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Theoretical Analysis of Critical Chloride Content in (Non)Carbonated Concrete Based on Characteristics of Hydration of Cement

시멘트 수화 특성 및 탄산화를 고려한 콘크리트의 임계 염소이온량에 대한 해석 기법

  • Yoon, In-Seok (Faculty of Civil Engineering and Geoscience, TU Delft)
  • 윤인석 (델프트공과대학 토목공학부)
  • Published : 2007.06.30

Abstract

Critical chloride content for corrosion initiation is a crucial parameter in determining the durability and integrity of reinforced concrete structures, however, the value is still ambiguous. Most of the studies reporting critical threshold chloride content have involved the experimental measurement of the average amount of the total chloride content at arbitrary time. The majority of these researches have not dealt with this issue combined with carbonation of concrete, although carbonation can significantly impact on critical threshold chloride content. Furthermore, the studies have tried to define the critical chloride content within the scope of their experimental concrete mix proportion at arbitrary time. However, critical chloride content for corrosion initiation is known to be affected by a lot of factors including cement content, type of binder, chloride binding, concentration of hydroxyl ions, and so on. It is necessary to define the unified formulation to express the critical chloride content for various mix proportions of concrete. The purpose of this study is to establish an analytical formulation of the critical chloride content of concrete. In this formulation, affecting factors, such as mix proportion, environment, chemical evolution of pore solution with elapsed time, carbonation of concrete and so on are taken into account. Based on the Gouda's experimental results, critical chloride content is defined as a function of $[Cl^-]$ vs. $[OH^-]$ in pore solution. This is expressed as free chloride content with mass unit to consider time evolution of $[OH^-]$ content in pore solution using the numerical simulation programme of cementitious materials, HYMOSTRUC. The result was compared with other experimental studies and various codes. It is believed that the approach suggested in this study can provide a good solution to determine the reasonable critical chloride content with original source of chloride ions, for example, marine sand at initial time, and sea water penetration later on.

철근의 부식을 유발하는 임계 염소이온량에 대한 연구는 콘크리트 구조물의 건전성을 판단하고 내구성 설계 기법에 필요한 핵심적인 재료 물성치 임에도 그값이 아직도 모호한 실정이다. 임계 염소이온량에 대한 대부분의 문헌들은 임의의 시간에 실험적 방법에 의하여 전 염소이온량을 구하는데 집중하였다 또한, 다수의 문헌들은 대다수의 콘크리트에서 탄산화가 진행되고 있음에도 비탄산화된 콘크리트를 대상으로 실험하여 임계 염소이온량을 결정하고 있다. 그러나, 임계 염소이온량은 시멘트량, 시멘트계 재료의 종류, 염소이온의 고정화, 수산기이온 등과 같은 다양한 인자에 의하여 지배된다. 그러므로 다양한 배합조건에서 이러한 인자들을 고려할 수 있는 단일화된 해석적 기법의 개발이 필요하다. 본 연구의 목적은 이러한 다양한 요인을 고려하여 임계 염소이온량의 해석적 기법을 개발하는 것이다. 배합 조건, 노출 환경, 공극수의 화학적 발현 특성, 탄산화 등과 같은 다양한 인자들이 고려되었다. Gouda의 실험적 결과인 공극수내의 $[Cl^-]/[OH^-]$의 비율을 토대로 임계 염소이온량을 구할 수 있는 해석 기법이 정립되었다. 이는 시멘트계 재료의 수화 시뮬레이션 프로그램인 HYMOSTRUC을 이용하여 질량 단위로 구해졌으며 발표된 실험적 결과 및 관련코드와 비교되었다. 본 연구의 접근 방법은 해사 혹은 해수와 같은 염소이온의 도입원 조건에 따라서 임계 염소이온량을 결정할 수 있는 합리적 해를 제공해줄 수 있을 것으로 기대된다.

Keywords

References

  1. D. A. Hausmann, 'Steel Corrosion in Concrete. How does it occur?', Journal of Materials Protection, Vol.5, 1967, pp.19-23
  2. V. K. Gouda, 'Corrosion and Corrosion Inhibition of Reinforcing Steel', British Corrosion Journal, Vol.5, 1970, pp.198-203 https://doi.org/10.1179/000705970798324450
  3. S. Goni andC. Andrade, 'Synthetic Concrete Pore Solution Chemistry and Rebar Corrosion Rate in the Presence of Chlorides', Cement and Concrete Research, Vol.20, 1990, pp.525-539 https://doi.org/10.1016/0008-8846(90)90097-H
  4. V. K. Gouda and W.Y. Halaka, 'Corrosion and Corrosion Inhibition of Reinforced Steel', British Corrosion Journal, Vol.5, 1970, pp.204-208 https://doi.org/10.1179/000705970798324478
  5. C. Andrade and C. L. Page, 'Pore Solution Chemistry and Corrosion in Hydrated Cement System Containing Chloride Salt', Cement and Concrete Research, Vol.21, 1986, pp.49-53
  6. C. M. Hansson and B. Sorensen, The Threshold Concentration of Chloride in Concrete for Initiation of Reinforcement Corrosion, Corrosion Rates of Steel in Concrete, ASTM Spec Tech Publish, 1988, pp.3-16
  7. P. Lambert, C. L. Page, and P. R. W. Vassie, 'Investigation of Reinforcement Corrosion Electrochemical Monitoring of Steel in Chloride Contaminated Concrete', Material Structures, Vol.24, 1991, pp.351-358 https://doi.org/10.1007/BF02472068
  8. O. A. Kayyali and M. N. Haque, 'The Ratio of CrlOH- in Chloride Contaminated Concrete', Magazine of Concrete Research, Vol.47, 1995, pp.235-242 https://doi.org/10.1680/macr.1995.47.172.235
  9. S. E. Hussain, S. E. Rasheeduzzafar, A. Al-Musallam, and A.S. AI-Gahtani, 'Factors Affecting Threshold Chloride for Reinforcement Corrosion in Concrete', Cement and Concrete Research, Vol.25, 1995, pp.1543-1555 https://doi.org/10.1016/0008-8846(95)00148-6
  10. P. Schiessel and W. Breit, 'Local Repair Measures at Concrete Structures Damaged by Reinforcement Corrosion', Proceedings of the Fourth International Symposium on Corrosion of Reinforcement in Concrete Construction, SCI, Cambridge, 1996, pp.525-534
  11. M. D. A Thomas, J. D. Matthews, and C. A. Haynes, Chloride Diffusion and Reinforcement Corrosion in Marine Exposed Concretes Containing PFA, Corrosion of Reinforcement in Concrete, Elsevier, Warwickshire, UK, 1990, pp.198-212
  12. M. Thomas, 'Chloride Thresholds in Marine Concrete', Cement and Concrete Research, Vol.26, 1996, pp.513-519 https://doi.org/10.1016/0008-8846(96)00035-X
  13. B. B. Hope and A. K. C. Ip, 'Chloride Corrosion Threshold in Concrete', ACI Materials Journals, July-August, 1987, pp.306-314
  14. B. H. Oh, S. Y. Jang, and Y. S. Shin, 'Experimental Investigation of the Threshold Chloride Concentration for Corrosion Initiation in Reinforced Concrete Structures', Magazine of Concrete Research, Vol.55, No.2, 2003, pp.117-124 https://doi.org/10.1680/macr.55.2.117.37558
  15. S. E. Hussain, A. S. AI-Gahtani, and Rasheeduzzafar, 'Chloride Threshold for Corrosion of Reinforcement in Corrosion', ACI Material Journal, Vol.93, No.6, 1996, pp.1-5
  16. K. van Breugel, Simulation ofHydration and Formation of Structures in Hardening Cement-Based Materials, Ph.D Dissertation, TU Delft, the Netherlands, 1991
  17. R. J. van Eijk and H. J. H. Brouwers, 'Prediction of Hydroxyl Concentrations in Cement Pore Water using a Numerical Cement Hydration Model', Cement and Concrete Research, Vol.30, 2000, pp.1801-1806 https://doi.org/10.1016/S0008-8846(00)00413-0
  18. CEB, Durable Concrete Structures: Design Guide, 2nd Edition, Thomas Telford, London, 1992
  19. J. P. Broomfield, Corrosion of Steel in Concrete, E&FN SPON, London, UK, 1997
  20. S. Diamond, 'Chloride Concentrations in Concrete Pore Solutions Resulting from Calcium and Sodium Chloride Admixtures', Cement, Concrete, and Aggregate, Vol.8, No.2, 1986, pp.97-102 https://doi.org/10.1520/CCA10062J
  21. ACI Committee 222R-01, Protection of Metals in Concrete against Corrosion, Manual of Concrete Practice, ACI, 2002
  22. ACI Committee 201, Durability of Concrete, Manual of Concrete Practice, ACI, 2002
  23. JSCE, Concrete Standard Specification, Part of Durability, 1999

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