Fire resistance and thermal performance of hybrid fibre-reinforced magnesium oxychloride cement-based composites

Magnesium oxychloride cement (MOC) is recognized as an eco-friendly alternative to Ordinary Portland Cement (OPC) with inherent fire resistance. However, its thermal and mechanical performance under fire and the underlying fire resistance mechanisms have not been well understood. This study examines the fire resistance and thermal performance of hybrid polyethylene (PE) and basalt fibre (BF) reinforced MOC-based composite (HFMOC) modified with ground granulated blast furnace slag (GGBFS) and metakaolin (MK), which was designed and developed to enhance the fire resistance capacity of HFMOC especially for non-structural application such as cladding. The compressive and tensile strength tests were conducted at elevated temperatures (200°C–800°C and 200°C–600°C, respectively) and the results revealed a significant strength reduction exceeding 90 % at 600°C. Moreover, the composite exhibited excellent resistance to spalling, good insulating properties, and non-combustibility, making it suitable for non-structural applications where residual strength is less critical. XRD analysis indicated that the reduction in strength at elevated temperatures was associated with the continuous degradation of the main hydration product, phase 5, which was entirely converted to MgO before 600°C. Morphological analysis verified the findings from XRD showing a weak and porous interfacial transition zone at elevated temperatures caused by the loss of crystalline phases, which was further supported by DSC analysis showing a mass loss of 36–38.1 %.