Effect of Modified Styrene Butadiene Rubber on Mechanical and Durability Properties of Hybrid Fiber-Reinforced High-Performance Concrete with Fly Ash and Nano Silica

Concrete structures are frequently exposed to aggressive environments, particularly infrastructure applications located in coastal areas, saline clays, and acidic soils. These harsh conditions speed up deterioration, reduce durability, and lead to frequent, costly repairs. Conventional concrete often cannot handle these environments over time, especially when high performance is required. These challenges highlight the growing demand for advanced, durable, and sustainable concrete materials. Therefore, this study investigates the effect of modified Styrene Butadiene Rubber (SBR) on the mechanical and durability properties of high-performance concrete reinforced with hybrid fibers. The concrete mix included steel fibers, polypropylene fibers, high-volume fly ash, and nano silica. SBR was added at 0% to 15% by weight of cement, with 2.5% identified as the optimal dosage based on fresh and hardened performance. Results indicate that SBR significantly improved workability, increasing the slump from 20 mm (control) to 95 mm (15% SBR). At 2.5% SBR, compressive strength increased by 4.2% at 7 days and 3.3% at 28 days. Flexural strength improved by 34.8% at 7 days and 18.4% at 28 days, while tensile strength increased by 21% and 25%, respectively. Durability also improved, with chloride penetration reduced by 15.2%, water penetration by 35.6%, and water absorption by 66.7%. These enhancements confirm that modified SBR, in combination with hybrid fibers and supplementary cementitious materials, improves both mechanical and durability performance. The addition of 2.5% SBR enhances both mechanical and durability properties of concrete, demonstrating optimal performance at this concentration.