Journal of the Korean Recycled Construction Resources Institute (한국건설순환자원학회논문집)

Korean Recycled Construction Resources Institute (한국건설순환자원학회)
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Quantification of Chloride Diffusivity in Steady State Condition in Concrete with Fly Ash Considering Curing and Crack Effect

재령 및 균열효과를 고려한 플라이애시 콘크리트의 정상상태 염화물 확산 특성의 정량화

  • Yoon, Yong-Sik (Department of Civil Engineering, Hannam University) ;
  • Cheon, Ju-Hyun (Construction Technology Research Center, Korea Conformity Laboratories) ;
  • Kwon, Seung-Jun (Department of Civil Engineering, Hannam University)
  • 윤용식 (한남대학교 건설시스템공학과) ;
  • 천주현 (한국건설생활환경시험연구원 건설기술연구센터) ;
  • 권성준 (한남대학교 건설시스템공학과)
  • Received : 2019.03.18
  • Accepted : 2019.04.10
  • Published : 2019.06.30
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Abstract

In case of the cracks in concrete, the penetration of deterioration ions such as chloride ions in to cracks is accelerated. According to the penetration of chloride ions, structural and durability problems to RC(Reinforced Concrete) structures are caused. In this study, the accelerated chloride diffusion coefficient which is in steady state is evaluated for 2 year aged normal and high strength FA(Fly Ash) concrete, after a range of crack depths are induced up to 1.0 mm in 56 aged day. Considering crack effect by linear regression analysis, high strength concrete has slightly less increasing ratio of diffusion coefficient by crack than normal strength concrete, and diffusion coefficient increases non-linearly as crack width is increased. Also, In two types of concrete, crack effect decrease as the curing period increase. In the case of quantifying crack and curing effect by using exponential function form, the coefficients of determination are higher than those of linear regression analysis. Under steady state, it is thought that there is not a high correlation between the crack effect and the curing effect, and considering the two independent effects, it is believed that reasonable prediction equation for diffusion of concrete with crack can be proposed.

콘크리트에 균열이 발생하는 경우 균열부로의 열화 이온의 침투가 확산되어 철근콘크리트 구조물에 구조적 내구적 문제를 야기한다. 본 연구에서는 보통 및 고강도 플라이애시 콘크리트를 대상으로 재령 56일에 최대 1.0mm까지 다양한 균열 폭을 유도한 후 재령 2년의 정상상태 촉진 염화물 확산계수를 평가하였다. 균열 효과를 선형회귀분석을 통해 고려하면 고강도 콘크리트는 보통 강도 콘크리트 보다 균열 폭에 의한 확산계수 증가가 다소 적었으며 균열 폭이 증가함에 따라 확산계수가 비선형적으로 증가하였다. 또한 두 가지 배합에서 재령이 증가할수록 균열에 의한 영향이 감소하였다. 지수함수 형태를 사용하여 균열 및 재령 효과를 정량화하는 경우, 선형회귀분석을 통한 경우보다 더 높은 결정계수를 나타내었다. 정상상태에서는 균열 효과와 재령의 영향 간의 상관성이 크지 않은 것으로 보이며 두 가지 독립영향을 고려하는 경우 합리적인 균열부 콘크리트 확산성 예측식을 제안할 수 있다고 사료된다.

Keywords

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Fig. 1. Loading for crack inducing and measuring

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Fig. 2. Measurement of current during accelerated chloride diffusion test

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Fig. 3. Compressive strength in FA based concrete for 2 years

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Fig. 4. Diffusion coefficient of normal strength with curing period

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Fig. 5. Diffusion coefficient of high strength with curing period

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Fig. 6. Gradient to sound concrete for crack effect

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Fig. 7. Procedure of regression analysis for crack and curing effect

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Fig. 8. Regression analysis results for crack and curing effect for normal strength concrete

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Fig. 9. Regression analysis results for crack and curing effect for high strength concrete

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Fig. 10. Changing patterns of parameter(A and E)

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Fig. 11. Diffusion contour considering age and crack width

Table 1. Mix proportions for FA based concrete

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Table 2. Physical and chemical properties of binder

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Table 3. Physical properties of aggregates

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Table 4. Linear analysis of diffusion coefficient considering crack and curing effect

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Table 5. Analysis results for regression analysis of exponential function

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