Quantification of crack-healing in novel bacteria-based self-healing concrete
TL;DR: In this article, a two-component bio-chemical self-healing agent consisting of bacterial spores and calcium lactate is released from the particle by crack ingress water, which results in physical closure of micro cracks.
Abstract: Crack formation is a commonly observed phenomenon in concrete structures. Although micro crack formation hardly affects structural properties of constructions, increased permeability due to micro crack networking may substantially reduce the durability of concrete structures due to risk of ingress of aggressive substances particularly in moist environments. In order to increase the often observed autogenous crack-healing potential of concrete, specific healing agents can be incorporated in the concrete matrix. The aim of this study was to quantify the crack-healing potential of a specific and novel two-component bio-chemical self-healing agent embedded in porous expanded clay particles, which act as reservoir particles and replace part of regular concrete aggregates. Upon crack formation the two-component bio-chemical agent consisting of bacterial spores and calcium lactate are released from the particle by crack ingress water. Subsequent bacterially mediated calcium carbonate formation results in physical closure of micro cracks. Experimental results showed crack-healing of up to 0.46 mm-wide cracks in bacterial concrete but only up to 0.18 mm-wide cracks in control specimens after 100 days submersion in water. That the observed doubling of crack-healing potential was indeed due to metabolic activity of bacteria was supported by oxygen profile measurements which revealed O2 consumption by bacteria-based but not by control specimens. We therefore conclude that this novel bio-chemical self-healing agent shows potential for particularly increasing durability aspects of concrete constructions in wet environments.
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TL;DR: In this paper, micro-capsules were applied to encapsulate bacterial spores for self-healing concrete and the results indicated that the healing ratio in the specimens with bio-microcapsules was higher (48%−80%) than in those without bacteria (18%−50%).
653 citations
TL;DR: A review of self-healing in concrete can be found in this article, where the types of healing agents and capsules used are evaluated based on the trigger mechanism used and attention has been paid to the properties regained due to selfhealing.
Abstract: Concrete is very sensitive to crack formation. As wide cracks endanger the durability, repair may be required. However, these repair works raise the life-cycle cost of concrete as they are labor intensive and because the structure becomes in disuse during repair. In 1994, C. Dry was the first who proposed the intentional introduction of self-healing properties in concrete. In the following years, several researchers started to investigate this topic. The goal of this review is to provide an in-depth comparison of the different self-healing approaches which are available today. Among these approaches, some are aimed at improving the natural mechanism of autogenous crack healing, while others are aimed at modifying concrete by embedding capsules with suitable healing agents so that cracks heal in a completely autonomous way after they appear. In this review, special attention is paid to the types of healing agents and capsules used. In addition, the various methodologies have been evaluated based on the trigger mechanism used and attention has been paid to the properties regained due to self-healing.
603 citations
Cites background or methods from "Quantification of crack-healing in ..."
...Wiktor and Jonkers [105] noticed that bacterial crack healing started after 20 days immersion in water and continued until 100 days of water immersion was reached....
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...After previous unsuccessful trials (see Section “Hydration and Crystallization”), Jonkers and coworkers [82,83,103–106], loaded expanded clay particles with both bacterial spores and calcium lactate (CaC6H10O6), which served as nutrient for the spores....
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TL;DR: In this article, the authors present the process of crack healing phenomenon in concrete by microbial activity of bacteria, Bacillus subtilis, which is introduced in concrete via direct incorporation, and thorough various carrier compounds namely light weight aggregate and graphite nano platelets.
375 citations
Ghent University1, Katholieke Universiteit Leuven2, University of Cambridge3, Polytechnic University of Turin4, Riga Technical University5, Institut national des sciences appliquées de Rennes6, Cardiff University7, Polytechnic University of Milan8, University of Novi Sad9, Lodz University of Technology10, University of Bath11, Warsaw University of Technology12, Polytechnic University of Valencia13, Delft University of Technology14
TL;DR: In this paper, the state-of-the-art of self-healing concrete is provided, covering autogenous or intrinsic healing of traditional concrete followed by stimulated autogenous healing via use of mineral additives, crystalline admixtures or (superabsorbent) polymers.
Abstract: The increasing concern for safety and sustainability of structures is calling for the development of smart self-healing materials and preventive repair methods. The appearance of small cracks (<300 µm in width) in concrete is almost unavoidable, not necessarily causing a risk of collapse for the structure, but surely impairing its functionality, accelerating its degradation, and diminishing its service life and sustainability. This review provides the state-of-the-art of recent developments of self-healing concrete, covering autogenous or intrinsic healing of traditional concrete followed by stimulated autogenous healing via use of mineral additives, crystalline admixtures or (superabsorbent) polymers, and subsequently autonomous self-healing mechanisms, i.e. via, application of micro-, macro-, or vascular encapsulated polymers, minerals, or bacteria. The (stimulated) autogenous mechanisms are generally limited to healing crack widths of about 100–150 µm. In contrast, most autonomous self-healing mechanisms can heal cracks of 300 µm, even sometimes up to more than 1 mm, and usually act faster. After explaining the basic concept for each self-healing technique, the most recent advances are collected, explaining the progress and current limitations, to provide insights toward the future developments. This review addresses the research needs required to remove hindrances that limit market penetration of self-healing concrete technologies.
355 citations
TL;DR: This review discusses how optimization of MICP is attempted for different engineering applications in an effort to highlight the key research and development questions necessary to move MICP technologies toward commercial scale applications.
Abstract: Microbially-induced calcium carbonate (CaCO3) precipitation (MICP) is a widely explored and promising technology for use in various engineering applications. In this review, CaCO3 precipitation induced via urea hydrolysis (ureolysis) is examined for improving construction materials, cementing porous media, hydraulic control, and remediating environmental concerns. The control of MICP is explored through the manipulation of three factors: (1) the ureolytic activity (of microorganisms), (2) the reaction and transport rates of substrates, and (3) the saturation conditions of carbonate minerals. Many combinations of these factors have been researched to spatially and temporally control precipitation. This review discusses how optimization of MICP is attempted for different engineering applications in an effort to highlight the key research and development questions necessary to move MICP technologies toward commercial scale applications.
303 citations
Cites background from "Quantification of crack-healing in ..."
...Another approach to concrete fracture remediation is self-healing, where healing agents are released or activated when fractures form (Wiktor & Jonkers 2011; Wang et al. 2012)....
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...Cracks form in concrete due to aging and/or freeze thaw cycles which lead to pathways for corrosive fluid intrusion (Bang et al. 2010; Jonkers et al. 2010; Achal et al. 2011b; Wiktor & Jonkers 2011)....
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References
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01 Dec 1968
TL;DR: In this article, the authors present the following properties of concrete: Elasticity, Shrinkage and Creep, Durabilty of Concrete, Freezing and Thawing, and Chlorides.
Abstract: 1. Portland Cement. 2. Cementitious Materials Of Different Types. 3. Properties Of Aggregate. 4. Fresh Concrete. 5. Admixtures. 6. Strength Of Concrete. 7. Further Aspects Of Hardened Concrete. 8. Temperature Effects In Concrete. 9. Elasticity, Shrinkage And Creep. 10. Durabilty Of Concrete. 11. Effects Of Freezing And Thawing And Of Chlorides. 12. Testing Of Hardened Concrete. 13. Concretes With Particular Properties. 14. Selection Of Concrete Mix Proportions (Mix Design). Appendices. Index.
5,713 citations
TL;DR: In this paper, the use of microbially induced carbonates as a binder material, i.e., biocementation, is discussed, for the improvement of compressive strength and the remediation of cracks.
1,074 citations
TL;DR: In this article, a specific group of alkali-resistant spore-forming bacteria related to the genus Bacillus was selected for this purpose, and the bacterial spores directly added to the cement mixture remained viable for a period up to 4 months.
1,070 citations
TL;DR: In this paper, the authors investigated the effect of self-healing in cracks on the functional reliability of structures subjected to water-pressure loads and showed that the formation of calcite in the crack is almost the sole cause for the autogenous healing.
Abstract: The well-known practical phenomenon of autogenous healing in cracks plays a significant role in relation to the functional reliability of structures subjected to water-pressure loads. Because of the autogenous healing, the water flow through the cracks gradually reduces with time, and in extreme cases, the cracks seal completely. In the past, there has been no deliberate technical exploitation of self-healing, because too little is known about the phenomenon itself and about the chemical/physical processes involved. Based on theoretical and experimental research, the effect of crack healing was investigated on a larger scale for the first time. The experimental studies showed the formation of calcite in the crack to be almost the sole cause for the autogenous healing. A comprehensive theoretical discussion of the laws, which govern the calcite nucleation and the subsequent crystal growth of water-bearing cracks in concrete, revealed that the crystal growth responds to two different crystal growth processes that are determined by the changes in the chemical and physical conditions in the crack. Further, the crystal growth rate is dependent on the crack width and water pressure, whereas concrete composition and water hardness have no influence on autogenous healing. On the basis of the experimental studies, an algorithm that can be used to estimate the reduction in water over time as a result of autogenous healing was developed.
775 citations