Improvement effect of a phase change material on microstructure of cement‐based materials at elevated temperatures

Abstract

In this investigation, a phase change material with a melting temperature of about 450 C (PCM-45) is prepared and applied to solve microstructure degradation problem of concrete matrix when exposed to temperatures more than 500 C. The morphology changes of PCM-45 and the improvement effects of PCM-45 on microstructure of cement matrix are investigated based on microstructure characteristics, ultrasonic pulse velocity of cement paste and compressive strengths of cement mortar with different dosages of PCM-45 at 500, 600, 700, 800 and 900 C. The results show that morphology of PCM-45 is changed, indicating that PCM-45 transforms from solid to liquid phase and that the liquefied PCM-45 can diffuse at elevated temperatures. When temperature returns to room temperature, the liquefied PCM-45 becomes solidified, during which process the microstructure of cement matrix is improved. Therefore, compressive strength and ultrasonic pulse velocity of specimens with PCM-45 are greatly increased compared to those of specimens without PCM-45.