• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.1
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• pp.92-100
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• 2022

In this paper, to evaluate the effect of SC on the crack self-healing performance and mechanical recovery performance of cement composites, encapsulated intumescent inorganic material-based solid healing materials were prepared. SC was mixed with cement composite materials to evaluate the basic properties, permeability test, and load reload test. SC slightly improved the flow of cement composites, and the compressive strength decreased by about 10 %. Also, the flexural strength decreased by about 30 %. It was found that when SC was mixed with the cement composite material by 5 %, the crack self-healing rate of Plain was improved by about 𝜟10 %. As a result of the load reload test, it was found that the mechanical recovery rate of Plain was improved by about 𝜟20 %. In addition, as a result of analyzing the correlation between the crack self-healing rate and the mechanical recovery rate by the load reload test, it is judged that the healing area of the Plain can be increased due to SC.

• Journal of the Korean Recycled Construction Resources Institute
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• v.11 no.4
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• pp.568-575
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• 2023

This paper aims to evaluate the quality characteristics and healing performance of precast concrete incorporating self-healing technology as a key technique for the construction of smart cities. The study found that precast concrete mixed with hybrid capsules exhibited a tendency of reduced slump and air content, impacting the quality characteristics. Specifically, the slump decreased by up to 14 %, and the air content by up to 9 %. Moreover, the inclusion of hybrid capsules in the concrete resulted in a maximum decrease of 16 % in compressive strength and 18 % in flexural strength. However, the introduction of hybrid capsules significantly enhanced the crack healing performance. The assessment through water permeability tests showed that the healing rate of 0.3 mm crack width after a 28-day healing period improved as the mixing ratio increased, with the healing rates at 1 %, 3 %, and 5 % hybrid capsule mixtures observed to increase by approximately 16 %, 25 %, and 32 %, respectively.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2006.11a
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• pp.166-168
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• 2006

$Si_3N_4/SiC$ composite ceramics was sintered in order to investigate their bending strength behavior after crack healing. $Y_2O_$ and $TiO_2$ power was added as sintering additives to enhance it's sintering property. A three-point bending specimen was cut out from sintered plates. About $100\;{\mu}m$ semi-circular surface cracks were made on the center of the tension surface of the three-point bending specimen using Vickers indenter. After the crack-healing processing from $500^{\circ}C$ to $1300^{\circ}C$, for 1 h, in air, the bending strength behavior of these crack-healed specimen coated with $SiO_2$ colloidal were determined systematically at room temperature. $Si_3N_4/SiC$ ceramics using additive powder ($Y_2O_3+TiO_2$) was superior to that of additive powder $Y_2O_3$. The additive powder $TiO_2$ exerted influence at growth of $Si_3N_4$. The optimum crack healing conditions coated $SiO_2$ colloidal were $1000^{\circ}C$ at $Si_3N_4/SiC$ using additive powder ($Y_2O_3+TiO_2$), and $1300^{\circ}C$ at $Si_3N_4/SiC$ using additive powder $Y_2O_3$.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.2
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• pp.79-87
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• 2011

In this study, the chloride penetration tests were performed for the initially cracked reinforced concrete members. The chloride diffusion characteristics and the critical crack width are compared, and the properties of self-healing are investigated. According to the test results, the chloride penetration resistance was greatly reduced as the surface crack width increased. When the mineral admixtures are added, the chloride penetration resistance of uncracked specimens were effectively increased, however, in case of the blast furnace slag and fly ash, the cracked specimens showed the more reduced resistance than OPC case, inversely. Also, the critical width was $29{\mu}m$, on average, for immersion test. The crack width with $4{\sim}15{\mu}m$ was restored by self-healing, The parts restored by self-healing were seemed to be visually restored, however, the chloride penetration resistance was not restored, perfectly.

• Journal of the Korea Concrete Institute
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• v.21 no.6
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• pp.689-696
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• 2009

In this study, electro-deposition method was applied to heal cracks in various blended concrete. The performance of the method was indirectly monitored by measuring impressed voltage, electrolyte, galvanic current monitoring, linear polarization resistance, and directly by image analysis of the cracks. The indirect and direct monitoring values are compared to develop guidelines for relating the indirect measures to actual crack healing. As a result, It was found that impressed voltage was convergence to 2.9V after 20000 minutes. From the galvanic current test results of artificial crack healing, the corrosion resistance showed that the order of 0.4 $>$ 0.6 $>$ 0.5 water to cement ratio. Furthermore, in view of binder, the corrosion resistance order was calculated OPC $>$ 60%GGBS $>$ 10%SF $>$ 30%PFA. Finally, It was found that 76.47% of healed crack surface calculated from the artificial crack healing technique using electrochemical deposition method.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.2A
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• pp.297-304
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• 2008

It is well known that cracks in concrete decrease permeability and durability of concrete because cracks enhance the penetration of water or corrosive chemicals like as chlorides, carbon dioxides, sulfates and some others. But some of cracks in hardened cements may be sealed in case of contacting water. This phenomenon is called "self healing" and it has a close relation to hydration products newly formed on surfaces of cracks. Many studies on self healing in concretes commonly showed that CSH gel has been observed on crack surfaces. And some studies have reported that calcium hydroxides and ettringite were observed as well as CSH gel on crack surfaces. This study was carried out to investigate hydration products formed by self healing process and also examine the influence of waterproof admixture for concretes on self healing of cement. As a result of XRD, DSC, SEM and EDX analysis of crack surfaces, it was found that self healing of cement was related to CSH gel, calcium hydroxides and ettringite. And waterproof admixture increased fibrous (needle-like) hydration products which were in network form. It is estimated that such fibrous products are effective for self healing process of cement system.

• Polymer(Korea)
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• v.37 no.3
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• pp.356-361
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• 2013

Microcapsules of two different self-healing agents, 5-ethylidene-2-norbornene (ENB) and ENB with a crosslinker, surrounded by a melamine-urea-formaldehyde shell were manufactured. In this work, a red dye was incorporated into the self-healing agents as a tracer for better visual observations. It revealed that the incorporation of a red dye into self-healing agents did not disturb the formation of microcapsules from the examination of thermal resistance, particle size/size distribution and morphology of the resulting microcapsules. Releasing of self-healing liquid into the induced crack from ruptured microcapsules and filling between crack planes were observed using an optical microscope. Also observed was the reaction of filled healing agent with embedded Grubbs' catalyst in an epoxy coating layer.

• 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 Korea institute for structural maintenance and inspection
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• v.24 no.1
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• pp.67-73
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• 2020

In this study, the self-healing performance of mortar beams containing self-healing materials was evaluated through experiments. Normal mortar beams and self-healing mortar beams were used In the experiments. The self-healing performance was evaluated by comparing the mortar compressive strength, member strength, and self-healing effects of cracks. The experimental results showed that the compressive strength of mortar containing self-healing material was smaller than that of normal mortar, but the ratio of 118 days compressive strength to 28 days compressive strength was the same. The member strength tended to increase with increasing curing period. In normal mortar specimens, the member strength did not recover even if the curing period increased, but the strength of the self-healing mortar specimens tended to recover as reaction products were produced. The crack width tended to decrease after the healing periods in both specimens, but the reaction product was observed only in the self-healing mortar specimens.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.11
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• pp.1715-1720
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• 2010

In this study, we analyzed the crack-healing characteristics of specimens; different crack lengths and coating methods of $Si_3N_4$ ceramic structures with long cracks were analyzed. Cracks with lengths of about $100-500\;{\mu}m$ were obtained using a Vickers indenter for a load of 24.5-98 N. In the case of a crack obtained by applying a load of 24.5 N, the crack-healed specimen with $SiO_2$ nanocolloid coating exhibited the highest bending strength, which was higher than that of a smooth specimen by 140%, but the bending strength of a crack-healed specimen that had a $SiO_2$ nanocolloid coating and originally had multiple cracks was lower than that of a smooth specimen. However, when compared to the cracked specimens, the bending strength of most specimens with multiple cracks increased slightly. On the basis of these results, the crack-healing characteristics of $Si_3N_4$ ceramic structures with multiple indentations were studied for different coating methods. The most effective coating method for long-crack specimens was hydrostatic pressure coating.