Thermal conductivity of 3D printed concrete with recycled fine aggregate composite phase change materials

In this study, a novel shape-stabilization phase change materials (PCM) for 3D printed concrete have been generated by impregnating paraffin into the recycled fine aggregates. Based on both steady state hot plate method and transient hotwire method, the impact of printing parameters, including printing layers, path, extrusion rate and materials on thermal conductivity of the 3D printed concrete was investigated. The relationship among thermal conductivity, dry density and porosity of the 3D printed concrete was analyzed. The results showed that recycled fine aggregates can be successfully used as a support material for paraffin. The melting temperature and latent heat is 36.52 °C and 40.65 J/g, respectively. The thermal conductivity of 3D printed concrete was significantly influenced by the multi-layer structure and with thermal anisotropy. Under the same size, density class or mix design, the thermal conductivity of the 3D printed concrete can reach up to 31.04% lower than that of mould cast concrete. The results also indicate that impregnating paraffin into the recycled fine aggregate can improve its thermal properties so as to upgrade the overall performance of 3D printed concrete.