• Proceedings of the Korean Ceranic Society Conference
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• 2002.10a
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• pp.23.1-23
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• 2002

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.3
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• pp.222-227
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• 2018

Recently, due to the deterioration and various natural disasters caused by the passage of concrete pole for 20~30 years or more, damage and destruction of the poles have increased the demand for maintenance. In this paper, 10 flexural strength test specimens were fabricated by using crack self - healing concrete of Fly ash, GGBS, CA, etc. The compressive strength of the concrete with slag was found to be excellent, but the concrete with fly ash was slightly below the reference strength. In addition, the crack loadings of the specimens satisfied the criteria of KS F 4304. In the case of the load-deflection and strain relations, the behavior of the fly ash specimens was similar, but in the specimens containing the blast furnace slag, The results showed that a large amount of strain occurred.

• Journal of the Korea Concrete Institute
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• v.20 no.3
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• pp.291-298
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• 2008

Cracks in concrete generally interconnect flow paths and increase concrete permeability. The increase in concrete permeability due to the progression of cracks allows more water or aggressive chemical ions to penetrate into concrete, facilitating deterioration. The goal of this research is to study the relationship between crack width and water permeability of cracked concrete. Tests have been carried out as a function of hydraulic pressure (0.1 $\sim$ 2 bar) and crack width (30 $\sim$ 100 ${\mu}m$). Splitting and reuniting method was used to manufacture cracked concrete specimens with controlled crack width. Crack widths are checked by using a microscope($\times$100). The results show a considerable increase of water transport with crack width and hydraulic pressure. When the crack width is smaller than 50${\mu}m$, the crack width has little effect on concrete permeability. Due to the autogenous healing, the water flow through the crack gradually reduces with time. When crack width is 100 ${\mu}m$ and hydraulic pressure increase from 0.1 bar to 0.25 bar, concrete permeability increases rapidly about 190 times according to the test results.

• 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.

• 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.

• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.4
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• pp.531-538
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• 2022

In this study, the self-healing hybrid capsules were prepared, were mixed with 3 %, 5 %, and 7 % based on cement mass. The healing performance were evaluated according to mixing ratio self-healing hybrid capsule. As a result of the experiment, it was found that the crack healing performance improved as the mixing rate of the self-healing hybrid capsule increased, but the quality performance tended to decrease. Therefore, it is judged that using the mixing ratio of the hybrid capsule within 5 % reduces the quality performance to within about 10 % and secures about 90 % or more of the healing performance.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.1
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• pp.88-96
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• 2020

In this study, the effect of cyclic wetting-drying on the self-healing of cementitious materials containing superabsorbent polymers (SAPs) were experimentally evaluated. In each cycle, cracked cement paste specimens containing various SAP dosages were exposed to wet conditions for 1 h, during which the capillary water absorption tests and water flow tests were conducted, and then exposed to dry conditions for 47 h. The capillary water absorption test results showed that the sorptivity values of the specimen without SAPs, SAP 0.5%, SAP 1.0%, and SAP 1.5% specimens were decreased by approximately 22.9%, 36.8%, 42.8%, and 46.3%, respectively, after 8 cycles. In addition, the water flow test results showed that the amount of water runoff through the cracks of all cracked specimens gradually decreased over wet/dry cycles, especially the reduction ratio of the amount of water runoff increased with increasing SAP dosage. Furthermore, the swelling behavior of SAPs in cracks by in gress water was con firmed via X-ray computed tomography (CT) analysis. These results indicate that the effective crack width can be reduced as SAPs absorb water and swell, while the water absorbed in SAPs can be released to crack surfaces under dry conditions, further promoting healing product formation. This study demon strates that the in corporation of SAPs can in crease the water tightness of cracks, thereby improving the self-healing efficiency of cementitious materials.

• Journal of the Korean Recycled Construction Resources Institute
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• v.4 no.4
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• pp.463-469
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• 2016

In this paper, compressive strength and water permeability performance for two types of crack self-healing materials such as SH-PO-0 composed of mineral admixtures(expansive agent, swelling material and crystal growth agent) and SH-PO-(5, 15, 30) blended with SH-PO-0 and phosphate additive(PO) dissolving easily calcium ion, were evaluated. The test results show that the water flow of SH-PO-0 decreased steeply at the early age although compressive strength decreased about 9% at 28 days compared with OPC. The higher PO replacement ratio is, the lower compressive strength and more improved water permeability performance is, and thus, based on such results, adequate PO replacement ratio is 15%. It is also found that the self-healing performance of SH-PO-15 was quite improved at the early ages and however, the performance of SH-PO-15 is similar to one of SH-PO-0 at long-term ages, and 28 days compressive strength of SH-PO-15 decreased about 8% compared with SH-PO-0. In addition, it is confirmed from the analysis of SEM-EDS that calcium ions of SH-PO-15 were crystallized more than those of SH-PO-0.

• Journal of Convergence for Information Technology
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• v.9 no.10
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• pp.87-93
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• 2019

Microcapsules were prepared by using a mixture of linseed oil and a small amount of fluorescent fluid as a core material. Self-healing protective coatings were prepared by applying coating formulations containing varying amounts of microcapsules on mortar surface. After scratch or crack was generated in the coating, when the damaged region was exposed to ultraviolet light (${\lambda}=365nm$), it was observed that fluorescence emission area increased with increasing microcapsule loading. In the cases of the self-healing coatings having 20wt% or more microcapsule loading, the damaged region was almost filled with the healing agent. In water sorptivity test, the self-healing coating having 20wt% or more microcapsule loading showed a healing efficiency of about 85%. The fluorescence emission from the damaged region was easily observed at a distance of 3 m. The self-healing protective coating is expected to be useful to confirm its self-healing function with the eye.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.2
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• pp.16-22
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• 2021

In this paper, a solid capsule was prepared using a crystal growth type inorganic material capable of hydration reaction. The solid capsules were mixed at 3, 5, and 10% according to the composition ratio of 8:2, 7:3, 6:4 based on the cement mass, and the self-healing mortar was mixed, Durable healing properties were evaluated through the water permeability test. As a result of the water level permeability test, the effect of optimally improving the natural healing performance was shown by mixing the solid capsules prepared in a composition ratio of 7:3 of the solid capsules. In the case of a crack width of 0.3mm or less, it is estimated that more than 90% of the self-healing performance can be secured. As a result, it was judged that the self-healing performance of the solid capsule had an effect on the durable healing properties through the water permeability test, It is judged that there is a tendency to improve self-healing performance according to the mixing of solid capsules.