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Self-Healing Concrete

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A special issue of Materials (ISSN 1996-1944).

Deadline for manuscript submissions: closed (15 November 2016) | Viewed by 89120

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Prof. Dr. Nele De Belie

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Magnel-Vandepitte Laboratory, Department of Structural Engineering and Building Materials, Ghent University, Technologiepark Zwijnaarde 60, B-9052 Gent, Belgium
Interests: sustainable construction; construction materials; concrete technology concrete durability; bacteria
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Dear Colleagues,

Concrete has become the most widely used construction material in the world. However, one important issue with concrete is its durability and long-term performance in non-ideal service environment.

Cracks are intrinsic concrete characteristics. However, cracking can endanger durability of the structure, since it eases the ingress of aggressive gasses and liquids. Certainly in case of chloride containing liquids or in case of high CO2 concentrations, there will be a higher risk of reinforcement corrosion, which compromises the long-term durability of the structure. Cracks furthermore drastically affect liquid tightness, which is a major problem in tunnels and underground structures. Current practice requires regular inspection, maintenance and repair, to ensure structural safety and functionality over the service life of the structure. These practices involve large direct and indirect costs, such as economic losses from traffic jams. Additionally, not all structures are easy to access for inspection and repair.

In their search to overcome these problems, researchers have been inspired by nature. Biological systems such as bones, skin or plants have the capacity to detect damage very quickly and repair the damage autonomously. The application of so-called “self-healing” concrete, which will in an autonomous way repair cracks, could reduce the maintenance costs drastically. Therefore, several concepts for self-healing concrete have been fundamentally explored, primarily during the last 10 years, with very promising results.

The intrinsic mechanism of crack healing in cementitious materials, due to hydration of unhydrated binder particles and precipitation of carbonate, is called autogenous healing. Since autogenous healing is more effective when crack widths are restricted, the use of a fiber reinforced engineered cementitious composite has been proposed. On the other hand, as water is always needed for autogenous healing to occur, several researchers investigated the possibility to add superabsorbent polymers (SAPs), also called hydrogels, to provide additional water. Finally, addition of agents, which are able to promote the deposition of crystals inside the crack has been studied. For instance, when certain types of (encapsulated) bacterial spores and nutrients are added into the concrete mix, the activation of the spores when a crack appears and water enters, will initiate the deposition of CaCO3 crystals at the crack faces.

Capsule based self-healing materials sequester a healing agent inside discrete capsules. When the capsules are ruptured by damage, the self-healing mechanism is triggered through the release and reaction of the healing agent in the region of damage. To make the capsule based approach practically applicable, research has been devoted to the development of capsules, which are able to survive the concrete mixing process while they do not influence the final mechanical properties too much. Vascular-based self-healing materials sequester the healing agent in a network of hollow tubes connected to the exterior of the structure.

Techniques to evaluate the self-healing efficiency also form an important research field. This includes regain in mechanical properties by destructive or non-destructive testing, e.g., by transmission of ultrasound waves, acoustic emission or resonance frequency measurements. Regain in air- and liquid-tightness is also very important. Fluid transmission can be registered directly or visualized by radiographic techniques, and related to durability test results. Early modelling work has been undertaken with lattice type models and hydration models, which can simulate self-healing due to the on-going hydration in a crack. Some analytical and numerical models are available to study the distribution of capsules in the concrete.

Prof. Dr. ir. Nele De Belie
Guest Editor

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Keywords

Concrete self-healing
Self-healing methodologies
Bacterial healing
Modelling of self-healing
Monitoring of self-healing

Published Papers (13 papers)

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Research

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2438 KiB

Open AccessArticle

Modeling Self-Healing of Concrete Using Hybrid Genetic Algorithm–Artificial Neural Network

by Ahmed Ramadan Suleiman and Moncef L. Nehdi

Materials 2017, 10(2), 135; https://doi.org/10.3390/ma10020135 - 07 Feb 2017

Cited by 73 | Viewed by 7416

Abstract

This paper presents an approach to predicting the intrinsic self-healing in concrete using a hybrid genetic algorithm–artificial neural network (GA–ANN). A genetic algorithm was implemented in the network as a stochastic optimizing tool for the initial optimal weights and biases. This approach can assist the network in achieving a global optimum and avoid the possibility of the network getting trapped at local optima. The proposed model was trained and validated using an especially built database using various experimental studies retrieved from the open literature. The model inputs include the cement content, water-to-cement ratio (w/c), type and dosage of supplementary cementitious materials, bio-healing materials, and both expansive and crystalline additives. Self-healing indicated by means of crack width is the model output. The results showed that the proposed GA–ANN model is capable of capturing the complex effects of various self-healing agents (e.g., biochemical material, silica-based additive, expansive and crystalline components) on the self-healing performance in cement-based materials. Full article

(This article belongs to the Special Issue Self-Healing Concrete)

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2890 KiB

Open AccessArticle

Optimization of a Binary Concrete Crack Self-Healing System Containing Bacteria and Oxygen

by Jinlong Zhang, Bixia Mai, Tingwei Cai, Jiayi Luo, Wanhan Wu, Bing Liu, Ningxu Han, Feng Xing and Xu Deng

Materials 2017, 10(2), 116; https://doi.org/10.3390/ma10020116 - 26 Jan 2017

Cited by 35 | Viewed by 5622

Abstract

An optimized strategy for the enhancement of microbially induced calcium precipitation including spore viability ensurance, nutrient selection and O2 supply was developed. Firstly, an optimal yeast extract concentration of 5 g/l in sporulation medium was determined based on viable spore yield and spore viability. Furthermore, the effects of certain influential factors on microbial calcium precipitation process of H4 in the presence of oxygen releasing tablet (ORT) were evaluated. The results showed that CaO2 is preferable to other peroxides in improving the calcium precipitation by H4. H4 strain is able to precipitate a highly insoluble calcium at the CaO2 dosage range of 7.5–12.5 g/l, and the most suitable spore concentration is 6 × 108 spores/ml when the spore viability (viable spore ratio) is approximately 50%. Lactate is the best carbon source and nitrate is the best nitrogen source for aerobic incubation. This work has laid a foundation of ternary self-healing system containing bacteria, ORT, and nutrients, which will be promising for the self-healing of cracks deep inside the concrete structure. Full article

(This article belongs to the Special Issue Self-Healing Concrete)

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3022 KiB

Open AccessArticle

Microcapsule-Type Self-Healing Protective Coating for Cementitious Composites with Secondary Crack Preventing Ability

by Dong-Min Kim, Hwan-Chul Yu, Hye-In Yang, Yu-Jin Cho, Kwang-Myong Lee and Chan-Moon Chung

Materials 2017, 10(2), 114; https://doi.org/10.3390/ma10020114 - 26 Jan 2017

Cited by 35 | Viewed by 4978

Abstract

A microcapsule-type self-healing protective coating with secondary crack preventing capability has been developed using a silanol-terminated polydimethylsiloxane (STP)/dibutyltin dilaurate (DD) healing agent. STP undergoes condensation reaction in the presence of DD to give a viscoelastic substance. STP- and DD-containing microcapsules were prepared by in-situ polymerization and interfacial polymerization methods, respectively. The microcapsules were characterized by Fourier-transform infrared (FT-IR) spectroscopy, optical microscopy, and scanning electron microscopy (SEM). The microcapsules were integrated into commercial enamel paint or epoxy coating formulations, which were applied on silicon wafers, steel panels, and mortar specimens to make dual-capsule self-healing protective coatings. When the STP/DD-based coating was scratched, self-healing of the damaged region occurred, which was demonstrated by SEM, electrochemical test, and water permeability test. It was also confirmed that secondary crack did not occur in the healed region upon application of vigorous vibration to the self-healing coating. Full article

(This article belongs to the Special Issue Self-Healing Concrete)

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16843 KiB

Open AccessArticle

A Novel Design of Autonomously Healed Concrete: Towards a Vascular Healing Network

by Pieter Minnebo, Glenn Thierens, Glenn De Valck, Kim Van Tittelboom, Nele De Belie, Danny Van Hemelrijck and Eleni Tsangouri

Materials 2017, 10(1), 49; https://doi.org/10.3390/ma10010049 - 08 Jan 2017

Cited by 83 | Viewed by 6287

Abstract

Concrete is prone to crack formation in the tensile zone, which is why steel reinforcement is introduced in these zones. However, small cracks could still arise, which give liquids and gasses access to the reinforcement causing it to corrode. Self-healing concrete repairs and seals these small (300 µm) cracks, preventing the development of corrosion. In this study, a vascular system, carrying the healing agent, is developed. It consists of tubes connected to a 3D printed distribution piece. This distribution piece has four outlets that are connected to the tubes and has one inlet, which is accessible from outside. Several materials were considered for the tubes, i.e., polymethylmethacrylate, starch, inorganic phosphate cement and alumina. Three-point-bending and four-point-bending tests proved that self-healing and multiple self-healing is possible with this developed vascular system. Full article

(This article belongs to the Special Issue Self-Healing Concrete)

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1753 KiB

Open AccessArticle

Ultrasonic Monitoring of the Interaction between Cement Matrix and Alkaline Silicate Solution in Self-Healing Systems

by Mohand Ait Ouarabi, Paola Antonaci, Fouad Boubenider, Antonio S. Gliozzi and Marco Scalerandi

Materials 2017, 10(1), 46; https://doi.org/10.3390/ma10010046 - 07 Jan 2017

Cited by 33 | Viewed by 5140

Abstract

Alkaline solutions, such as sodium, potassium or lithium silicates, appear to be very promising as healing agents for the development of encapsulated self-healing concretes. However, the evolution of their mechanical and acoustic properties in time has not yet been completely clarified, especially regarding their behavior and related kinetics when they are used in the form of a thin layer in contact with a hardened cement matrix. This study aims to monitor, using linear and nonlinear ultrasonic methods, the evolution of a sodium silicate solution interacting with a cement matrix in the presence of localized cracks. The ultrasonic inspection via linear methods revealed that an almost complete recovery of the elastic and acoustic properties occurred within a few days of healing. The nonlinear ultrasonic measurements contributed to provide further insight into the kinetics of the recovery due to the presence of the healing agent. A good regain of mechanical performance was ascertained through flexural tests at the end of the healing process, confirming the suitability of sodium silicate as a healing agent for self-healing cementitious systems. Full article

(This article belongs to the Special Issue Self-Healing Concrete)

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4917 KiB

Open AccessArticle

Experimental Study on Mechanical Properties and Porosity of Organic Microcapsules Based Self-Healing Cementitious Composite

by Xianfeng Wang, Peipei Sun, Ningxu Han and Feng Xing

Materials 2017, 10(1), 20; https://doi.org/10.3390/ma10010020 - 01 Jan 2017

Cited by 70 | Viewed by 5723

Abstract

Encapsulation of healing agents embedded in a material matrix has become one of the major approaches for achieving self-healing function in cementitious materials in recent years. A novel type of microcapsules based self-healing cementitious composite was developed in Guangdong Provincial Key Laboratory of Durability for Marine Civil Engineering, Shenzhen University. In this study, both macro performance and the microstructure of the composite are investigated. The macro performance was evaluated by employing the compressive strength and the dynamic modulus, whereas the microstructure was represented by the pore structure parameters such as porosity, cumulative-pore volume, and average-pore diameter, which are significantly correlated to the pore-size distribution and the compressive strength. The results showed that both the compressive strength and the dynamic modulus, as well as the pore structure parameters such as porosity, cumulative-pore volume, and average-pore diameter of the specimen decrease to some extent with the amount of microcapsules. However, the self-healing rate and the recovery rate of the specimen performance and the pore-structure parameters increase with the amount of microcapsules. The results should confirm the self-healing function of microcapsules in the cementitious composite from macroscopic and microscopic viewpoints. Full article

(This article belongs to the Special Issue Self-Healing Concrete)

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4668 KiB

Open AccessArticle

Simulation-Aided Design of Tubular Polymeric Capsules for Self-Healing Concrete

by Branko Šavija, João Feiteira, Maria Araújo, Sutima Chatrabhuti, Jean-Marie Raquez, Kim Van Tittelboom, Elke Gruyaert, Nele De Belie and Erik Schlangen

Materials 2017, 10(1), 10; https://doi.org/10.3390/ma10010010 - 24 Dec 2016

Cited by 33 | Viewed by 6875

Abstract

Polymeric capsules can have an advantage over glass capsules used up to now as proof-of-concept carriers in self-healing concrete. They allow easier processing and afford the possibility to fine tune their mechanical properties. Out of the multiple requirements for capsules used in this context, the capability of rupturing when crossed by a crack in concrete of a typical size is one of the most relevant, as without it no healing agent is released into the crack. This study assessed the fitness of five types of polymeric capsules to fulfill this requirement by using a numerical model to screen the best performing ones and verifying their fitness with experimental methods. Capsules made of a specific type of poly(methyl methacrylate) (PMMA) were considered fit for the intended application, rupturing at average crack sizes of 69 and 128 μm, respectively for a wall thickness of ~0.3 and ~0.7 mm. Thicker walls were considered unfit, as they ruptured for crack sizes much higher than 100 μm. Other types of PMMA used and polylactic acid were equally unfit for the same reason. There was overall good fitting between model output and experimental results and an elongation at break of 1.5% is recommended regarding polymers for this application. Full article

(This article belongs to the Special Issue Self-Healing Concrete)

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2045 KiB

Open AccessArticle

Quantification of the Service Life Extension and Environmental Benefit of Chloride Exposed Self-Healing Concrete

by Bjorn Van Belleghem, Philip Van den Heede, Kim Van Tittelboom and Nele De Belie

Materials 2017, 10(1), 5; https://doi.org/10.3390/ma10010005 - 23 Dec 2016

Cited by 64 | Viewed by 8053

Abstract

Formation of cracks impairs the durability of concrete elements. Corrosion inducing substances, such as chlorides, can enter the matrix through these cracks and cause steel reinforcement corrosion and concrete degradation. Self-repair of concrete cracks is an innovative technique which has been studied extensively during the past decade and which may help to increase the sustainability of concrete. However, the experiments conducted until now did not allow for an assessment of the service life extension possible with self-healing concrete in comparison with traditional (cracked) concrete. In this research, a service life prediction of self-healing concrete was done based on input from chloride diffusion tests. Self-healing of cracks with encapsulated polyurethane precursor formed a partial barrier against immediate ingress of chlorides through the cracks. Application of self-healing concrete was able to reduce the chloride concentration in a cracked zone by 75% or more. As a result, service life of steel reinforced self-healing concrete slabs in marine environments could amount to 60–94 years as opposed to only seven years for ordinary (cracked) concrete. Subsequent life cycle assessment calculations indicated important environmental benefits (56%–75%) for the ten CML-IA (Center of Environmental Science of Leiden University–Impact Assessment) baseline impact indicators which are mainly induced by the achievable service life extension. Full article

(This article belongs to the Special Issue Self-Healing Concrete)

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9312 KiB

Open AccessArticle

Micromechanical Properties of a New Polymeric Microcapsule for Self-Healing Cementitious Materials

by Leyang Lv, Erik Schlangen, Zhengxian Yang and Feng Xing

Materials 2016, 9(12), 1025; https://doi.org/10.3390/ma9121025 - 20 Dec 2016

Cited by 79 | Viewed by 7061

Abstract

Self-healing cementitious materials containing a microencapsulated healing agent are appealing due to their great application potential in improving the serviceability and durability of concrete structures. In this study, poly(phenol–formaldehyde) (PF) microcapsules that aim to provide a self-healing function for cementitious materials were prepared by an in situ polymerization reaction. Size gradation of the synthesized microcapsules was achieved through a series of sieving processes. The shell thickness and the diameter of single microcapsules was accurately measured under environmental scanning electron microscopy (ESEM). The relationship between the physical properties of the synthesized microcapsules and their micromechanical properties were investigated using nanoindentation. The results of the mechanical tests show that, with the increase of the mean size of microcapsules and the decrease of shell thickness, the mechanical force required to trigger the self-healing function of microcapsules increased correspondingly from 68.5 ± 41.6 mN to 198.5 ± 31.6 mN, featuring a multi-sensitive trigger function. Finally, the rupture behavior and crack surface of cement paste with embedded microcapsules were observed and analyzed using X-ray computed tomography (XCT). The synthesized PF microcapsules may find potential application in self-healing cementitious materials. Full article

(This article belongs to the Special Issue Self-Healing Concrete)

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7221 KiB

Open AccessArticle

New Surface-Treatment Technique of Concrete Structures Using Crack Repair Stick with Healing Ingredients

by Tae-Ho Ahn, Hong-gi Kim and Jae-Suk Ryou

Materials 2016, 9(8), 654; https://doi.org/10.3390/ma9080654 - 04 Aug 2016

Cited by 9 | Viewed by 6233

Abstract

This study focused on the development of a crack repair stick as a new repair method along with self-healing materials that can be used to easily repair the cracks in a concrete structure at the construction site. In developing this new repair technique, the self-healing efficiency of various cementitious materials was considered. Likewise, a crack repair stick was developed to apply to concrete structures with 0.3 mm or lower crack widths. The crack repair stick was made with different materials, such as cement, an expansive material (C₁₂A₇), a swelling material, and calcium carbonate, to endow it with a self-healing property. To verify the performance of the crack repair stick for concrete structures, two types of procedures (field experiment and field absorption test) were carried out. As a result of such procedures, it was concluded that the developed crack repair stick could be used on concrete structures to reduce repair expenses and for the improved workability, usability, and serviceability of such structures. On the other hand, to evaluate the self-healing performance of the crack repair stick, various tests were conducted, such as the relative dynamic modulus of elasticity test, the water tightness test, the water permeability test, observation via a microscope, and scanning electron microscope (SEM) analysis. From the results, it is found that water leakage can be prevented and that the durability of a concrete structure can be improved through self-healing. Also, it was verified that the cracks were perfectly closed after 28 days due to application of the crack repair stick. These results indicate the usability of the crack repair stick for concrete structures, and its self-healing efficiency. Full article

(This article belongs to the Special Issue Self-Healing Concrete)

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Review

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2868 KiB

Open AccessReview

Principles and Applications of Ultrasonic-Based Nondestructive Methods for Self-Healing in Cementitious Materials

by Eunjong Ahn, Hyunjun Kim, Sung-Han Sim, Sung Woo Shin and Myoungsu Shin

Materials 2017, 10(3), 278; https://doi.org/10.3390/ma10030278 - 10 Mar 2017

Cited by 61 | Viewed by 7079

Abstract

Recently, self-healing technologies have emerged as a promising approach to extend the service life of social infrastructure in the field of concrete construction. However, current evaluations of the self-healing technologies developed for cementitious materials are mostly limited to lab-scale experiments to inspect changes in surface crack width (by optical microscopy) and permeability. Furthermore, there is a universal lack of unified test methods to assess the effectiveness of self-healing technologies. Particularly, with respect to the self-healing of concrete applied in actual construction, nondestructive test methods are required to avoid interrupting the use of the structures under evaluation. This paper presents a review of all existing research on the principles of ultrasonic test methods and case studies pertaining to self-healing concrete. The main objective of the study is to examine the applicability and limitation of various ultrasonic test methods in assessing the self-healing performance. Finally, future directions on the development of reliable assessment methods for self-healing cementitious materials are suggested. Full article

(This article belongs to the Special Issue Self-Healing Concrete)

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2682 KiB

Open AccessReview

Crack Mitigation in Concrete: Superabsorbent Polymers as Key to Success?

by Arn Mignon, Didier Snoeck, Peter Dubruel, Sandra Van Vlierberghe and Nele De Belie

Materials 2017, 10(3), 237; https://doi.org/10.3390/ma10030237 - 28 Feb 2017

Cited by 119 | Viewed by 10458

Abstract

Cracking is a major concern in building applications. Cracks may arise from shrinkage, freeze/thawing and/or structural stresses, amongst others. Several solutions can be found but superabsorbent polymers (SAPs) seem to be interesting to counteract these problems. At an early age, the absorbed water by the SAPs may be used to mitigate autogenous and plastic shrinkage. The formed macro pores may increase the freeze/thaw resistance. The swelling upon water ingress may seal a crack from intruding fluids and may regain the overall water-tightness. The latter water may promote autogenous healing. The use of superabsorbent polymers is thus very interesting. This review paper summarizes the current research and gives a critical note towards the use of superabsorbent polymers in cementitious materials. Full article

(This article belongs to the Special Issue Self-Healing Concrete)

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20608 KiB

Open AccessReview

A Comprehensive Review of the Study and Development of Microcapsule Based Self-Resilience Systems for Concrete Structures at Shenzhen University

by Ning-Xu Han and Feng Xing

Materials 2017, 10(1), 2; https://doi.org/10.3390/ma10010002 - 22 Dec 2016

Cited by 52 | Viewed by 6108

Abstract

A review of the research activities and achievements at Shenzhen University is conducted in this paper concerning the creation and further development of novel microcapsule based self-resilience systems for their application in concrete structures. After a brief description of pioneering works in the field starting about 10 years ago, the principles raised in the relevant research are examined, where fundamental terms related to the concept of resilience are discussed. Several breakthrough points are highlighted concerning the three adopted comprehensive self-resilience systems, namely physical, chemical and microbial systems. The major challenges regarding evaluation are emphasized and further development concerning self-resilience in concrete structures will be addressed. Full article

(This article belongs to the Special Issue Self-Healing Concrete)

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