Chloride Penetration Resistance of Hybrid Fibre Reinforced SCC

Abstract

Self-compacting concrete (SCC) offers high flowability and consolidation under its own weight, but cracking and connected pore pathways can accelerate chloride ingress in aggressive environments. This investigation evaluated the fresh, mechanical, and chloride-resistance performance of M40 SCC reinforced with hooked-end steel fibres and polypropylene microfibres. A control mixture (SCC-C) was compared with HF-SCC1, HF-SCC2, and HF-SCC3 containing steel/polypropylene fibre contents of 0.5/0.1%, 0.75/0.15%, and 1.0/0.2%, respectively. Fresh properties were assessed using slump flow, T50 flow, V-funnel, and L-box tests; hardened performance was measured by compressive, split-tensile, and flexural strength; and durability was evaluated through chloride penetration depth and rapid chloride penetration testing. All mixtures remained within the reported EFNARC acceptance ranges, although increasing fibre content reduced flowability. HF-SCC2 achieved the highest 28-day compressive, split-tensile, and flexural strengths of 53.4, 4.96, and 6.78 MPa, corresponding to improvements of 14.84%, 28.83%, and 30.38% over SCC-C. It also recorded the lowest chloride penetration depth (10.8 mm) and RCPT charge (1580 coulombs), representing reductions of 41.62% and 44.56%. The results identify HF-SCC2 as the optimum mixture, providing the best balance between SCC workability, mechanical strength, and chloride resistance.