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Strength and Carbonation Characteristics in OPC Concrete under Long-Term Exposure Conditions in Various Sea Environments

다양한 해양환경에 장기 노출된 OPC 콘크리트의 강도 및 탄산화 특성

  • 이현우 (한남대학교 건설시스템공학과 ) ;
  • 신금채 (한남대학교 건설시스템공학과) ;
  • 권성준 (한남대학교 건설시스템공학과)
  • Received : 2023.12.14
  • Accepted : 2024.01.10
  • Published : 2024.02.28

Abstract

Compressive strength in concrete has many affecting parameters and varies with exposure conditions. Although the concrete has same mix proportions, its properties are different with exposure conditions, and sea-environment can be classified into three groups such as tidal, atmospheric, and sea submerged region particularly. In this study, compressive strength was evaluated on 7-year-cured concrete and the results from previous equations (KDS, ACI, CEB, and JSCE) were compared with them. Furthermore the strength and carbonation progress were evaluated on concrete cured for 7 years exposed to three different sea environment. Three levels of w/c (water to cement) ratio (0.37, 0.42, and 0.47) and three different exposure conditions (tidal, atmospheric, and submerged) were considered. The results from wet-cured condition are all higher than those from the previously proposed equations, and the results from different sea exposure conditions (tidal, atmospheric, and submerged region) were lower than those from wet-cured condition. A reduction of strength was evaluated with increasing w/c ratio and the minimum strength was evaluated in the sea-submerged conditions. Several experimental constants applicable to the previous equations were obtained from regression analysis since the strength change with w/c ratios were not considered in those equations. Regarding carbonation depth with different exposure conditions, higher carbonation depth clearly was observed with increasing w/c ratios, and evaluated in the order of atmospheric, submerged, and tidal region. Considerable carbonation depth was observed in submerged and tidal region due to sulfate ion and dissloved carbon dioxide as well.

콘크리트의 압축강도는 다양한 영향인자가 있으며, 노출환경에 따라 변화한다. 동일한 배합을 가진 콘크리트라도 노출환경에 따라 콘크리트 특성은 변화하며, 특히 해수의 영향을 받는 지역은 간만대, 비말대, 해수중과 같이 세가지 영역으로 구분할 수 있다. 본 연구에서는 7년 동안 습윤양생된 OPC 콘크리트를 대상으로 강도 변화를 분석하였으며, 기존의 이론식(KDS, CEB, ACI, JSCE)과의 비교를 수행하였다. 또한 7년동안 비말대, 간만대, 해수중에 장기 폭로된 시편을 대상으로 강도 특성 및 탄산화 특성을 평가하였다. 콘크리트의 배합은 3수준의 물-시멘트비(0.37, 0.42, 0.47)를 가지고 있으며, 환경조사를 수행하여 침지대, 간만대, 비말대 3 수준의 해양환경을 고려하였다. 7년동안 습윤양생된 시편의 경우 기존의 제안식들에 비하여 높은 강도를 가지고 있었으며, 옥외 폭로된 시편(간만대, 비말대, 해수중)의 강도는 습윤양생한 시편의 강도보다 낮게 평가되었다. 또한 물-시멘트비가 증가할수록 뚜렷한 강도저하가 발생하였으며, 해수중에서 가장 낮은 강도가 평가되었다. 기존의 강도 제안식에서는 물-시멘트비에 따른 변화를 고려하지 못하므로 기존 이론식에 적용할 수 있는 실험상수를 회귀분석을 통하여 도출하였다. 탄산화 평가결과, 물-시멘트비의 증가에 따라 높은 탄산화 깊이가 평가되었으며, 비말대, 침지대, 간만대 순서로 탄산화 진행이 발생하였는데, 침지대 및 간만대에서도 황산염 및 용존 이산화탄소 영향으로 상당한 중성화 깊이가 발생하였다.

Keywords

Acknowledgement

본 연구는 정부의 지원으로 한국연구재단 중견연구자지원사업의 지원을 받아 수행되었으며 이에 감사드립니다(NRF-2020R1A2C2009462).

References

  1. ACI Committee 209 (2008), Guide for Modeling and Calculating Shrinkage and Creep in Hardened Concrete (ACI 209.2R-08), Farmington Hills, MI: American Concrete Institute. 
  2. Al-Khaiat, H., and Fattuhi, N. (2001), Long-term strength development of concrete in arid conditions, Cement and Concrete Composites, 23(4-5), 363-373.  https://doi.org/10.1016/S0958-9465(01)00004-X
  3. Broomfield, J. P. (1997), Corrosion of Steel in Concrete: Understanding, Investigation and Repair, London, E&FN, 1-15. 
  4. CEB FIB (2010), Lausanne, Switzerland; International Federation for Structural Concrete (fib), Comite Euro-International du Beton. 
  5. Chindaprasirt, P., Rukzon, S., and Sirivivatnanon, V. (2008), Effect of carbon dioxide on chloride penetration and chloride ion diffusion coefficient of blended Portland cement mortar, Construction and Building Materials, 22(8), 1701-1707.  https://doi.org/10.1016/j.conbuildmat.2007.06.002
  6. Escalante, J. I., Gomez, L. Y., Johal, K. K., Mendoza, G., Mancha, H., and Mendez, J. (2001), Reactivity of blast-furnace slag in Portland cement blends hydrated under different conditions, Cement and Concrete Research, 31(10), 1403-1409.  https://doi.org/10.1016/S0008-8846(01)00587-7
  7. Ganjian, E., and Pouya, H. S. (2009), The effect of Persian Gulf tidal zone exposure on durability of mixes containing silica fume and blast furnace slag, Construction and Building Materials, 23(2), 644-652.  https://doi.org/10.1016/j.conbuildmat.2008.02.009
  8. Jang, S. Y., Karthick, S., and Kwon, S. J. (2017), Investigation on durability performance in early aged high-performance concrete containing GGBFS and FA, Advances in Materials Science and Engineering. 
  9. JSCE (2010), Standard Specifications for Concrete Structures - 2007 design, Dokyo, Japan: Japan society of Civil Engineers (JSCE). 
  10. KCI (2022), KDS 14 20 01 General Standards for Concrete Structure Design (Strength Design Method)Sejong, Korea: Ministry of Land, Infrastructure and Transport (MOLIT). 
  11. Korea Meteorological Administration, https://data.kma.go.kr/stcs/gr 
  12. Kwon, S. J., Song, H. W., and Byun, K. J. (2007), A Study on analysis technique for chloride penetration in cracked concrete under combined deterioration, Journal of the Korea Concrete Institute, 19(3), 359-366.  https://doi.org/10.4334/JKCI.2007.19.3.359
  13. Lee, B. N., and Lee, J. S. (2023), Review of Compressive Strength Development Models by W/C Ratio Involving Concrete Specimens Exposed to a Seaside Environment for 15 Years, Journal of the Korea Concrete Institute, 35(4), 389-395.  https://doi.org/10.4334/JKCI.2023.35.4.389
  14. Lee, C. S., and Yoon, I. S. (2003), Prediction of deterioration process for concrete considering combined deterioration of carbonation and chlorides Ion, Journal of the Korea Concrete Institute, 15(6), 902-912.  https://doi.org/10.4334/JKCI.2003.15.6.902
  15. Mun, J. S., Yang, K. H., and Jeon, Y. S. (2014), Maturity-Based Model for Concrete Compressive Strength with Different Supplementary Cementitious Materials, Journal of the Korea Institute for Structural Maintenance and Inspection, 18(6), 82-89.  https://doi.org/10.11112/JKSMI.2014.18.6.082
  16. Neithalath, N. (2008), Quantifying the effects of hydration enhancement and dilution in cement pastes containing coarse glass powder, Journal of Advanced Concrete Technology, 6(3), 397-408.  https://doi.org/10.3151/jact.6.397
  17. Neville, A. M. (2011), Properties of concrete 5th edition, London, England. 
  18. Saeki, T. (1991), Mechanism of carbonation and prediction of carbonation process of concrete, Concrete Library International of JSCE, 17, 23-36. 
  19. Song, H. W., Kim, H. J., Kwon, S. J., Lee, C. H., Byun, K. J., and Park, C. K. (2005), Prediction of service life in cracked reinforced concrete structures subjected to chloride attack and carbonation, In Cement Combinations for Durable Concrete: Proceedings of the International Conference held at the University of Dundee, Scotland, UK, 767-775. 
  20. Song, H. W., and Kwon, S. J. (2007), Permeability characteristics of carbonated concrete considering capillary pore structure, Cement and Concrete Research, 37(6), 909-915.  https://doi.org/10.1016/j.cemconres.2007.03.011
  21. Thomas, M. D. A., and Matthews, J. D. (2004), Performance of pfa concrete in a marine environment 10-year results, Cement and Concrete Composites, 26(1), 5-20.  https://doi.org/10.1016/S0958-9465(02)00117-8
  22. Yang, K. H., Hwang, H. Z., Kim, S. Y., and Song, J. K. (2007), Development of a cementless mortar using hwangtoh binder, Building and Environment, 42(10), 3717-3725.  https://doi.org/10.1016/j.buildenv.2006.09.006
  23. Yang, K. H., Mun, J. H., and Yoon, Y. S. (2018), Effects of loading conditions and cold joint on service life against chloride ingress, Computers and Concrete, An International Journal, 22(3), 319-326. 
  24. Yoon, Y. S., and Kwon, S. J. (2019), Evaluation of apparent chloride diffusion coefficient and surface chloride contents of FA concrete exposed splash zone considering crack width, Journal of the Korea Institute for Structural Maintenance and Inspection, 23(6), 18-25.  https://doi.org/10.11112/JKSMI.2019.23.6.18
  25. Yoon, Y. S., and Kwon, S. J. (2022), Behavior of apparent chloride diffusion coefficient of fly ash concrete under long-term marine exposure, Available at SSRN 4051149. 
  26. Zhu, X., Zi, G., Cao, Z., and Cheng, X. (2016), Combined effect of carbonation and chloride ingress in concrete, Construction and Building Materials, 110, 369-380. https://doi.org/10.1016/j.conbuildmat.2016.02.034