Journal of the Korea institute for structural maintenance and inspection (한국구조물진단유지관리공학회 논문집)

Korea Institute for Structural Maintenance Inspection (한국구조물진단유지관리공학회)
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A Study on the Highest Exposure Temperatures of Exposed Reinforced Concrete Structures at Fire

화재에 노출된 철근콘크리트 구조물의 최고노출온도 추정을 위한 연구

  • Received : 2012.06.26
  • Accepted : 2012.10.04
  • Published : 2013.03.30
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Abstract

In this paper, Machinery analysis was conducted, in order to predict highest exposure temperatures and the analyze fire damage in the case of fire on reinforced concrete structure. After analyzing differential thermal of reference materials in accordance with temperature of concrete reference core specimen, it turned out that powerful endothermic peak came resulting from evaporation of capillary water and get water untill $200^{\circ}C$, another endothermic peak came resulting from decomposition of calcium hydroxide at $520^{\circ}C$, and then mass of reference materials remarkably decreased due to endothermic reaction. Another powerful endothermic reaction came after decomposition of calcite at $720^{\circ}C$. After analyzing X-ray diffraction of reference materials in accordance with temperature of concrete reference core specimen, it turned out that calcium hydroxide existed until the temperature of $400^{\circ}C$, but CH almost disappeared and CaO appeared from $600^{\circ}C$. The production increased in proportion to the temperature. This is because that calcium hydroxide and calcite are decomposed and CaO is produced when the temperature of concrete increases with fire. It is estimated that calcium hydroxide and calcite are utterly decomposed and peak disappears, and peak of CaO is remarkably formed instead, at the temperature of $700-800^{\circ}C$.

본 논문은 철근콘크리트 구조물이 화재를 입었을 경우의 최고 노출 온도 예측 및 화재손상 분석을 위하여 콘크리트 시험체에 대한 기기 분석적 고찰을 실시하였다. 시차열분석 결과, $200^{\circ}C$까지는 모세관수 및 겔수의 증발로 인한 강한 흡열피크가 일어났으며, $520^{\circ}C$정도에서 수산화칼슘 ($Ca(OH)_2$)의 분해로 인해 흡열피크가 생성되었고, 흡열 반응으로 인해 시료의 중량이 크게 감소되었다. $720^{\circ}C$정도에서 칼사이트 ($CaCO_3$)의 분해로 인해 또 한번의 강한 흡열반응이 발생한 것을 알 수 있었다. 또한 X-선 회절분석 결과, $400^{\circ}C$까지는 $Ca(OH)_2$가 존재하지만 $600^{\circ}C$이상부터는 CH성분은 거의 소멸되고 CaO의 성분이 나타났으며, 온도가 높을수록 생성량이 증가하였다. 이것은 화재 시 콘크리트의 온도가 증가될수록 $Ca(OH)_2$과 $CaCO_3$가 분해되어 CaO로 변환되기 때문이며, $Ca(OH)_2$와 $CaCO_3$가 완전히 분해되어 피크가 없어지고 대신 CaO의 피크가 크게 형성되는 온도 범위를 약 $700{\sim}800^{\circ}C$로 추정할 수 있다. 주사형 전자현미경 분석 결과, 고열에 의해 콘크리트를 구성하고 있는 시멘트 반응생성물에서 결합수 및 겔수의 탈수로 인해 콘크리트의 수축이 발생함으로써 미세한 균열이 전반적으로 심하게 발생되는 것을 볼 수 있다. 이를 통해 보통 콘크리트가 열을 받으면 $300^{\circ}C$부터 미세균열이 발생되어 $500^{\circ}C$에서는 상당히 심하게 균열이 발생되는 것을 알 수 있다.

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References

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