• Title/Summary/Keyword: NT BUILD 492

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Chloride Diffusion Coefficient Model Considering the Initiation Time of Exposure to Chloride Environment (염소이온 노출개시시기를 고려한 기존 확산계수 모델 수정제안)

  • Kim, Ki-Hyun;Cha, Soo-Won
    • Journal of the Korea Concrete Institute
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    • v.21 no.3
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    • pp.377-386
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    • 2009
  • A reference diffusion coefficient model from ACI life-365 is drawn from test results by NT build 443. This test method gives a time-averaged diffusion coefficient during immersion period, thus the ACI model uses the time-averaged diffusion coefficient as a reference value. ACI model needs to be revised, considering the difference between the time-average value and reference value at specified time. In this study, firstly the analytic solutions of diffusion equation are derived considering the initiation time and period of exposure to chloride, and secondly the time-averaged diffusion coefficient from NT build 443 is converted into the diffusion coefficient at reference time. From this study, the reference diffusion coefficient of ACI model should be modified to be about 10% larger values than those of present ACI model. For convenient design of service life, previous relationship between the chloride diffusion coefficient from NT build 443 and that from NT build 492 is also modified. To compare the chloride diffusion coefficients of ACI and JCI models, the reference chloride diffusion coefficient with respect to the JCI model is drawn in the similar form of ACI model's, and service life prediction by ACI life-365 method is confirmed to give a conservative result.

Diffusion Characteristics for Chloride Ion of Concrete Subjected to Sulfate Attack (황산염 침투를 받은 콘크리트의 염소이온 확산특성)

  • Park, Jae-Im;Bae, Su-Ho;Yu, Jae-Won;Lee, Kwang-Myong
    • Proceedings of the Korea Concrete Institute Conference
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    • 2010.05a
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    • pp.213-214
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    • 2010
  • An objective of this experimental research is to investigate the diffusion characteristics for chloride ion of concrete subjected to sulfate attack. For this purpose, concretes with three types of cement such as ordinary portland cement(OPC), binary blended cement(BBC), and ternary blended cement(TBC) containing mineral admixtures were made for water-binder ratios of 32% and 43%. The concrete specimens were immersed in sulfate solution for 365 days, and then the resistance against chloride ion penetration of them were estimated by using NT BUILD 492. It was observed from the test results that the resistance to chloride ion penetration of concrete subjected to sulfate attack was greatly decreased than that of standard curing concrete under the same age.

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A Study on Chloride Diffusion in Concrete Containing Lightweight Aggregate Using Crushed Stone-powder (폐석분을 활용한 경량골재 콘크리트의 염화물 확산에 관한 연구)

  • Lee, Dae-Hyuk;Jee, NamYong;Kim, Jae-Hun;Jeong, Yong;Shin, Jae-Kyung
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2009.11a
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    • pp.127-131
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    • 2009
  • The purpose of this study is to provide fundamental data on chloride diffusion from lightweight aggregate concrete by utilizing crushed stone-powder. Accordingly, the study performed experiments using concrete aggregates of Crushed Aggregate (CG), Single-sized Lightweight Aggregate (SLG), Continuous Graded Lightweight Aggregate (CLG), and using water-binder ratio of 0.4, 0.5, 0.6, and using binder of FA and BFS. The chloride diffusion coefficient is calculated after experiment based on NT BUILD 492. Diffusion coefficient of SLG and CLG were little bit higher than CG Concrete, but the difference is meaningless. Also, chloride diffusion coefficient indicates that it is highly affected by water-binder ratio, and it decreases with the decrease in water-binder ratio. The admixture substitution indicates decrease only with water-binder ratio of 0.4 for FA15% case, but admixture substitution indicates decrease with all levels of ratio for FA10 + BFS20% which means more appropriate. According to the analysis result of chloride diffusion from lightweight aggregate concrete, crushed stone-powder utilized lightweight aggregate concrete indicates higher chloride diffusion coefficient than CG concrete, which is not a significant difference, and can improve resistance through water-binder ratio and admixture substitution.

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Evaluation of Chloride Attack Resistibility of Heavyweight Concrete Using Copper Slag and Magnetite as Aggregate (동슬래그 및 자철석을 골재로 사용한 중량 콘크리트의 회파블록 적용을 위한 염해저항성 평가)

  • Moon, Hoon;Kim, Ji-Hyun;Lee, Jae-Yong;Chung, Chul-Woo
    • Journal of the Korea Institute of Building Construction
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    • v.17 no.6
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    • pp.483-492
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    • 2017
  • Recently, the coastal area has become the popular place for infrastructure development. To provide a beautiful scenary of costal area to nearby facilities without any hinderance, and also to protect those facilities from the sea water overflow, it is necessary to develop a new type of wave dissipating block, which is a turning wave block. It is noticeable that the top of the turning wave block is flat and thus can provide spaces for various purposes. However, the unit weight of the block decreases due to the presence of pipeline that is installed for turning the direction of the waves. In order to mitigate such problem, a heavyweight concrete needs to be used to increase the resistance against tidal waves. The copper slag and magnetite were used as a source of fine and coarse aggregate, respectively. The 28 day compressive strength of concrete incorporating ordinary and heavyweight aggregate did not show significant differences. It should be noted that the chloride ion penetration resistance was evaluated using NT-BUILD 492 rather than ASTM C 1202 method because concrete incorporating magnetite as a coarse aggregate showed excessive current flow by ASTM C 1202 method. According to the results from NT Build 492 method, which uses the penetration depth of chlorine ions to obtain chloride ion diffusivity, the heavyweight concrete incorporating the copper slag and the magnetite showed the best resistance against the chloride ion penetration. Therefore, it is reasonable to say that heavyweight concrete made with copper slag and magnetite can be used for production of turning wave block.

A Study on Chloride Diffusion in Concrete Containing Lightweight Aggregate Using Crushed Stone-powder (폐석분을 활용한 경량골재 콘크리트의 염화물 확산에 관한 연구)

  • Lee, Dae-Hyuk;Yoon, Sang-Chen;Jeong, Yong;Shin, Jae-Kyung;Jee, Nam-Yong
    • Journal of the Korea Concrete Institute
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    • v.22 no.2
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    • pp.255-262
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    • 2010
  • The purpose of this study is to provide preliminary data on chloride diffusion of lightweight aggregate concrete containing crushed stone-powder. Accordingly, the study performed experiments using concrete aggregates of Crushed Aggregate (CG), Single-sized Lightweight Aggregate (SLG), Continuous Graded Lightweight Aggregate (CLG), and using water-binder ratio of 0.4, 0.5, 0.6, and using binder of FA and BFS. The chloride diffusion coefficient is calculated according to the NT BUILD 492. Diffusion coefficient of SLG and CLG were higher than that of CG concrete, but the difference was not significant. Also, chloride diffusion coefficient data indicated that it was highly affected by water-binder ratio, and it decreased with the decrease in waterbinder ratio. The admixture substitution of FA15% was effective in decreasing the diffusion coefficient only with water-binder ratio of 0.4 while admixture substitution of FA10+BFS20% was effective with all levels of water-binder ratio. The result of study shows lightweight aggregate concrete containing crushed stone-powder has slightly higher chloride diffusion coefficient than CG concrete, but the difference is not significant such that it can be overcome by adjusting water-binder ratio and admixture substitution. In addition, the data indicate the chloride diffusion coefficient of lightweight aggregate concrete can be estimated from the strength of lightweight aggregate.

Life Expectation of Salt Attack for Fire Damaged RC Structure (화재피해를 입은 콘크리트 건축물의 염해 내구수명 산정)

  • Park, Dong-Cheon
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2017.05a
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    • pp.15-16
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    • 2017
  • The properties of concrete damaged by fire change according to the temperature. Diffusion coefficient of chloride ion also can change which affect the life expectation under salt circumstance. Diffusion coefficient was measured by NT BUILD 492 using the concrete specimen damaged by high temperature. FEM analysis was performed to predict the life expectancy which can help to diagnose the concrete diagnose and to design maintenance strategy.

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Case Study on the Mixing Proportions of 100 Year Life Time Concrete (내구수명 100년 해양 콘크리트의 배합사례)

  • Jang, Bong-Seok;Ahn, Jeong-Hwan
    • Proceedings of the Korea Concrete Institute Conference
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    • 2008.04a
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    • pp.1073-1076
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    • 2008
  • This study shows some results of concrete mixing design has 100 years life time. The ratios of ternary blended cement are 4 types. the ratios of blast furnace slag cement are 3 types. In this case study, 40%, 50% and 60% replacement ratio of blast furnace slag(BSF) to OPC are used, also 35:45:20, 30:35:35, 30:40:30 and 35:40:25 ratio of OPC:BSF:FA are used. The mixing design tests include slump, air content, compressive strength and thermal properties of concrete. The compressive strength tests are executed at the age of 3, 7, 28, 56, and 91 days. The coefficient of chloride diffusion is determined by NT Build 492 method. The purpose of this study is to shows the results of case studies as the ratio of blended cement varies.

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An Experimental Study on the Resistance of Nylon Fiber Reinforced Concrete to Chloride Ion Penetration (나일론섬유보강 콘크리트의 염소이온 침투 저항성에 대한 실험적 연구)

  • Jeon, Joong-Kyu;Moon, Jae-Heum;You, Jin-O
    • Proceedings of the Korea Concrete Institute Conference
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    • 2008.04a
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    • pp.557-560
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    • 2008
  • Fiber reinforcement has been being widely used in concrete to enhance the mechanical properties and to reduce the micro-cracking caused by plastic and drying shrinkage. While researches has been focused on the benefits of fiber reinforcement, the properties of fiber reinforced concrete are strongly dependent on the type, shape and the amount of fibers in concrete. In this study, the resistance of nylon fiber reinforced concrete against the chloride ion penetration was experimentally observed by NT Build 492. The test results showed that the addition of nylon fiber has little effect on the change of the resistivity of concrete to the chloride ion penetration.

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