Understanding carbonation in 3D printed cement-based materials with exposed bottom surface

Despite the continuously increasing scale and number of concrete 3D printing applications, current research on the durability of printed cement-based materials remains limited. The insufficient understanding of durability will hinder the widespread adoption and application of 3D printed cement-based materials in practical construction scenarios. In this study, the carbonation performance of printed samples, with exposure of the bottom surface, was assessed. A concave carbonation front is observed when the bottom side is exposed due to the non-uniform carbonation. This phenomenon is linked to the density gradient distribution of printed materials and is more pronounced with increased deformation of samples. Silica fume decreases the carbonation resistance of printed samples and leads to even more non-uniform carbonation.