STUDY ON EXPLOSIVE SPALLING PROCESS OF HIGH-STRENGTH CONCRETE BY MEANS OF ACOUSTIC EMISSION

The explosive spalling of high-strength concrete due to fire is a problem that has garnered increasingly widespread attention, particularly the explosive spalling of reactive powder concrete (RPC). For years, based on the vapor pressure mechanism, the addition of fibers has been demonstrated to be somewhat effective in protecting against spalling. However, relevant experiments indicate that fibers are not effective for dense concrete, which is a challenge for the simple vapor pressure mechanism in providing spalling resistance for RPC. The authors found that silica fume plays an important role in the explosive spalling of RPC. Thus, four classes of RPCs with different ratios of silica fume were prepared, and the spalling phenomena and the inner temperature distribution during heating were investigated. The results show that silica fume content has a prominent effect on the spalling process of RPC.

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Fire Resistance of Ultra-High-Strength Concrete: a Review

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.477.333 ◽

2011 ◽

Vol 477 ◽

pp. 333-339 ◽

Cited By ~ 1

Author(s):

Gai Fei Peng ◽

Yan Teng

Keyword(s):

Fire Resistance ◽

High Strength Concrete ◽

High Strength ◽

Strength Loss ◽

Engineering Practice ◽

Explosive Spalling ◽

Strength Concrete ◽

Normal Strength ◽

Reactive Powder ◽

Near Future

This paper presents a review of advances in research on fire resistance of high-strength concrete (HSC) and ultra-high-strength concrete (UHSC). Further research needs in the near future on UHSC, especially on reactive powder concrete (RPC), are also discussed. It is commonly recognized that HSC suffers strength loss in a manner basically similar to that of normal strength concrete. But the main problem of HSC is explosive spalling under high temperature, which can be solved by employing either polymer fiber or steel fiber. Since RPC200 is a type of RPC which has been successfully prepared in many counties and is to be applied to engineering practice, fire resistance of RPC200 needs a series of investigations urgently. The objectives of such investigations are to restrain explosive spalling and minimizing spalling probability, so as to ensure satisfactory fire resistance of RPC. It is expected that a research will be carried out on explosive spalling behavior, fracture properties, and micro-structure, to establish a mechanism as well as technical measures for improving fire resistance of RPC.

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Effect of Types and Contents of Polymer Resin on Spalling Prevention of High-Strength Concrete Subjected to Fire

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.466.85 ◽

2011 ◽

Vol 466 ◽

pp. 85-95 ◽

Cited By ~ 1

Author(s):

Cheon Goo Han ◽

Min Cheol Han ◽

Chan Chun Pei ◽

Seong Hwan Yang

Keyword(s):

Compressive Strength ◽

Melting Point ◽

High Strength Concrete ◽

Polyvinyl Acetate ◽

High Strength ◽

Slight Reduction ◽

Explosive Spalling ◽

Strength Concrete ◽

Polymer Resin ◽

Acetate Copolymer

In this study, the fundamental and spalling properties of high-strength concrete were examined, especially when various types and varying content of polymer resin were added. Two types of polymers were used in this study: ethylene vinyl acetate copolymer (EVA-P) and polyvinyl acetate copolymer (PVA-P) as powders and polyvinyl acetate copolymer (PVA-F) and polypropylene copolymer (PP-F) as fibers. Test results showed that the addition of EVA-P and PVA-F to concrete slightly decreased flowability, whereas the addition of PP-F and PVA-P enhanced the viscosity, leading to a remarkable reduction in flowability. The air content of concrete containing EVA-P, PVA-F, and PP-F showed no significant variation. The addition of PVA-P to concrete also caused a slight reduction in compressive strength, whereas the other additives had insignificant effects. After a fire test, the control concrete and concretes with EVA-P, PVA-P, and PVA-F exhibited severe explosive spalling regardless of the dosages. This was because the polymer does not provide sufficient void networks, which is important for vapor evacuation, which enables the release of steam pressure inside the concrete. However, when more than 0.10% of PP-F was added, spalling was effectively prevented. For the residual compressive strength, higher polymer dosage in the concrete produced better results regardless of the polymer type. The powder-type polymers did not contribute to preventing spalling in concrete subjected to fire. This is due to their geometric shape and high melting point. It is concluded that a high aspect ratio and low melting point is critical during polymer selection to prevent spalling in high-strength concrete.

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Reliability Analysis of High-Strength Concrete Columns during a Fire

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.629-630.273 ◽

2014 ◽

Vol 629-630 ◽

pp. 273-278 ◽

Cited By ~ 1

Author(s):

Jian Zhuang Xiao ◽

Qing Hai Xie ◽

Yi Zhao Hou ◽

Zhi Wei Li

Keyword(s):

Reliability Analysis ◽

Fire Resistance ◽

High Strength Concrete ◽

Elevated Temperatures ◽

Axial Loading ◽

High Strength ◽

Concrete Columns ◽

Explosive Spalling ◽

Strength Concrete ◽

High Strength Concrete Columns

A reliability analysis was conducted on high-strength concrete (HSC) columns during a fire. The influences of fire’s randomness and explosive spalling of concrete were investigated. The fire resistance for axial loading capacity of HSC columns was in terms of steel yield strength and concrete compressive strength with considering the effect of elevated temperatures. The load random variables included dead load and sustained live load. The JC method was applied to calculate the reliability index of the fire resistance of axially loaded HSC columns. It was found that the randomness of fire and explosive spalling of concrete had a significant influence on reliability of HSC columns.

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ASSESSMENT OF MECHANICAL PROPERTIES OF HIGH STRENGTH CONCRETE (HSC) AFTER EXPOSURE TO HIGH TEMPERATURE

Journal of Civil Engineering and Management ◽

10.3846/jcem.2018.457 ◽

2018 ◽

Vol 24 (2) ◽

pp. 138-144 ◽

Cited By ~ 4

Author(s):

Tomasz DRZYMAŁA ◽

Wioletta JACKIEWICZ-REK ◽

Jerzy GAŁAJ ◽

Ritoldas ŠUKYS

Keyword(s):

Mechanical Properties ◽

High Temperature ◽

High Strength Concrete ◽

High Performance Concrete ◽

High Strength ◽

Hardened Concrete ◽

Explosive Spalling ◽

Polypropylene Fibres ◽

Strength Concrete ◽

Temperature Conditions

There has been a tendency to design ever slender building construction using high strength concrete in recent years. Application of HSC is also growing in tunnel construction. One of the most important challenges is to control explosive spalling of concrete and the method recommended by Eurocode 2 (EN 1992-1-2:2008/NA:2010P) is addition of polypropylene fibres to the mix. The purpose of the research described in this paper was to evaluate the changes of mechanical properties of HSC exposed to the effect of high temperature. The tests were carried out on three types of high strength concrete: air-entrained concrete, polypropylene fibre-reinforced concrete and reference concrete having constant water/cement ratio. The properties of hardened concrete including compressive strength, tensile splitting strength, flexural strength and E-modulus were studied. The latter tests were carried out on both on concrete cured at 20 °C and concrete subjected to high-temperature conditions at 300 °C, 450 °C and 600 °C. The results enabled us to evaluate the effect of high-temperature conditions on the properties of high-performance concrete and compare the effectiveness of the two methods designed to improve the high-temperature performance of the concrete: addition of polypropylene fibres and entrainment of air.

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Performance of Ultra High Strength Concrete Expose to High Rise Temperature

Annales de Chimie Science des Matériaux ◽

10.18280/acsm.450411 ◽

2021 ◽

Vol 45 (4) ◽

pp. 351-359

Author(s):

Noor Alhuda Sami Aljabbri ◽

Mohammed Noori Hussein ◽

Ali Abdulmohsin Khamees

Keyword(s):

Tensile Strength ◽

Compressive Strength ◽

Fire Resistance ◽

High Strength Concrete ◽

High Strength ◽

Splitting Tensile Strength ◽

Explosive Spalling ◽

Strength Concrete ◽

Direct Tensile ◽

Direct Tensile Strength

Fire or high temperature is a serious issue to ultra-high-strength concrete (UHSC). Strength reduction of UHPCs may amount to as high as 80 percent after exposure to 800℃. A sum of four UHSC mixes was synthesized and evaluated in this study after getting exposed to extreme temperatures that reach 1000°C. Steel and polypropylene (PP) fibers were used in this experiment. A total of four mixes were made of UHSC without fibres as a control mix (UHSC-0), UHSC with 2% steel fibres (UHSC-S), UHSC with 2% PP fibres (UHSC-P) and UHSC with 1% steel fibres + 1% PP fibres (UHSC-SP). Workability, direct tensile strength, compressive strength, and splitting tensile strength were examined. Particularly, emphasis was devoted to explosive spalling since UHPCs are typically of compact structure and hence more prone to explosive spalling than other concretes. It was determined that the mixture UHSC-SP had high fire resistance. Following exposure to 1000℃, this mixture preserved a residual compressive strength of 36 MPa, splitting tensile strength of 1.62 MPa and direct tensile strength of 0.8 MPa. On the other hand, UHSC-P also had good fire resistance while UHSC-0 and UHSC-S experienced explosive spalling after heating above 200ᴼC. The incorporation of steel fibers in UHSC-S and UHSC-SP mixtures reveals higher tensile and compressive strength findings at different elevated temperatures as compared to UHSC-0 and UHSC-P. In addition, the result of direct tensile strength appears to be lower than splitting tensile strength at different raised temperatures.

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