• Title, Summary, Keyword: 확산계수

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Chloride Diffusion Coefficient Evaluation in 1 Year-Cured OPC Concrete under Loading Conditions and Cold Joint (하중조건과 콜드조인트를 고려한 1년 양생된 OPC 콘크리트의 염화물 확산계수 평가)

  • Oh, Kyeong-Seok;Kwon, Seung-Jun
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.21 no.5
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    • pp.21-29
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    • 2017
  • Cold joint caused by construction delay is vulnerable to shear stress and it allows more rapid chloride penetration and diffusion. In the paper, investigation of chloride diffusion coefficient is performed for 1-year cured concrete considering compressive and tensile loading level and cold joint. The results are compared with the previous results in 91-day cured concrete. In the 1-year cured concrete without loading, 10.7% and 10.5% of diffusion reduction are evaluated for those in 91-day cured concrete, respectively. The reduction ratios are almost similar however the result in cold joint concrete shows much higher values. The results in 1-year cured concrete under 30% and 60% of compressive loading show reduction of chloride diffusion by 10.9% and 5.8% compared with 91-day cured results, which is caused by steady hydration of cement particles, so called, time effect. In the case of tensile loading, the differences in results are not significant regardless of time effect and cold joint since micro cracks which is weak point of concrete is much dominant despite of long term curing.

Service life evaluation in RC structure near to sea shore through accelerated chloride diffusion test (촉진 염화물 시험결과를 이용한 비말대 콘크리트 구조물의 내구수명 평가)

  • Kim, Jeong-Su;Kwon, Seung-Jun
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.23 no.5
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    • pp.30-36
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    • 2019
  • In order to evaluate service life of RC (Reinforced Concrete) structures exposed to chloride attack, chloride penetration analysis is required referred to the chloride diffusion coefficient from the actual mix proportions. In this work, accelerated diffusion coefficients are obtained from NT BUILD 492 and ASTM C 1202 and the related apparent diffusion coefficients are derived via the previously proposed relationship for RC structures near to sea shore. Considering the properties of the mix proportions and the most conservative analysis conditions like critical and surface chloride contents, service lifes in column and exterior wall member are evaluated through conventional program LIFE 365 ver.2. The different built-up period of 10 and 15 years has no significant effect on service life. The results from mix proportions with slag show longer than 75 years of service life with the help of higher time dependent parameter and lower initial diffusion coefficient.

Analysis on Changes in Strength, Chloride Diffusion, and Passed Charges in Normal Concrete Considering Ages and Mix Proportions (재령 및 배합특성을 고려한 보통 콘크리트의 강도, 염화물 확산계수, 통과전하량 변화 분석)

  • Lee, Hack-Soo;Kwon, Seung-Jun
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.5 no.1
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    • pp.1-7
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    • 2017
  • Concrete behavior in early-age is changing due to hydration reaction with time, and a resistance to chloride attack and strength development are different characterized. In the present work, changing strength and resistance to chloride attack are evaluated with ages from 28 days to 6 months. For the purpose, strength, diffusion coefficient, and passed charge are evaluated for normal concrete with 3 different mix proportions considering 28-day and 6-month curing conditions. With increasing concrete age, the changing ratio of strength falls on the level of 135.3~138.3%, while diffusion coefficient and passed charge shows 41.8%~51.1% and 53.6%~70.0%, respectively. The results of chloride diffusion coefficient and passed charge show relatively similar changing ratios since they are much dependent on the chloride migration velocity in electrical field. The changing ratios in chloride behaviors are evaluated to be much larger than those in compressive strength since the ion transport mechanism is proportional to not porosity but square of porosity.

Chloride Diffusion Coefficients in Cold Joint Concrete with GGBFS (고로슬래그 미분말을 혼입한 콜드조인트 콘크리트의 염화물 확산계수)

  • Oh, Kyeong-Seok;Mun, Jin-Man;Kwon, Seung-Jun
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.20 no.5
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    • pp.44-49
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    • 2016
  • Among the deteriorating agents, chloride ion is reported to be one of the most harmful ions due to its rapid diffusion and direct effect on steel corrosion. Cold joint which occurs in mass concrete placing is vulnerable to shear resistance and more severe deterioration. The paper presents an quantitative evaluation of chloride diffusion coefficient in OPC(Ordinary Portland Cement) and GGBFS(Ground Granulated Blast Furnace Slag) concrete containing cold joint. GGBFS concrete shows $6.6{\times}10^{-12}m^2/sec$ which is almost 30% level of OPC concrete results and the trend is repeated in the case of cold joint concrete. Compared with OPC concrete, GGBFS concrete is evaluated to have better resistance to chloride penetration, showing 0.30 times of chloride diffusion coefficient in concrete without cold joint 0.39 times with cold joint, respectively.

Solvent diffusion model in polymer membrane (고분자막내에서 용매 확산 모델)

  • 김종수;이광래
    • Proceedings of the Membrane Society of Korea Conference
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    • pp.59-62
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    • 1998
  • 1. 서론 : 막내부에서 물질전달을 설명하는 이론으로 현재 solution-diffusion model과 pore-flow model 두 가지가 있다. 이 중에서 흡착, 확산, 탈착의 3과정을 거치는 solution-diffusion model이 주로 사용되고 있다. 본 연구에서는 solution-diffusion model 에서 상호확산계수를 구하기 위해서 Vrentas-Duda식을 이용하여 자기확산계수를 구하고 Bearman식으로부터 상호확산계수를 구하는 과정을 UNIFAC-FV와 modified UNIFAC-FV을 이용하여 계산하였으며 Flory-Huggins식을 이용한 기존방법과 비교하였다.(생략)

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Effect of Higher Order Form Factors on the Prediction of Room Acoustics by Extended Radiosity Method (확장 라디오시티법에 의한 실내음향 예측에 있어 고차형태계수의 영향)

  • Lee Heewon;Goh Ildu;Oh Yangki;Doo Sejin;Jeong Dae-up
    • Proceedings of the Acoustical Society of Korea Conference
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    • pp.519-522
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    • 2002
  • 컴퓨터에 의한 실내음향 예측에 있어 확산반사의 고려는 매우 중요한 요소의 하나로 간주된다. 지난 수년 동안 음선추적법을 이용하여 실내음향을 예측하는 경우에 확산 반사를 고려하기 위한 방안들이 다양하게 제시되었으나 경면반사를 근본으로 하는 영상법에서는 확산 반사를 고려하기가 어려운 것으로 알려져 있다. 본 연구에서는 컴퓨터 그래픽 분야에서 제안된 확장 라디오 시티법을 적용하여 영상법에서 확산반사를 고려하는 방안을 제시하였다. 부분적으로 확산성을 갖는 반사면에서의 음향에너지 반사는 확산반사와 경면반사의 형태로 나누어 볼 수 있으며 반사의 횟수를 거듭함에 따라 확산-확산, 확산-경면, 경면-확산, 경면-경면의 형태로 반사에너지의 전환이 이루어진다. 본 연구에서는 고차 형태계수의 개념을 이용하여 이 네가지 형태의 반사음전달과정을 모두 고려할 수 있도록 함으로써 실내의 벽면을 부분적 확산반사의 특성을 갖는 반사면으로 모델링 할 수 있도록 하였다. 본 논문에서는 확장라디오시티법의 개념과 이에 따른 고차형태계수의 근사 계산법을 제시하고 고차형태계수가 실내음향 씨뮬레이션의 결과에 미치는 영향 등을 분석해 보았다. [본 연구는 한국과학재단 특정기초 연구 (과제번호 1999-1-310-004-3)의 지원에 의한 연구결과의 일부임]

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Effect of the Kinds and Replacement Ratios of Mineral Admixtures on the Development of Concrete Resistance against the Penetration of Chloride Ions (혼화재 종류 및 치환율이 콘크리트의 내염성능 향상에 미치는 영향에 관한 연구)

  • Kim Young-Jin;Lee Sang-Soo;Kim Dong-Seuk;Yoo Jae-Kang
    • Journal of the Korea Concrete Institute
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    • v.16 no.3
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    • pp.319-326
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    • 2004
  • This paper investigates the effect of the concrete containing mineral admixtures(pozzolanic materials such as fly-ash, ground granulated blast-furnace slag, silica fume and meta kaolin) on the resistance properties to chloride ion invasion. The purposed testing procedure was applied to the concrete replaced mineral admixtures for 3${\~}$4 replacement ratios under water-binder ratios ranged from 0.40 to 0.55. For the electro-migration test, Tang and Nilsson's method was used to estimate the diffusion coefficient of chloride ion. As a results, the water-binder ratios, kinds of mineral admixtures and replacement ratios, water curing periods had a great effect on the diffusion coefficient of chloride ion, and the optimal replacement ratios had a limitation for each mineral admixtures. Also, the use of mineral admixtures by mass(replacement of OPC) enhance the resistance ability against chloride penetration compared with the plain concrete. The compressive strength was shown related to the diffusion coefficient of chloride ion, the compressive strength increases with the diffusion coefficient of chloride ion decreasing. Below the 50 MPa, the variation of diffusion coefficient of concrete replaced mineral admixtures was bigger than that of plain concrete.

Analysis Technique for Chloride Penetration using Double-layer and Time-Dependent Chloride Diffusion in Concrete (콘크리트내의 이중구조와 시간의존성을 고려한 염화물 해석기법의 개발)

  • Mun, Jin-Man;Kim, Jin-Yeong;Kim, Young-Joon;Oh, Gyeong-Seok;Kwon, Seung-Jun
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.19 no.5
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    • pp.83-91
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    • 2015
  • With varying conditions of concrete surface, induced chloride contents are changed and this is a key parameter for steel corrosion and service life in RC (Reinforced Concrete) structures. Many surface enhancement techniques using impregnation have been developed, however the evaluation techniques for chloride behavior through doubly layered media and time-dependent diffusion are rarely proposed. This paper presents an analysis technique considering double-layer concrete and time-dependent diffusion behavior, and the results are compared with those from the previous test results through reverse analysis. The chloride profiles from the surface-impregnated concrete exposed to atmospheric, tidal, submerged zone for 2 years are adopted. Furthermore surface chloride contents and diffusion coefficients are obtained, and are compared with those from Life365. Through consideration of time effect, the relative error decreases from 0.28 to 0.20 in atmospheric, 0.29 to 0.11 in tidal, and 0.54 to 0.40 in submerged zone, respectively, which shows more reasonable results. Utilizing the diffusion coefficients from Life365, relative errors increases and it needs deeper penetration depth (e) and lower diffusion coefficient ratio ($D_1/D_2$) due to higher diffusion coefficient.

Optimal Parameters Estimation of Diffusion Analogy-GIUH Model for Estimation of Reservoir Flood Inflow (저수지 홍수유입량 산정을 위한 확산-유추 지형학적 순간단위도 모형의 최적매개변수 추정)

  • Choi, Yong-Joon;Kim, Joo-Cheol;Lee, Gi-Ha;Jeong, Kwan-Sue
    • Proceedings of the Korea Water Resources Association Conference
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    • pp.1322-1326
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    • 2010
  • 확산-유추 지형학적 순간단위도는 통계물리적인 모형으로 이론적 물리적으로 뛰어난 모형임에도 불구하고 유역의 동적 매개변수인 특성유속과 확산계수의 산정이 어려워 실제적인 사용이 제한되어 왔다. 이러한 난제를 해결하기 위하여 본 연구에서는 금강수계의 보청천 산성유역을 대상으로 전역최적화 기법인 SCE-UA를 이용하여 확산-유추 지형학적 순간단위도 모형의 동적 매개변수 산정하였으며, 모형의 재현성을 3개의 수문사상을 이용하여 검토하였다. 매개변수의 최적화 결과 차수 단계별 특성유속 및 확산계수의 증감은 변동을 보이지만, 전체적인 경향성은 특성유속의 경우 하천차수가 커질수록, 즉 하류방향에 대해 증가 경향을 나타내며, 반대로 확산계수는 감소되는 경향을 나타냈다. 본 연구에서 적용한 최적화 방법에 향후 지체시간, 분산 및 왜곡도 등의 통계적인 제약조건과 동적 매개변수의 공간적 변화 등의 물리적인 의미를 갖는 제약조건 등이 결합된다면 좀 더 발전된 모형으로 개선될 수 있을 것으로 판단된다.

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Effect of Time-dependent Diffusion and Exterior Conditions on Service Life Considering Deterministic and Probabilistic Method (결정론 및 확률론적 방법에 따라 시간의존성 염화물 확산계수 및 외부 영향인자가 내구수명에 미치는 영향)

  • Kwon, Seung-Jun
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.20 no.6
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    • pp.65-72
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    • 2016
  • Service life evaluation for RC Structures exposed to chloride attack is very important, however the previous two methods(deterministic and probabilistic method) show a big difference. The paper presents a service life simulation using deterministic and probabilistic method with time-dependent diffusion coefficient. Three different cases are considered for diffusion coefficient, concrete cover depth, and surface chloride content respectively, and then the PDF(probability of durability failure) and the related service life are obtained. Through adopting time-dependent diffusion, the discrepancy between the two methods can be reduced, which yields reasonable service life. When diffusion coefficient increases from $2.5{\times}10^{-12}m^2/sec$ to $7.5{\times}10^{-12}m^2/sec$, the service life decreases to 25.5~35.6% level, and cover depth does from 75 mm to 125 mm, it increases to 267~311% level as well. In the case of surface chloride content from $5.0kg/m^3$ to $15.0kg/m^3$, it changes to 40.9~54.5%. The effect of cover depth is higher than the others by 8~10 times and also implies it is a key parameter to service life extension.