• Title/Summary/Keyword: Durability Performance Evaluation

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Performance Based Evaluation of Concrete Carbonation from Climate Change Effect on Curing Conditions of Wind Speed and Sunlight Exposure Time (기후변화의 풍속과 일조시간 양생조건에 따른 콘크리트 탄산화 성능중심평가)

  • Kim, Tae-Kyun;Shin, Jae-Ho;Choi, Seung-Jai;Kim, Jang-Ho Jay
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.19 no.5
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    • pp.45-55
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    • 2015
  • Currently, extreme weather events such as super typhoon, extreme snowfall, and heat wave are frequently occurring all over the world by natural and human caused factors. After industrial growth in the 1970s, earth's temperature has risen sharply. due to greenhouse effect. Global warming can be attributed to gases emitted from using fossil fuel such as average carbon dioxide, perfluorocarbons, nitrous oxide, and methane. Especially, carbon dioxide has the highest composition of about 90%. in the fossile fuel usage emitted gas. Concrete has excellent durability as a building material climate change. However, due to various of physical and chemical environmental effect such as conditions during its curing process, the performance degradation may occur. Carbon dioxide in the atmosphere causes steel corrosion and durability decreases by lowering the alkalinity of concrete. Therefore, in this study, concrete durability performance with respect to carbonation from curing conditions change due to wind speed and sunshine exposure time. Concrete carbonation experiment are performed. using wind speed (0, 2, 4, 6) m/s and sunlight exposure time (2, 4, 6, 8) hrs. Also, performance based evaluation through the satisfaction curve based on the carbonation depth and carbonation rate test results are performed.

Chemical Durability Test of Thin Membrane in Proton Exchange Membrane Fuel Cells (고분자전해질 연료전지에서 박막의 화학적 내구성 평가)

  • Sohyeong Oh;Donggeun Yoo;Sunggi Jung;Jihong Jeong;Kwonpil Park
    • Korean Chemical Engineering Research
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    • v.61 no.3
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    • pp.362-367
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    • 2023
  • Recently, research and development of proton exchange membrane fuel cells (PEMFC) membranes are progressing in the direction of thinning to reduce prices and improve performance. Demand for hydrogen-powered vehicles for commercial vehicles is also increasing, and their durability should be five times greater than those for passenger vehicles. Despite the thinning of the membranes, the durability of the membranes must be increased five times, so the improvement of the durability of the membranes has become more important. Since the acceleration durability evaluation time also needs to be shortened, the protocol using oxygen instead of air in the existing protocol was applied to a 10 ㎛ thin membrane to evaluate durability. The accelerated durability test (Open circuit voltage holding) was terminated at 720 hours. If the air-based department of energy (DOE) protocol was used, a lifespan of 450,000 km of driving hours would be expected, with a durability of about 1,500 hours. During the chemical durability evaluation, the active area of the electrode decreased by 51%, suggesting that catalyst degradation had an effect on membrane durability. Reducing the catalyst degradation rate is expected to increase membrane durability.

Durability Evaluation of Cathode Open-type Proton Exchange Membrane Fuel Cells Stacks (Cathode 개방형 고분자연료전지 스택 내구성 평가)

  • Yoo, Donggeun;Kim, Hyeonsuck;Oh, Sohyeong;Park, Kwon-Pil
    • Korean Chemical Engineering Research
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    • v.60 no.1
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    • pp.12-19
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    • 2022
  • Cathode open-type PEMFC (Proton Exchange Membrane Fuel Cells) stacks, which are widely used in small transport-type PEMFC, have a problem with poor durability. Through the accelerated durability test of the 13-cell PEMFC stack, we tried to find the cause of the degradation of the stack and to contribute to the improvement of the durability of the cathode open stack. A hydrogen/air boundary is formed during start-up/shut-down (SU/SD) due to the structural problem of the cathode open stack in which the cathode is open to the atmosphere and it is difficult to maintain airtightness, thereby deteriorating the cathode. In this study, it was possible to evaluate the durability in a relatively short time by reducing the 54% of the initial performance by repeating SU/SD 1,800 times on the cathode open stack. After dismantling the stack, each cell was divided into two and the performance was analyzed. Overall, the anode outlet MEA, which facilitates air inflow, showed more severe electrode deterioration than the inlet MEA, confirming that the hydrogen/air boundary formation during SU/SD is the main cause of degradation.

Evaluation on Durability of High Performance Concrete with Expansive Additive and Shrinkage Reducing Admixture (팽창재와 수축저감제를 사용한 고성능 콘크리트의 내구성 평가)

  • Koh, Kyung-Taek;Kang, Su-Tae;Park, Jung-Jun;Ryu, Gum-Sung
    • Journal of the Korea Concrete Institute
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    • v.18 no.2 s.92
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    • pp.205-211
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    • 2006
  • The objective of this study was to evaluate the durability of low shrinkage high performance concrete(LSHPC), which was combined with expansive additives and shrinkage reducing admixtures. We tested for not only LSHPC but also high performance concrete(HPC) and normal concrete(NC) to be compared with the durability of LSHPC. HPC was made in the same water-binder ratio of LSHPC without expansive additives and shrinkage reducing admixture. As a result, it was found that LSHPC had higher compressive and tensile strength than that of HPC. LSHPC showed more excellent performance than HPC and NC in the case of resistance to chloride ion penetration and resistance to carbonation and also showed nearly 100 durability factor in the freeze-thawing test with 500 cycles. From the examination about the watertightness and the pore distribution, it was found that the durability of LSHPC was improved because its hardened cement paste is organized closer. So we can conclude that when LSHPC is applied to structures in field, it is possible to reduce the shrinkage and crack in concrete and improve the durability.

Experimental Study on Evaluation of Material Properties in Cement Mortar with Pond Ash (매립회를 사용한 시멘트 모르타르의 재료 물성 평가에 대한 실험적 연구)

  • Jung, Sang Hwa;Kim, Joo Hyung;Kwon, Seung Jun
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.17 no.3
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    • pp.108-117
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    • 2013
  • Among the byproducts from thermal power plant using coal combustion, fly ash as mineral admixture is widely utilized in concrete manufacturing for its engineering merits. However residuals including bottom ash are usually reclaimed. This study presents an evaluation of engineering properties in cement mortar with pond ash (PA). For this work, two types of pond ash (anthracite and bituminous coal) are selected from two reclamation sites. Cement mortar specimens considering two w/c (0.385 and 0.485) ratios and three replacement ratio of sand (0%, 30%, and 60%) are prepared and their workability, mechanical, and durability performance are evaluated. Anthracite pond ash has high absorption and smooth surface so that it shows reasonable workability, strength development, and durability performance since it has dense pore structure due to smooth surface and sufficient mixing water inside. Reuse of PA is expected to be feasible since PA cement mortar has reasonable engineering performance compared with normal cement mortar.

A Study on the Reinforcement Corrosion Evaluation of Repair Material and Method for Reinforced Concrete Structure by Long Term Exposure Experiment (장기폭로실험에 의한 철근콘크리트구조물 보수재료$\cdot$공법의 철근부식특성 평가)

  • Kim Young Sun;Lee Eui-Bae;Kim Young Duck;Cho Bong Suk;Kim Jae Hwan;Kim Moo Han
    • Proceedings of the Korea Concrete Institute Conference
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    • 2005.05b
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    • pp.197-200
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    • 2005
  • In this study, for the establishment of the performance evaluation methods and the quality control standards of durability recovery method, the quantitative exposure data by long term exposure test under the coast is accumulated and analyzed Investigating and evaluating the result of exposure test at 30 month of exposure age under the coastal environment, carbonation and salt damage are not happened at all but the difference in electric potential are found. Therefore, it is considered that the reinforcement corrosion at replacement with repair material are caused by active-passive corrosion macrocells.

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An Experimental Study on the Concrete Pore Structure Property (콘크리트의 공극 특성에 관한 실험적 연구)

  • Lee, Mun-Hwan;Jung, Mi-Kyung;Oh, Se-Chul;Seo, Chee-Ho
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.3 no.4
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    • pp.179-189
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    • 1999
  • This study attempts to propose an evaluation considering the property of concrete pore which affects the deterioration of neutralization and the rebar resistance of concrete. Understanding pore property of concrete in using extent, for practical using of concrete manufacturing condition. basic quality property and durability estimation etc, the results of the experiment are as follows. 1) The result of analysis pore property of every specimen with the method of area ratio, in limitation of $10^{-6}{\sim}10^{-5}m$, the pore distribution ratio was maximum. It was high value as W/C was increased and the unit cement content was decreased. 2) In case of using admixture. the volume of pores was some increased as variation of mixing content. In high W/C range, it was very increased compared with plain concrete. 3) Concerned with compressive strength and volume of pores in hardened concrete, it is possible compressive strength estimation using the property of concrete pores. 4) Direct measurement of concrete pore property is difficult. the valuation of the dynamic modulus of elasticity using ultrasonic wave velocity was available. 5) Quantitatively evaluation of concrete structure durability by past result of pore distribution estimation, and it can be estimative scale of property study on the concrete materials.

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Analysis on the Current Evaluation items for the Performance-focused Management of the Concrete Retaining Wall (콘크리트 옹벽의 성능위주평가를 위한 평가항목 분석 연구)

  • Lee, Dong Yul;Seong, Joo Hyun;Jeong, Hae Sang;Oh, Tae Keun
    • Journal of the Korean Society of Safety
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    • v.30 no.6
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    • pp.56-62
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    • 2015
  • Recently, one of countermeasures against aging SOC infrastructures, performance-focused management including the serviceability, functionality, durability, and economics has been changed from the structural safety-focused evaluation has changed into The current inspection and diagnosis for the major SOC facilities in Korea has been carried out by the specific principle of details, and most of them checked by the visual inspection are focused on the repair and rehabilitation of the damaged structures, thus they are the preventive maintenance. However, the performance-focused management should be replaced for the effective and economic maintenance as wells as for the minimization of the damage. In this regard, this study the appropriacy of the current evaluation items about the concrete retaining wall, one of SOC infrastructures as the previous step forward the performance-focused management. In order to deduct the effective evaluation items in order, the entropy, analytic hierachy process (AHP), and promethee analysis were peformed and the results were compared and discussed.

A Study on a Performance evaluation for Quality Liguid Siliceous of waterproof agent using on the concrete Structure (콘크리트구조물에 적용하는 액상형 규산질계 침투성 방수재의 성능평가에 관한 연구)

  • Kang Hyo Jin;Kwon Shi-Won;Oh Sang-Keun
    • Proceedings of the Korea Concrete Institute Conference
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    • 2004.05a
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    • pp.184-187
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    • 2004
  • There are many factors that generate the early deterioration of the concrete structure. As the one of the representative factors, we can think an invasion of the water, air and so on. The water and air invade in inside void along the capillarity and they become the cause that the durability like corrosion of layer department due to freezing and thawing, inside steel frame corrosion, and so on blacks. Therefore with covering permeability covering waterproofing material of fluid condition in outer wall, intercepting the deterioration factor due to the infiltration of water from outside and for salt damage of concrete layer department, freezing damage and neutralization, it needs to improve durability of structure. This study separately examined physical and chemical specific of quality liguid siliceous of waterproofing material. Therefore as this applys the construction site, it improves the durability of concrete structure. Further this presents the application plan from the construction market against the new material.

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Evaluation of durability of an ECC(Engineered Cementitious Composite) designed with ground granulated blast furnace slag (고로슬래그 미분말이 혼입된 ECC(Engineered Cementitious Composite)의 내구성 평가)

  • Kim, Jeong-Su;Kim, Yun-Yong;Kim, Jin-Keun;Ha, Gee-Joo
    • Proceedings of the Korea Concrete Institute Conference
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    • 2006.05b
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    • pp.329-332
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    • 2006
  • This paper presents the experimental results for durability of an ECC designed with ground granulated blast furnace slag (BFS) through the test method of chloride ion resistance and freezing-thawing resistance. In order to compare with ECC, normal mortar was also tested. Test results showed that BFS ECC exhibited higher durability performance than ordinary mortar. These results suggest that by adding BFS in ECC, its matrix density is increased which results in decreased of deterioration and it also adds to the fiber bridging that contributes in control of cracking.

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