Influence of elevated temperature on the interfacial adhesion properties of cement composites reinforced with recycled coconut fiber

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Magnesium phosphate cement (MPC) is the preferred material for rapid repair due to its rapid setting and early strength properties. However, its inherent brittleness renders it less suitable for use in assembled building nodes. To address the brittleness of MPC, coconut fiber (CF), a natural fiber known for its toughness, is often employed as a reinforcement. However, CF-MPC encounter difficulties in high-temperature settings, such as fire emergencies, which may compromise the interfacial bonding properties of this materials. This paper presents an investigation into the interfacial bonding properties of CF-MPC at elevated temperatures. The study employed microscopic analysis to observe the material changes of CF at elevated temperatures, evaluated the mechanical property changes by means of Fiber Tensile Test, and assessed the interfacial bonding performance by means of Fiber Drawing Test between CF and MPC. The findings indicated that as the temperature increased, the carbonized residue of the CF gradually decomposed, resulting in a notable decline in mechanical strength. Upon exceeding 400 °C, the carbonization of CF was complete, resulting in the loss of its mechanical properties. Besides the results also demonstrated that the interfacial bond strength of CF-MPC at a burial depth of 7.5 mm reaches its maximum value of 2.14 MPa at 20 °C. As the temperature rises to 200 °C, the interfacial bond strength at a burial depth of 12.5 mm reaches its maximum value of 1.08 MPa at this temperature. The findings of this study are conducive to promoting the application of CF-MPC at high temperatures and provide a theoretical basis for the subsequent optimization of this material.