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].

scholarly journals Perpendicular-to-crack chloride ingress in cracked and autonomously healed concrete

2018 ◽  
Vol 199 ◽  
pp. 02011
Author(s):  
Bjorn Van Belleghem ◽  
Philip Van den Heede ◽  
Kim Van Tittelboom ◽  
Nele De Belie
Keyword(s):  
Concrete Structures ◽  
Chloride Ions ◽  
Chloride Penetration ◽  
Chloride Ingress ◽  
Crack Healing ◽  
Crack Location ◽  
Spray Method ◽  
Surface Visualization ◽  
Chloride Profiles ◽  
Concrete Matrix

Cracks in reinforced concrete structures exposed to a marine environment or de-icing salts can cause major durability issues due do accelerated ingress of chloride ions. In this study, the influence of autonomous crack healing by means of encapsulated polyurethane on the chloride ingress perpendicular to cracks was evaluated. This was done quantitatively by determining perpendicular-to-crack chloride profiles by means of profile grinding followed by potentiometric titration and qualitatively through visualization of the chloride penetration front by means of the AgNO3 spray method. The resulting chloride profiles showed that the healing mechanism was able to reduce the chloride concentrations in the direct vicinity of the crack to a large extent and to reduce the perpendicular-to-crack chloride penetration, especially further away from the exposed surface. Visualization of the chloride penetration front showed some variation in crack healing. For some healed samples almost no additional chloride ingress was found compared to uncracked samples, others showed a slightly enhanced ingress at the crack location but less perpendicular-to-crack chloride penetration compared to untreated cracked samples. Generally, the reduced amount of chlorides present in the concrete matrix due to crack healing will enhance the durability and service life of concrete structures.

scholarly journals Tracking capsule activation and crack healing in a microcapsule-based self-healing polymer

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
S. A. McDonald ◽  
S. B. Coban ◽  
N. R. Sottos ◽  
P. J. Withers
Keyword(s):  
Healing Process ◽  
Polymeric Materials ◽  
Time Lapse ◽  
Repair Process ◽  
Three Dimensions ◽  
Crack Plane ◽  
Self Healing ◽  
Crack Healing ◽  
Healing Agent ◽  
First Time

AbstractStructural polymeric materials incorporating a microencapsulated liquid healing agent demonstrate the ability to autonomously heal cracks. Understanding how an advancing crack interacts with the microcapsules is critical to optimizing performance through tailoring the size, distribution and density of these capsules. For the first time, time-lapse synchrotron X-ray phase contrast computed tomography (CT) has been used to observe in three-dimensions (3D) the dynamic process of crack growth, microcapsule rupture and progressive release of solvent into a crack as it propagates and widens, providing unique insights into the activation and repair process. In this epoxy self-healing material, 150 µm diameter microcapsules within 400 µm of the crack plane are found to rupture and contribute to the healing process, their discharge quantified as a function of crack propagation and distance from the crack plane. Significantly, continued release of solvent takes place to repair the crack as it grows and progressively widens.

Bio-inspired self-healing cementitious mortar using Bacillus subtilis immobilized on nano-/micro-additives

2018 ◽  
Vol 30 (1) ◽  
pp. 3-15 ◽  
Author(s):  
Rao Arsalan Khushnood ◽  
Siraj ud din ◽  
Nafeesa Shaheen ◽  
Sajjad Ahmad ◽  
Filza Zarrar
Keyword(s):  
Compressive Strength ◽  
Bacillus Subtilis ◽  
Iron Oxide ◽  
Cement Mortar ◽  
Healing Process ◽  
Main Concern ◽  
Scanning Electron Micrographs ◽  
Self Healing ◽  
Micro Cracks ◽  
Cracked Specimens

Bio-inspired self-healing strategies are much innovative and potentially viable for the production of healable cement mortar matrix. The present research explores the feasibility of gram-positive “Bacillus subtilis” microorganisms in the effective healing of nano-/micro-scale-induced structural and non-structural cracks. The main concern related to the survival of such microorganisms in cementitious environment has been successfully addressed by devising proficient immobilization scheme coherently. The investigated immobilizing media includes iron oxide nano-sized particles, micro-sized limestone particles, and milli-sized siliceous sand. The effect of induced B. subtilis microorganisms immobilized on nano-micro-additives was analyzed by the quantification of average compressive resistance of specimens (ASTM C109) and healing evaluation. The healing process was mechanically gauged by compressive strength regain of pre-cracked specimens after the healing period of 28 days. The pre-cracking load was affixed at 80% of ultimate compressive stress “[Formula: see text]” while the age of pre-cracking was kept variable as 3, 7, 14, and 28 days to precisely correlate healing effectiveness as the function of cracking period. The healing mechanism was further explored by examining the healed micro-crack using field emission scanning electron micrographs, energy dispersive x-ray spectrographs, and thermogravimetry. The results revealed that B. subtilis microorganisms contribute extremely well in the improvement of compressive strength and efficient healing process of pre-cracked cement mortar formulations. The iron oxide nano-sized particles were found to be the most effective immobilizer for preserving B. subtilis microbes till the generation of cracks followed by siliceous sand and limestone particles. The micro-graphical and chemical investigations endorsed the mechanical measurements by evidencing calcite precipitation in the induced nano-/micro-cracks as a result of microbial activity.

scholarly journals Performance of corrosion protection of carbon steel with cerium modified phosphate–permanganate coatings and a layer of silane doped with cerium

Chemija ◽  
2019 ◽  
Vol 30 (3) ◽  
Author(s):  
O. Girčienė ◽  
L. Gudavičiūtė ◽  
A. Martušienė ◽  
V. Jasulaitienė ◽  
A. Selskienė ◽  
...  
Keyword(s):  
Carbon Steel ◽  
Photoelectron Spectroscopy ◽  
Electrochemical Impedance ◽  
Corrosion Behaviour ◽  
Low Frequency ◽  
Cerium Nitrate ◽  
Self Healing ◽  
Nacl Solution ◽  
Composition And Structure ◽  
Eis Measurements

This work was aimed to evaluate the effect of bis-[triethoxysilylpropyl] tetrasulfide (BTESPT) doped with cerium nitrate, as a corrosion inhibitor, on improved corrosion resistance of samples of carbon steel with a phosphate–permanganate layer in a 0.5 M NaCl solution. The main goal of the present work was to compare self-healing capacities of cerium conversion coatings and cerium as an additive inhibitor to silane. The composition and structure of the investigated samples were characterized by scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS) techniques, while the corrosion behaviour was investigated applying voltametric and electrochemical impedance spectroscopy (EIS) measurements. The results of EIS measurements performed during 24 h immersion of the investigated samples into the 0.5 M NaCl solution revealed that the layer of silane doped with Ce was more protective than that of the non-modified one. It has been determined that the presence of cerium nitrate in the silane coating can lead to high values of low frequency impedance due to the healing of the defect.

scholarly journals The influence of SAPs on chloride ingress in cracked concrete

2019 ◽  
Vol 289 ◽  
pp. 08007 ◽  
Author(s):  
Tim Van Mullem ◽  
Robby Caspeele ◽  
Nele De Belie
Keyword(s):  
Chloride Solution ◽  
Chloride Ingress ◽  
Self Healing ◽  
Cracked Concrete ◽  
Chloride Migration ◽  
Swelling Capacity ◽  
Healing Agent ◽  
Additional Water ◽  
Lower Chloride ◽  
Concrete Matrix

Super Absorbent Polymers (SAPs) have proven to be effective as a self-healing agent for regaining the liquid tightness of cracked concrete. This is due to their large swelling capacity which allows them to (partially) block cracks which are in contact with water or moisture. Additionally, they are able to release this water when the climate becomes drier, thereby promoting the autogenous healing capacity of the concrete matrix. The effect SAPs have on chloride migration into cracked concrete is still unknown. The swelling capacity of the SAPs might partially block the crack, but this does not necessarily mean that the chloride ingress into the crack is lower. Especially, since the porosity of concrete with SAPs is slightly higher when additional water is added to compensate for the loss in workability. This paper compares the chloride ingress in cracked mortar with and without SAPs. The specimens were saturated in a chloride solution during 1 or 5 weeks after which the chloride ingress could be visualised using silver nitrate. The specimens which healed prior to chloride saturation had a significantly lower chloride ingress. The SAPs were able to delay the chloride ingress, as well as limit the influence of the crack on the chloride ingress.

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.

scholarly journals Injectable Self-Healing Adhesive pH-Responsive Hydrogels Accelerate Gastric Hemostasis and Wound Healing

2021 ◽  
Vol 13 (1) ◽  
Author(s):  
Jiahui He ◽  
Zixi Zhang ◽  
Yutong Yang ◽  
Fenggang Ren ◽  
Jipeng Li ◽  
...  
Keyword(s):  
Wound Healing ◽  
Endoscopic Treatment ◽  
Healing Process ◽  
Gelation Time ◽  
Type I ◽  
Self Healing ◽  
Ph Responsive ◽  
Gastric Hemorrhage ◽  
Wound Model ◽  
Arterial Bleeding

AbstractEndoscopic mucosal resection (EMR) and endoscopic submucosal dissection (ESD) are well-established therapeutics for gastrointestinal neoplasias, but complications after EMR/ESD, including bleeding and perforation, result in additional treatment morbidity and even threaten the lives of patients. Thus, designing biomaterials to treat gastric bleeding and wound healing after endoscopic treatment is highly desired and remains a challenge. Herein, a series of injectable pH-responsive self-healing adhesive hydrogels based on acryloyl-6-aminocaproic acid (AA) and AA-g-N-hydroxysuccinimide (AA-NHS) were developed, and their great potential as endoscopic sprayable bioadhesive materials to efficiently stop hemorrhage and promote the wound healing process was further demonstrated in a swine gastric hemorrhage/wound model. The hydrogels showed a suitable gelation time, an autonomous and efficient self-healing capacity, hemostatic properties, and good biocompatibility. With the introduction of AA-NHS as a micro-cross-linker, the hydrogels exhibited enhanced adhesive strength. A swine gastric hemorrhage in vivo model demonstrated that the hydrogels showed good hemostatic performance by stopping acute arterial bleeding and preventing delayed bleeding. A gastric wound model indicated that the hydrogels showed excellent treatment effects with significantly enhanced wound healing with type I collagen deposition, α-SMA expression, and blood vessel formation. These injectable self-healing adhesive hydrogels exhibited great potential to treat gastric wounds after endoscopic treatment.

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