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The mechanical and thermal properties of thermal energy storage mortar usually have the characteristics of mutual restrictions and are difficult to synergistically improve. In this study, steel fibers (SFs) and carbon fibers (CFs) with high thermal conductivity were innovatively used to enhance the thermal and mechanical properties of sulphoaluminate cement-based composites for thermal energy storage (SCCTES). The influence of SFs and CFs on the thermal and mechanical properties of SCCTES were comparatively analyzed through the experimental tests. The test results demonstrated that the influence of SFs and CFs on the thermal and mechanical properties of SCCTES are different, which is due to the difference of surface roughness and dispersion between the two fibers. The thermal conductivity, flexural strength and compressive strength of SFs modified SCCTES (SCCTES-SF) all show an increasing rule when the content of SFs increases from 0% to 3.5vol%. However, when the content of CFs increases from 0% to 0.47vol%, the flexural strength and thermal conductivity of the CFs modified SCCTES (SCCTES-CF) show a non-linear change rule that first increases and then decreases. In addition, adding an appropriate dosage of SFs or CFs can improve the shrinkage characteristics of SCCTES, but the influence of SFs on the shrinkage characteristics of SCCTES is better than that of CFs. [ABSTRACT FROM AUTHOR]

• The addition of PVA is helpful to improve the workability and mechanical property of SCARM. • The incorporation of PVA and PP can improve the mechanical property, toughness and adhesive property of SCARM, especially when mixed together. • PVA increases the compactness of SCARM. • PVA can enhance the interface combination of PP and SCARM. Alkali-activated slag (AAS) cement shows the characteristics of fast hardening and high early strength, which is particularly suitable for repair materials. However, its high brittleness, poor toughness and poor workability hinder its application. The effects of polyvinyl alcohol (PVA) latex powder and polypropylene (PP) fiber on the fluidity, mechanical properties including toughness and adhesive property of self-compacting alkali-activated slag repair mortar (SCARM) were studied. Their effects on the microstructure of SCARM were also studied. The results show that the addition of PVA is helpful to improve the workability. With the increase of PVA content, the 30 min fluidity increases greatly. The addition of PP reduces the fluidity of SCARM. The incorporation of PVA and PP can improve the mechanical property, toughness and adhesive property, especially when mixed together. PVA increases the compactness of SCARM. In addition, it also enhances the interface combination of PP and SCARM. The addition of PVA does not change the hydration products of AAS cement, but slightly increases the hydration degree. [ABSTRACT FROM AUTHOR]

• Potential phase change materials (PCMs) for the buildings were summarized. • Preparation methods of shape-stabilized PCMs (SSPCMs) were reviewed. • Effects of incorporating SSPCMs into cementitious materials were identified. • The application of thermal energy storage cementitious materials was revealed. Phase change materials (PCMs) have attracted considerable attention as potential energy storage media for improving the energy storage densities of building envelopes. Therefore, researchers have committed to introducing PCMs into cementitious materials to develop structural–functional integrated thermal energy storage cementitious materials (TESCMs). Nevertheless, TESCMs have not been widely applied in large-scale engineering and remain in a trial or test stage. This review provides an overview of TESCMs for passive buildings to keep researchers abreast of the latest research trends and technological advances. Among the different types of PCMs, inorganic PCMs with low cost and high thermal conductivity have the most potential for application in buildings; however, their supercooling and phase separation must be addressed before use. Vacuum impregnation and micro-encapsulated and macro-encapsulated techniques are the main methods to encapsulate PCMs for preparing shape-stabilized PCMs (SSPCMs) and preventing PCM leakage from TESCMs. The inclusion of SSPCMs was found to have a negative effect on the workability, mechanical strength, and thermal conductivity of cementitious materials. However, thermal energy storage buildings (TESBs) composed of TESCMs can regulate the indoor temperature within the thermal comfort range, significantly decreasing energy consumption. This is because the effectiveness of TESBs depends highly on such factors as PCM dosages, climatic conditions, and the phase change temperature of PCMs; thus, a multi-objective optimization design is required to design TESB layouts. [ABSTRACT FROM AUTHOR]

Efficient use of solar energy by thermal energy storage composites and utilizing environmentally friendly cementitious materials are important trends for sustainable building composite materials. In this study, a paraffin/low density polyethylene (LDPE) composite shape-stabilized phase change material (SSPCM) was prepared and incorporated into a sulphoaluminate cement (SAC) mortar to prepare thermal energy storage mortar. The thermal and mechanical properties of SSPCM and a SAC-based thermal energy storage material (SCTESM) were investigated. The result of differential scanning calorimeter (DSC) analysis indicates that the latent heat of SCTESM is as high as 99.99 J/g. Thermogravimetric analysis demonstrates that the SCTESM does not show significant decomposition below 145 °C. The volume stability test shows the volume shrinkage percentage of the SCTESM is less than that of pure SAC mortar and far less than that of ordinary Portland cement mortar. The SCTESM has high early strength so that the compressive strength at 1-, 3-, and 7-day curing age is up to that at 28-day curing age of 67.5%, 78.3%, and 86.7%, respectively. Furthermore, a mathematical prediction model of the SCTESM compressive strength was proposed. The investigation of latent heat storage characteristics and the thermoregulating performance reveals that SCTESMs have the excellent capacity of heat storage and thermoregulating. [ABSTRACT FROM AUTHOR]