Heat-stored calcined clay limestone cement: Role of microencapsulated n-octadecane with calcium carbonate shell

Heat-stored functional cement-based composites with low-carbon cementitious material and microencapsulated phase change materials (PCMs) have shown great potentials in energy conservation and emission reduction of buildings. In this study, a novel heat-stored cement-based composite system was proposed by incorporating microencapsulated PCMs into limestone calcined clay cement (LC³), in which a microencapsulated n-octadecane with calcium carbonate shell (ODE@CaCO₃) was synthesized via in-situ self-assembly method and it was employed as a substitute for limestone in LC³. The micromorphology, chemical compatibility and phase transition properties of ODE@CaCO₃ were investigated. ODE@CaCO₃ had the latent heat of 86.0 J/g and the phase transition temperature of 26.8 °C, and its average particle size was 2.19 μm. Moreover, the experimental results of mechanical property indicated the 28d compressive strength of heat-stored LC³ containing ODE@CaCO₃ (i.e., limestone was completely replaced) was 26.7 MPa, which was decreased by 48.2 % as compared to the pure heat-stored LC³. The analysis on hydration reaction and microstructure evolution of heat-stored LC³ was carried out, and the influence mechanisms behind ODE@CaCO₃ on the mechanical strength were unveiled. In overall, this work provided novel insights into the optimized design of low-carbon heat-stored construction materials with PCM.