• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.3
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• pp.375-382
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• 2021

Self-healing concrete is in the spotlight in that it can effectively extend the lifespan of concrete structures by healing cracks in the structure by themselves without additional repairing or retrofiting actions. Currently, self-healing concrete is a field that is being actively studied around the world, but since most studies focus on the improvement of healing performance, there is a lack of methods to rationally evaluate the self-healing performance of concrete. Although the gas diffusion test method has been developed for the use in the performance evaluation of self-healing concrete, it has revealed that for gas diffusion through the matrix affect the crack diffusion coefficients depending on the environmental conditions such as the saturation of the specimen, the temperature, and humidity during the experiment. Therefore, in this study, the method has been proposed to eliminate the influence of the matrix diffusion when calculating the crack diffusion coefficient. In addition, a pre-conditioning process was introduced to shorten the experimental time. As a result, the crack width could be estimated with an error level of less than 3% in the test time of about 20 minutes.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.2
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• pp.122-129
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• 2019

Cracks in concrete structures are inevitable phenomena caused by shrinkage, hydration heat, and external loads. These cracks facilitate the penetration of external harmful ions into the concrete, which greatly reduces its durability. Recently, self-healing concrete has been actively studied. Also, self-healing fiber-reinforced concrete have been studied to control the crack in concrete and to maximize the shelf-healing capability. In this study, mortar specimens containing PVA fiber, fly ash and crystalline admixture were fabricated. The compressive and flexural strength were evaluated. Also, the self-healing performance was evaluated by the absorption test. From the results, it was confirmed that the amount of water absorbed by healing of the crack decreased as time increased. It was also found that PVA fiber is beneficial for the production of calcium carbonate, an additional healing product.

• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.4
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• pp.514-522
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• 2022

In this study, as part of a study to improve the self-healing performance of concrete structures by applying self-healing capsules made of cementitious materials to cement composite materials, the engineering characteristics of mortars according to PCC(Powder Compacted Capsule) size and mixing ratio were compared and analyzed. For this, fluidity, compressive strength, reload test, carbonation, ultrasonic velocity, and water permeability characteristics were measured according to PCC size and mixing ratio of mortar. As a result of the measurement, the fluidity and compressive strength increased as the mixing ratio of PCC increased, and in the case of the load reload test, the healing ratio increased as the mixing ratio of PCC increased in the 03PC formulation. In the case of water permeability test, it was found that when PCC was used, the reduction ratio of water flow was up to 35 % higher than that of Plain, and when PCC with a size of 0.3 to 0.6 mm was mixed with 15 %, it was found to be effective in improving the crack healing ratio of the mortar.

• Journal of Digital Convergence
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• v.11 no.11
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• pp.783-793
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• 2013

Neo-liberalism after IMF bailout made the Korean book market flushing with rose due to the alleged self-development books. Vision of self-development books under neoliberal social system is inevitably reduced to a means of capital pursuing commercialization in line with improving the competitiveness of privates through the development of human resources. Characteristics of self-development books, which attributes personal fail to personal responsibility and lack of essential element compared to others in a competitive society, trap individuals forced to choose into anxiety and helplessness. Self-development and healing is a complementary relationship. Human beings needs healing -healing humanities- in the process of self-development. Therefore, humanities should trigger developing and perceiving his own 'reflexive life skills'. Individual's sense of happiness in life and his own experience is very important, and the conscious relationship about their own feelings could elicit 'self-reinforcement'.

• Journal of the Korea Concrete Institute
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• v.29 no.3
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• pp.267-273
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• 2017

Recently, the researches of self-healing concrete technology are being carried out actively due to the advent of importance for the maintenance of concrete structures. A water permeability test has been widely used for the evaluation of self-healing performance. However, it is difficult to compare tests results since there is no standard test method related to the self-healing. A standard method for measuring the crack width does not exist neither though the self-healing performance is significantly influenced by the initial crack width. In this study, the effect of water head and crack width on water flow was investigated using a constant water head permeability test equipment. The correlation equation between the initial crack width and water flow was suggested through the regression analysis of test data, and the predicted crack widths agree well with the real crack widths measured using microscopy.

• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.4
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• pp.584-592
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• 2022

In this paper, a study was conducted to improve self-healing and strength properties using sodium acetate. The developed inorganic-organic self-healing materials and recycled sodium acetate were manufactured to evaluate self-healing and permeability reduction properties. As a result of the experiment with recycled sodium acetate, the compressive strength of the material prepared with anhydrous and trihydrate at a ratio of 7:4 was higher than that of the mixture using anhydrous. It was confirmed that the compressive strength was improved by 3~7 %. In addition, the maximum permeability reduction rate was 92.6 %, which satisfied the self-healing properties.

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.6
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• pp.10-19
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• 2016

The objective of this study is to investigate the self-healing properties of ternary blended cement(TBC) paste made with OPC, GGBFS and FA. The influence of OPC-GGBFS-FA on the self-healing ability of ternary blended cement paste was researched by ultrasonic pulse velocity(UPV) measurement. The TBC paste with GGBFS-FA replacement ratios of 20%, 40% and 60% were prepared having a constant water-cementitious materials ratios os 0.5. The research focuses on behavior after 28days(after loading). Four-point bending tests are used to pre-cracked the prismatic specimens at 28days. For specimens (uncracked and cracked) submerged in tap-water and sea-water until 60days. According to the experimental results, the TBC paste system has self-healing ability increased when the fraction of GGBFS increased. Because GGBFS and FA continues to hydrate after 28days, it is likely that hydrated products from GGBFS and FA may modify microstructures, seal these cracks. From these results, it is clear that the crack in all samples experience self-healing and that this occurs mostly in the first 30days of submerging. Futhermore, most of the healing for both specimens of submerged in sea-water and tap-water occurred during the first 30days. Sea-water submerged specimens healed cracks as fast as those in tap-water. Differences in healing effects of submerged in sea-water and tap-water may be attributed to the presence of specific sea-water ions. Therefore, self-healing effects considered age-effects was more strong effect occurred mostly in the first 30days, and then gradually weaken.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.4
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• pp.435-441
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• 2017

Studies on self-healing have currently been diversified and the methods to evaluate the studies have become more diversified as well. Among them, the back-scattered electron (BSE) image acquired through the scanning electron microscope (SEM) is attempted as the means to evaluate the self-healing effect on cracks. In order evaluate by the BSE image, sophisticated pre-processing of specimen is critical and this injected inside the particle, pore and artificial crack of the hardener to stabilize the structure of the newly generated self-healing product and it enables to endure the stress on polishing without deformation. The impregnated specimen smoothen the surface to obtain the BSE image of high resolution that polishing is made for diamond suspension for wet polishing after dry polishing. As a result of evaluating the self-healing product on the impregnated and polished self-healing specimen, the generated product is formed from the surface of the artificial crack and the self-healing substances are confirmed as $Ca(OH)_2$ and C-S-H.

• The KIPS Transactions:PartD
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• v.15D no.2
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• pp.271-284
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• 2008

Self-healing is an approach to evaluating constraints defined in target system and to applying an appropriate strategy when violating he constrains. Today, the computing environment is very complex, so researches that endow a system with the self-healing's ability that recognizes problem arising in a target system are being an important issues. However, most of the existing researches are that self-healing developers need much effort and time to analyze and model constraints. Thus, this paper proposes an automated approach to determine problem arising in external and internal system environment. The approach proposes: 1) Specifying the target system through the models created in design phase of target system. 2) Automatically creating constraints for external and internal system environment, by using the specified contents. 3) Deriving a dependency model of a component based on the created internal state rule. 4) Translating the constraints and dependency model into code evaluating behaviors of the target system, and determinating problem level. 5) Monitoring an internal and external status of system based on the level of problem determination, and applying self-healing strategy when detecting abnormal state caused in the target system. Through these, we can reduce the efforts of self-healing developers to analyze target system, and heal rapidly not only abnormal behavior of target system regarding external and internal problem, but also failure such as system break down into normal state. To evaluate the proposed approach, through video conference system, we verify an effectiveness of our approach by comparing proposed approach's self-healing activities with those of the existing approach.

• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.3
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• pp.389-396
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• 2021

In this paper, it was evaluated that the effect of self-healing microcapsules on the quality and healing properties of cement composites. In the mixing of microcapsules, the plastic viscosity and yield stress of the cement composites decreased due to the particle properties of the microcapsules, and decreased in proportion to the mixing ratio. The table flow showed a tendency to decrease as the core material acted as a stimulant due to the loss of microcapsules, and the compressive strength could be supplemented through unit quantity correction. As a result of evaluating the effect of microcapsule mixing on the healing properties of cement composites, it was found that the unit water flow rate decreased by the healing reaction immediately after crack initiation. When more than 3% of microcapsules were mixed, it was found that there was a healing rate of more than 95% at 7 days of healing age.