The development of mini-vascular networks for self-healing concrete

Akin to vascular networks carrying clotting agents in the human body, vascular networks in concrete deliver liquid healing agents to areas of damage [1]. Connection to an external supply of healing agent allows for an unlimited volume of damage to be repaired on a reoccurring basis. Vascular networks in concrete have assumed many forms and have been created using a variety of materials and techniques. Early studies used long thin glass channels embedded within concrete, whilst recent studies have focused on networks formed using 3D printed polymers and hollow channels formed by the removal of shrinkable polymers [2]. The most significant obstacle preventing wide-scale use of vascular networks in concrete remains the challenge associated with the manufacture and placement of the network during the concrete casting stage. Recent work has focused on overcoming this challenge though the development of mini-vascular networks (MVNs), which allow for more complex arrangements of channels in both two and three dimensions and for ready inclusion during the concrete mixing stage. This paper presents the development of MVNs which assume the form of 3D tetrahedral units (TETs) with hollow ligaments, manufactured from Polylactic Acid (PLA) using 3D printing techniques. The optimisation of the dimensions, surface topography and disposition of the units is considered, alongside their material properties and response to damage events. A range of healing agents, including cyanoacrylates (PC) and sodium silicate (SS) have been explored, with initial results demonstrating the importance of healing agent selection when considering the temporal and spatial scale of the target damage. Further tests have explored the potential to achieve multiple healing events, with promising results. Future refinement of the MVNs includes the formation of dual hollow channels for bi-component healing agents, and adaption of the form of the MVN for a range of structural applications