Correlation of fiber dispersion, rheology and mechanical performance of FRCs

Özyurt, Nilüfer; Mason, Thomas O.; Shah, Surendra P.

doi:10.1016/j.cemconcomp.2006.08.006

Cited by 141 publications

(69 citation statements)

References 15 publications

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“…The fiber spatial distribution in the concrete volume is associated with the casting process, i.e., the manner in which concrete is poured into the mold and the vibrating time (Ozyurt, 2007), which depends on the rheological properties of the concrete and the boundary conditions (wall effects) imposed by the mold. In this sense, using selfcompacting concrete (SCC) can help to ensure a uniform fiber dispersion due to their self-compacting rheological stability; as a result, compaction by vibration is not required (Ferrara et al, 2008).…”

Section: Fiber Distribution In the Frcmentioning

confidence: 99%

“…To determine the actual reinforcement available in each direction of the concrete volume, due to the relevance of the distribution and orientation of the fibers in the development of suitable and reliable material properties for structural design, many researchers have studied the distribution of fibers theoretically and/or at the laboratory level, for example, Akkaya et al (2000), Chermant et al (2001), Chung (2001), Lawler et al (2003, Dupont and Vandewalle (2005), Ozyurt (2007), Lataste et al (2008), Lee and Kim (2010), and the comprehensive RILEM TC 162 (2003), among others.…”

Section: Introductionmentioning

confidence: 99%

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Distribution of fibers in SFRC segments for tunnel linings

Carmona

Molins

Aguado

et al. 2016

Tunnelling and Underground Space Technology

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This paper presents research results regarding the distribution of steel fibers in concrete used to build precast tunnel segments for Line 9 of the Barcelona Metro. The fiber distribution was studied using the actual fiber contents obtained by means of crushed cores drilled from different points of three full-scale tunnel lining segments. A statistical analysis determined that the fiber content in the ends of segments tend to be greater than in the central zone. In addition, cores with a diameter of 150 mm were found to have a lower scatter in the fiber content than smaller diameter specimens. Finally, based on probabilistic approaches, a minimum of 11 cores is proposed to control the fiber content in FRC segments.

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Section: Fiber Distribution In the Frcmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Distribution of fibers in SFRC segments for tunnel linings

Carmona

Molins

Aguado

et al. 2016

Tunnelling and Underground Space Technology

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“…The discussers' idea of monitoring fibres through imaging of the fracture surface is rather crude and time consuming, as it will show only the location of fibres, and only those at the fracture surface. For monitoring fibre orientation, segregation and clumping, alternating current-impedance spectroscopy (AC-IS) has been used (Ozyurt et al, 2006(Ozyurt et al, , 2007, but this method can only be used for conductive fibres. An alternative method to AC-IS is image analysis, whereby the fibres of a cross-section are counted using a probe sensitive to the magnetic properties of the steel fibres (Ferrara et al, 2012;Ozyurt et al, 2006Ozyurt et al, , 2007Stroeven and Hu, 2006).…”

Section: Dispersion Of Fibresmentioning

confidence: 99%

“…For monitoring fibre orientation, segregation and clumping, alternating current-impedance spectroscopy (AC-IS) has been used (Ozyurt et al, 2006(Ozyurt et al, , 2007, but this method can only be used for conductive fibres. An alternative method to AC-IS is image analysis, whereby the fibres of a cross-section are counted using a probe sensitive to the magnetic properties of the steel fibres (Ferrara et al, 2012;Ozyurt et al, 2006Ozyurt et al, , 2007Stroeven and Hu, 2006). Recently some researchers (Le et al, 2008;Suuronen et al, 2013;Wuest et al, 2009) have employed X-ray tomography to determine the distribution and orientation of metallic fibres in hardened concrete samples.…”

Section: Dispersion Of Fibresmentioning

confidence: 99%

Discussion: Mechanical properties of hybrid fibre-reinforced concrete – analytical modelling and experimental behaviour

Abadel

Abbas

Almusallam

et al. 2016

Magazine of Concrete Research

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The discussers appreciate the effort made by the authors in proposing an analytical model to predict the mechanical behaviour of hybrid fibre-reinforced concrete (HyFRC or HFRC) taking into consideration the synergy concept (Abadel et al., 2016). However, their experimental results contradict this concept. For example, all the properties of mix M4 (0·2% PPF + 1·2% SF) are lower than those of steel fibre-reinforced concrete (SFRC) having only 1·2% SF, mix M1, that is, negative synergy. Generally, for the same fibre volume fraction (F Vf ), all the properties of HyFRC mixes are lower than those of SFRC mixes, as shown in Figure 10. Furthermore, the modulus of rupture, splitting tensile strength and flexural toughness of SFRC with a lower F Vf , mix 1, are greater than those of mix 3 (SFRC with a higher F Vf ). Although the authors mentioned that 'The fibres were added to plain concrete in parts to prevent fibre balling and to ensure the homogeneity of the concrete mixture. The mixing was done for about 3 min to ensure the proper distribution of fibres in the concrete mass', they did not show the readers any validation for this, such as images of the fracture surfaces of the different types of specimens showing the uniform dispersion of the three different types of fibres, or any statistical analysis of the experimental results, such as the standard deviation or the coefficient of variation. Casting and compaction affect the fibre orientation throughout the specimen and could potentially lead to fibre segregation. Furthermore, different types of fibres require different optimum ranges of rheology of the cementitious mortar to achieve good fibre dispersion. This can lead to a significant challenge in processing hybrid fibres in the same matrix; see, for example, Abou El-Mal et al. (2015). Authors' replyThe authors would like to thank the discussers for their interest in this paper and their insightful comments on the work. The authors' responses to the individual comments are given below under two main headings. Synergy in HFRC mixesIn the study under discussion, the synergy in different HFRC mixes was only observed to some extent for mix M7, as mentioned in the section of the original paper entitled 'Discussion of test results'. As the main objective of adding fibres to concrete is to improve the tensile characteristics of the concrete, such as modulus of rupture, splitting tensile strength and direct tensile strength, these properties of HFRC mixes having 1·4% volume fraction of fibres are compared with mix M3 (containing only steel fibres) and shown in Figure 11. It is to be noted here that the tensile characteristics presented in the figure are in terms of the compressive strength of concrete, that is, the ratio of tensile characteristics to the compressive strength. The figure shows the presence of synergy in mix M7. As the ratio of M7 to M3 is slightly greater than unity, the synergy in mix M7 was not strongly claimed in the paper. Other researchers (e.g. Banthia and Gupta, 2004) have also reported synergy eff...

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“…Several studies have demonstrated that the main benefits of adding steel fibres in self-compacting concrete are to achieve uniform distribution of fibres in the matrix as well as rheological stability without compaction and vibration (Ozyurt et al 2007;Ferrara and Meda 2006). This indicates that fibre dispersion and orientation could be crucial for the key properties of steel fibre reinforced self-compacting concrete (SFR-SCC), and the link between its fresh-and hardenedstate performances (Ferrara et al 2012).…”

Section: Introductionmentioning

confidence: 99%

Anchorage Effects of Various Steel Fibre Architectures for Concrete Reinforcement

Abdallah

Fan

Zhou

et al. 2016

Int J Concr Struct Mater

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This paper studies the effects of steel fibre geometry and architecture on the cracking behaviour of steel fibre reinforced concrete (SFRC), with the reinforcements being four types, namely 5DH (Dramix Ò hooked-end), 4DH, 3DH-60 and 3DH-35, of various hooked-end steel fibres at the fibre dosage of 40 and 80 kg/m 3 . The test results show that the addition of steel fibres have little effect on the workability and compressive strength of SFRC, but the ultimate tensile loads, post-cracking behaviour, residual strength and the fracture energy of SFRC are closely related to the shapes of fibres which all increased with increasing fibre content. Results also revealed that the residual tensile strength is significantly influenced by the anchorage strength rather than the number of the fibres counted on the fracture surface. The 5DH steel fibre reinforced concretes have behaved in a manner of multiple crackings and more ductile compared to 3DH and 4DH ones, and the end-hooks of 4DH and 5DH fibres partially deformed in steel fibre reinforced self-compacting concrete (SFR-SCC). In practice, 5DH fibres should be used for reinforcing high or ultra-high performance matrixes to fully utilize their high mechanical anchorage.

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Correlation of fiber dispersion, rheology and mechanical performance of FRCs

Cited by 141 publications

References 15 publications

Distribution of fibers in SFRC segments for tunnel linings

Distribution of fibers in SFRC segments for tunnel linings

Discussion: Mechanical properties of hybrid fibre-reinforced concrete – analytical modelling and experimental behaviour

Anchorage Effects of Various Steel Fibre Architectures for Concrete Reinforcement

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