• Fire Science and Engineering
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• v.23 no.6
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• pp.126-134
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• 2009

In an attempt to control the spalling in high strength concrete, spalling reducer was mixed to identify the effect and thermal characteristics of concrete beam member at high temperature. The member was manufactured in such as way of adding 40~60MPa of high strength concrete into spalling reducer, and then fire resistance performance were monitored under the ISO standard fire load condition in accordance with KS F 2257. As a result of test, fore rate performance of 40MPa beam without spalling reducer was 180minutes, 50MPa was 174minutes and 60MPa was 152minutes, indicating that 50MPa and 60MPa beam appeared 6~28minutes short to become a 3-hour rate. However, 50 and 60MPa beam mixed with spalling reducer appeared to have satisfied the requirements for 180minutes. A spalling was occurred in surface of 50 and 60MPa beam mixed without spalling reducer, while no spalling or surface failure was occurred with 50 and 60MPa beam mixed with spalling reducer. Thus polypropylene fiber mixed with the concrete proved to be effective, but viewing that the surface of 60MPa was peeled off partially, the steel fiber mixed appeared not to be effective for the beam more than 60MPa.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2007.11a
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• pp.3-8
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• 2007

초고층건축물이 증가함에 따라 고강도콘크리트의 사용량이 증가하는 추세이다. 고강도콘크리트는 내구성 및 사용성이 우수한 장점을 가지고 있는 반면 화재시 심각한 폭렬현상을 발생시켜 콘크리트 내역 감소 및 철근의 노출로 인해 건물이 붕괴까지 이르게 되는 원인이 된다. 따라서 고강도콘크리트의 내화특성을 고려한 해석(열응력, 질량 이동, 폭렬) 과정을 거쳐 폭렬 저감방안을 모색하여야 한다. 이러한 폭렬 저감방안을 표층부의 온도상승 온도구배 저감 방안, 수중기압 저감/수분 이동을 용이하게 하는 방안, 폭렬억제형 피복콘크리트 이용방안, 폭렬에 의한 콘크리트의 비산을 방지하는 방안 등이 있으며 각 방안들은 장단점을 내포하고 있어 상황에 따라 탄력적으로 적용하여야 하며, 향후 고강도 콘크리트의 역학적 성상을 고려하여 단점을 보완하고 추가적인 대책용 수립할 수 있도록 많은 연구가 필요 할 것으로 판단된다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.5
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• pp.171-178
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• 2006

It was presented that the spalling of high strength concrete exposed to high temperature could be reduced by using polypropylene fiber. However, as the concrete strength increase, the demanded quantity of PP fiber increase and this results in the loss of workability of ultra high strength concrete. The silica fume which is essentially mixed in ultra high strength concrete decrease the permeability of concrete, and this will increase the degree of spalling. In this study the effect of silica fume on the spalling of ultra high strength concrete and the fire resisting efficiency of PP fiber and poly vinyl alchol, instead of PP fiber, for the security of workability were experimentally examined.

• Journal of the Korea Concrete Institute
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• v.24 no.2
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• pp.173-183
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• 2012

Recently, experimental studies to prevent explosive spalling based on spalling mechanism and addition of Polypropylene fiber in high strength concrete (HSC) are performed actively. However, with respect to ultra high strength concrete (UHSC), its compact internal structure is more difficult release vapor pressure at rapid rising temperature compared to HSC. Therefore, in this study, an experiment was conducted to evaluate spalling properties of UHSC using ${\Box}$ $100mm{\times}100{\times}H200mm$ rectangular specimen according to ISO-834 standard fire curve. With respect melting point of fiber, three fiber types of Polyethylene, Polypropylene, and Nylon fibers with melting temperature of $110^{\circ}C$, $165^{\circ}C$, and $225^{\circ}C$, respectively, were considered. Mixed fiber of 0.15% and 0.25% of concrete volume was used to consider spalling properties based on water vapor pressure release. Then, TGDTA test on fiber and FEM analysis were performed. The results showed that it is difficult to prevent initial spalling without loss of fiber mass even if fiber melting temperature is low. Also, in preventing thermal spalling, fiber that melts to rapidly create porosity within 10 minutes of fire is more effective than that of low melting temperature property of fiber.

• Journal of the Korea Institute of Building Construction
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• v.20 no.4
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• pp.305-311
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• 2020

Polymer modified cement mortar (PCM) can improve the performance of adhesion strength, flexural strength, chemical resistance, etc., compared with cement mortar, and is widely used when repairing RC structures. However, PCM causes a burst in an environment with high temperature and fire rate, which causes problems in the stability of the structure. In this study, for the purpose of developing explosive reduction PCM, the polymer mixing ratio is 2%, 4%, 6%, the fiber length is 6mm, 12mm, 6+12mm, and the PP fiber mixing rate is 0.05 Vol% and 0.1 Vol%. Furnace heating experiment (600℃, 800℃) was carried out. As a result of comparative analysis of the explosive properties, it was confirmed that the explosive reduction effect due to the fiber incorporation was insufficient when the polymer mixing amount was 6% or more.

• Cement Symposium
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• s.38
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• pp.124-132
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• 2011

• Cement Symposium
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• s.37
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• pp.140-148
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• 2010

• Proceedings of the Korean Institute of Building Construction Conference
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• 2014.11a
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• pp.32-33
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• 2014

In this study, evaluation on weight loss properties of spalling control fiber with heating rates has been conducted. For evaluation of this study, 3types of organic fibers(Polyethylene, Polypropylene, Nylon) are used as spaling control fiber. Also, to evaluate the effect of heating rate to spallin control fiber, heating rates are set as 10, 25℃/min. As a result, the start time of weight loss of fiber with various heating rate was delayed as heating rate was increased.

• Fire Science and Engineering
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• v.23 no.4
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• pp.1-6
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• 2009

High Strength Concrete has a disadvantage of the brittle failure under fire due to the spalling. It is reported that spalling is caused by the vapor pressure under fire and polypropylene (PP) fiber has an important role in protecting from spalling. The silica fume which is essentially mixed in high strength concrete decrease the permeability of concrete, and this will increase the degree of spalling. The fire resistance characteristics of high-strength reinforced concrete columns with various contents of PP fiber and silica fume were investigated in this study. In results, the ratio of unstressed residual strength of columns increases as the content of PP fiber increases from 0% to 0.2% and the ratio decreases as the content of silica fume increases from 7% to 21%.

• Journal of the Korea Concrete Institute
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• v.23 no.5
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• pp.637-645
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• 2011

It is well known that high strength concrete with compressive strength higher than 50 MPa shows severe material and structural damages under fire due to spalling. To understand degradation of structural capacity of fire damaged high strength concrete structures, not only thermo-mechanical behavior needs to be defined, but also structural behavior of high strength concrete member under high temperature needs to be investigated. In this study, structural tests are performed by applying axial loads on high strength concrete columns exposed at elevated temperatures for assigned amount of time. The tested columns are prepared to have different concrete strength and polypropylene fiber percentage. The test results show that structural capacity of the columns decreased with increased compressive strength of concrete under same heating condition. Especially, it is interesting to note that high strength concrete columns with polypropylene fiber for spalling proof did not improve structural capacity compared to the columns without polypropylene fiber. The findings from the test are able to improve fire proof design of high strength concrete structural members and predicting structural performance of fire damaged structural members.