• 한국화재소방학회논문지
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• 제23권6호
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• pp.126-134
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• 2009

본 연구는 고강도 콘크리트의 폭렬 발생을 제어하기 위하여 폭렬 저감재를 혼입함에 따른 폭렬 저감효과를 살펴보고 콘크리트 보 부재의 고온 가열시의 열적 특성을 평가하기 위하여 실시하였다. 이에 고강도 콘크리트 40~60MPa를 폭렬 저감재를 혼입하여 부재를 제작하였으며, KS F 2257의 ISO 표준화재 재하조건에서의 내화성능을 살펴보았다. 실험결과 폭렬 저감재를 혼입하지 않은 40MPa은 180분, 50MPa 174분, 60MPa 152분으로 50, 60MPa보는 기준에서 정하는 3시간 내화성능에 6~28분 부족한 것으로 나타났다. 그러나 폭렬 저감재를 혼입한 50, 60MPa 보는 모두 법에서 정하는 내화 성능 시간인 180분을 만족하였다. 폭렬 저감재를 혼입하지 않은 50, 60MPa의 콘크리트 보는 화재에 노출된 모든 면에서 폭렬이 발생되었으나 폭렬 저감재를 혼입한 50, 60MPa 보에서는 표면탈락 및 폭렬은 거의 발생되지 않았다. 따라서 콘크리트의 폭렬 방지를 위해 혼입한 PP섬유는 폭렬 방지 효과를 나타내고 있으나 60MPa 표면이 일부 탈락 된 것으로 보아 표면 탈락 방지를 위해 혼입한 강섬유는 60MPa 이상의 강도에서는 크게 효과가 나타나지 않았다.

• 대한금속재료학회지
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• 제48권11호
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• pp.1041-1046
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• 2010

The reactions between a Sn-3.0Ag-0.5Cu solder alloy and electroless Ni/electroless Pd/immersion Au (ENEPIG) surface finishes with various Pd layer thicknesses (0, 0.05, 0.1, 0.2, $0.4{\mu}m$) were examined for the effect of the Pd layer on the massive spalling of the $(Cu,Ni)_6Sn_5$ layer during reflow at $235^{\circ}C$. The thin layer deposition of an electroless Pd (EP) between the electroless Ni ($7{\mu}m$) and immersion Au ($0.06{\mu}m$) plating on the Cu substrate significantly retarded the massive spalling of the $(Cu,Ni)_6Sn_5$ layer during reflow. Its retarding effect increased with an increasing EP layer thickness. When the EP layer was thin (${\leq}0.1{\mu}m$), the retardation of the massive spalling was attributed to a reduced growth rate of the $(Cu,Ni)_6Sn_5$ layer and thus to a lowered consumption rate of Cu in the bulk solder during reflow. However, when the EP layer was thick (${\geq}0.2{\mu}m$), the initially dissolved Pd atoms in the molten solder resettled as $(Pd,Ni)Sn_4$ precipitates near the solder/$(Cu,Ni)_6Sn_5$ interface with an increasing reflow time. Since the Pd resettlement requires a continuous Ni supply across the $(Cu,Ni)_6Sn_5$ layer from the Ni(P) substrate, it suppressed the formation of $(Ni,Cu)_3Sn_4$ at the $(Cu,Ni)_6Sn_5/Ni(P)$ interface and retarded the massive spalling of the $(Cu,Ni)_6Sn_5$ layer.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2017년도 춘계 학술논문 발표대회
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• pp.246-247
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• 2017

In this study, it reviewed the effect of moisture migration in concrete with heating rate on concrete spalling. Concrete specimens with compressive strength 30MPa and 110MPa are used and its size is □100×100×h200mm. And, two kinds of heating rate are set such as IS0 834 and 1℃/min. As a result, in the concrete specimen exposed to ISO 834 standard heating condition, moisture could migrate through pore network and surface concrete pieces fall out by generating moisture clog near the surface in 110MPa concrete specimen. Meanwhile, In the case of concrete specimens exposed to 1℃/min. heating condition, it is appeared that moisture could not migrate because temperature is distributed uniformly. Therefore, surface spalling is not occurred with low heating rate. However, in the case of 110MPa concrete specimen is exploded even though it heated by low heating rate.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 봄 학술발표회 논문집(I)
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• pp.76-79
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• 1999

The purpose of this study is to investigate the spalling properties of high-performance concrete with the kinds of aggregates and polypropylene(below PP) fiber contents. According to the experimental results, concrete contained no PP fiber take place in the form of the surface spalling and the failure of specimens after fire test regardless of the kinds of aggregates. Concrete contained more than 0.05% of PP fiber with the kinds of aggregates does not take place the spalling. Concrete using basalt has better performance in spalling resistance that concrete using granite and limestone. It is found that residual compressive strength has 50~60% of their original strength. Although specimens after exposed at high temperature are cured at water for 28days, they do not recover their original strength.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2005년도 춘계 학술발표회 논문집
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• pp.423-430
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• 2005

Fire accidents in underground space may bring much loss of lives as well as properties and result in catastrophic disasters. This study aimed to manufacture the high-temperature furnace capable of simulating fire scenarios (RABT and RWS) and carry out the preliminary fire tests to evaluate fire-induced damage in underground structures. Specimens used in the fire tests were the concrete segments generally used in shield TBM tunnels. The simulated fire scenario was set to the RABT curve that is the most representative fire scenario in underground space. From the fire tests, the spalling was estimated to reach approximately 20cm from the surface exposed to fire. In addition, from the observation of core specimens obtained after fire tests, the deteriorated zone of unspalled specimens amounted to approximately 10cm from the surface of spalling.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 세계 도시지반공학 심포지엄
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• pp.584-590
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• 2009

One of the critical design problems involved in deep tunnelling in brittle rock, is the creation of surface spalling damage and breakouts. If weak fault zone is developed in deep tunnel, squeezing problem is added to the problems. According to the results of ground investigation in the study area, hard granitic rockmass and distinguished high angle fault zone are distributed on the tunnel level over 400m depth. To analyse the probability of brittle failure and squeezing, ground characterization with special lab. and field test were carried out. By the results, probability of brittle failures like spalling and rock burst is very low. But squeezing may be probable, if weak fault zone observed surface and drill core is extended to designed tunnel level.

• 한국화재소방학회:학술대회논문집
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• 한국화재소방학회 2008년도 추계학술논문발표회 논문집
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• pp.195-201
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• 2008

When reinforced concrete is subjected to high temperature as in fire, there is deterioration in its properties of particular importance are loss in compressive strength, cracking and spalling of concrete, destruction of the bond between the cement paste and the aggregates and the gradual deterioration of the hardend cement paste. Assessment of fire-damaged concrete usually starts with visual observation of color change, cracking and spalling of the surface. In this paper, it was reported the trends of research and practical use on the Explosive Spalling Properties of the High-Strength Concrete.

• 열처리공학회지
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• 제21권1호
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• pp.10-19
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• 2008

To investigate the effect of ultrasonic nano-crystalline surface modification (UNSM) treatment on rolling contact fatigue and residual stress properties of bearing steels, this paper carried out a rolling contact fatigue test, measured residual stress and retained austenite, performed a wear test, observed microstructure, measured micro hardness, and analyzed surface topology. After the UNSM treatment, it was found that the surface became minute by over $100{\mu}m$. The micro surface hardness was changed from Hv730~740 of base material to Hv850~880 with about 20% improvement, and hardening depth was about 1.3 mm. The compressive residual stress was measured as high as -700~-900 MPa, and the quantity of retained austenite was reduced to 27% from 34%. The polymet RCF-6 ball type rolling contact fatigue test showed over 4 times longer fatigue lifetime after the UNSM treatment under 551 kgf load and 8,000 rpm. In addition, this paper observed the samples, which went through the rolling contact fatigue test, with OM and SEM, and it was found that the samples had a spalling phenomenon (the race way is decentralized) after the UNSM treatment. However, before the treatment, the samples had excessive spalling and complete exploration. Comparison of the test samples before and after the UNSM treatment showed a big difference in the fatigue lifetime, which seems to result from the complicated effects of micro particles, compressive residual stress, retained austenite, and surface topology.

• 한국화재소방학회논문지
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• 제25권1호
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• pp.42-49
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• 2011

화재와 같은 고온 환경에서 고강도화 된 콘크리트는 폭렬(Explosive Spalling)이 발생할 가능성이 있으며, 이러한 폭렬의 원인으로는 콘크리트 내부의 수증기압이 가장 큰 원인으로 제기되고 있다. 본 논문은 콘크리트의 압축강도 및 함수율이 초기 폭렬특성에 미치는 영향을 실험적으로 규명하는 것을 목적으로 하였다. 실험변수는 양생방법, 압축강도, 함수율로 설정하였으며, KS F 2257 화재온도이력곡선을 15분, 30분 적용하여 콘크리트의 초기 폭렬특성을 실험적으로 검토하였다. 그 결과 압축강도 함수율이 증가할수록 폭렬발생이 증대되는 경향이 나타났으며, 초기 15분 이내에서 대부분의 폭렬이 발생하는 것으로 나타났다. 또한 압축강도 및 함수율에 따른 폭렬발생영역을 분석하였으며, 압축강도 50~100MPa의 경우 함수율 3% 이하, 100MPa 이상의 경우는 1% 이하로 제어할 경우 폭렬현상이 발생하지 않을 것으로 판단되었다. 공극구조에 대한 분석 결과 고강도화 될수록 공극이 세공화됨으로써 탈수현상이 지연되었으며, 이러한 원인으로 인한 수분의 위상변화에 따른 폭렬압 증가는 고강도콘크리트의 심각한 폭렬에 대한 원인중 하나가 될 것으로 판단되었다.

• 한국방재학회 논문집
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• 제10권5호
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• pp.9-15
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• 2010

최근 사용이 늘어나고 있는 고강도 콘크리트는 화재에 취약하여 고열에 의해 내부 수증기압의 상승으로 폭렬 현상이 발생하게 된다. 이러한 폭렬 현상의 방지 방안으로 유기질 섬유를 이용한 방법이 가장 많이 연구되고 있지만 이 방법은 결국 화재 후 콘크리트의 강도 저하를 초래하게 된다. 따라서 본 연구는 포비성 Alkali-Silicates계 내화재를 피복하여 유기질 섬유를 적용한 경우와 폭렬 특성 및 잔존 압축강도 특성을 검토하였다. 유기질 섬유의 혼입 방법으로 P.P, Nylon 섬유를 사용하였고, 내화 피복의 방법으로 포비성 Alkali-Silciates계 내화재를 사용하였다. 내화 시험은 자체 제작한 가열로에서 화염방사기를 이용하여 3시간 동안 화염 실험을 실시하였다. P.P 섬유를 혼입한 경우 폭렬은 방지 하였지만 잔존 압축강도는 측정할 수 없었고, 포비성 Alkali-Silicates계 내화재로 피복한 경우 폭렬 방지뿐만 아니라 잔존 압축강도가 최고 96%까지 유지되었다.