Study on functional and mechanical properties of cement mortar with graphite-modified microencapsulated phase-change materials

Abstract To achieve high heat exchange efficiency of a microencapsulated phase change material (MPCM) and energy storage for buildings, a graphite-modified MPCM (GM-MPCM) was prepared and incorporated into the cement mortar to develop a type of cement mortar with both high heat storage efficiency and considerable mechanical strength. The thermophysical properties of the GM-MPCM and the thermal and mechanical properties of the GM-MPCM mortar were investigated. The results indicated that more than 50% of the paraffin (PCM used in this study) could be effectively encapsulated in the GM-MPCM. A thermal cycle test showed that thermal energy storage capacity of the GM-MPCM had not been reduced undergoing 10 thermal cycles. In addition, the diameters of the most GM-MPCM with approximately 7.74 μm polyurea shell ranges from 150 to 350 μm. Thermal performance tests using room models revealed that the small room models prepared with GM-MPCM-CM panels can reduce both the temperature fluctuations and maximum indoor centre temperature effectively. The cement mortars with GM-MPCM can be used for thermal energy storage in buildings. Moreover, adding GM-MPCM into cement would also lower and delay the hydration heat, which is helpful to reduce the thermal cracking of cement-based materials. Although adding GM-MPCM can weaken the mechanical strength of cement mortar, the compressive and flexural strengths of cement mortar with 20% GM-MPCM by weight of cement were still as high as 32.9 MPa and 7.6 MPa, respectively. Therefore, the cement mortars with different GM-MPCM are suitable structural and functional building materials.