Properties of 3D printed concrete (3DPC) containing microencapsulated phase change material (PCM)

3D printing of cementitious materials is a novel approach to fabricating structural components with many applications, including rapid structural recovery in remote areas since it can function almost autonomously. However, since the newly built components are instantly exposed to the outside environment, their thermal properties can have major impact on their energy efficiency and the long-term operating costs for heating, ventilation, and air conditioning (HVAC) systems. To address this challenge, and for the first time, this study combines an outdoor thermal monitoring system with a detailed material performance evaluation for 3D printed concrete (3DPC) containing melamine–formaldehyde-based phase change materials (PCMs). To uncover the impact of PCMs in 3DPC sections, a series of standardized and advanced tests, including nano-indentation, µCT scanning, SEM, and thermal efficiency measurements, were performed. Results show that the inclusion of PCM increased total porosity from 14.44 % to 21.49 % and water absorption from 8.57 % to 11.20 %. Surface hardness decreased from 1296.11 MPa to 764.58 MPa, accompanied by a higher variability (standard deviation rising from 256.60 MPa to 414.55 MPa) for PCM-containing samples, as compared to the reference 3DPC samples. The addition of PCMs also reduced thermal conductivity by ∼10%, while it also remained stable after 100 cycles of freeze-thawing. The results of the study are found to be significant and contribute to the development of energy-efficient and resilient materials.