Study on the Durability Properties of Self Compacting Concrete Incorporating Hybrid Fiber Reinforced
Self-Compacting Concrete (SCC) is a highly workable concrete that consolidates under its self weight, eliminates the need mechanical vibration, and is well suited for placement in congested reinforcement zones. While SCC offers excellent filling ability and surface finish, it generally exhibits lower tensile and post-cracking performance than conventional vibrated concrete (CVC). The mix was proportioned using OPC 53-grade cement, manufactured sand (M-Sand), 10 mm crushed angular coarse aggregate, a polycarboxylate-ether (PCE) based superplasticizer, and a viscosity-modifying admixture (VMA), with hybrid steel and polypropylene fibers incorporated in five dosages (0%, 0.5%, 1%, 1.5%, and 2%) according to EFNARC guidelines. Fresh properties were gauged using the Slump Flow and T50 test, L-Box test, and V-Funnel test, while hardened properties were calculated through compressive strength testing at 3, 7, and 21 days of curing. Durability was assessed through an acid attack test using 5% sulfuric acid (H2SO4) and a Rapid Chloride Penetration Test (RCPT). The results shows that cumulative fiber content reduced flowability, with slump flow decreasing from 650 mm at 1% fiber content to 600 mm at 2%, while all mixes maintained an L-Box ratio between 0.83 and 0.96, confirming good passing ability. Compressive strength increased consistently with fiber content up to 1.5% hybrid fiber dosage, beyond which a marginal reduction was observed, indicating 1.5% as the optimum hybrid fiber content. Durability testing showed an average weight loss of 2.38% and compressive strength loss of 8.70% later 28 days of acid exposure, while the RCPT recorded an average charge passed of 1155 coulombs, placing the concrete in the "low" chloride permeability category. The study concludes that hybrid steel-polypropylene fiber reinforcement, combined with coal ash and GGBS blending, is an effective strategy for enhancing the durability, crack resistance, and long-term performance of Self-Compacting Concrete for high-performance structural applications.