Journal of the Korea Concrete Institute (콘크리트학회논문집)

Korea Concrete Institute (한국콘크리트학회)
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Evaluation of Shrinkage Cracking Characteristics and Degree of Restraint for Ultra-High-Strength Concrete

초고강도 콘크리트의 수축 균열 특성 및 구속도 평가

  • Yoo, Doo-Yeol (School of Civil, Environmental and Architectural Engineering, Korea University) ;
  • Min, Kyung-Hwan (School of Civil, Environmental and Architectural Engineering, Korea University) ;
  • Yang, Jun-Mo (School of Civil, Environmental and Architectural Engineering, Korea University) ;
  • Yoon, Young-Soo (School of Civil, Environmental and Architectural Engineering, Korea University)
  • 류두열 (고려대학교 건축사회환경공학부) ;
  • 민경환 (고려대학교 건축사회환경공학부) ;
  • 양준모 (고려대학교 건축사회환경공학부) ;
  • 윤영수 (고려대학교 건축사회환경공학부)
  • Received : 2010.04.01
  • Accepted : 2010.06.15
  • Published : 2010.10.31
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Abstract

The concrete cracking from the restrained stress caused by the shrinkage may play significant cause of deterioration of concrete structures by allowing the permeation of sulphate and chloride ions which in turn triggers corrosion of steel reinforcement. In particular, the cracking becomes more critical as water binder ratio (W/B) is reduced and concrete strength increases. Therefore, it needs to evaluate correctly the comprehensive shrinkage behavior of concrete with high strength: high-strength concrete (HSC), ultra-highstrength concrete (UHSC). The unrestrained shrinkage tests, however, cannot estimate the net shrinkage effectively which affects cracking after full development of strength and stiffness because it does not consider the degree of restraint, strength development, stress relaxation, and so on. Therefore, in this study, both free and restrained shrinkage tests with variables of W/B (W/B of 30, 25 and 16%) and admixtures (fly ash (FA) and granulated blast-furnace slag (BFS)) for HSC, very-high-strength concrete (VHSC) and UHSC were performed. The test results indicated that the autogenous shrinkage and total shrinkage at drying condition were reduced as W/B increased and FA, BFS were added, and the cracking behavior was suppressed as W/B increased and FA was added.

콘크리트의 수축으로부터 발생하는 구속응력은 균열을 유발하고, 그에 따라 황산염 및 염화이온의 침투로 인한 철근의 부식으로 인해 콘크리트 구조물의 내구성을 저하시킨다. 특히, W/B가 감소할수록 균열 발생 가능성이 크며, 따라서 고강도 콘크리트(HSC), 초고강도 콘크리트(UHSC)의 수축 및 균열 거동의 정확한 이해와 평가가 필요하다. 하지만, 기존의 비구속 수축 실험은 콘크리트의 강도발현, 응력의 이완, 균열강도 및 구속도 등을 고려할 수 없으며, 균열 발생에 영향을 미치는 수축량의 평가에 한계가 있었다. 따라서 이 연구에서는 비구속 수축실험과 구속 수축실험(ring-test)을 통하여 W/B(30, 25, 16%) 및 혼화재에 따른 HSC, UHSC의 수축, 균열 거동을 평가하였다. 실험 결과, 자기수축 및 총 건조수축은 W/B가 클수록, 플라이애쉬(FA) 및 고로슬래그미분말(BFS)의 치환율이 증가할수록 감소하는 것으로 나타났으며, W/B의 증가 및 콘크리트 두께의 증가, FA의 혼입은 균열 발생을 효과적으로 억제하는 것으로 나타났다.

Keywords

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  1. Deformation Characteristics of Ultrahigh-Strength Concrete under Unrestrained and Restrained States vol.2017, pp.1687-8442, 2017, https://doi.org/10.1155/2017/3679323