scholarly journals Self-healing of bio-cementitious mortar incubated within neutral and acidic soil

2021 ◽  
Vol 54 (2) ◽  
Author(s):  
Mohamed Esaker ◽  
Omar Hamza ◽  
Adam Souid ◽  
David Elliott
Keyword(s):  
Soil Ph ◽  
Healing Process ◽  
Chemical Exposure ◽  
Acidic Soil ◽  
Self Healing ◽  
Chemical Attack ◽  
Before And After ◽  
Ground Conditions ◽  
Neutral Soil ◽  
Healing Agent

AbstractThe efficiency of bio self-healing of pre-cracked mortar specimens incubated in sand was investigated. The investigation examined the effect of soil pH representing industrially recognised classes of exposure, ranging from no risk of chemical attack (neutral pH ≈ 7) to very high risk (pH ≈ 4.5). Simultaneously, the soil was subjected to fully and partially saturated cycles for 120 days to resemble groundwater-level fluctuation. Bacillus subtilis with nutrients were impregnated into perlite and utilised as a bacterial healing agent. The healing agent was added to half of the mortar specimens for comparison purposes. Mineral precipitations were observed in both control and bio-mortar specimens, and the healing products were examined by SEM–EDX scanning. The healing ratio was evaluated by comparing (1) the repair rate of the crack area and (2) by capillary water absorption and sorptivity index—before and after incubation. The results indicated that bacteria-doped specimens (bio-mortar) exhibited the most efficient crack-healing in all incubation conditions i.e. different chemical exposure classes. In the pH neutral soil, the average healing ratios for the control and bio-mortar specimens were 38% and 82%, respectively. However, the healing ratio decreased by 43% for specimens incubated in acidic soil (pH ≈ 4) compared with specimens incubated in neutral soil (pH ≈ 7). The study implies that bio self-healing is generally beneficial for concrete embedded within soil; however, aggressive ground conditions can inhibit the healing process.

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.

Finite Element Modelling and Analysis of Micro-Capsule Based Self-Healing Polymeric Composites

2018 ◽  
Vol 10 (6) ◽  
Author(s):  
J. Lilly Mercy ◽  
S. Prakash
Keyword(s):  
Polymer Matrix ◽  
Healing Process ◽  
Polymeric Composites ◽  
Polymerization Reaction ◽  
Self Healing ◽  
Functional Composites ◽  
Laminate Theory ◽  
Static Mechanical ◽  
Healing Agent ◽  
The Many

Self-healing polymeric composites are a class of functional composites which heal itself during damage. Out of the many methods of self-healing, micro-capsule based self-healing process is the proven and established method where the healing agent stored in the capsule breaks and seals up the gap after the polymerization reaction with the suitable catalyst. The incorporation of the capsule in a polymer matrix in a random fashion makes it challenging to model the composite material. This paper explains the modelling and simulation of the self-healing composite using MIDAS NFX FEA software. The effect of self-healing composition - micro-capsule size and concentration on the static mechanical properties of the composite is explored. The capsules are integrated in the polymer matrix as a representative volume element using the rule of mixtures. The classical laminate theory was used to identify the critical ply failure.

scholarly journals Biological Self-Healing of Cement Paste and Mortar by Non-Ureolytic Bacteria Encapsulated in Alginate Hydrogel Capsules

Materials ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 3711
Author(s):  
Mohammad Fahimizadeh ◽  
Ayesha Diane Abeyratne ◽  
Lee Sui Mae ◽  
R. K. Raman Singh ◽  
Pooria Pasbakhsh
Keyword(s):  
Cement Paste ◽  
Healing Process ◽  
Cementitious Materials ◽  
The Self ◽  
Self Healing ◽  
Alkaline Conditions ◽  
Healing Agent ◽  
Encapsulated Bacteria ◽  
The Right

Crack formation in concrete is one of the main reasons for concrete degradation. Calcium alginate capsules containing biological self-healing agents for cementitious materials were studied for the self-healing of cement paste and mortars through in vitro characterizations such as healing agent survivability and retention, material stability, and biomineralization, followed by in situ self-healing observation in pre-cracked cement paste and mortar specimens. Our results showed that bacterial spores fully survived the encapsulation process and would not leach out during cement mixing. Encapsulated bacteria precipitated CaCO3 when exposed to water, oxygen, and calcium under alkaline conditions by releasing CO32− ions into the cement environment. Capsule rupture is not required for the initiation of the healing process, but exposure to the right conditions are. After 56 days of wet–dry cycles, the capsules resulted in flexural strength regain as high as 39.6% for the cement mortar and 32.5% for the cement paste specimens. Full crack closure was observed at 28 days for cement mortars with the healing agents. The self-healing system acted as a biological CO32− pump that can keep the bio-agents retained, protected, and active for up to 56 days of wet-dry incubation. This promising self-healing strategy requires further research and optimization.

The Evaluation of Sawdust Swine Waste Compost on the Soil Ecosystem, Pollution and Vegetable Production

1993 ◽  
Vol 27 (1) ◽  
pp. 123-131 ◽  
Author(s):  
M.-M. Kao
Keyword(s):  
Soil Ph ◽  
Acidic Soil ◽  
Vegetable Production ◽  
Swine Waste ◽  
Total N ◽  
Feeding Technique ◽  
Zn And Cu In ◽  
Neutral Soil ◽  
Compost Treatment ◽  
Microbial Agent

We have successfully developed so called “biological sawdust bed pig-feeding technique” to prevent the production of swine waste water and reduction of offensive odor from piggeries by means of a specific microbial agent under mesophilic, aerobic and solid fermentation conditions. The mixture of swine feces, urine, microbial agent and sawdust is the only by-product in this pig-feeding technique. This type of compost is called “sawdust swine waste compost or SSW compost.” The main characteristics of SSW compost include as follows: pH 8.0, moisture content 40%, total N 2.2%, P2O5 3.9%, K20 3.0%, Zn 480 ppm, Cu 190 ppm, total C 39.8%, C/N ratio 18.0 and some special microorganisms such as Asperqillusterreus, Bacillussubtilis etc. Field experiment has shown that when the SSW compost was applied to the acidic soil (pH 5.0) and neutral soil (pH 7.1) at the rate of 50 Tons/ha (w/w), respectively, after 1 year application, the amount of Zn and Cu in acidic soil was significantly increased from 15 to 22.8 ppm and 14.5 to 26.7 ppm, respectively. However, the amount of Zn and Cu in neutral soil was only slightly increased from 5.7 to 6.3 ppm and 6.5 to 7.0ppm, respectively, as compared with the check (noncompost) treatment. Furthermore, the production of Chinese cabbage in acidic soil was remarkably increased 18-19% in 25 and 50 Tons/ha SSW compost treatment and Zn and Cu content of leaves in SSW compost treatment was 30-36% and 20-30% higher than in check treatment, respectively. The proper application of SSW compost not only improves the soilfertilitybut also increases the vegetable production. However, the accumulation of Zn and Cu in acidic soil and in crop leaves should be carefully considered if the compost was treated for the long term application.

Fatigue response of a solid state self-healing resin

2020 ◽  
pp. 096739112095509
Author(s):  
Mohd Suzeren Md Jamil ◽  
Noor Nabilah Muhamad ◽  
Wan Naqiuddin Wan Zulrushdi
Keyword(s):  
Fatigue Life ◽  
Solid State ◽  
Fatigue Behavior ◽  
Fatigue Cracks ◽  
Healing Process ◽  
Fatigue Tests ◽  
Self Healing ◽  
Healing System ◽  
Healing Agent ◽  
Modified Epoxy

The present work verified the capability of a solid state self-healing system for retarding or arresting fatigue cracks in epoxy materials subjected to cyclic loading at room temperature. A solid state self-healing material is demonstrated using a thermosetting epoxy polymer which was modified by incorporating a linear thermoplastic polydiglycidyl ether bisphenol-A (PDGEBA) as a healing agent. The stress-controlled constant amplitude (CA) tensile fatigue behavior at stress ratio, R = 0.1 and frequency 10 Hz for both the neat and the modified epoxy was investigated. Fatigue life and residual strength degradation were continuously monitored during the fatigue tests. The modified epoxy fatigue life was shown to be increased by ∼50% after healing periods. The fatigue-healing process was proven through the surface and cross-section resin morphology analyses using microscopy optic and scanning electron microscope (SEM). On the whole, the solid state self-healing system has proven to be very effective in obstructing fatigue crack propagation, effectively improved the self-healing polymeric material to achieve higher endurance limits.

scholarly journals Detecting the Activation of a Self-Healing Mechanism in Concrete by Acoustic Emission and Digital Image Correlation

2013 ◽  
Vol 2013 ◽  
pp. 1-10 ◽  
Author(s):  
E. Tsangouri ◽  
D. G. Aggelis ◽  
K. Van Tittelboom ◽  
N. De Belie ◽  
D. Van Hemelrijck
Keyword(s):  
Acoustic Emission ◽  
Digital Image Correlation ◽  
Digital Image ◽  
Crack Formation ◽  
Healing Process ◽  
Image Correlation ◽  
Activation Process ◽  
Self Healing ◽  
Emission Analysis ◽  
Healing Agent

Autonomous crack healing in concrete is obtained when encapsulated healing agent is embedded into the material. Cracking damage in concrete elements ruptures the capsules and activates the healing process by healing agent release. Previously, the strength and stiffness recovery as well as the sealing efficiency after autonomous crack repair was well established. However, the mechanisms that trigger capsule breakage remain unknown. In parallel, the conditions under which the crack interacts with embedded capsules stay black-box. In this research, an experimental approach implementing an advanced optical and acoustic method sets up scopes to monitor and justify the crack formation and capsule breakage of concrete samples tested under three-point bending. Digital Image Correlation was used to visualize the crack opening. The optical information was the basis for an extensive and analytical study of the damage by Acoustic Emission analysis. The influence of embedding capsules on the concrete fracture process, the location of capsule damage, and the differentiation between emissions due to capsule rupture and crack formation are presented in this research. A profound observation of the capsules performance provides a clear view of the healing activation process.

scholarly journals Self-healing cement materials – microscopic techniques

2020 ◽  
Vol 19 (2) ◽  
pp. 033-040
Author(s):  
Marta Dudek
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Healing Process ◽  
Optical Microscope ◽  
Cementitious Materials ◽  
Self Healing ◽  
Advantages And Disadvantages ◽  
Before And After ◽  
Scanning Electron

The article presents a general classification of intelligent materials with self-healing (self-repairing) properties, focusing on self-healing cementitious materials. The purpose of the paper is to describe the prospects of two of the most popular micro-observation techniques, i.e. with the use of an optical and scanning electron microscope. In addition, it describes the advantages of using a tensile stage mounted in the microscope chamber for testing self-healing materials. The advantages and disadvantages of these devices have been characterized, and the results of preliminary research have been provided. The tests include the optical microscopy and scanning electron microscopy observations of the microstructure of cracks before and after the process of healing. They were carried out using ZEISS Discovery V20 optical microscope and ZEISS EVO-MA 10 scanning electron microscope on mortar samples modified with macro capsules filled with polymer. In addition to observations, chemical analysis was performed with the use of an EDS detector. The microscopic observations and chemical analyses provide the basis for assessing the effectiveness of the self-healing process, showing that the crack has been healed. Moreover, the preliminary results of the tests of micro-mechanical properties, carried out with the use of a tensile stage, have been described. The problems of using this research technique are also listed. This study shows the usefulness of this kind of tests for microcapsules for self-healing materials.

Modeling microcapsule-enabled self-healing cementitious composite materials using discrete element method

2017 ◽  
Vol 26 (2) ◽  
pp. 340-357 ◽  
Author(s):  
Shuai Zhou ◽  
Hehua Zhu ◽  
J Woody Ju ◽  
Zhiguo Yan ◽  
Qing Chen
Keyword(s):  
Discrete Element Method ◽  
Healing Process ◽  
Compressive Loading ◽  
Discrete Element ◽  
Cementitious Materials ◽  
Self Healing ◽  
Healing Effect ◽  
Healing Agent ◽  
Damage Healing ◽  
Element Method

Concrete with a micro-encapsulated healing agent is appealing due to its self-healing capacity. The discrete element method (DEM) is emerging as an increasingly used approach for investigating the damage phenomenon of materials at the microscale. It provides a promising way to study the microcapsule-enabled self-healing concrete. Based on the experimental observation and DEM, a three-dimensional damage-healing numerical model of microcapsule-enabled self-healing cementitious materials under compressive loading is proposed. The local healing effect can be simulated in our model, as well as the stress concentration effect and the partial healing effect. The healing variable of the DEM model is developed to describe the healing process. We examine the dependence of the mechanical properties of the microcapsule-enabled self-healing material on (a) the stiffness of the solidified healing agent, (b) the strength of the solidified healing agent, (c) the initial damage of specimens, and (d) the partial healing effect. In particular, the proposed numerical damage-healing model demonstrates the potential capability to explain and simulate the physical behavior of microcapsule-enabled self-healing materials on the microscale.

Self-Healing Epoxy Composites – Part II: Healing Performance

2013 ◽  
Vol 716 ◽  
pp. 387-390
Author(s):  
Tao Yin ◽  
Min Zhi Rong ◽  
Ming Qiu Zhang
Keyword(s):  
Fracture Toughness ◽  
Epoxy Composites ◽  
Repair System ◽  
Self Healing ◽  
Single Edge ◽  
Healing Efficiency ◽  
Two Component ◽  
Before And After ◽  
Healing Agent

Epoxy composites were provided with healing capability by pre-dispersing a novel repair system in the composites matrix cured by 2-ethyl-4-methylimidazole (2E4MIm). The healing agent consisted of ureaformaldehyde microcapsules containing epoxy and latent hardener CuBr2(2-MeIm)4 (the complex of CuBr2 and 2-methylimidazole). Single-edge notched bending (SENB) test were conducted to evaluate fracture toughness of the composites before and after healing. Moreover, healing efficiency was studied as a function of the content of the two-component healing agents. It was found that a healing efficiency of 173% relative to the fracture toughness of virgin composites was obtained in the case of 15 wt% epoxy-loaded microcapsules and 3 wt% CuBr2(2-MeIm)4.

scholarly journals Self-Repairing Composites for Corrosion Protection: A Review on Recent Strategies and Evaluation Methods

Materials ◽  
2019 ◽  
Vol 12 (17) ◽  
pp. 2754 ◽  
Author(s):  
P ◽  
Al-Maadeed
Keyword(s):  
Electrochemical Impedance ◽  
Protective Coatings ◽  
Healing Process ◽  
Cellulose Nanofibers ◽  
Aloe Vera ◽  
Immersion Test ◽  
The Self ◽  
Self Healing ◽  
Metal Substrates ◽  
Healing Agent

The use of self-healing coatings to protect metal substrates, such as aluminum alloys, stainless steel, carbon steel, and Mg alloys from corrosion is an important aspect for protecting metals and for the economy. During the past decade, extensive transformations on self-healing strategies were introduced in protective coatings, including the use of green components. Scientists used extracts of henna leaves, aloe vera, tobacco, etc. as corrosion inhibitors, and cellulose nanofibers, hallyosite nanotubes, etc. as healing agent containers. This review gives a concise description on the need for self-healing protective coatings for metal parts, the latest extrinsic self-healing strategies, and the techniques used to follow-up the self-healing process to control the corrosion of metal substrates. Common techniques, such as accelerated salt immersion test and electrochemical impedance spectroscopy (EIS), for evaluating the self-healing process in protective coatings are explained. We also show recent advancements procedures, such as scanning vibrating electrode technique (SVET) and scanning electrochemical microscopy (SECM), as successful techniques in evaluating the self-healing process in protective coatings.

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