3D printable reactive magnesia cement: The role of the interlayer interface in the carbonation process

This is the authors' abstract. We don't add key points for this paper.

The porous interlayer interface is typically considered a weak zone in 3D-printed concrete (3DPC), compromising mechanical performance and long-term durability. This study investigated the integration of 3DPC with reactive magnesia cement (RMC), aiming to strategically repurpose the porous interface as an efficient pathway for CO 2 penetration. Fresh paste rheology and setting behavior were first evaluated to optimize the mix design for 3D printing. The role of the interlayer interface was then studied through analyses of phase composition, carbonation distribution, microstructural evolution, CO 2 penetration path, and physical properties of 3D-printed (bulk and interface regions) and cast specimens. It has been found that the interlayer interface in 3D-printed paste serves as a more efficient pathway for CO 2 transport and subsequent mineralization compared with bulk paste. In the shallow regions (0–10 mm), the carbonation degree in the 3D-printed sample is almost four times that of the cast sample, with even more pronounced differences observed in the deep regions (10–20 mm). The interface also facilitated CO 2 diffusion into adjacent regions, promoting the formation of crystalline carbonate phases and contributing to microstructural densification. This leads to a 26.1% – 32.2% increase in compressive strength in the 3D-printed samples compared to the cast samples. Overall, this study demonstrated the advantages of the 3DPC and RMC combination, which transforms the typically weak interface into a functional feature, advancing the design and performance of RMC-based materials.