• Title/Summary/Keyword: Evaluation method of self-healing performance

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Compressive Strength and Healing Performance of Mortar Using Self-healing Inorganic Materials (자기치유형 무기계 혼합재를 사용한 모르타르의 압축강도 및 치유성능)

  • Hyung-Suk, Kim;Woong-Jong, Lee;Sung, Choi;Kwang-Myong, Lee
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.10 no.4
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    • pp.577-583
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    • 2022
  • In this study, the characteristics of self-healing mortars produced using an inorganic self-healing material consisting of ground granulated blast furnace slag, expansion agent, and anhydrite, were investigated. For three types of self-healing mortars with different amounts of the inorganic healing material, compressive strength was measured and the self-healing performance was evaluated through the constant water head permeability test. The healing rate and equivalent crack width according to crack-induced aging were used as indicies of healing performance evaluation. Considering the development of compressive strength of the self-healing mortars, the change in the healing rate with healing periods, and the economic feasibility, the optimal amount of inorganic self-healing materials was suggested as 20 % of the mass of cement.

Evaluation Method of Self-healing Performance of Cement Composites (시멘트 복합체의 자기치유 성능평가 방법)

  • Lee, Kwang-Myong;Kim, Hyung-Suk;Min, Kyung-Sung;Choi, Sung
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.8 no.1
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    • pp.134-142
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    • 2020
  • In this study, in order to evaluate the self-healing performance of cement composites the self-healing test method and the analysis method were suggested by applying constant water head permeability test, chloride migration test and repeated bending test. The method of making a cracked specimen and controlling crack width are also proposed. Constant head water permeability test can evaluate the healing performance by using the decreasing rate of water flow passing through the crack zone of a specimen. Furthermore, the equivalent crack width can be used to intuitively investigate the healing effect with healing period. The chloride migration test can evaluate the healing rate by the decreasing rate of the diffusion coefficient obtained by ASTM C 1202. Mechanical healing performance can be evaluated using ISR and IDR estimated from load vs. CMOD relationship graph obtained through the repeated bending test. Finally, the applicability of proposed self-healing evaluation methods was examined by testing mortar specimens with or without self-healing agents.

Development of Oxygen Diffusion Test Method for Crack Width Evaluation of Self-Healing Concrete (자기치유 콘크리트의 균열치유 성능평가를 위한 개선된 산소확산 시험방법 제안)

  • Lee, Do-Keun;Shin, Kyung-Joon
    • 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.

Healing Performance of Concrete Containing Hybrid Self-healing Materials (하이브리드 자기치유 소재를 혼입한 콘크리트의 치유성능)

  • Mih-ho, Hwang;Hyuk, Kwon;Hyung-Suk, Kim;Sung, Choi;Kwang-Myong, Lee
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.10 no.4
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    • pp.569-576
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    • 2022
  • In this study, the healing performance of hybrid self-healing concrete was investigated by mixing bacterial pellets(BP) and solid phase capsules(SC), respectively, based on organic-inorganic self-healing material(MC). Constant water head permeability test was applied as a method of evaluating the healing performance, and the healing rate and the healed crack width calculated by the equivalent crack width were used as evaluation indicies. As a result of the water permeability test, when the initial crack width was 0.3 mm, the healing rates of MC-BP and MC-SC were 2.1~3.0 %pt higher than that of MC, and the healed crack width of hybrid concrete increased by 0.017~0.018 mm. In conclusion, it was found that the self-healing performance was not significantly improved even if the two types of healing materials are used together.

Performance Evaluation Method of Self-Healing Concrete Using Gas Diffusion Experiment (기체확산 실험을 활용한 자기치유 콘크리트의 성능평가 방법)

  • Lee, Do-Keun;Shin, Kyung-Joon
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.8 no.1
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    • pp.143-151
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    • 2020
  • Recently, research on self-healing concrete has been actively conducted, and various methods have been attempted for use in the maintenance of structures. However, contrary to the technical development of self-healing concrete, the method for evaluating the performance is insufficient. Although surface observation and permeability experiments are widely used to observe the healing of cracks, microscopic observation of surface may be insufficient to assess the overall performance. Also, permeation experiments should consider the losses caused by the dissolution of self-healed product and viscosity of water. Although a gas diffusion experiment have been proposed to overcome the shortcomings of these two test methods, verification has not been made on specimens with actual healing. Therefore, in this study, gas diffusion experiments were performed on the mortar specimens that had healed, and the adequacy of self-healing evaluation by the gas diffusion experiment was verified.

Evaluation Method of Healing Performance of Self-Healing Materials Based on Equivalent Crack Width (등가균열폭에 기반한 자기치유 재료의 치유성능 평가 방법)

  • Lee, Woong-Jong;Kim, Hyung-Suk;Choi, Sung;Park, Byung-Sun;Lee, Kwang-Myong
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.9 no.3
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    • pp.383-388
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    • 2021
  • In this study, constant head water permeability test was adopted to evaluate self-healing performance of mortars containing inorganic healing materials which consist of blast furnace slag, sodium sulfate and anhydrite. Clinker powder and sand replaced for a part of cement and fine aggregates. On constant head water permeability test for self-healing mortars, unit water flow rate of mortar specimens were measured according to crack width and healing period. As a result of evaluating the healing performance of self-healing mortar, it was confirmed that with the initial crack width of 0.3mm, the healing rate at healing period of 28 days increased by more than 30%p compared to plain mortar, greatly improving the healing performance. Furthermore, the coefficient(α) which was estimated from the relationship between crack width and unit water flow rate was used for calculating equivalent crack width. By analyzing the correlation of healing rate and equivalent crack width, the time and initial crack width attaining healing target crack width were predicted.

Evaluation of Crack Self-healing Performance in Centrifugal Molding Concrete by Permeability Test (원심성형 콘크리트의 투수시험을 통한 균열 자기치유 성능평가)

  • Hwang, Chul Sung;Woo, Hae Sik;Choi, Young Cheol
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.22 no.3
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    • pp.84-89
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    • 2018
  • Recently, study on self-healing materials have been performed to increase the life by repairing the damage of structures themselves, which are difficult to repair or require high maintenance costs. A water permeability test has been widely used for the evaluation of self-healing performance. However, in the self-healing performance test method, the initial crack width of the concrete greatly affects on the self-healing performance but it does not have a consistent standard. Therefore, in this study, the correlation between crack and permeability and that between time and permeability were analyzed based on crack width and permeability. In addition, since the initial crack width measured by optical microscope is not reliable, the value is derived from the Poiseuille flow and the tendency of time-permeability and time-crack width are analyzed.

Correlation between Crack Width and Water Flow of Cracked Mortar Specimens Measured by Constant Water Head Permeability Test (정수위 투수시험에 의해 측정된 균열 모르타르 시편의 유출수량과 균열폭의 상관관계)

  • Choi, Seul-Woo;Bae, Won-Ho;Lee, Kwang-Myong;Shin, Kyung-Joon
    • 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.

Self-healing Performance Evaluation of Cement Mortar with Inorganic Additives Based on Clinker Binder (클링커 바인더 기반 무기계 혼합재를 활용한 시멘트 모르타르의 치유성능 평가)

  • Jung-Il, Suh;Yoon-Suk, Choi;Byung-Sun, Park;Kwang-Myong, Lee
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.10 no.4
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    • pp.561-568
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    • 2022
  • In this study, the mechanical properties and self-healing performance of cement mortar containing clinker binder, calcium sulfoaluminate(CSA), and sodium sulfate(Na2SO4) were evaluated. The mechanical properties of cement mortar were investigated by measuring compressive strength and flexural strength, and the healing performance was evaluated through hydrostatic water permeability test and gas diffusion test. In addition, the healing products precipitated in the cracks were visually observed through an optical microscope and a scanning electron microscope(SEM). As a result, the incorporation of the clinker binder-based inorganic additives improved the initial and 28-day strength by about 20 %. Depending on the healing performance evaluation method, there was a difference in the healing rate, and the healing rate showed a tendency to be underestimated. Nevertheless, CaCO3 was precipitated as the main healing product inside the 0.3 mm crack when the inorganic additives were mixed with cement mortar, improving the self-healing performance.

Evaluation of field applicability for grouting method using self-healing grout material (자기치유 물질을 이용한 그라우팅공법의 현장적용성 평가)

  • Choi, Yong-Sung;Kim, Byoung-Il;Yoo, Wan-Kyu;Lee, Jae-Dug;Choi, Yong-Ki
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.22 no.5
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    • pp.485-500
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    • 2020
  • Due to various advantages such as small facilities, ease of construction and so on, the grouting technology which is widely used in construction field has developed remarkably compared with the past. However, the efforts to improve the homogeneity of quality, long-term durability and environmental problems have been continued. In recent years, new grouting method has been developed in order to solve problems such as low strength, durability and leaching phenomenon of liquid glass (sodium silicate) grouting material in Korea. A newly developed method integrates the injection material with the ground by the self-healing material of crystallization growth type. For this reason, it is known that improvement of the durability and water quality of the ground, prevention of leaching, and environment friendliness can be expected. The present study applied a newly developed method to test sites and verified its effect such as injection range, improvement effect, waterproofing performance and so on. Standard penetration test, field permeability test, borehole shear test, pressuremeter test and pH test were conducted, and the results were compared between before and after developed method application. As results of tests, the field applicability and improvement effect of developed method were proved to be excellent.