Effect of modified diatomite based shape-stabilized phase change materials on multiphysics characteristics of thermal storage mortar

In this study, a new product was developed by incorporating fatty acids/diatomite shape-stabilized phase change material (SSPCMs) into mortar. SSPCMs were prepared by impregnating hydrophobic modified diatomite with ternary fatty acids composed of lauric acid, myristic acid and palmitic acid. The melting temperature of this fabricated composite PCM is 29.82 °C and the latent heat is 65.84 J/g, which is 14.4% higher than that of the unmodified diatomite-based PCMs. Scanning electron microscope and Fourier transform infrared results show that PCMs can be fully impregnated into diatomite pores with a good compatibility. Furthermore, SSPCMs were incorporated into cement-based materials at 5%, 10% and 15% by weight of sand. It can be found that the maximum reductions of 28-day compressive strength and thermal conductivity reached 53.3% and 37.9%, respectively. This strength descend is mainly attributed to a special evolution of microporous structure and insufficient hydration degree caused by SSPCMs in cement-based composites. Even so, the phase change cement-based panel achieves a 28-day compressive strength of as high as 24.5 MPa and good temperature regulation performance. Therefore, it can be potentially used as a structural-thermal storage wall material in buildings. • Hydrophobic-modified diatomite shows higher adsorption efficiency for fatty acids. • Thermal storage mortar (TSM) has good mechanical properties and encapsulation performance. • Lower degree of hydration in mortar with SSPCM was experimentally verified. • The maximum temperature difference between NC and TSM room reached up to 4.4 °C.