scholarly journals Development of 3D Printed Networks in Self-Healing Concrete

Materials ◽  
2020 ◽  
Vol 13 (6) ◽  
pp. 1328 ◽  
Author(s):  
Cristina De Nardi ◽  
Diane Gardner ◽  
Anthony Duncan Jefferson
Keyword(s):  
Vascular System ◽  
Physical And Mechanical Properties ◽  
Self Healing ◽  
Vascular Networks ◽  
Minimal Impact ◽  
Cementitious Matrix ◽  
Healing Agent ◽  
3D Printed ◽  
Series Of Experiments ◽  
Concrete Elements

This paper presents a new form of biomimetic cementitious material, which employs 3D-printed tetrahedral mini-vascular networks (MVNs) to store and deliver healing agents to damage sites within cementitious matrices. The MVNs are required to not only protect the healing agent for a sufficient period of time but also survive the mixing process, release the healing agent when the cementitious matrix is damaged, and have minimal impact on the physical and mechanical properties of the host cementitious matrix. A systematic study is described which fulfilled these design requirements and determined the most appropriate form and material for the MVNs. A subsequent series of experiments showed that MVNs filled with sodium silicate, embedded in concrete specimens, are able to respond effectively to damage, behave as a perfusable vascular system and thus act as healing agent reservoirs that are available for multiple damage-healing events. It was also proved that healing agents encapsulated within these MVNs can be transported to cracked zones in concrete elements under capillary driving action, and produce a recovery of strength, stiffness and fracture energy.

scholarly journals Pressurized vascular systems for self-healing materials

2011 ◽  
Vol 9 (70) ◽  
pp. 1020-1028 ◽  
Author(s):  
A. R. Hamilton ◽  
N. R. Sottos ◽  
S. R. White
Keyword(s):  
Fracture Toughness ◽  
Vascular System ◽  
Damage Zone ◽  
Capillary Forces ◽  
Self Healing ◽  
Vascular Networks ◽  
Healing System ◽  
Healing Efficiency ◽  
Healing Agent ◽  
Reactive Fluids

An emerging strategy for creating self-healing materials relies on embedded vascular networks of microchannels to transport reactive fluids to regions of damage. Here we investigate the use of active pumping for the pressurized delivery of a two-part healing system, allowing a small vascular system to deliver large volumes of healing agent. Different pumping strategies are explored to improve the mixing and subsequent polymerization of healing agents in the damage zone. Significant improvements in the number of healing cycles and in the overall healing efficiency are achieved compared with prior passive schemes that use only capillary forces for the delivery of healing agents. At the same time, the volume of the vascular system required to achieve this superior healing performance is significantly reduced. In the best case, nearly full recovery of fracture toughness is attained throughout 15 cycles of damage and healing, with a vascular network constituting just 0.1 vol% of the specimen.

A New Vascular System Highly Efficient in the Storage and Transport of Healing Agent for Self-Healing Wind Turbine Blades

2019 ◽  
Vol 141 (5) ◽  
Author(s):  
Rulin Shen ◽  
Ryoichi S. Amano ◽  
Giovanni Lewinski ◽  
Arun Kumar Koralagundi Matt
Keyword(s):  
Wind Tunnel ◽  
Wind Turbine ◽  
Vascular System ◽  
Copper Wire ◽  
Turbine Blades ◽  
Real Life ◽  
Transport Processes ◽  
Self Healing ◽  
Wind Turbine Blades ◽  
Healing Agent

Self-healing wind turbine blades offer a substantial offset for costly blade repairs and failures. We discuss the efforts made to optimize the self-healing properties of wind turbine blades and provide a new system to maximize this offset. Copper wire coated by paraffin wax was embedded into fiber-reinforced polymer (FRP) samples incorporated with Grubbs' first-generation catalyst. The wires were extracted from cured samples to create cavities that were then injected with the healing agent, dicyclopentadiene (DCPD). Upon sample failure, the DCPD and catalyst react to form a thermosetting polymer to heal any crack propagation. Three-point bending flexural tests were performed to obtain the maximum flexural strengths of the FRP samples before and after recovery. Using those results, a hierarchy of various vascular network configurations was derived. To evaluate the healing system's effect in a real-life application, a prototype wind turbine was fabricated and wind tunnel testing was conducted. Using ultraviolet (UV) dye, storage and transport processes of the healing agent were observed. After 24 h of curing time, Raman spectroscopy was performed. The UV dye showed dispersion into the failure zone, and the Raman spectra showed the DCPD was polymerized to polydicyclopentadiene (PDCPD). Both the flexural and wind tunnel test samples were able to heal successfully, proving the validity of the process.

scholarly journals Development of Multi-Dimensional 3D Printed Vascular Networks for Self-Healing Materials

2017 ◽  
Author(s):  
Isabel P. S. Qamar ◽  
Richard S. Trask
Keyword(s):  
Fused Deposition Modeling ◽  
External Source ◽  
Additive Manufacture ◽  
Crack Plane ◽  
Self Healing ◽  
Vascular Networks ◽  
Free Standing ◽  
Damage Site ◽  
Fused Deposition ◽  
3D Printed

Self-healing materials have emerged as an alternative solution to the repair of damage in fibre-reinforced composites. Recent developments have largely focused on a vascular approach, due to the ability to transport healing agents over long distances and continually replenish from an external source. However fracture of the vascular network is required to enable the healing agents to infiltrate the crack plane, ceasing its primary function in transporting fluid and preventing the repair of any further damage events. Here we present a novel approach to vascular self-healing through the development and integration of 3D printed, porous, thermoplastic networks into a thermoset matrix. This concept exploits the inherently low surface chemistry of thermoplastic materials, which results in adhesive failure between the thermoplastic network and thermoset matrix on arrival of a propagating crack, thus exposing the radial pores of the network and allowing the healing agents to flow into the damage site. We investigate the potential of two additive manufacturing techniques, fused deposition modeling (FDM) and stereolithography, to fabricate free-standing, self-healing networks. Furthermore, we assess the interaction of a crack with branched network structures under static indentation in order to establish the feasibility of additive manufacture for multi-dimensional 3D printed self-healing networks.

scholarly journals Experimental Investigation of a Novel Formulation of a Cyanoacrylate-Based Adhesive for Self-Healing Concrete Technologies

2021 ◽  
Vol 7 ◽  
Author(s):  
Cristina De Nardi ◽  
Diane Gardner ◽  
Giulia Cazzador ◽  
Davide Cristofori ◽  
Lucio Ronchin ◽  
...  
Keyword(s):  
Bond Strength ◽  
Shelf Life ◽  
Sessile Drop ◽  
Cement Mortar ◽  
Self Healing ◽  
Vascular Networks ◽  
Concrete Technology ◽  
Scanning Calorimetry ◽  
Liquid Form ◽  
Healing Agent

The selection of an appropriate healing agent is critical to the success of vascular and mini-vascular networks. In self-healing concrete technology, commercially available cyanoacrylate (CA) adhesives have been shown to produce good strength recoveries; however, their rapid curing rate and short shelf-life make them unsuitable for site application. The aim of this study was to develop a modified cyanoacrylate (n-CA) with an extended shelf-life suitable for incorporation in a self-healing system. A series of n-CAs were formed from a commercial Ethyl Cyanoacrylate adhesive mixed with acrylic acid (AA) and nitro-anthraquinone (nAq) in varying ratios. When encapsulated within 3D printed mini-vascular networks (MVNs), the n-CAs remained dormant in liquid form for up to 5 days. The contact angle between the n-CAs and the cement mortar substrate, as measured via the sessile drop technique, decreased significantly with increasing AA content. The mechanical properties (bond strength) and the polymerization hardening of the n-CAs were evaluated over a curing period of 7–21 days, via a series of pull-off tests using cement mortar cubes. The 4:1:02 (CA:AA:nAq) n-CA formulation showed a significant increase in bond strength from 14 to 21 days, with a ceiling value of 2.6 MPa, while the 2:1 (CA:AA) n-CA formulation exhibited a good bond strength after 21 days (1 MPa). Nuclear Magnetic Resonance (NMR) conducted on the n-CAs suggested the formation of several new polymeric species, whilst differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) on the pre- and post-printed MVN material confirmed no significant changes in chemistry with no evidence of polymer degradation. Considered together, the experimental results show the potential for different n-CA formulations to act efficiently as a healing agent.

scholarly journals Effects of Layer-Interface Properties on Mechanical Performance of Concrete Elements Produced by Extrusion-Based 3D-Printing

2018 ◽  
Author(s):  
Venkatesh Naidu Nerella ◽  
Simone Hempel ◽  
Viktor Mechtcherine
Keyword(s):  
Flexural Strength ◽  
Mechanical Performance ◽  
Time Interval ◽  
Self Healing ◽  
Layer Interface ◽  
Material Deposition ◽  
Macro Scale ◽  
3D Printed ◽  
Pozzolanic Additives ◽  
Concrete Elements

Interfaces between layers in 3D-printed elements produced by extrusion-based material deposition were investigated on both macro- and micro-scales. On the macro-scale, compression and bend tests were performed on two 3D-printable cement-based compositions (3PCs), namely C1 and C2. The influences of binder composition and time interval between layers on layer-interface strength were critically analyzed. In the context of additive manufacturing, the optimized composition C2, containing pozzolanic additives, exhibited mechanical performance superior to that of the mixture with Portland cement as the sole binder. In particular, Mixture C2 showed a less pronounced decrease in interface tensile strength. Even for time intervals between depositions of two layers as long as 1 day the loss in corresponding flexural strength was below 25%, as compared with C2 specimens tested in the perpendicular direction. In contrast, the decrease in flexural strength measured for C1 specimens amounted to over 90% for the same set of parameters. Higher porosity at the interfaces of the printed concrete layers was identified as the cause for the lower interface strengths of C1. Microscopic observations supported the findings of the macroscopic investigations. While a pronounced recovery (“self-healing”) of the porous, discontinuous interlayers was observed with increasing age for Mixture C2, in case of C1 the filling products grown in the porous interlayer were found to be non-strengthening.

Modeling of the behaviour of concrete elements containing a self- healing agent

2021 ◽  
Author(s):  
Todor Zhelyazov ◽  
Radan Ivanov
Keyword(s):  
Finite Element ◽  
Damage Mechanics ◽  
Mechanical Response ◽  
Numerical Procedure ◽  
Plain Concrete ◽  
General Purpose ◽  
Self Healing ◽  
Structural Element ◽  
Healing Agent ◽  
Concrete Elements

<p>This contribution focuses on the numerical modelling and simulation of the mechanical behaviour of structural elements containing a self-healing agent. Specifically, the finite element modelling of the mechanical response of plain concrete structural element, containing a healing agent and subject to various loading conditions is discussed. A customized numerical procedure designed to implement the Damage Mechanics-based constitutive relation for concrete into a general-purpose finite element code is developed. The procedure comprises algorithms for evaluation of the volume of newly-formed cracks, the recovery of stiffness of the structural element due to crack closure, the initiation of healing and its effect on the overall response of the structural element. The procedure is demonstrated by simulations of a concrete cylinder subjected to compression and torsion.</p>

scholarly journals Feasibility of Using 3D Printed Polyvinyl Alcohol (PVA) for Creating Self-Healing Vascular Tunnels in Cement System

Materials ◽  
2019 ◽  
Vol 12 (23) ◽  
pp. 3872 ◽  
Author(s):  
Zijing Li ◽  
Lívia Ribeiro de Souza ◽  
Chrysoula Litina ◽  
Athina E. Markaki ◽  
Abir Al-Tabbaa
Keyword(s):  
Polyvinyl Alcohol ◽  
Early Stage ◽  
Cementitious Materials ◽  
Self Healing ◽  
Vascular Networks ◽  
X Ray Diffraction ◽  
Cement Pastes ◽  
Polymer Compound ◽  
3D Printed

Pursuing long-term self-healing infrastructures has gained popularity in the construction field. Vascular networks have the potential to achieve long-term self-healing in cementitious infrastructures. To avoid further monitoring of non-cementitious tubes, sacrificial material can be used as a way of creating hollow channels. In this research, we report a new method for fabrication of complex 3D internal hollow tunnels using 3D printing of polyvinyl alcohol (PVA). The behaviour of 3D printed PVA structures in cement pastes was investigated using computed-tomography (CT) combined with X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy with energy dispersive spectroscopy (SEM/EDX). Results showed that (i) 1300 min were needed to fully dissolve 1 g of a 3D printed PVA structure, and different pH solutions did not significantly change the PVA dissolving process compared with a neutral environment; (ii) a low water/cement ratio can minimize early stage cracking resulting from PVA expansion; (iii) and PVA-cement interaction products were mainly calcite and a Ca-polymer compound. In conclusion, controlling the PVA expansion by decreasing the water/cement (w/c) ratio provides a promising approach to achieve 3D hollow channels in cement and, therefore, makes it possible to create complex tunnels within self-healing cementitious materials.

scholarly journals Efficiency of self-healing cementitious materials with encapsulated polyurethane to reduce water ingress through cracks

2018 ◽  
Vol 68 (330) ◽  
Author(s):  
B. Van Belleghem ◽  
K. Van Tittelboom ◽  
N. De Belie
Keyword(s):  
Large Range ◽  
High Viscosity ◽  
Cementitious Materials ◽  
Self Healing ◽  
Large Scatter ◽  
Crack Healing ◽  
Water Ingress ◽  
Low Viscosity ◽  
Healing Agent ◽  
Concrete Elements

Cracks in reinforced concrete elements can cause major durability issues due do the accelerated ingress of aggressive substances. In this study, repair of cracks was addressed by incorporating encapsulated polyurethane based healing agents in the cementitious material as an autonomous healing mechanism. Capillary sorption tests showed that a high viscosity healing agent could reduce the water ingress in cracked mortar, but a large scatter in the results was found, resulting in a large range of healing efficiencies (18 – 108%). The low viscosity polyurethane showed a more complete and consistent crack healing. Healing efficiencies ranging from 95 to 124% were observed (crack width up to 295 μm). The proposed healing mechanism is very effective in blocking the ingress of water. This will enhance the durability of cementitious materials and consequently extend their lifetime.

scholarly journals Rapid synchronized fabrication of vascularized thermosets and composites

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Mayank Garg ◽  
Jia En Aw ◽  
Xiang Zhang ◽  
Polette J. Centellas ◽  
Leon M. Dean ◽  
...  
Keyword(s):  
Large Scale ◽  
Capillary Flow ◽  
External Heat ◽  
Frontal Polymerization ◽  
Self Healing ◽  
Vascular Networks ◽  
Ambient Conditions ◽  
External Energy ◽  
Imaging Phantoms ◽  
Vascular Structures

AbstractBioinspired vascular networks transport heat and mass in hydrogels, microfluidic devices, self-healing and self-cooling structures, filters, and flow batteries. Lengthy, multistep fabrication processes involving solvents, external heat, and vacuum hinder large-scale application of vascular networks in structural materials. Here, we report the rapid (seconds to minutes), scalable, and synchronized fabrication of vascular thermosets and fiber-reinforced composites under ambient conditions. The exothermic frontal polymerization (FP) of a liquid or gelled resin facilitates coordinated depolymerization of an embedded sacrificial template to create host structures with high-fidelity interconnected microchannels. The chemical energy released during matrix polymerization eliminates the need for a sustained external heat source and greatly reduces external energy consumption for processing. Programming the rate of depolymerization of the sacrificial thermoplastic to match the kinetics of FP has the potential to significantly expedite the fabrication of vascular structures with extended lifetimes, microreactors, and imaging phantoms for understanding capillary flow in biological systems.

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