High temperature resistance of a phase change cementitious material at elevated temperatures

Abstract When ordinary Portland cementitious concrete is subjected to elevated temperatures, lots of pores and cracks are produced in the cement matrix. In order to solve the problem of pore and crack repairing, a phase change material (PCM) with a melting temperature of 450 °C was prepared in the laboratory. Ordinary Portland cement with addition of the PCM is termed as phase change cementitious material (PCCM). High temperature resistance of PCCM was investigated according to changes in surface morphology, mechanical strength and mass, as well as micro and meso structures of the PCCM matrix at high temperatures of 500 °C,600 °C,700 °C,800 °C and 900 °C. The results show that the compressive strength of PCCM mortar specimens is increased with temperature lower than 600 °C compared with that at room temperature, and that compressive strength loss of PCCM mortar specimens after exposed to 900 °C can be reduced to 48.5%. The PCM in PCCM matrix experience phase changes from solid to liquid phase at elevated temperatures. The melted PCM is able to fill pores and cracks in PCCM matrix. Once the temperature decreases to room temperature, the melted PCM becomes in solid phase again. Pores and cracks in PCCM matrix are thus repaired, resulting in improved microstructure of PCCM compared with that of ordinary Portland cement. Therefore, high temperature resistance of PCCM is much better than that of ordinary Portland cement.