrete. The modulus of elasticity similarly improved by 15-20%, contributing to enhanced stiffness and load-bearing capacity. Workability remained within acceptable limits, with slump reductions not exceeding 15% due to superplasticizer use. Scanning electron microscopy confirmed that fiber incorporation densifies the matrix and strengthens the interfacial transition zones, effectively mitigating micro- and macro-crack propagation. These findings demonstrate that carefully optimized hybrid fiber combinations can provide a durable, high-performance concrete solution suitable for demanding structural applications.