Effect of Seawater on Mechanical and Microstructure Properties  of Polypropylene Fibre Reinforced Concrete (PPFRC)

Enhanced concrete strength can lead to increased brittleness and susceptibility to cracking. Traditional reinforcement methods with deformed steel bars aim to mitigate this problem, but corrosion issues can compromise the durability of concrete. Harsh weather like seawater can cause micro-cracks, allowing aggressive ions and water to penetrate and gradually deteriorate the concrete. Meanwhile, chemical reactions triggering steel corrosion led to rust formation, internal stress, cracking and delamination that caused structural risks. Fibre-reinforced concrete (FRC) offers a great solution by replacing steel bars with corrosion-resistant fibres hence improving both strength and flexibility. The study comprehensively analyses mechanical properties, particularly flexural strength, to assess how polypropylene fibre (PPF) affects FRC's overall strength. Microstructure evaluations examine changes in pore structure and durability. The research also tests FRC performance cured in freshwater (FW) and seawater (SW) conditions. Based on this study, the low workability of fresh concrete was observed. This is due to the surface area increment in the concrete mix. Optimal PPF incorporation was recorded as 0.25% for compressive and flexural strength tests in both curing methods applied. Higher incorporation of PPF causes noncontinuous fibres congestion in the concrete mix. In this regard, it leads to the reduction of concrete strength which induces the formation of cracks. As for microstructure analysis, the sample with 0.25% PPF shows well-dispersed fibres throughout the concrete matrix. Therefore, it is proven that the inclusion of PPF in the concrete matrix improves the overall concrete performance.