Biological Self-Healing of Cement Paste and Mortar by Non-Ureolytic Bacteria Encapsulated in Alginate Hydrogel Capsules

Crack formation in concrete is one of the main reasons for concrete degradation. Calcium alginate capsules containing biological self-healing agents for cementitious materials were studied for the self-healing of cement paste and mortars through in vitro characterizations such as healing agent survivability and retention, material stability, and biomineralization, followed by in situ self-healing observation in pre-cracked cement paste and mortar specimens. Our results showed that bacterial spores fully survived the encapsulation process and would not leach out during cement mixing. Encapsulated bacteria precipitated CaCO3 when exposed to water, oxygen, and calcium under alkaline conditions by releasing CO32− ions into the cement environment. Capsule rupture is not required for the initiation of the healing process, but exposure to the right conditions are. After 56 days of wet–dry cycles, the capsules resulted in flexural strength regain as high as 39.6% for the cement mortar and 32.5% for the cement paste specimens. Full crack closure was observed at 28 days for cement mortars with the healing agents. The self-healing system acted as a biological CO32− pump that can keep the bio-agents retained, protected, and active for up to 56 days of wet-dry incubation. This promising self-healing strategy requires further research and optimization.

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Application of GGBFS and Bentonite to Auto-Healing Cracks of Cement Paste

Journal of Advanced Civil and Environmental Engineering ◽

10.30659/jacee.1.1.38-48 ◽

2018 ◽

Vol 1 (1) ◽

pp. 38 ◽

Cited By ~ 1

Author(s):

J J Ekaputri ◽

M S Anam ◽

Y Luan ◽

C Fujiyama ◽

N Chijiwa ◽

...

Keyword(s):

Cement Paste ◽

Surface Crack ◽

Crack Width ◽

Healing Process ◽

Crack Depth ◽

The Self ◽

External Loading ◽

Self Healing ◽

Carbonation Reaction ◽

Granulated Blast Furnace Slag

Cracks are caused by many factors. Shrinkage and external loading are the most common reason. It becomes a problem when the ingression of aggressive and harmful substance penetrates to the concrete gap. This problem reduces the durability of the structures. It is well known that self – healing of cracks significantly improves the durability of the concrete structure. This paper presents self-healing cracks of cement paste containing bentonite associated with ground granulated blast furnace slag. The self-healing properties were evaluated with four parameters: crack width on the surface, crack depth, tensile strength recovery, and flexural recovery. In combination with microscopic observation, a healing process over time is also performed. The results show that bentonite improves the healing properties, in terms of surface crack width and crack depth. On the other hand, GGBFS could also improve the healing process, in terms of crack depth, direst tensile recovery, and flexural stiffness recovery. Carbonation reaction is believed as the main mechanism, which contributes the self-healing process as well as the continuous hydration progress.

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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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Modeling microcapsule-enabled self-healing cementitious composite materials using discrete element method

International Journal of Damage Mechanics ◽

10.1177/1056789516688835 ◽

2017 ◽

Vol 26 (2) ◽

pp. 340-357 ◽

Cited By ~ 23

Author(s):

Shuai Zhou ◽

Hehua Zhu ◽

J Woody Ju ◽

Zhiguo Yan ◽

Qing Chen

Keyword(s):

Discrete Element Method ◽

Healing Process ◽

Compressive Loading ◽

Discrete Element ◽

Cementitious Materials ◽

Self Healing ◽

Healing Effect ◽

Healing Agent ◽

Damage Healing ◽

Element Method

Concrete with a micro-encapsulated healing agent is appealing due to its self-healing capacity. The discrete element method (DEM) is emerging as an increasingly used approach for investigating the damage phenomenon of materials at the microscale. It provides a promising way to study the microcapsule-enabled self-healing concrete. Based on the experimental observation and DEM, a three-dimensional damage-healing numerical model of microcapsule-enabled self-healing cementitious materials under compressive loading is proposed. The local healing effect can be simulated in our model, as well as the stress concentration effect and the partial healing effect. The healing variable of the DEM model is developed to describe the healing process. We examine the dependence of the mechanical properties of the microcapsule-enabled self-healing material on (a) the stiffness of the solidified healing agent, (b) the strength of the solidified healing agent, (c) the initial damage of specimens, and (d) the partial healing effect. In particular, the proposed numerical damage-healing model demonstrates the potential capability to explain and simulate the physical behavior of microcapsule-enabled self-healing materials on the microscale.

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Self-Repairing Composites for Corrosion Protection: A Review on Recent Strategies and Evaluation Methods

Materials ◽

10.3390/ma12172754 ◽

2019 ◽

Vol 12 (17) ◽

pp. 2754 ◽

Cited By ~ 8

Author(s):

P ◽

Al-Maadeed

Keyword(s):

Electrochemical Impedance ◽

Protective Coatings ◽

Healing Process ◽

Cellulose Nanofibers ◽

Aloe Vera ◽

Immersion Test ◽

The Self ◽

Self Healing ◽

Metal Substrates ◽

Healing Agent

The use of self-healing coatings to protect metal substrates, such as aluminum alloys, stainless steel, carbon steel, and Mg alloys from corrosion is an important aspect for protecting metals and for the economy. During the past decade, extensive transformations on self-healing strategies were introduced in protective coatings, including the use of green components. Scientists used extracts of henna leaves, aloe vera, tobacco, etc. as corrosion inhibitors, and cellulose nanofibers, hallyosite nanotubes, etc. as healing agent containers. This review gives a concise description on the need for self-healing protective coatings for metal parts, the latest extrinsic self-healing strategies, and the techniques used to follow-up the self-healing process to control the corrosion of metal substrates. Common techniques, such as accelerated salt immersion test and electrochemical impedance spectroscopy (EIS), for evaluating the self-healing process in protective coatings are explained. We also show recent advancements procedures, such as scanning vibrating electrode technique (SVET) and scanning electrochemical microscopy (SECM), as successful techniques in evaluating the self-healing process in protective coatings.

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MECHANICAL PROPERTIES AND SELF-HEALING MECHANISM OF EPOXY MORTAR

Jurnal Teknologi ◽

10.11113/jt.v77.6306 ◽

2015 ◽

Vol 77 (12) ◽

Cited By ~ 5

Author(s):

Nur Farhayu Ariffin ◽

Mohd Warid Hussin ◽

Abdul Rahman Mohd Sam ◽

Han Seung Lee ◽

Nur Hafizah A. Khalid ◽

...

Keyword(s):

Epoxy Resin ◽

Healing Process ◽

Control Sample ◽

Pulse Velocity ◽

The Self ◽

Fine Aggregate ◽

Self Healing ◽

Velocity Measurements ◽

Hydroxyl Ion ◽

Healing Agent

Crack deformation in concrete start with hairline crack or micro-crack which can lead to major crack if not prevented. Crack can cause a major deterioration to the structure as liquid can penetrate inside and cause damage as a result; the durability of concrete will decrease. Self-healing concrete was introduced to automatically repair hairline crack or micro-crack without external intervention. Previous study had shown that by introducing bacteria into the concrete, the crack will heal itself. This paper presents the study on self-healing mortar by using epoxy resin without hardener as a self-healing agent. The self-healing process was evaluated using Ultrasonic Pulse Velocity measurements up to 180 days. Mortar specimens were prepared with mass ratio of 1:3 (cement: fine aggregate), water-cement ratio of 0.48 and 10% epoxy resin of cement content. All tested specimens were subjected to wet-dry curing; where compressive strength, flexural strength, and tensile splitting strength and self-healing mechanism were measured. The results obtained shows that, all strength properties of the self-healing epoxy mortar were significantly higher than the control sample and became constant at 10 % of epoxy resin content. Based on the pulse velocity measurements, after 60 days the cracks of the mortar healed automatically as a result of the reaction between the unhardened epoxy resin and hydroxyl ion from cement hydrate. This shows the ability of the epoxy to be used as self-healing agent.

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