Multiscale Characteristics of Layer Interface in 3D Printed Cement-Based Materials

3D printed cement-based materials have a multi-layered structure due to extrusion layer by layer and without vibration. Interlayer zones are considered weak connections. In order to improve interface quality and accelerate the application of extrusion-based 3D printed cement-based materials, a comprehensive understanding of the formation mechanism of layer interface zone is necessary. Here, we reveal the multi-scale characteristics of phase distribution at the layer interface zone in printed materials by optical microscopy and scanning electron microscopy with energy dispersive spectroscopy. Results show that compared to the matrix, the interface is not merely porous, but also deficient in aggregate and enriched in calcium hydroxide. In addition, the heterogeneous phase distribution dominates the interlayer bonding strength.