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Evaluation of Chloride Behavior and Service Life in Long-Term Aged FA Concrete through Probabilistic Analysis

장기재령 FA 콘크리트에 대한 염화물 거동 및 확률론적 염해 내구수명 평가

  • Yoon, Yong-Sik (Department of Civil and Environmental Engineering, Hannam University) ;
  • Kwon, Seung-Jun (Department of Civil and Environmental Engineering, Hannam University)
  • 윤용식 (한남대학교 토목환경공학과) ;
  • 권성준 (한남대학교 토목환경공학과)
  • Received : 2020.08.03
  • Accepted : 2020.09.22
  • Published : 2020.09.30

Abstract

In this study, accelerated chloride diffusion tests were performed on OPC(Ordinary Portland Cement) and FA(Fly Ash) concrete considering three levels o f W/B(Water to Binder) ratio o n 1,095 curing days. The accelerated chloride diffusion coefficient and the passed charge were evaluated in accordance with Tang's method and ASTM C 1202, and the resistance performance to chloride attack improved over time. FA concrete showed excellent resistance performance against chloride penetration with help of pozzolanic reaction. As the result of the passed charge, FA concrete showed durability improvement, "low" grade to "very low" grade, but OPC concrete changed "moderate" grade to "low" grade at 1,095 curing days. After assuming the design variables used for durability design as normal distribution functions, the service life of each case was evaluated by the probabilistic analysis method based on MCS(Monte Carlo Simulation). In FA concrete, the increase of probability of durability failure was lower than that of OPC concrete with increasing time, because the time-dependent coefficient of FA concrete was up to 3.2 times higher than OPC concrete. In addition, the service life by probabilistic analysis was evaluated lower than the service life by deterministic analysis, since the target probability of durability failure was set to 10%. It is considered that more economical durability design will be possible if the mo re suitable target probability of durability failure is set for various structures through researches on actual conditions and indoor tests under various circumstances.

본 연구에서는 3가지 수준의 물-결합재 비를 고려한 OPC 및 FA 콘크리트를 대상으로 재령 1,095일에 촉진 염화물 확산 시험을 수행하였다. Tang's method 및 ASTM C 1202에 준하여 촉진 염화물 확산계수 및 통과 전하량을 평가하였으며 시간의 존적으로 개선되는 염화물 확산 거동을 고찰하였다. FA 배합에서는 포졸란 반응에 의해 뛰어난 염해저항성능을 나내었는데, 통과 전하량 평가 결과에 따르면 FA 콘크리트는 재령 1,095일에 "Low" 등급에서 "Very low" 등급으로 감소하였으나, OPC 배합의 경우 "Moderate" 등급에서 "Low" 등급으로 감소하였다. 염해 내구수명 해석 시 사용되는 설계변수를 정규분포 함수로 가정한 후, MCS를 기반으로 각 배합의 내구수명을 확률론적 해석 방법으로 평가하였다. FA 콘크리트에서는 OPC 콘크리트 대비 시간의 증가에 따른 내구적 파괴확률의 증가가 낮게 나타났는데 이는 FA 콘크리트의 시간의존성지수가 OPC 배합 대비 최대 3.2배 높기 때문이다. 또한 목표 내구적 파괴확률을 10%로 설정하였기 때문에 확률론적 해석에 의한 내구수명이 결정론적 해석에 의한 내구수명보다 낮게 평가되었다. 다양한 환경 하의 실태조사 및 실내 시험을 통해 각 구조물에 적합한 목표 내구적 파괴확률을 설정한다면 더욱 경제적인 내구성능 설계가 가능해지리라 사료된다.

Keywords

References

  1. ASTM C 1202. (2005). Standard Test Method for Electrical Indication of Concrete's Ability to Resist Chloride Ion Penetration, American Society for Testing and Materials, USA.
  2. Berke, N.S., Hicks, M.C. (1994). Predicting chloride profiles in concrete, CORROSION, 50(3), 234-239. https://doi.org/10.5006/1.3293515
  3. Bilodeau, A., Malhotra, V.M., Golden, D.M. (1998). Mechanical properties and durability of structural lightweight concrete incorporating high-volumes of fly ash, ACI International, 178, 449-474.
  4. CEB. (2006). Model Code for Service Life Design. The International Federation for Structural Concrete(fib), Task Group 5.6.
  5. EN 1991. (2000). Eurocode 1: Basis of Design and Actions on Structures, CEN.
  6. KCI. (2012). Concrete Standard Specification-Durability Part, Korea Concrete Institute [In Korean].
  7. KDS 14 20 40. (2016). Standard for Durability Design of Concrete Structures. Ministry of Land, Infrastructure and Transport, Korea, 12-18 [In Korean].
  8. Kim, H.J., Yoon, Y.S., Yang, K.H., Kwon, S.J. (2019). Durability and purification performance of concrete impregnated with silicate and sprayed with photocatalytic $TiO_2$, Construction and Building Materials, 199(2019), 106-114. https://doi.org/10.1016/j.conbuildmat.2018.12.035
  9. Kouloumbi, N., Batis, G., Malalmi, C. (1994). The anticorrosive effect of fly ash, slag and a greek pozzolan in reinforced concrete, Cement & Concrete Composites, 16(4), 253-260. https://doi.org/10.1016/0958-9465(94)90037-X
  10. Koyama, K., Hanada, J. (1998). Design guidelines for durability of concrete structures(Draft), Journal of JSCE, 585, 199-203.
  11. KS L 5405. (2016). Fly Ash, Korea Standard Service Network, Korea, 1-8 [In Korean].
  12. Kwon, S.J. (2016). Effect of time-dependent diffusion and exterior conditions on service life considering deterministic and probabilistic method, Journal of the Korea Institute for Structural Maintenance and Inspection, 20(6), 65-72 [In Korean]. https://doi.org/10.11112/jksmi.2016.20.6.065
  13. Kwon, S.J., Na, U.J., Park, S.S., Jung, S.H. (2009). Service life prediction of concrete wharves with early-aged crack: probabilistic approach for chloride diffusion, Structural Safety, 31(1), 75-83. https://doi.org/10.1016/j.strusafe.2008.03.004
  14. Lee, B.K., Kim, G.Y., Kim, G.T., Shin, K.S,. Nam, J.S. (2017). Chloride ion penetration resistance of slag-replaced concrete and cementless slag concrete by marine environmental exposure, Journal of the Korea Concrete Institute, 29(3), 299-306 [In Korean]. https://doi.org/10.4334/JKCI.2017.29.3.299
  15. Lee, J.W., Kim, K.M., Bae, Y.K., Lee, J.S. (2004). "Study on the field application according to the early strength of the concrete admixed with polycarboxylate superplasticizer," Korea Concrete Institute academic conference, Korea Concrete Institute, Pyoengchang, Korea, 200-203 [In Korean].
  16. Metha, P.K., Monteiro, P.M. (2009). Concrete-Structure, properties, and materials, 2nd edition, Prentice Hall, New-Jersey, 113-178.
  17. Moon, H.Y., Kim, H.S., Lee, S.T. (2002). Examination on the deterioration of concrete due to seawater attack, Journal of the Korean Society of Civil Engineers, 22(1A), 171-179 [In Korean].
  18. Nath, P., Sarker, P. (2011). Effect of fly ash on the durability properties of high strength concrete, Procedia Engineering, 14, 1149-1156. https://doi.org/10.1016/j.proeng.2011.07.144
  19. Oh, K.S., Moon, J.M., Park, K.T., Kwon, S.J. (2016). Evaluation of load capacity reduction in RC beam with corroded FRP hybrid bar and steel, Journal of the Korea Institute for Structural Maintenance and Inspection, 20(2), 10-17 [In Korean]. https://doi.org/10.11112/jksmi.2016.20.2.010
  20. Polder, R.B., van der Wegen, G., Boutz, M. (2007). "Performance based guideline for service life design of concrete for civil engineering structures - A proposal discussed in the Netherlands," International RILEM Workshop on Performance Based Evaluation and Indicators for Concrete Durability, Madrid, Spain, 31-39.
  21. SERI. (2003). Evaluation of Chloride Ion Diffusion Characteristics of High Durability Concrete, Samsung Engineering Research Institute, Final Report [In Korean].
  22. Stewart, M.G., Mullard, J.A. (2007). Spatial time-dependent reliability analysis of corrosion damage and the timing of first repair for RC structures, Engineering Structures, 29(7), 1457-1464. https://doi.org/10.1016/j.engstruct.2006.09.004
  23. Tang, L., Nilsson, L.O. (1992). Rapid determination of the chloride diffusivity in concrete by applying an electrical field, ACI Materials Journal, 89(1), 49-53.
  24. Thomas, M.D,A., Bentz, E.C. (2002). Computer Program for Predicting the Service Life and Life-cycle Costs of Reinforced Concrete Exposed to Chlorides, Life 365 Manual, SFA, 2-28.
  25. Yang K.H., Mun, J.H., Yoon, Y.S., Kwon, S.J. (2018). Effects of loading conditions and cold joint on service life against chloride ingress, Computers and Concrete, 22(3), 319-326. https://doi.org/10.12989/CAC.2018.22.3.319
  26. Yoon, Y.S., Hwang, S.H., Kwon, S.J. (2019). Evaluation of chloride diffusion characteristics in concrete with fly ash cured for 2 years, Journal of the Korean Recycled Construction Resources Institute, 7(1), 8-15 [In Korean]. https://doi.org/10.14190/JRCR.2019.7.1.8
  27. Yoon, Y.S., Kwon, S.J. (2018). Evaluation of time-dependent chloride resistance in HPC containing fly ash cured for 1 year, Journal of the Korea Institute for Structural Maintenance and Inspection, 22(4), 52-59 [In Korean]. https://doi.org/10.11112/JKSMI.2018.22.4.052
  28. Yoon, Y.S., Ryu, H.S., Lim, H.S., Koh, K.T., Kim, J.S., Kwon, S.J. (2018). Effect of grout conditions and tendon location on corrosion pattern in PS tendon in grout, Construction and Building Materials, 186(2018), 1005-1015. https://doi.org/10.1016/j.conbuildmat.2018.08.023