Creating vascular self-healing concrete using direct ink writing

One of the most promising approaches to create self-healing concrete is the use of vascular networks – hollow channels within the concrete through which a (liquid) repair or healing agent can be transported to the crack region. Traditionally, these vascular networks have been made using glass or plastic tubes cast into the concrete. Herein, we attempt to intentionally create a network of transport channels in the concrete using direct ink writing. In this study, a 3D-printable fiber reinforced mortar was first developed. Three groups of specimens were fabricated using direct ink writing, where the two top and bottom printing layers were printed with different printing directions.
The macrostructure of the hardened specimens was studied using CT scanning. Four-point bending tests were carried out to investigate the initial flexural strength and the strength recovery after healing with injected epoxy resin. Fur-thermore, water permeability test was used to evaluate the healing potential of the samples. Experiments showed that printing direction influences the volume of the hollow channels in the achieved prints, the flexural strength, and the water permeability. Although the healing effectiveness regarding flexural strength is remarkable for all specimens, it was only possible to perform a single healing process as hollow channels were then blocked by the epoxy resin. This initial study shows that direct ink writing has great potential to create vascular self-healing concrete.