Effects of Paraffin/Sisal Composite Phase Change Fibers on the Rheological and Heat-Transfer Behaviors of 3D-Printed Concrete

This study incorporated self-prepared paraffin/sisal composite phase change fibers (PCFs) into three-dimensional printed concrete (3DPC) to enhance its thermal properties. The effects of fiber type and dosage on the rheological and thermal properties of 3DPC were systematically investigated. The mechanisms underlying these effects were examined in terms of the internal pore distribution and fiber dispersion. The results indicate that differences in fiber dispersion, which are likely governed by fiber surface characteristics, are closely associated with the pore distribution within the 3DPC and, consequently, with its rheological and thermal properties. Compared with sisal-fiber-reinforced and fiber-free 3DPC, PCF-containing 3DPC exhibited lower thermal conductivity and a slower surface temperature rise under the tested conditions, and its heat-transfer behavior differed among the X, Y, and Z directions. These findings suggest that the incorporation of PCFs can enhance the thermal insulation of 3DPC under the tested conditions.