Abstract
Nature has always been a source of inspiration in engineering applications and vascular networks, as in human skin and in a tree leaf, are one attribute that has received attention in the design of resilient structures. A vascular system houses healing agents within its hollow channels or interconnected networks which are incorporated within a cement matrix. It is the only self-healing approach that has the capability to address different scales of damage in cementitious materials. The main aim of this work is to develop a novel vascular network inspired by nature for self-healing in cementitious systems. To achieve this, a biomimetic three-dimensional (3D) vascular network was designed and generated following Murray's law for circulatory blood volume transfer. The designed structures were constructed through 3D printing and assessed in a cement-based matrix. One-dimensional (1D) and two-dimensional (2D) models were also designed, printed and embedded into cement prisms to compare with the 3D vascular system. Load recovery was used to assess recovery in mechanical properties after the sample was cracked and pumped with sodium silicate for 28 days. Mechanical testing assessed the compatibility of the system with the surrounding matrix as well as the functionality of the network in delivering and releasing the healing agent at the location of damage. This initial proof of concept work confirmed the ability of all vascular systems to deliver the healing agent after a damage event, and the 3D vascular system demonstrated a significantly enhanced healing performance.
Highlights
Nature has always been a source of inspiration for ideas in addressing engineering materials challenges given that natural materials can be flexible, strong and lightweight and many are able to self-heal (Wegst et al, 2014)
A variety of capsules have been developed, capsule-based self-healing provides a limited amount of healing agent; this precludes the healing of larger cracks and repeated damage repair
The biomimetic design aims to (i) increase vessel coverage; (ii) avoid weakening the cement matrix; (iii) ensure strong bonding between the walls and cementitious materials (iv)avoid blockage while the healing agent pumped throughout the system, thereby achieving rapid physical triggering response and effective healing process the printed structure should be strongly bonded with the cementitious matrix to assure successful Physical triggering of the tubes
Summary
Nature has always been a source of inspiration for ideas in addressing engineering materials challenges given that natural materials can be flexible, strong and lightweight and many are able to self-heal (Wegst et al, 2014). Natural vascular systems have been an inspiration in the development of self-healing systems in polymer-based composites and more recently cement-based infrastructure and construction material systems (Williams et al, 2008). Cement-based infrastructure materials have limited intrinsic ability to heal very small cracks (0.15 μm) through a combination of continued hydration and carbonation processes under optimum curing conditions (De Rooij et al, 2013). To enhance the ability to self-heal larger and more complex damage, functional engineered additions have been developed cementitious systems. A variety of capsules have been developed, capsule-based self-healing provides a limited amount of healing agent; this precludes the healing of larger cracks and repeated damage repair. With a circulation system, healing agents could be recycled and refined, which provides a way for continuous healing agent delivery
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