Stress–strain relationship of steel-fibre reinforced reactive powder concrete at elevated temperatures

Zheng, Wenzhong; Luo, Bin; Wang, Ying

doi:10.1617/s11527-014-0312-9

Cited by 74 publications

(43 citation statements)

References 22 publications

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“…Therefore, even if exposed to the same temperature, the concrete containing the steel fiber in its entire volume can not only transfer heat to the inside faster, but also expand itself (i.e., steel fiber) more significantly. As a result, the higher the ratio of steel fiber in concrete, the lower the compressive strength after high temperature exposure [18]. This can be confirmed by comparing HPC and UHPC in this study.…”

Section: Effect Of Steel Fiber On Fire Resistance Of Concrete -supporting

confidence: 81%

Mechanical properties of various concrete after high temperature exposure Mechanical property of various types of concrete after high temperature exposure is investigated. Considering compressive strength requirement for a vertical element in high rise building, concrete specimens with various design strengths of 35, 80, 100, and 150 MPa were tested. Particularly, the influence of incorporated steel fiber on fire resistance is of interest in this study. Experimental results show that the fire resistance de

2017

IJLTET

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INTRODUCTIONIt is generally known that the mechanical performance decreases when a concrete is exposed to high temperatures. In particular, the reduction of the performance becomes more pronounced with a higher strength, and even a brittle failure such as explosion may occur. This type of failure, known as explosive spalling, is due to the sudden splitting of concrete into numerous pieces at high temperature [1,2]. When a concrete is exposed to high temperature, various types of internal water (free water, capillary water, and adsorbed water) are desorbed or evaporated and converted into vapor or gas [3]. This gas, whose volume has been significantly expanded, increases the internal water vapor pressure and eventually cracks the concrete [4]. Compared with normal strength concrete (NSC), high strength or high performance concrete (HPC) makes it difficult for internal water vapor to escape out. This is due to its dense internal structure and low permeability, resulting in much greater internal pressure [5]. Therefore, the explosive spalling that is a totally different phenomenon compared to that NSC experiences [3]. Phan and Carino reported that this type of spalling occurs between 200-325 °C [6]. The structural elements of high-rise buildings or skyscrapers are typically made of various types of concrete to effectively resist self-weight and wind load. In particular, vertical elements such as columns can have different compressive strengths in the range of 30-150 MPa depending on their vertical position. In other words, as a vertical load applied to the elements increases, the design compressive strength should be increased unless the cross-section area is increased. Moreover, in the case of high or ultra-high strength concrete, whose design strength is 80 MPa or higher, steel fiber is frequently included to alleviate its brittle failure characteristic. Therefore, in order to accurately evaluate the structural safety of fire-exposed high-rise buildings, the mechanical performance of concrete with various strengths at high temperatures should be firstly investigated. In this study, the mechanical properties of concrete after high temperature exposure were investigated. The compressive strength and spalling characteristics of concrete of various design strengths (35, 80, 100 and 150 MPa) were evaluated by experiments. In addition, the effect of incorporated steel fiber on the fire resistance was examined. The results of this study can contribute to assess structural safety or to develop guidelines of fire resistance for high-rise buildings.

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Section: Effect Of Steel Fiber On Fire Resistance Of Concrete -supporting

confidence: 81%

Mechanical properties of various concrete after high temperature exposure Mechanical property of various types of concrete after high temperature exposure is investigated. Considering compressive strength requirement for a vertical element in high rise building, concrete specimens with various design strengths of 35, 80, 100, and 150 MPa were tested. Particularly, the influence of incorporated steel fiber on fire resistance is of interest in this study. Experimental results show that the fire resistance de

2017

IJLTET

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“…The mix proportion was optimized through basic trial experiments and the effectiveness of the raw materials was confirmed by comparing the 7 days strength with the earlier studies [29,34,38]. The weight ratios of cement: silica fume: slag: quartz: and superplasticizer are 1:0.3:0.15:1.2:0.04.…”

Section: Experimentationmentioning

confidence: 95%

“…In the last decade, extensive fire-resistance studies of RPC were mainly carried out at ambient condition after exposure to high temperature [7,24,26,27,28,29,30,31,32,33,34,35,36]. However, there are fewer studies exist which cover RPC under hot-state as well [37,38]. But the study regarding the effect of different types of fibers on the mechanical properties of RPC at high temperature is scarce.…”

Section: Introductionmentioning

confidence: 99%

Effect of Fibers on High-Temperature Mechanical Behavior and Microstructure of Reactive Powder Concrete

et al. 2019

Self Cite

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This study was aimed to investigate the effect of steel, polypropylene (PP), and hybrid (steel + PP) fibers on high-temperature mechanical properties of reactive powder concrete (RPC). The mechanical properties considered are cubic compressive strength, axial or prismatic compressive strength, split-tensile strength, flexural strength, elastic modulus, peak strain, and stress-strain behavior. The strength recession due to high temperature was investigated at micro level by scanning electron microscope, energy dispersive X-ray spectroscopy, X-ray diffraction, mercury intrusion porosity, thermogravimetric, and differential scanning calorimetry analyses. The high-temperature tests were carried out at target temperatures of 120, 300, 500, 700, and 900 °C. The hot-state compressive strength of RPC started to decrease at 120 °C; however, a partial recovery at 300 °C and a gradual decrease above 300 °C were observed. The degradation of split-tensile strength, flexural strength, and elastic modulus were gradual with increasing temperature despite the effect of different fibers. Whereas, the peak strain was gradually increasing up to 700 °C. However, after 700 °C, it remained unchanged. Steel fiber reinforced RPC (SRPC) and hybrid fiber reinforced RPC (HRPC) showed a ductile behavior. PP fiber reinforced RPC (PRPC) showed a quite brittle behavior up to 300 °C; however, further heating made the microstructure porous and it became ductile too. Overall the performance of SRPC and HRPC were superior to PRPC because of higher modulus of elasticity, higher strength, and better fire resistance of steel fibers. Fiber reinforced RPC was found to have better fire resistance than traditional types of concrete based on comparative studies with the provisions of design codes and earlier research. The constitutive equations developed can be utilized in computer programs for structural design of RPC structures exposed to fire.

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“…The optimum fiber content was 2%-3%. Zheng et al [17][18] presented the stress-strain curves of RPC specimens in compression tests at increasing temperatures to study the fire resistance of RPC. Yu et al [19] studied the failure mode, strength characteristics, and deformation law of RPC through conventional triaxial compression tests of RPC cylinder specimens under different confining pressures.…”

Section: State Of the Artmentioning

confidence: 99%

Stress-Strain Model for Reactive Powder Concrete Confined by Steel Tube

Luo¹,

Wang²,

Shen³

et al. 2017

JESTR

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The reliable prediction using nonlinear methods for reactive powder concrete (RPC)-filled steel tube columns relies on the use of an accurate model for core RPC. However, the existing stress-strain model for core concrete has some disadvantages, such as a complicated form, excessive unknown parameters, and inapplicability to RPC. To establish a stress-strain model for RPC confined by a steel tube in finite element analysis (FEA), compressive experiments were carried out on RPC-filled steel tube columns. Calculation formulas of the theory-character parameters (peak stress and peak strain) for RPC-filled circular steel tube were also presented, and a multiparameter stress-strain model for RPC confined by steel tube was proposed based on the existing constitutive model for concrete-filled steel tube. Several nonlinear finite element models were established with ABAQUS, applying the proposed stress-strain model for RPC confined by a steel tube, and the calculating results were compared with the test results of six groups of RPC-filled steel tube stub columns. Experimental results demonstrate that the confining pressure varies from 14.43 MPa to 32.85 MPa; hence, the core RPC is in a low confining pressure state. The peak strength of core RPC increases with the increasing material strength and hoop coefficient. Thus, hoop coefficient and material strength are key parameters that affect the peak strength of the core RPC. The load-strain curves of the specimens obtained by experiments and finite element simulation are in good agreement, thereby verifying the reliability of the proposed model in this study. This study provides a theoretical reference for FEA and calculation of an RPC-filled steel tube structure.

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Stress–strain relationship of steel-fibre reinforced reactive powder concrete at elevated temperatures

Cited by 74 publications

References 22 publications

Effect of Fibers on High-Temperature Mechanical Behavior and Microstructure of Reactive Powder Concrete

Stress-Strain Model for Reactive Powder Concrete Confined by Steel Tube

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