新型相变水泥砂浆热力学性能研究

为降低温度变化对隧道水泥砂浆材料强度和变形的影响，在隧道工程中引入具有自调温能力的相变材料，制备成相变材料水泥砂浆。首先,将石蜡、高密度聚乙烯和膨胀石墨熔融共混，获得复合相变材料；然后，掺入水泥砂浆中，得到新型相变水泥砂浆。通过搭建热响应测试平台，分析其热应变随温度变化规律，评估其蓄热性能,并对比得出相变材料对不同水灰比砂浆试样的热力学性能影响。结果表明： 复合相变水泥砂浆能发挥相变材料的蓄热性能，其相变潜热为34.82 J/g，热应变比普通水泥砂浆材料最大降低36.63%。相变材料的掺入有效降低了试样的表面温度和热应变，这对改善水泥砂浆材料的温度变形及控制裂缝的发展具有重要作用，可为能源地铁隧道及其裂缝修复等提供新型材料。

Thermodynamic Properties of Phase Change Material/Cement Composite Slurry

To reduce the negative effect of a large temperature gradient on the strength and deformation of tunnel cement mortar material, a phase change material (PCM) with automatic temperature regulating ability is introduced to prepare PCM/cement mortar mixture. The PCMs are firstly made from paraffin wax, high density polyethylene, and expanded graphite by melt blending method. Then, they are mixed into the cement paste material to produce the PCM/cement composite slurry. A thermal response test platform is built to test the performance of the thermal strain development with temperature. The heat storage performance is evaluated by the results of thermal response. Furthermore, the thermal and mechanical behaviors of the composite slurry with different mixing proportions of PCM are compared with those of common cement slurry with 0% PCM. It can be concluded that PCM/cement composite slurry can store heat during the process in the form of latent heat, which is 34.82 J/g in this test. The thermal strain of composite slurry with different mixing proportions of PCM is 36.63% lower than that of the common cement slurry, indicating that the PCMs can effectively reduce the sample′s surface temperature and thermal strain. The PCM/cement composite slurry can provide a new method for controlling temperature deformation and the development of cracks in energy tunnels and related crack repairing engineering.