Microcapsule-Type Self-Healing Protective Coating That Can Maintain Its Healed State upon Crack Expansion

The purpose of this study was to develop a microcapsule-type self-healing coating system that could self-heal cracks and then maintain the healed state even upon crack expansion. Mixtures consisting of a photoinitiator and two methacrylate components, bismethacryloxypropyl-terminated polydimethylsiloxane (BMT-PDMS) and monomethacryloxypropyl-terminated PDMS (MMT-PDMS), were transformed into viscoelastic semi-solids through photoreaction. The viscoelasticity of the reacted mixtures could be controlled by varying the mass ratio of the two methacrylates. Through a stretchability test, the optimal composition mixture was chosen as a healing agent. Microcapsules loaded with the healing agent were prepared and dispersed in a commercial undercoating to obtain a self-healing coating formulation. The formulation was applied onto mortar specimens, and then cracks were generated in the coating by using a universal testing machine (UTM). Cracks with around a 150-μm mean width were generated and were allowed to self-heal under UV light. Then, the cracks were expanded up to 650 μm in width. By conducting a water sorptivity test at each expanded crack width, the self-healing efficiency and capability of maintaining the healed state were evaluated. The B-M-1.5-1-based coating showed a healing efficiency of 90% at a 150-μm crack width and maintained its healing efficiency (about 80%) up to a 350-μm crack width. This self-healing coating system is promising for the protection of structural materials that can undergo crack formation and expansion.

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Mechanical responses of microencapsulated self-healing cementitious composites under compressive loading based on a micromechanical damage-healing model

International Journal of Damage Mechanics ◽

10.1177/10567895211011239 ◽

2021 ◽

pp. 105678952110112

Author(s):

Kaihang Han ◽

Jiann-Wen Woody Ju ◽

Yinghui Zhu ◽

Hao Zhang ◽

Tien-Shu Chang ◽

...

Keyword(s):

Fracture Toughness ◽

Compressive Strength ◽

Micromechanical Model ◽

Cementitious Composites ◽

Self Healing ◽

Damage Degree ◽

Healing Efficiency ◽

The Matrix ◽

Healing Agent ◽

Damage Healing

The cementitious composites with microencapsulated healing agents have become a class of hotspots in the field of construction materials, and they have very broad application prospects and research values. The in-depth study on multi-scale mechanical behaviors of microencapsulated self-healing cementitious composites is critical to quantitatively account for the mechanical response during the damage-healing process. This paper proposes a three-dimensional evolutionary micromechanical model to quantitatively explain the self-healing effects of microencapsulated healing agents on the damage induced by microcracks. By virtue of the proposed 3 D micromechanical model, the evolutionary domains of microcrack growth (DMG) and corresponding compliances of the initial, extended and repaired phases are obtained. Moreover, the elaborate studies are conducted to inspect the effects of various system parameters involving the healing efficiency, fracture toughness and preloading-induced damage degrees on the compliances and stress-strain relations. The results indicate that relatively significant healing efficiency, preloading-induced damage degree and the fracture toughness of polymerized healing agent with the matrix will lead to a higher compressive strength and stiffness. However, the specimen will break owing to the nucleated microcracks rather than the repaired kinked microcracks. Further, excessive higher values of healing efficiency, preloading-induced damage degree and the fracture toughness of polymerized healing agent with the matrix will not affect the compressive strength of the cementitious composites. Therefore, a stronger matrix is required. To achieve the desired healing effects, the specific parameters of both the matrix and microcapsules should be selected prudently.

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Self-Healing Biogeopolymers Using Biochar-Immobilized Spores of Pure- and Co-Cultures of Bacteria

10.20944/preprints202011.0566.v2 ◽

2020 ◽

Author(s):

Jadin Zam S. Doctolero ◽

Arnel B. Beltran ◽

Marigold O. Uba ◽

April Anne S. Tigue ◽

Michael Angelo B. Promentilla

Keyword(s):

Image Analysis ◽

Crack Width ◽

Ultrasonic Pulse ◽

Self Healing ◽

Weak Effect ◽

Bacterial Cultures ◽

Healing Agent ◽

Optimum Response ◽

Maximum Crack ◽

Cultured Bacteria

A sustainable solution for crack maintenance in geopolymers is necessary if they are to be the future of modern green construction. This study thus aimed to develop self-healing biogeopolymers that could potentially rival bioconcrete. First, a suitable healing agent was selected from Bacillus subtilis, B. sphaericus, and B. megaterium by directly adding their spores in the geopolymers and subsequently exposing them to a large amount of nutrients for 14 days. SEM-EDX analysis revealed the formation of biominerals for B. subtilis and B. sphaericus. Next, the effect of biochar-immobilization and co-culturing (B. sphaericus and B. thuringiensis) on the healing efficiencies of the geopolymers were tested and optimized by measuring their ultrasonic pulse velocities weekly over a 28-day healing period. The results show that using co-cultured bacteria significantly improved the observed efficiencies, while biochar-immobilization had a weak effect but yielded an optimum response between 0.3-0.4 g/mL. The maximum crack width sealed was 0.65 mm. Through SEM-EDX and FTIR analyses, the biominerals precipitated in the cracks were identified to be mainly CaCO3. Furthermore, image analysis of the XCT scans of some of the healed geopolymers confirmed that their pulse velocities were indeed improving due to the filling of their internal spaces with biominerals. With that, there is potential in developing self-healing biogeopolymers using biochar-immobilized spores of bacterial cultures.

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Encapsulation Techniques and Test Methods of Evaluating the Bacteria-Based Self-Healing Efficiency of Concrete: A Literature Review

Nordic Concrete Research ◽

10.2478/ncr-2020-0006 ◽

2020 ◽

Vol 62 (1) ◽

pp. 63-85

Author(s):

Rahul Roy ◽

Emanuele Rossi ◽

Johan Silfwerbrand ◽

Henk Jonkers

Keyword(s):

Service Life ◽

Polymeric Materials ◽

Cementitious Materials ◽

Test Methods ◽

Self Healing ◽

Load Factors ◽

Healing Efficiency ◽

Healing Agent ◽

Maximum Crack ◽

Encapsulated Bacteria

AbstractCrack formation in concrete structures due to various load and non-load factors leading to degradation of service life is very common. Repair and maintenance operations are, therefore, necessary to prevent cracks propagating and reducing the service life of the structures. Accessibility to affected areas can, however, be difficult as the reconstruction and maintenance of concrete buildings are expensive in labour and capital. Autonomous healing by encapsulated bacteria-based self-healing agents is a possible solution. During this process, the bacteria are released from a broken capsule or triggered by water and oxygen access. However, its performance and reliability depend on continuous water supply, protection against the harsh environment, and densification of the cementitious matrix for the bacteria to act. There are vast methods of encapsulating bacteria and the most common carriers used are: encapsulation in polymeric materials, lightweight aggregates, cementitious materials, special minerals, nanomaterials, and waste-derived biomass. Self-healing efficiency of these encapsulated technologies can be assessed through many experimental methodologies according to the literature. These experimental evaluations are performed in terms of quantification of crackhealing, recovery of durability and mechanical properties (macro-level test) and characterization of precipitated crystals by healing agent (micro-level test). Until now, quantification of crack-healing by light microscopy revealed maximum crack width of 1.80mm healed. All research methods available for assesing self-healing efficiency of bacteria-based healing agents are worth reviewing in order to include a coherent, if not standardized framework testing system and a comparative evaluation for a novel incorporated bacteria-based healing agent.

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Development of an improved cracking method to reduce the variability in testing the healing efficiency of self-healing mortar containing encapsulated polymers

MATEC Web of Conferences ◽

10.1051/matecconf/201819902017 ◽

2018 ◽

Vol 199 ◽

pp. 02017 ◽

Cited By ~ 3

Author(s):

Tim Van Mullem ◽

Kim Van Tittelboom ◽

Elke Gruyaert ◽

Robby Caspeele ◽

Nele De Belie

Keyword(s):

Crack Width ◽

Control Technique ◽

Self Healing ◽

Concrete Cracking ◽

Crack Control ◽

Control Techniques ◽

Healing Efficiency ◽

Flow Test ◽

Equivalent Reduction ◽

External Intervention

Concrete cracking can result in a significant reduction of the durability and the service life due to the ingress of aggressive agents Self-healing concrete is able to heal cracks without external intervention, thereby mitigating the need for manual repair. In the assessment of the healing efficiency of self-healing concrete the to-be-healed crack width is an important parameter and different researchers have emphasised that the variability of the crack width significantly hampers an accurate assessment of the healing efficiency. With two new crack control techniques the variability of the crack width was reduced in order to decrease the variability on the calculated healing efficiency. This paper reports on the application of these techniques for the assessment of self-healing mortar containing encapsulated polyurethane. The healing potential was investigated by looking at the degree of sealing using a water flow test setup. It was observed that by using a crack control technique the variability on the crack width can indeed be reduced. Nonetheless, this does not translate in an equivalent reduction on the variability of the healing efficiency. This indicates that other factors contribute to the variability of the healing efficiency.

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Self-Healing EPDM Rubbers with Highly Stable and Mechanically-Enhanced Urea-Formaldehyde (UF) Microcapsules Prepared by Multi-Step In Situ Polymerization

Polymers ◽

10.3390/polym12091918 ◽

2020 ◽

Vol 12 (9) ◽

pp. 1918 ◽

Cited By ~ 1

Author(s):

Hyeong-Jun Jeoung ◽

Kun Won Kim ◽

Yong Jun Chang ◽

Yong Chae Jung ◽

Hyunchul Ku ◽

...

Keyword(s):

Mechanical Stability ◽

In Situ Polymerization ◽

Urea Formaldehyde ◽

Testing Machine ◽

Optical Microscope ◽

The Self ◽

Self Healing ◽

Grubbs Catalyst ◽

Healing Efficiency

The mechanically-enhanced urea-formaldehyde (UF) microcapsules are developed through a multi-step in situ polymerization method. Optical microscope (OM) and field emission scanning electron microscope (FE-SEM) prove that the microcapsules, 147.4 μm in diameter with a shell thickness of 600 nm, are well-formed. From 1H-nuclear magnetic resonance (1H-NMR) analysis, we found that dicyclopentadiene (DCPD), a self-healing agent encapsulated by the microcapsules, occupies ca. 40.3 %(v/v) of the internal volume of a single capsule. These microcapsules are mixed with EPDM (ethylene-propylene-diene-monomer) and Grubbs’ catalyst via a solution mixing method, and universal testing machine (UTM) tests show that the composites with mechanically-enhanced microcapsules has ca. 47% higher toughness than the composites with conventionally prepared UF microcapsules, which is attributed to the improved mechanical stability of the microcapsule. When the EPDM/microcapsule rubber composites are notched, Fourier-transform infrared (FT-IR) spectroscopy shows that DCPD leaks from the broken microcapsule to the damaged site and flows to fill the notched valley, and self-heals as it is cured by Grubbs’ catalyst. The self-healing efficiency depends on the capsule concentration in the EPDM matrix. However, the self-healed EPDM/microcapsule rubber composite with over 15 wt% microcapsule shows an almost full recovery of the mechanical strength and 100% healing efficiency.

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Self-healing efficiency of cementitious materials containing tubular capsules filled with healing agent

Cement and Concrete Composites ◽

10.1016/j.cemconcomp.2011.01.004 ◽

2011 ◽

Vol 33 (4) ◽

pp. 497-505 ◽

Cited By ~ 189

Author(s):

Kim Van Tittelboom ◽

Nele De Belie ◽

Denis Van Loo ◽

Patric Jacobs

Keyword(s):

Cementitious Materials ◽

Self Healing ◽

Healing Efficiency ◽

Healing Agent

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Impact of Bio-Carrier Immobilized with Marine Bacteria on Self-Healing Performance of Cement-Based Materials

Materials ◽

10.3390/ma13184164 ◽

2020 ◽

Vol 13 (18) ◽

pp. 4164 ◽

Cited By ~ 1

Author(s):

Hayeon Kim ◽

Hyeongmin Son ◽

Joonho Seo ◽

H. K. Lee

Keyword(s):

Mechanical Properties ◽

Mercury Intrusion Porosimetry ◽

Tap Water ◽

Bottom Ash ◽

Self Healing ◽

Mixing Process ◽

Mercury Intrusion ◽

Healing Efficiency ◽

Cement Based Materials ◽

Healing Agent

The present study evaluated the self-healing efficiency and mechanical properties of mortar specimens incorporating a bio-carrier as a self-healing agent. The bio-carrier was produced by immobilizing ureolytic bacteria isolated from seawater in bottom ash, followed by surface coating with cement powder to prevent loss of nutrients during the mixing process. Five types of specimens were prepared with two methods of incorporating bacteria, and were water cured for 28 days. To investigate the healing ratio, the specimens with predefined cracks were treated by applying a wet–dry cycle in three different conditions, i.e., seawater, tap water, and air for 28 days. In addition, a compression test and a mercury intrusion porosimetry analysis of the specimens were performed to evaluate their physico-mechanical properties. The obtained results showed that the specimen incorporating the bio-carrier had higher compressive strength than the specimen incorporating vegetative cells. Furthermore, the highest healing ratio was observed in specimens incorporating the bio-carrier. This phenomenon could be ascribed by the enhanced bacterial viability by the bio-carrier.

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Self-Healing Biogeopolymers Using Biochar-Immobilized Spores of Pure- and Co-Cultures of Bacteria

10.20944/preprints202011.0566.v1 ◽

2020 ◽

Author(s):

Jadin Zam S. Doctolero ◽

Arnel B. Beltran ◽

Marigold O. Uba ◽

April Anne S. Tigue ◽

Michael Angelo B. Promentilla

Keyword(s):

Image Analysis ◽

Crack Width ◽

Ultrasonic Pulse ◽

Self Healing ◽

Weak Effect ◽

Bacterial Cultures ◽

Healing Agent ◽

Optimum Response ◽

Maximum Crack ◽

Cultured Bacteria

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Recovery of Fracture Toughness on Self-Healing Epoxies Using Ternary Nanomodified Microcapsules: A Parametric Study

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.827.258 ◽

2019 ◽

Vol 827 ◽

pp. 258-262 ◽

Cited By ~ 1

Author(s):

Maria Kosarli ◽

Kyriaki Tsirka ◽

Stella Chalari ◽

Antigoni Palantza ◽

Alkiviadis S. Paipetis

Keyword(s):

Electron Microscopy ◽

Thermal Stability ◽

Parametric Study ◽

External Surface ◽

Self Healing ◽

Healing Efficiency ◽

Mean Diameter ◽

Healing Agent ◽

The Mean ◽

Scanning Electron

This study is focused on the effect of the nanomodification of the microcapsules healing agent on the healing efficiency. In detail, nanomodified epoxy resin with both carbon nanotubes (CNTs) and carbon black (CB) diluted with a non-toxic solvent was encapsulated into UF capsules. The morphology of the external surface and the mean diameter was investigated via Scanning Electron Microscopy (SEM). In addition, the thermal stability was estimated with Thermogravimetric analysis and healing efficiency was evaluated for the polymer epoxy matrix. A parametric study was performed at various solvent percentages and catalyst percentages. Results indicated an increase of the healing efficiency with nanomodified capsules against of the use of conventional microcapsules.

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Microscopic Tests on Evaluation of Self-Healing Efficiency in Cementitious Materials with a Novel Self-Healing System

Materials Science Forum ◽

10.4028/www.scientific.net/msf.996.104 ◽

2020 ◽

Vol 996 ◽

pp. 104-109 ◽

Cited By ~ 1

Author(s):

Zhen Hong Yang ◽

Xian Feng Wang ◽

Ning Xu Han ◽

Feng Xing

Keyword(s):

Joint Action ◽

Cementitious Materials ◽

Cementitious Material ◽

Self Healing ◽

Test Results ◽

Expansive Agent ◽

Healing System ◽

Healing Efficiency ◽

Healing Agent

In this study, Na2CO3 solution as a self-healing agent was impregnated in LWA for autonomic self-healing on cracked cementitious material. The results showed that under the joint action of expansive agent, crystalline additive, phosphate and carbonate, the crack area showed a high self-healing efficiency (close to 70%) after curing in the still water 28d. SEM-EDS test results showed that in addition to ettringite and C-S-H/C-A-S-H, there was also a large amount of CaCO3 crystal in the depths of the crack.

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