Self-healing concrete by use of microencapsulated bacterial spores

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.

https://biblio.ugent.be/publication/4144354/file/4144368.pdf

Self-Healing in Cementitious Materials—A Review

Crack healing in concrete using various bio influenced self-healing techniques

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.

/pdf/a-review-of-self-healing-concrete-for-damage-management-of-51xbtkvzxq.pdf

A review of self-healing concrete for damage management of structures

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.

/pdf/engineered-applications-of-ureolytic-biomineralization-a-koh27fqr30.pdf

Engineered applications of ureolytic biomineralization: a review.

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.

Quantification of crack-healing in novel bacteria-based self-healing concrete

Bacteria-based self-healing concrete to increase liquid tightness of cracks

Self-healing concrete holds promising benefits to reduce the cost for concrete maintenance and repair as cracks are autonomously repaired without any human intervention. In this study, the application of a carbonate precipitating bacterium Bacillus sphaericus was explored. Regarding the harsh condition in concrete, B. sphaericus spores were first encapsulated into a modified-alginate based hydrogel (AM-H) which was proven to have a good compatibility with the bacteria and concrete regarding the influence on bacterial viability and concrete strength. Experimental results show that the spores were still viable after encapsulation. Encapsulated spores can precipitate a large amount of CaCO3 in/on the hydrogel matrix (around 70% by weight). Encapsulated B. sphaericus spores were added into mortar specimens and bacterial in situ activity was demonstrated by the oxygen consumption on the mimicked crack surface. While specimens with free spores added showed no oxygen consumption. This indicates the efficient protection of the hydrogel for spores in concrete. To conclude, the AM-H encapsulated carbonate precipitating bacteria have great potential to be used for crack self-healing in concrete applications.

https://biblio.ugent.be/publication/7095976/file/7095983.pdf

Application of modified-alginate encapsulated carbonate producing bacteria in concrete: a promising strategy for crack self-healing

This work presents a bacteria-based bead for potential self-healing concrete applications in low-temperature marine environments. The bead consisting of calcium alginate encapsulated bacterial spores and mineral precursor compounds was assessed for: oxygen consumption, swelling, and its ability to form a biocomposite in a simulative marine concrete crack solution (SMCCS) at 8 °C. After six days immersion in the SMCCS the bacteria-based beads formed a calcite crust on their surface and calcite inclusions in their network, resulting in a calcite–alginate biocomposite. Beads swelled by 300% to a maximum diameter of 3 mm, while theoretical calculations estimate that 0.112 g of the beads were able to produce ~1 mm3 of calcite after 14 days immersion; providing the bead with considerable crack healing potential. The bacteria-based bead shows great potential for the development of self-healing concrete in low-temperature marine environments, while the formation of a biocomposite healing material represents an exciting avenue for self-healing concrete research.

http://iopscience.iop.org/article/10.1088/0964-1726/25/8/084008/pdf

A bacteria-based bead for possible self-healing marine concrete applications

The concept of self-healing concrete—a concrete which can autonomously repair itself after crack formation, with no or limited human intervention—has received a lot of attention over the past 10 years as it could help structures to last longer and at a lower maintenance cost. This paper gives an overview on the key aspects and recent advances in the development of the bacteria-based self-healing concrete developed at the University of Technology of Delft (The Netherlands). Research started with the screening and selection of concrete compatible bacteria and nutrients. Several types of encapsulated bacteria and nutrients have been developed and tested. The functionality of these healing agents was demonstrated by showing metabolic activity of activated bacterial spores by oxygen consumption measurements and by regain of material functionality in form of regain of water tightness. Besides development of bacteria-based self-healing concrete, a bacteria-based repair mortar and liquid system were developed for the treatment of aged concrete structures. Field trials have been carried out with either type of bacteria-based systems and the promising results have led to a spinoff company Basilisk Self-Healing Concrete with the aim to further develop these systems and bring them to the market.

https://iopscience.iop.org/article/10.1088/0964-1726/25/8/084006/pdf

Virginie Wiktor

Papers

Quantification of crack-healing in novel bacteria-based self-healing concrete

Bacteria-based self-healing concrete to increase liquid tightness of cracks

Application of modified-alginate encapsulated carbonate producing bacteria in concrete: a promising strategy for crack self-healing

A bacteria-based bead for possible self-healing marine concrete applications

Bacteria-based concrete: from concept to market