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Method of Decreasing Cracking Index by Different Mix Conditions for Separated Placement and its Field Application

콘크리트 배합요인별 상·하부 분리타설에 의한 수화열 균열지수 저감방안 및 현장적용

  • Kim, Min-Ho (Department of Architectural Engineering, Cheongju University) ;
  • Han, Cheon-Goo (Department of Architectural Engineering, Cheongju University)
  • Received : 2016.09.01
  • Accepted : 2016.09.22
  • Published : 2016.09.30

Abstract

In this research, considering the practical situation of separated placing method for mass concrete structure, an efficient method of controlling the heat of hydration is suggested by comparing between the simulated values and actual measurements conducted with the optimum mix design obtained from the various mix conditions with different types and amount of supplementary cementitious materials(SCMs). As the result of the research, firstly, the optimum mix designs for top and bottom layers were determined by Midas gen as OPC to FA of 85 to 15, and OPC to FA to BS of 50 to 20 to 30, respectively. The concrete mixtures prepared with the mix designs determined from the simulation satisfied the target performance range in slump, air content and compressive strength. Additionally, from temperature measurement for the actual mass concrete placed during spring, the maximum temperature difference between surface and core was about $10^{\circ}C$ with 59 and $49^{\circ}C$ for top and bottom layers, respectively, and 1.4 of cracking index was obtained. Therefore, considering the practical conditions of mass concrete construction, it is considered that the different heat of hydration method using different mix designs with SCMs can be an efficient method for controlling thermal cracking and settling cracking of mass concrete.

본 연구에서는 매스 매트 콘크리트에 있어, 상 하부를 구분하여 타설하는 실무조건을 고려하여, 상부 및 하부배합의 혼화재 종류와 치환율을 동일 및 달리하는 배합 조건 변화로부터 최적치를 도출한 다음, 실구조체에 적용하여 해석치와 실측치간을 비교하므로서, 혼화재를 활용한 매스콘크리트의 효율적인 수화열균열 저감방안을 제안하고자 하였다. 연구결과 먼저, 현장적용 전 사전검토를 위해 Midas gen을 이용하여 수화열 해석을 실시한 결과 상부는 OPC : FA = 85 : 15 배합, 하부는 OPC : FA : BS = 50 : 20 : 30 배합을 본 대상 구조물 매스 매트콘크리트의 최적배합으로결정하였다. 이를 적용한 실제 현장의 시험결과 슬럼프, 공기량 및 압축강도는 모두 목표범위를 만족하였다. 또한, 봄철 실제 현장의 매스 매트콘크리트의 온도특성으로 최적배합의 경우는 중심부의 최고 온도 약 $59^{\circ}C$, 표층부 온도 약 $49^{\circ}C$로 나타나, 약 $10^{\circ}C$의 온도차가 나타났으며, 수화열 해석결과 약 1.4의 균열지수를 나타내었다. 따라서, 실무를 고려한 매스 매트콘크리트의 경우 상 하부 타설 콘크리트간의 저발열 배합정도를 달리 고려하는 수화발열량차 공법적용은 침하균열 방지 및 수화열 균열제어에 효과적인 방법이 될 것으로 사료된다.

Keywords

References

  1. Han, M.C., Kim, S.Y., Han, D.B. (2008). Hydration heat analysis of mass concrete, Journal of the Architectural Institute of Korea, 24(1), 63-70 [in Korean].
  2. Kim, H.S., Han, M.C., Kim, J.Y., Han, S.B. (2008). Hydration heat analysis of mass concrete considering low heat mixture and block placement, Journal of the Architectural Institute of Korea, 24(1), 63-70 [in Korean].
  3. Kim, J.S. (2013). Characteristics of Hydration Heat in Mass Concrete Using Low-Heat Cements, Master's Thesis, Chungnam University [in Korean].
  4. Kim, Y.R., Lee, S.H., Kim, D.S., Khil, B.S., Choi, T.H., Lee, H.I. (2008). An application of thermal crack control technology using PSLB in mass concrete, Proceedings of the Korea Concrete Institute, 20(3), 62-66 [in Korean].
  5. Lee, M.H., Khil, B.S., Yun, H.D. (2013). Hydration heat property of mass concrete according to cements of ternary cement, Proceedings of the Korea Concrete Institute, 25(2), 575-576 [in Korean].