Optimization Of Fiber Content in Hybrid Fibre Reinforced Self Compacting Concrete

Self-Compacting Concrete is widely used in modern construction because of its capability to by its self-weight without the requirement for vibration, making it appropriate for heavily steel-clad and composite structural elements. However, Integration of fibres to improve the mechanical efficiency of SCC can harmfully affect its workability. This study investigates the optimization of hybrid fibre content in Hybrid Fibre Reinforced Self-Compacting Concrete (HFRSCC) by evaluating the combined effect of steel and polypropylene fibres on the rehardened and hardened properties of SCC. Five concrete mixes containing total hybrid fibre contents of 0%, 1.0%, 1.25%, 1.5%, and 1.75% were prepared using OPC 53 Grade cement, fly ash, GGBS, river sand, 10 mm coarse aggregate, viscosity adjusting agent. The mix amounts are planned in accord to IS 10262:2019, while the fresh concrete characteristics are evaluated following EFNARC (2005) guidelines. Fresh concrete trials comprised slump flow, V-funnel, L-box, and J-ring tests, whereas hardened concrete properties are measured with compression strength, flexural strength and split tensile strength tests at 3, 7 and 28 days. consequences specified that increasing the hybrid fibre content decreased the workability of SCC due to increased internal friction and viscosity, although all mixes satisfied the EFNARC acceptance criteria. The hardened concrete characteristics enhanced with increasing fibre amount up to 1.25%, after which a minor drop was observed because of fibre agglomeration and reduced workability. The optimum mix containing 1.0% steel fibre and 0.25% polypropylene fibre (1.25% total hybrid fibres) attained maximum 28-day compression strength of 47 MPa, flexural strength of 5.4 MPa and tensile strength of 3.9 MPa. The study concludes that an optimum hybrid fibre content of 1.25% provides the best stability between workability and mechanical performance making it appropriate for high-performance and durable SCC applications.