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Effect of Compressive Strength and Curing Condition on the Direct Tensile Strength Properties of Ultra High Performance Concrete

압축강도 및 양생조건에 따른 초고성능 콘크리트의 직접인장강도 특성

  • Park, Ji Woong (Department of Architecture, Korea National University of Transportation) ;
  • Lee, Gun Cheol (Department of Architecture, Korea National University of Transportation)
  • Received : 2017.02.15
  • Accepted : 2017.02.28
  • Published : 2017.04.20

Abstract

The purpose of this study is evaluating the characteristics of tensile strength of UHPC and examining tensile performance of notched specimens by direct tensile test. For test variables, 120, 150, and 180MPa of target design standard strength were aimed at. With general water curing and $90^{\circ}C$ high temperature steam as curing conditions, the properties were reviewed. Overall, it was represented that the specimens of notch-type direct tensile strength concrete was effective in inducing central cracks compared with existing direct tension specimens. Through this, it was judged that data construction with high reliability was possible. Above all, in a graph of direct tensile strength and strain, in the case of steam curing at high temperature, there was great difference of initial tensile strength compared with water curing. As passing of ages, an aspect that the difference gradually decreased was shown. Maximum tensile strength was found to increase steadily with increasing age for all target design strengths in water curing, in the case of steam curing, the tendency to increase significantly due to the initial strength development effect at 7 days of age. The initial crack strength increases with age in case of underwater curing, in the case of steam curing, it was higher than that of water curing in 7 days, while the strength of 28 days was lowered. In this part, it is considered necessary to examine the arrangement condition of the steel fiber.

본 연구는 초고강도 섬유보강 콘크리트의 인장강도 특성을 파악하기 위한 일환의 연구로서 직접인장시험에 의한 노치가 도입된 시험체의 인장성능을 파악하기 위하여 시험변수는 목표 설계기준강도 120, 150 및 180MPa를 대상으로 하였으며, 양생조건을 일반 수중양생과 $90^{\circ}C$ 고온증기 양생조건으로 하여 그 특성을 검토하였다. 전반적으로 노치타입의 직접인장강도 시험체는 기존 직접인장 시험체에 비해 중앙균열 유도가 효과적인 것으로 나타났으며 데이터를 직접 인장강도-변형률 그래프로 나타낸 결과 먼저 재령 측면에서는 28일에서 56일로 진행할 때의 강도 상승이 가장 높은 것으로 측정 되었으며, 양생조건 측면에서는 고온증기 양생의 경우 수중양생의 비해 초기 강도가 높으나 장기 재령에 가까워질수록 두 가지 양생조건의 직접인장강도 차이가 미비해지는 것을 알 수 있었다. 최대인장강도는 수중양생의 경우 모든 목표설계강도가 재령이 증가할수록 일정하게 증가하는 것으로 나타났으며, 증기양생의 경우 재령 7일에서 초기강도 발현 효과로 인해 상당히 증가하는 경향을 나타내었다. 초기균열 강도는 수중양생의 경우 재령경과에 따라 증가하며, 증기양생의 경우 7일에서 수중양생에 비해 높은 것으로 나타난 반면에 28일 강도는 저하하는 경향을 나타내었다. 이부분에 대해서는 강섬유의 배열상태 등의 검토가 필요할 것으로 사료된다.

Keywords

References

  1. Kim DJ. Measurement of tensile properties of fiber reinforced concrete. Journal of the Korea Concrete Institute. 2009 Nov;21(6):94-7.
  2. Choi JG, Lee GC, Lee GY, Park DC. Characteristics of flexural behavior of high strength concrete according to the mixture rate of steel fiber. Proceeding of Korea Institute of Building Construction; 2015 May 28-29; Yeosu, Korea. Seoul (Korea): Institute of building Construction; 2015. p. 82-3.
  3. Yang IH, Kim KC, Joh CB. Flexural strength of hybrid steel fiber-reinforced ultra-high strength concrete beams. Journal of the Korea Concrete Institute. 2015 Jun;27(3):280-7.
  4. Ministry of Land, Infrastructure and Transport. Highway Bridge Standard Specification. 521st ed. Korea: Ministry of Land, Infrastructure and Transport; 2016. Chapter 3-8, Fiber reinforced concrete; p. 199.
  5. AFNOR. NF P 18-470. France: AFNOR; 2016. 96p.
  6. Lee JW, Joh CB. The effect of specimen size & shape on tensile strength of K-UHPC. Proceeding of Korea Concrete Institute; 2012 May 2-4; Gyeongju, Korea. Seoul (Korea): Korea Concrete Institute; 2012. p. 97-8.