Smart Additives for Self-Sealing and Self-Healing Concrete

2012 ◽  
Vol 1488 ◽  
Author(s):  
Nele De Belie ◽  
Kim Van Tittelboom ◽  
Didier Snoeck ◽  
Jianyun Wang
Keyword(s):  
Polymer Structure ◽  
Self Healing ◽  
Crack Healing ◽  
Broken Bones ◽  
Crack Sealing ◽  
Healing Efficiency ◽  
The Matrix ◽  
First Results ◽  
Small Cracks ◽  
Concrete Matrix

ABSTRACTLike broken bones are able to heal themselves, it would be desirable that damaged concrete may be repaired autonomously as high costs are related to the repair. Actually, concrete already has some self-healing properties; when cracks appear, water enters and reacts with unhydrated cement grains which results in crack healing. However, only small cracks can be healed in this way. Therefore, we want to improve the self-healing efficiency by adapting the concrete matrix. By introducing high amounts of fibers several small cracks appear instead of one large crack. Combination with superabsorbent polymers, also called hydrogels, provides immediate crack sealing. Another methodology is to embed encapsulated polymeric agents in the matrix. When cracks appear, the capsules break and the agent is released. Upon contact of both components, they react and the crack is healed. This technique is also combined with CaCO3 precipitation of bacteria. In that case, not only polymers but also bacteria and nutrients are encapsulated and released upon cracking. First the polymer reacts, later the bacteria start to convert the nutrients into CaCO3 crystals which make the polymer structure denser and thus seal the cracks completely. As crack healing by means of bacteria uses a repair material which is more compatible with concrete we also try to seal cracks by only using bacterial CaCO3. Therefore, bacteria are embedded inside aggregates. Upon cracking, bacteria are exposed to the air and when water enters the crack bacteria become active and fill the crack with CaCO3. From the first results it was noticed that due to autonomous crack healing, water permeability is reduced and regain in mechanical properties is obtained. This means that more durable concrete structures may be obtained by using the proposed self-healing techniques.

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

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.

scholarly journals Feasibility and Compatibility of a Biomass Capsule System in Self-Healing Concrete

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 958
Author(s):  
Arkabrata Sinha ◽  
Qi Wang ◽  
Jianqiang Wei
Keyword(s):  
Strength Degradation ◽  
Survival Ratio ◽  
Self Healing ◽  
Crack Healing ◽  
Mortar Strength ◽  
Concrete Properties ◽  
Promising Strategy ◽  
Healing Efficiency ◽  
Biomass Component ◽  
Crack Repair

Cracking can facilitate deteriorations of concrete structures via various mechanisms by providing ingress pathways for moisture and aggressive chemicals. In contrast to conventional maintenance methods, self-healing is a promising strategy for achieving automatic crack repair without human intervention. However, in capsule-based self-healing concrete, the dilemma between capsules’ survivability and crack healing efficiency is still an unfathomed challenge. In this study, the feasibility of a novel property-switchable capsule system based on a sustainable biomass component, polylactic acid, is investigated. Capsules with different geometries and dimensions were studied focusing on the compatibility with concrete, including survivability during concrete mixing, influence on mortar and concrete properties, and property evolution of the capsules. The results indicate that the developed elliptical capsules can survive regular concrete mixing with a survival ratio of 95%. In concrete containing 5 vol.% of gravel-level capsules, the compressive strength was decreased by 13.5% after 90 days, while the tensile strength was increased by 4.8%. The incorporation of 2 vol.% of sand-level capsules did not impact the mortar strength. Degradation and switchable properties triggered by the alkaline matrix of cement were observed, revealing the potential of this novel biomass capsule system in achieving both high survivability and self-healing efficiency in concrete.

scholarly journals Durability of self-healing concrete

2019 ◽  
Vol 289 ◽  
pp. 01003 ◽  
Author(s):  
Nele De Belie ◽  
Bjorn Van Belleghem ◽  
Yusuf Çağatay Erşan ◽  
Kim Van Tittelboom
Keyword(s):  
Corrosion Behaviour ◽  
Healing Process ◽  
Chloride Ingress ◽  
Self Healing ◽  
Crack Healing ◽  
Nacl Solution ◽  
Visual Damage ◽  
Chloride Profiles ◽  
Cracked Specimens ◽  
Concrete Matrix

Application of self-healing concrete reduces the need for expensive maintenance and repair actions. However, the durability of self-healing concrete has only been scarcely investigated. Here, recent results are presented regarding the resistance of self-healing concrete to chloride ingress. For self-healing concrete with macro-encapsulated polyurethane, chloride profiles and electron probe microanalysis indicated that this mechanism was efficient to reduce the chloride penetration into the crack and from the crack into the concrete matrix [1]. Furthermore, the corrosion behaviour of reinforced concrete specimens subjected to cyclic exposure with a NaCl solution was studied [2]. The electrochemical measurements indicated that autonomous crack healing could significantly reduce the corrosion in the propagation stage. No visual damage could be detected on the rebars after 44 weeks of exposure. On the contrary, cracked specimens without integrated self-healing mechanism, reached a state of active corrosion after 10 weeks of exposure and after 26 weeks clear pitting damage was observed on the rebars. While self-healing by encapsulated polyurethane is complete after one day, bacteria-based products take several weeks to heal a 300 µm crack. Bacterial granules containing denitrifying cultures released nitrite as an intermediate metabolic product which protected the reinforcement during the crack healing process [3].

Evaluating the Self-Healing Efficiency of Hydrogel-Encapsulated Bacteria in Concrete

2020 ◽  
Vol 2674 (6) ◽  
pp. 113-123 ◽  
Author(s):  
Ahsennur Soysal ◽  
Jose Milla ◽  
Gary M King ◽  
Marwa Hassan ◽  
Tyson Rupnow
Keyword(s):  
Alginate Beads ◽  
The Self ◽  
Self Healing ◽  
Bacterial Strains ◽  
Crack Sealing ◽  
Healing Efficiency ◽  
Maximum Crack ◽  
Encapsulated Bacteria ◽  
Curing Regime ◽  
Bacterial Concrete

Bacterial concrete has become one of the most promising self-healing alternatives owing to its capability to seal crack widths through microbial-induced calcite precipitation (MICP). In this study, two bacterial strains were embedded at varying dosages (by weight of cement) in concrete. Beam specimens were used to quantify the maximum crack-sealing efficiency, whereas cylinder samples were used to determine their effects on the intrinsic mechanical properties of concrete, as well as its stiffness recovery over time after inducing damage. The concrete specimens were cured in wet–dry cycles to enable healing. Results showed that the specimen groups with the highest calcium alginate concentrations (including the control specimens with embedded alginate beads but no bacteria) resulted in the greatest increase in stiffness recovery. Similarly, the beam samples containing alginate beads (also including the Control 3%C specimen group) had superior crack-healing efficiencies to the control samples without alginate beads (Control NC). This was attributed to the alginate beads acting as a reservoir that can further enhance the autogenous healing capability of concrete. Based on the results of this study, further research is recommended to explore factors that can maximize the self-healing mechanism of bacterial concrete through MICP and determine whether an alternative encapsulation mechanism, nutrient selection, curing regime, or bacterial strain is needed.

scholarly journals Analytical solution on dosage of self-healing capsules in materials with two-dimensional multi-shaped crack patterns

2018 ◽  
Vol 25 (6) ◽  
pp. 1229-1239 ◽  
Author(s):  
Jianjun Lin ◽  
Huisu Chen ◽  
Zhong Lv ◽  
Yujiang Wang
Keyword(s):  
Crack Size ◽  
Self Healing ◽  
Two Dimensional ◽  
Crack Healing ◽  
Crack Patterns ◽  
Hitting Probability ◽  
Crack System ◽  
Healing Efficiency ◽  
Shaped Crack ◽  
Complex Crack

AbstractThis article presents a numerical method for determining the dosage of pre-embedded capsules in self-healing materials with complex crack patterns. The crack distribution on the surface of materials is simplified into a two-dimensional (2D) multi-shaped geometrical structure composed of triangles, rhombuses, and hexagons with specified area fractions, and further decomposed into three separate mono-shaped crack systems. Then, the dosage of capsules required to heal the cracks in each mono-shaped crack system is computed. According to the area fraction of each mono-shaped polygon in the whole system, the integrated models of crack-hitting probability by the capsules and the capsule dosage for the multi-shaped crack system are derived. The analytical results reveal that the dosage of capsules significantly depends on the spatial distribution of the cracks and the ratio of the capsule length to the crack size. For a certain fixed crack pattern, the size and dosage of capsules will strongly affect crack healing efficiency.

scholarly journals Understanding the Impacts of Healing Agents on the Properties of Fresh and Hardened Self-Healing Concrete: A Review

Processes ◽  
2021 ◽  
Vol 9 (12) ◽  
pp. 2206
Author(s):  
Harry Hermawan ◽  
Peter Minne ◽  
Pedro Serna ◽  
Elke Gruyaert
Keyword(s):  
Mix Design ◽  
Hardened Concrete ◽  
Self Healing ◽  
Conventional Concrete ◽  
Concrete Mix Design ◽  
Crack Sealing ◽  
Healing Efficiency ◽  
Concrete Mix ◽  
Healing Agent ◽  
The Impact

Self-healing concrete has emerged as one of the prospective materials to be used in future constructions, substituting conventional concrete with the view of extending the service life of the structures. As a proof of concept, over the last several years, many studies have been executed on the effectiveness of the addition of self-healing agents on crack sealing and healing in mortar, while studies on the concrete level are still rather limited. In most cases, mix designs were not optimized regarding the properties of the fresh concrete mixture, properties of the hardened concrete and self-healing efficiency, meaning that the healing agent was just added on top of the normal mix (no adaptations of the concrete mix design for the introduction of healing agents). A comprehensive review has been conducted on the concrete mix design and the impact of healing agents (e.g., crystalline admixtures, bacteria, polymers and minerals, of which some are encapsulated in microcapsules or macrocapsules) on the properties of fresh and hardened concrete. Eventually, the remaining research gaps in knowledge are identified.

Novel Self-Healing Systems: Expanding and Inhibited Healing Agents

2014 ◽  
Author(s):  
S. I. Rae ◽  
I. P. Bond ◽  
R. S. Trask ◽  
D. F. Wass
Keyword(s):  
Matrix Material ◽  
Fibre Reinforcement ◽  
Self Healing ◽  
New Approach ◽  
Healing Efficiency ◽  
Mechanical And Physical Properties ◽  
The Matrix ◽  
Healing Agent ◽  
To Come ◽  
And Performance

A new approach to self-healing systems is presented that aims to overcome the inherent drawbacks of conventional liquid resin based healing systems within composites. Finite embedded systems offer limited healing potential for small volume delaminations and as such cannot effectively heal large damage volumes often associated with shear damaged sandwich panel structures or debonding between skin and core. An expanding polymer based approach aims to overcome such limitations. The mechanical and physical properties of a prepared polyepoxide foam are investigated and how the inclusion of a carbon fibre reinforcement within the foam affects processability and performance. The healing efficiency of different polymer foams to heal damaged structures is also investigated. A secondary investigation is also presented that aimed to overcome the drawbacks associated with the requirement for stoichiometric mixing of two part healing agents, or for healing agent to come into direct contact with a catalyst embedded within the matrix material. Different approaches were taken to develop a self-healing system that once deployed required no additional mixing or stimuli for healing to occur.

scholarly journals Bacteria-based self-healing concrete: evaluation of full scale demonstrator projects

2020 ◽  
Vol 4 ◽  
pp. 138-144
Author(s):  
Renée Mors ◽  
Henk M. Jonkers
Keyword(s):  
Crack Width ◽  
Functional Performance ◽  
Full Scale ◽  
Self Healing ◽  
Crack Healing ◽  
Repair Mortar ◽  
Crack Sealing ◽  
University Of Technology ◽  
Healing Agent ◽  
Negative Side Effects

Bacteria-based self-healing concrete is an innovative concrete that contains a self-healing agent that provides the material with enhanced autonomous crack-sealing performance. A specific type of this concrete, based on a healing agent composed of bacterial spores and lactate as carbon source, has been developed and applied by the Delft University of Technology for over ten years. Under laboratory conditions it was proven that, depending on the dosage of healing agent, self-healing of cracks up to 0.8 mm widths occurs. As such the material potentially allows reduction of steel reinforcement used for crack width limitation in watertight constructions. Application of  self-healing concrete would therefore not only result in a reduction of costs but also in improvement of environmental performance (lower CO2 footprint) and ease of in situ casting due to reduction of use of steel in waterproof applications. However, according to the EN 1990 Eurocode (Basis of structural design), customary application of a novel type of concrete must be preceded by full scale demonstrators proving evidence for safe and functional performance. In this contribution we portray full scale application of bacteria-based self-healing agent as developed by the Delft research group in two repair mortar- and in two concrete construction demonstrator projects. These demonstrator projects show that addition of the bacteria-based self-healing agent to the concrete mix is safe as no negative side effects on construction performance was observed. However, it also proved difficult to find evidence for increased crack-healing performance as cracking in the demonstrator constructions hardly occurred. In further full scale demonstrators we therefore plan to drastically reduce amount of crack width-restraining reinforcement to show crack-healing capacity and potential to save on use of reinforcement steel in watertight concrete constructions.

scholarly journals Ultrarobust, tough and highly stretchable self-healing materials based on cartilage-inspired noncovalent assembly nanostructure

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Yuyan Wang ◽  
Xin Huang ◽  
Xinxing Zhang
Keyword(s):  
Spider Silk ◽  
Self Healing ◽  
High Toughness ◽  
Healing Efficiency ◽  
Strong Interfacial Interaction ◽  
Highly Stretchable ◽  
Noncovalent Bonds ◽  
Actuation Devices ◽  
Noncovalent Bonding ◽  
Polyurethane Matrix

AbstractSelf-healing materials integrated with excellent mechanical strength and simultaneously high healing efficiency would be of great use in many fields, however their fabrication has been proven extremely challenging. Here, inspired by biological cartilage, we present an ultrarobust self-healing material by incorporating high density noncovalent bonds at the interfaces between the dentritic tannic acid-modified tungsten disulfide nanosheets and polyurethane matrix to collectively produce a strong interfacial interaction. The resultant nanocomposite material with interwoven network shows excellent tensile strength (52.3 MPa), high toughness (282.7 MJ m‒3, which is 1.6 times higher than spider silk and 9.4 times higher than metallic aluminum), high stretchability (1020.8%) and excellent healing efficiency (80–100%), which overturns the previous understanding of traditional noncovalent bonding self-healing materials where high mechanical robustness and healing ability are mutually exclusive. Moreover, the interfacical supramolecular crosslinking structure enables the functional-healing ability of the resultant flexible smart actuation devices. This work opens an avenue toward the development of ultrarobust self-healing materials for various flexible functional devices.

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