A novel method to enhance the interlayer bonding of 3D printing concrete: an experimental and computational investigation

This study focuses on one of the bottlenecks facing the concrete 3D printing technology, the lack of proper bonding between the two adjacent layers of 3D printed concrete. Herein, a new polymer consisting of black carbon and sulfur was used to glue the two layers together. The experimental results, verified via molecular dynamics and density functional theory calculations, showed a considerable increase in the interlayer bonding strength. Two-fold rise in interlayer tensile strength as well as chemical cohesion depicted by scanning electron microscopy proves this approach to be successful in providing enhanced bonding between two adjacent printed mortar layers without hindering the printing process. The improvement arises from different types of forces in the interlayer region of modified samples, compared to that of the interlayer region of original sample. The uniform surface provided by the hardened polymer is a good substrate for the top layer in addition to extending the time gap between printing layers. This novel method can accelerate the automation of the construction industry, while reducing the costs in terms of both human labor and capital.