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Mechanical properties and deterioration severity of fibre reinforced concrete exposed to elevated temperature

Fibre reinforced concrete (FRC) has been proven in enhancing the strength, ductility and durability of concrete structures. However, when encountered with temperature exposure, there is limited information regarding the impact towards the mechanical properties of FRC. In this study, two different types of fibres namely the steel (SF) and polypropylene (PPF) were combined and mixed in concrete. The deterioration severity is the main concerned due to the variability of temperature exposure on the FRC. Therefore, the main aim of this study was to investigate the fundamental behaviour on the mechanical properties of FRC when exposed to elevated temperature. The temperature variations varied between 27C (room temperature) and 800C, with an increment of every 200C i.e. 27C, 200C, 400C, 600C and 800C. Altogether, there were 5 proportions for the combined fibre mix percentage at volume fraction of 1.5%, which are SF-PPF (100-0%), SF-PPF (75-25%), SF-PPF (50-50%), SF-PPF (25-75%) and SF-PPF (0-100%). Several tests were carried out in determining the mechanical properties of FRC which include compression test, flexural test, splitting tensile test, Young’s Modulus test, Poisson’s ratio test, toughness test and residual flexural tensile strength test. Morphology analysis using Scanning Electron Microscopy (SEM) was also carried out on the FRC after the temperature exposure and mechanical testing. In general, the experimental results show that the strength of FRC decreases as the temperature variation increases. The FRC encountered small declining strength when exposed to temperature below 400C. However, when it was exposed above 400C, significant impact on the FRC strength was observed. The study also suggested that the optimum dosage of the fibres percentage proportion is SF-PPF (75-25). With the addition of PPF, the explosive spalling effect was reduced due to the existence of tiny channel created by the PPF when it melted. Meanwhile, the existence of SF provided better post-cracking behaviour on the FRC. Addition of SF and PPF were very effective in minimizing the deterioration and spalling effect when FRC exposed to elevated temperature.