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.

中文翻译：

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相变材料对高温下水泥基材料微观结构的改善作用

在这项研究中，制备了一种熔化温度约为 450°C 的相变材料 (PCM-45)，并将其应用于解决混凝土基体在超过 500°C 的温度下的微观结构退化问题。基于微观结构特征、水泥浆体超声脉冲速度和水泥砂浆在500、600不同掺量PCM-45的抗压强度，研究了PCM-45的形貌变化以及PCM-45对水泥基体微观结构的改善作用。 、700、800 和 900°C。结果表明，PCM-45的形貌发生了变化，表明PCM-45从固相转变为液相，液化的PCM-45可以在高温下扩散。当温度恢复到室温时，液化的 PCM-45 会凝固，在此过程中，水泥基体的微观结构得到改善。因此，与没有 PCM-45 的试样相比，具有 PCM-45 的试样的抗压强度和超声脉冲速度大大提高。