Properties and interfacial performances with magnesium phosphate cement of coir fiber treated by an efficient water bath method: Effect of immersion temperatures and times

The pronounced brittleness and crack-prone nature of magnesium phosphate cement (MPC) can be efficiently addressed by coir fiber (CF). For coir fiber reinforced magnesium phosphate cement composite (CF-MPC), the ability of the fibers to fully exploit their mechanical properties is the key to enhancing the matrix's ability to bear the load, which in turn affects the interfacial bonding between CF and MPC. While the water bath treatment is superior to chemical treatment in improving the properties and the interfacial performances with MPC of CF, less research on the optimal treatment temperature and time has been conducted. In this study, the results of the fiber axial tensile test and monofilament pull-out test are used to determine the ideal water bath treatment settings. In order to better clarify the microscopic process, the structural alterations of the materials were further examined using Fourier transform infrared (FTIR) spectroscopy, Van Soest (VS), and scanning electron microscopy (SEM). The results suggested that, when the immersion temperature is 80°C and the immersion time is 120 minutes, the tensile strength of CF is even higher than that of polypropylene fibers, reaching the maximum value of 304.9 MPa. The interfacial bond-bearing capacity and interfacial damage energy of CF-MPC reached the highest values of 14.5 N and 117.4 N·mm at 100°C and 80°C for 120 minutes of immersion, respectively. Moreover, there was an effective embedment length of CF in MPC after water bath modification. In addition, the computational modeling of immersion temperatures, times and embedment length on the bond-bearing capacity of the CF-MPC interface was established with a good fit.