A review of vascular networks for self-healing applications
Abstract: Abstract Increasing awareness for sustainability has led to the development of smart self-healing materials, which can extend the service life and improve safety without human intervention. Vascular networks are observed in biological systems, such as leaf venation and blood vascular systems, and provide inspiration for self-healing mechanisms in engineered systems. Embedding a vascular network in a host material has the advantage of addressing varying magnitudes of damage and allowing for an indefinite replenishment of the healing agent, which are current limitations of intrinsic and capsule-based self-healing systems. These networks are demonstrated in polymer and composite materials, with fabrication methods including removal of sacrificial elements, electrospinning, and an array of additive manufacturing (AM) techniques. Advances in AM allow more complex network configurations to be realized that optimize fluid distribution and healing potential. This review intends to provide a comprehensive overview of the current progress and limitations of the design approaches, fabrication methods, healing mechanisms, and relevant applications of embedded vascular networks. Additionally, significant research gaps and future research directions for vascular self-healing materials are described.
Reference of this article: Shields, Y., De Belie, N., Jefferson, A., & Van Tittelboom, K. (2021). A review of vascular networks for self-healing applications. SMART MATERIALS AND STRUCTURES, 30(6)
Addressing the need for standardization of test methods for self-healing concrete: an inter-laboratory study on concrete with macrocapsules
Abstract: Development and commercialization of self-healing concrete is hampered due to a lack of standardized test methods. Six inter-laboratory testing programs are being executed by the EU COST action SARCOS, each focusing on test methods for a specific self-healing technique. This paper reports on the comparison of tests for mortar and concrete speci-mens with polyurethane encapsulated in glass macrocapsules. First, the pre-cracking method was analysed: mortar specimens were cracked in a three-point bending test followed by an active crack width control technique to restrain the crack width up to a predefined value, while the concrete specimens were cracked in a three-point bending setup with a displacement-controlled loading system. Microscopic measurements showed that with the application of the active control technique almost all crack widths were within a narrow predefined range. Conversely, for the concrete specimens the variation on the crack width was higher. After pre-cracking, the self-healing effect was characterized via durability tests: the mortar specimens were tested in a water permeability test and the spread of the healing agent on the crack surfaces was determined, while the concrete specimens were subjected to two capillary water absorption tests, executed with a different type of waterproofing applied on the zone around the crack. The quality of the waterproofing was found to be important, as different results were obtained in each absorption test. For the permeability test, 4 out of 6 labs obtained a comparable flow rate for the reference specimens, yet all 6 labs obtained comparable sealing efficiencies, highlighting the potential for further standardization.
Reference of this article: Tim Van Mullem, Giovanni Anglani, Marta Dudek, Hanne Vanoutrive, Girts Bumanis, Chrysoula Litina, Arkadiusz Kwiecień, Abir Al-Tabbaa, Diana Bajare, Teresa Stryszewska, Robby Caspeele, Kim Van Tittelboom, Tulliani Jean-Marc, Elke Gruyaert, PaolaAntonaci & Nele De Belie (2020) Addressing the need for standardization of test methods forself-healing concrete: an inter-laboratory study on concrete with macrocapsules, Science andTechnology of Advanced Materials, 21:1, 661-682,
Self-healing concrete research in the European projects SARCOS and SMARTINCS
Abstract: Self-healing concrete and preventive repair of structures will slow down the development of cracks and/or arrest the ingress of aggressive agents. When the cracks are closed or a decrease in crack width is achieved, this will be associated with improved durability of the structure. This paper describes the literature review and inter-laboratory comparison carried out within the COST Action CA15202 (SARCOS), as well as the research planned within the recently started International Training Network SMARTINCS.
Reference of this article: De Belie, N., Van Tittelboom, K., Sánchez Moreno, M., Ferrara, L., Gruyaert, E. (2020). Self-healing concrete research in the European projects SARCOS and SMARTINCS. Plenary keynote lecture. RILEM Spring Convention, University of Minho, Guimarães, Portugal, 9-10 March 2020. (In press).
As Riccardo Maddalena and Diane Gardner report, self-healing concrete represents an environmentally-friendly choice, for increasing the service life of a structure, and reducing its overall maintenance and the subsequent usage of concrete.