Enabling superior thermo-mechanical performance of hydrated salt-based phase change energy storage cementitious composite using graphene oxide reinforced micro-interface

Thermal energy storage cementitious composites (TESCCs) with encapsulated phase change materials (PCMs) were promising candidates for thermal comfort and energy saving in solar passive buildings. However, serious deterioration of mechanical properties and low heat transfer efficiency had hindered their application. In this study, a high-strength encapsulated PCM with a simple production process was developed by encapsulating eutectic hydrated salt PCM within UVcurable polyurethane acrelate resin, and the presented encapsulated PCM (UPE) was used to partially replace sand in cement mortar to prepare TESCC/UPE. Moreover, graphene oxide (GO) modification was conducted to form GO-TESCC/UPE, synergistically enhancing the mechanical strength and heat transfer efficiency. The compressive strength, microstructure and thermal conductivity of TESCCs were studied. Surface heat storage coefficient was presented to further assess the heat transfer and heat storage capacity of TESCCs. Moreover, GO-TESCC/UPE containing 20 vol% encapsulated PCM exhibited 28-day compressive strength of 35.3 MPa, with a 25% improvement over TESCC/UPE. The thermal conductivity and surface heat storage coefficient were also optimized by GO modification. The enhancement of thermal and mechanical properties can be attributed to the fact that GO-TESCC/UPE had a denser interface transition zone (ITZ) and lower harmful porosity due to the excellent compatibility between cement matrix and UPE. In addition, a simplified meso-mechanical model demonstrated that a denser ITZ can mitigate the stress concentration inside the matrix, thus enhancing mechanical properties of TESCCs. This study confirmed the effectiveness of reinforcing ITZ to enhance the thermomechanical properties of heat storage cementitious materials.