Improving latent heat storage capacity of polyethylene glycol/cement composite prepared via solution blending method

• SPEG was prepared by blending PEG-water solution with sulphoaluminate cement as cementitious material . • The heat storage capacity of SPEG was optimized by adding different water-cement ratios. • The heat enthalpy of SPEG could reach as high as 40.31 J/g. • The thermal and mechanical performances increased with increasing water-cement ratio. Adding phase change materials in building walls or roofs can help control the inner temperature of buildings. A kind of composite phase change material, sulphoaluminate cement-based polyethylene glycol (SPEG), can be prepared by blending polyethylene glycol (PEG)-water solution with sulphoaluminate cement. This study aims at improving the heat storage capacity of SPEG using five water-cement ratios (i.e., 0.2, 0.3, 0.4, 0.5 and 0.6). The microstructure, chemical composition, phase change characteristic, thermal and mechanical properties of the SPEGs were investigated, respectively. The results showed that with the increase of water-cement ratio, more hydration products were generated, and the precipitated PEG adhered to the surfaces of the hydration products. Although PEG did not change the hydration product types, it slowed the hydration process. When the water-cement ratio was 0.5, the heat enthalpy of SPEGs could reach up to 40.31 J/g. All the prepared SPEGs could keep their thermal stability under the temperature of 300 °C. After 200 thermal cycles the phase change enthalpy and temperature of SPEGs changed in a very small range. The thermal conductivity, compressive and flexural strength all increased with the increase of water-cement ratio, although the addition of PEG negatively affected the above indicators. The findings in this study are expected to help prepare cement-based phase change materials with high heat storage capacity.