• Title/Summary/Keyword: concrete spalling

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An Experimental study on Explosive spalling of Concrete According to Kinds of Fine Aggregate and Admixture (잔골재 및 혼화재 종류에 따른 콘크리트의 폭열 성상에 관한 실험적 연구)

  • 장재봉;김갑수;김재환;김용로;권영진;김무한
    • Proceedings of the Korea Concrete Institute Conference
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    • 2003.11a
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    • pp.667-670
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    • 2003
  • The purpose of this study is to present data for the reusing, reinforcement and estimation of safety of the RC structure damaged by fire, and for the prevention of explosive spalling by checking the character of explosive spalling according to kinds of fine aggregate, admixture and water-cement ratios. The materials used fine aggregates were sea sand, crushed sand and recycled sand, and the admixtures were fly ash and blast-furnace slag. Also the water-cement ratios was 55% and 30.5%. After those were heated respectively for 30 and 60 minutes in accordance with Standard Time-Temperature Curve. And then conditions of explosive spalling were divided into five grades, and characters of explosive spalling were investigated.

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Field Application of Spalling Prevention Method of High Performance Concrete (고성능 콘크리트의 폭렬방지 공법 현장적용 사례)

  • Kim Kyoung-Min;Heo Young-Sun;Lee Jae-Sam;Jee Suk-Won;Lee Seong-Yeun;Han Cheon-Goo
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2005.11a
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    • pp.7-10
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    • 2005
  • This paper is about manufacture of spalling resistance concrete and also investigates the spalling mechanism and spalling resistance method with diverse materials, mixture proportion and lateral confinement. The present work with the basic experiment achieved successful method for spatting resistance using both proper amounts of fiber contents and lateral confinement using metal lath. Moreover, the developed spatting resistance method was applied for full sized column construction in the Doosan We've Poseidon I field, located in Busan city. The author investigated the physical properties examining workability, placeability and pumpability. These studies are continuously processing to develop new technology expecting remarkable impact on the spatting resistance and fire resistance performance of high-raise building construction in the future.

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Basic Characteristics of High Performance Concrete Mixing Organic Fiber (유기섬유 복합 혼입 고성능 콘크리트의 기초적 특성)

  • Park, Byung-Kwan;You, Ji-Young;Lee, Joung-Ah;Jin, Cheng-Ri;Han, Min-Cheol;Han, Cheon-Goo
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2008.05a
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    • pp.87-91
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    • 2008
  • The study examined fire resistance of concrete followed by change of mixed rate in PP and NY composite fiber and the results were as follows. In the event of fluidity in concrete not set, plane satisfied 600±100, its target slump flow, and fluidity was reduced as organic fiber's mixed rate was increased. Air amount satisfied 3.0±1.0, its target air amount, and didn't have distinct differences in reduction and increase according to organic fiber's kind and change of its mixed rate. However, it had a tendency that fluidity was reduced as the mixed rate was increased. In characteristics of hardening concrete, the 28th day compressive strength followed by organic fiber's kind and change of its mixed rate didn't have a lot of differences and satisfied high strength scope as about 70MPa. In spalling characteristics after fire resistance test, spalling was happened in non-mixture, plane combination, and P1N0. In other combinations, spalling resistance was happened. The relic compressive strength rate was 56%, the best condition, in P3N1(PP0.03%, NY0.01% compositeness) mixing PP fiber with NY fiber at once.

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A Study on the Structural Fire Resistance Performance Design of RC Structural according to the Explosive Spalling(I) - The Countermeasures of General Construction Company - (폭렬현상을 고려한 RC구조물의 PBD기반 구조내화설계 기술개발에 관한 연구(I) - 국내외 주요 건설사의 대응방안 -)

  • Lee, Jae-Young;Kim, Se-Jong;Kwon, Young-Jin
    • Proceedings of the Korea Institute of Fire Science and Engineering Conference
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    • 2008.11a
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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.

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Post-peak response analysis of SFRC columns including spalling and buckling

  • Dhakal, Rajesh P.
    • Structural Engineering and Mechanics
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    • v.22 no.3
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    • pp.311-330
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    • 2006
  • Standard compression tests of steel fiber reinforced concrete (SFRC) cylinders are conducted to formulate compressive stress versus compressive strain relationship of SFRC. Axial pullout tests of SFRC specimens are also conducted to explore its tensile stress strain relationship. Cover concrete spalling and reinforcement buckling models developed originally for normal reinforced concrete are modified to extend their application to SFRC. Thus obtained monotonic material models of concrete and reinforcing bars in SFRC members are combined with unloading/reloading loops used in the cyclic models of concrete and reinforcing bars in normal reinforced concrete. The resulting path-dependent cyclic material models are then incorporated in a finite-element based fiber analysis program. The applicability of these models at member level is verified by simulating cyclic lateral loading tests of SFRC columns under constant axial compression. The analysis using the proposed SFRC models yield results that are much closer to the experimental results than the analytical results obtained using the normal reinforced concrete models are.

The Study on the Explosive Spalling Properties of High Performance Concrete According to the Heating Time (가열시간에 따른 고성능콘크리트의 폭렬특성에 관한 연구)

  • Na, Chul-Sung;Roh, Kyung-Min;Cho, Bong-Suk;Gwon, Yeong-Jin;Kim, Gyu-Yong;Kim, Moo-Han
    • Proceedings of the Korea Concrete Institute Conference
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    • 2006.11a
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    • pp.461-464
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    • 2006
  • Recently, as structures become bigger and higher, it is needed that high strength, high flow and high durability concrete. Demanding of High performance concrete that equality is maintained without material separation while flow, strength is increased by using low W/C rate and admixture, carbonation does not occur because of dense filling and has high durability is increasing rapidly. Because this high performance concrete is superior to general concrete in workability and durability, it is widely used in many construction and engineering works fields. However, it is reported that when it was exposed in fire, violent explosive spalling would be happened. Therefore, the purpose of this study evaluates explosive spalling properties of fire damaged high performance concrete according to the heating time.

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Estimation of Optimum PP Fiber Content for the Spalling Control of High Strength Reinforced Concrete Columns (고강도 철근콘크리트 기둥의 폭열제어를 위한 최적의 PP섬유함유량 산정)

  • Kim, In Ki;Yoo, Suk Hyeong;Shin, Sung Woo
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.11 no.2
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    • pp.155-163
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    • 2007
  • High Strength Concrete (HSC) has weakness that in a fire, it is spalled and brittles. The phenomenon of spalling is made by water vapor's (resulting from evaporation in the material at over $100{^{\circ}C}$)' being confined in watertight concrete. As the concrete strength increases, the degree of damage caused by the spalling becomes more serious because of the permeability. It is reported that the polypropylene(PP) fiber has an important role in protecting concrete from spalling and the optimum dosage of PP fiber is 0.2%. This study was conducted on the nonreinforced concrete specimens. The high-temperature behavior of high-strength reinforced concrete columns with various concrete strength and various dosage of PP fibers was investigated in this study. The results show that the ratio of unstressed residual strength of columns increases as the concrete strength increases and the ratio of unstressed residual strength of columns increases as the dosage of PP fiber increases from 0% to 0.2%, however, the effect of fiber dosage on residual strength of column barely changes above 0.2%.

Evaluation on Spalling Properties of Ultra High Strength Concrete with Melting and Vaporization of Fiber (유기섬유의 용융 및 기화에 따른 초고강도 콘크리트의 폭렬 특성 평가)

  • Kim, Gyu-Yong;Choe, Gyeong-Cheol;Lee, Joo-Ha;Lee, Seung-Hoon;Lee, Tae-Gyu
    • 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.

Evaluation of Spalling Property and Water Vapor Pressure of Concrete with Heating Rate (가열 속도에 따른 콘크리트의 폭렬 특성 및 내부 수증기압력 평가)

  • Choe, Gyeong-Cheol;Lee, Tae-Gyu;Nam, Jeong-Soo;Park, Byung-Keun;Kim, Gyu-Yong
    • 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.

Spalling Reduction Effect of PP Fibers and Silica Fume on High Strength Reinforced Concrete Columns (PP섬유 및 실리카흄이 고강도 철근콘크리트 기둥의 폭열 저감에 미치는 영향)

  • Yoo, Suk-Hyeong
    • 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%.