Abstract: 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.

Key words:  , energy tunnel, composite phase change material, PCM/cement composite slurry, heat storage capacity, thermal strain, mechanical property