• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.1105-1108
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• 2008

This paper investigated measures of spalling prevention and mechanism to secure stability of subjected to a fire circumstance. The results were summarized as following. 1) There were 4 kinds of methods for spalling prevention, such as declining percentage of water content and cement water ratio, isolating from high temperature with fire proof covering, giving lateral resistance stress, and discharging vapor pressure using fibers. 2) It was confirmed that methods using fibers to a new construction and fire proof covering to a existing construction on the basis of investigation for the spalling mechanism through the existing theory of spalling and a new theory of WPB.

• 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.

• Magazine of the Korea Concrete Institute
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• v.19 no.1
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• pp.94-100
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• 2007

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.935-940
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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 and Performance Based of Structural Design of the High-Strength Concrete.

• Journal of the Korea Concrete Institute
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• v.24 no.5
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• pp.605-612
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• 2012

Spalling of concrete occurs due to vapor pressure ignited explosion, temperature difference across a section, and combination of these factors. Factors affecting spalling can be classified into internal and external factors such as material property and environmental condition, respectively, have to be considered to precisely understand spalling behavior. An external environmental factor such as differences in heating rate cause internal humidity cohesion and different vapor pressure behavior. Therefore, spalling property, vapor pressure and thermal strain property were measured from concrete with compressive strengths of 30 MPa, 50 MPa, 70 MPa, 90 MPa, and 110 MPa, applied with ISO-834 standard heating curve of $1^{\circ}C/min$ heating rate. The experimental results showed that spalling occurred when rapid heating condition was applied. Also, when concrete strength was higher, the more cross section loss from spalling occurred. Also, spalling property is influenced by first pressure cancellation effect of thermal expansion caused by vapor pressure and heating rates.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2008.04a
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• pp.313-316
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• 2008

Nowadays, the use of high strength concrete has become increasingly popular. Thus, the theory of this study gives a definition of HSC mechanism through study factors of spalling occurrence of HSC and solutions of failure mechanism. During the fire goes on, building structure using HSC causes explosive spalling and finally it gets to the breaking of the structure down. As a result of this failure mechanism, it remains to be investigated to prevent from explosive spalling of HSC and needs to provide basic problems of HSC at high temperature.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.6
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• pp.63-71
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• 2015

The objective of the present study is to investigate how elevated temperature ranging from $100^{\circ}C$ to $800^{\circ}C$ as well as room temperature affects the variation of mechanical properties of high strength concrete ($over\;f_{ck}=60MPa\;grade$). In this experiment, specimens were exposed for a period of $2^{\circ}C/min$ to temperatures of $20^{\circ}C$, $100^{\circ}C$, $200^{\circ}C$, $300^{\circ}C$ $400^{\circ}C$, $500^{\circ}C$, $600^{\circ}C$, $700^{\circ}C$ and $800^{\circ}C$, respectively. Accordingly, the study investigated the fire resistance performance of high strength concrete mixed with composite fibers which composed with hybrid fibers and steel fibers. After cooling down to ambient temperature, the following basic mechanical properties were then evaluated and compared with reference values obtained prior to thermal exposure: (i) compressive strength in room temperature; (ii) residual compressive strength; (iii) Poisson's ratio; (iv) weight change; (v) SEM analysis & XRD analysis In addition, XRD and SEM Images analyses were performed to investigate chemical and physical characteristics of high strength concrete with composite fibers according to high temperature.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.3
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• pp.28-39
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• 2014

This paper reviews past literatures relevant to fire-resistance properties of high strength concrete and investigates spalling mechanism of high strength concrete in fire. First, literatures were reviewed on spalling occurrence and fire-resistance methods. Second, a chemical change of concrete components in an elevated temperature was presented. Finally, the mechanism of the spalling occurrence and spalling resistance were examined in terms of hybrid fiber content. The focus of the experimental study as part of this research is to investigate the effects of fire on the variation of thermal properties of high strength concrete, which tends to be used in super tall buildings. This experimental study was devised to investigate the fire-resistance performance of high strength concrete containing hybrid fibers. A total of 48 test specimens were exposed to high temperature ranging from $100^{\circ}C$ to $700^{\circ}C$, including room temperature (${\sim}20^{\circ}C$). Test results provide valuable information regarding fire-resistance properties of strength concrete with 100 MPa or greater.