Investigation on the influence of fine steel fiber and carbon fiber on the thermo-mechanical properties of cement-based thermal energy storage mortar

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.