Study on the thermo-mechanical properties of PEG/ordinary Portland cement-based phase change composite modified by calcium aluminate cement

Mixing polyethylene glycol (PEG) solution and ordinary Portland cement (OPC) to prepare cement-based phase change composite (CPCC) is an emerging paradigm that has attracted much attention. However, the non-setting problem of CPCC at high PEG content limits the improvement of its heat storage capacity. In this study, the setting process of CPCC was promoted by the modification of calcium aluminate cement (CAC), furthermore, its phase evolution, microstructure and thermo-mechanical properties were investigated by Rietveld quantization, SEM, DSC and conductometer. The results show that monocalcium aluminate from CAC reacts with gypsum from OPC to accelerate the formation of ettringite, thus shortening the setting time of CPCC. Alternatively, the excess aluminum ions inhibit the hydration of alite, thereby reducing the compactness of CPCC. A looser microstructure means a larger pore diameter and porosity, the former reducing the confining effect of pores on PEG, resulting in an increase in latent heat, but the latter increases the thermal conduction path, resulting in a decrease in thermal conductivity. Nevertheless, the mechanical strength of CPCC increases with the increase of CAC content, which is inferred to be due to the increased content of high-strength AFm and strätlingite. When the CAC content is increased from 0 wt% to 40 wt%, the setting time of CPCC is shortened by 86.0 %, the latent heat and 28d compressive strength are increased by 71.3 % and 50.2 %, respectively. This study provides a methodological and theoretical reference for improving the paradigm of CPCC. • Mixing PEG solution and OPC prepare cement-based phase change composite (CPCC). • The hydration process and microstructure of CPCC doped with CAC are studied. • The setting progress of CPCC is analyzed based on its phase evolution. • The thermo-mechanical properties of CPCC are discussed based on its microstructure.