Effect of curing age on pullout behavior of aligned and inclined steel fibers embedded in UHPFRC

Krahl, Pablo Augusto; Gidrão, Gustavo de Miranda Saleme; Neto, Romeu Bessan; Carrazedo, Ricardo

doi:10.1016/j.conbuildmat.2020.121188

Cited by 30 publications

(5 citation statements)

References 31 publications

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“…The study of Huang [ 19 ] obtained that the ultimate pullout load and pullout energy increased with the increase in inclination angle from 0° to 45° for the brass-coated straight steel fiber embedded in reactive powder concrete. Similarly, other investigations also indicated that the pullout load reached the peak for straight steel fibers with inclination angle of 30° [ 20 , 21 ], 30° or 45° [ 22 ] and 45° [ 30 ], regardless of the fiber size and the matrix strength, although the consumption energy during pullout could keep increasing as angles to 60° [ 20 ].…”

Section: Introductionmentioning

confidence: 78%

Bond Behaviors of Steel Fiber in Mortar Affected by Inclination Angle and Fiber Spacing

Ding

Zhao

et al. 2022

Materials

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Considering the random orientation and distribution of steel fibers in concrete, the synergistic reinforcement of steel fibers on concrete is much complex than the bond of single fiber. It is meaningful to study the bond behavior of steel fiber during many actions. With the inclination angle of steel fiber to pullout direction and the fiber spacing as main factors, this paper carried out fifteen groups of pullout tests for hook-end steel fiber embedded in manufactured sand mortar. The inclination angle ranged from 0 to 60°, and the fiber spacing ranged from 3.5 mm to 21.2 mm. The characteristic pullout load-slip (PL-S) curve of steel fibers are given out after treating the original complete curves of each group test. The values of key points featured the debonding, peak and residual pullout loads and slips are determined from the characteristic PL-S curves. Based on a multi-index synthetical evaluation method, the nominal debonding strength, bond strength, residual bond strength and the debonding work, slipping work, and pullout work, as well as the debonding energy ratio, slipping energy ratio, and pullout energy ratio are analyzed. Results indicate that the bond performance represented by above indexes changes with the inclination angle and spacing of steel fibers. Except for the bond mechanism performing the same as aligned steel fibers by pullout test, the bond is dominated by the resistance of mortar to peeling off near pullout surface and scraping along pullout direction. When the inclination angle is over 15° or 30°, the bond performance is generally decreased, due to the peeling off of mortar on surface of transversal section with a certain depth. When the fiber spacing is over than 5 mm, the bond performance becomes worst due to the scraping out of mortar along with the slip of steel fibers.

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Section: Introductionmentioning

confidence: 78%

Bond Behaviors of Steel Fiber in Mortar Affected by Inclination Angle and Fiber Spacing

Ding

Zhao

et al. 2022

Materials

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“…Considering the standard deviation, small differences of were observed for all the tested angles, especially for VF ber. During the pullout test, when the bond had already been lost, the frictional resistance mechanism was mobilized, generating an upward pressure in the matrix around the exit point, increasing the friction and consequently the force necessary to pullout the ber [5,6]. This additional resistance to the pullout force can compensate for the reduced e ciency when considering only the angle of inclination [3,28] Localized pressure (snubbing effect) when θ ≠ 0 can cause plastic deformations in bers and matrix fragmentation depending on the properties of the matrix and ber stiffness [6, 28].…”

Section: Resultsmentioning

confidence: 99%

“…The pulling process, as suggested by Li et al [3] and Wu & Li [4], is analogous to a cable passing over a friction pulley. A concentration of stresses occurs on the pullout surface, close to the support point, increasing the frictional resistance due to the high contact pressures (snubbing effect) [3,5]. Owing to the tensions applied to the matrix at the ber exit point, a local fragmentation may occur as the angle increases [3,6].…”

Section: Introductionmentioning

confidence: 99%

Influence of fiber orientation on the behavior of macro synthetic fiber in short- and long-term pullout tests

Rocha,

Bitencourt,

Cardoso

2024

Preprint

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Synthetic fibers deforming over time can be a concern in structural design, particularly in serviceability limit states. Short-term pullout tests are commonly used to predict fiber–matrix interactions, but even in this case, an individualized evaluation of the pullout behavior of single fibers oriented parallel to the load direction may not be sufficient to predict the efficiency of the composite. In the present work, short- and long-term pullout tests were performed with fibers oriented at angles of 15°, 30°, and 45° with respect to the direction of the load to investigate the influence of macro synthetic fibers orientation on fiber–matrix interactions. In short-term tests, optical microscopy images were obtained on the pulled-out fibers to correlate the surface degradation of the fibers with the stress versus strain curves. In quasi-static pullout (short-term), small reductions in pullout strength were observed for all fibers and angles, in addition to an intensive degradation of their surfaces owing to the significant snubbing effect of this type of fiber. In contrast, for the long-term tests, a creep reduction was observed with increasing fiber inclination angle caused by the creep reduction of the fiber due to non-axial loading and additional force components produced by the deviation of the axial force. The parameters of Burgers rheological model were written as a function of the fiber orientation angle, with excellent adjustment to the experimental data.

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“…The fiber pullout test must be performed with straight and inclined fibers, as most fibers have inclinations with the crack surface in the composite. Krahl et al (2021) [35] tested fibers with inclinations of 0 • , 30 • , and 45 • to the loading direction. The snubbing and spalling effect mechanisms occur in inclined fibers due to frictional stresses increasing at the exit point of the fiber cavity.…”

Section: Fiber Pulloutmentioning

confidence: 99%

Modeling the Tensile Behavior of Fiber-Reinforced Strain-Hardening Cement-Based Composites: A Review

et al. 2023

Self Cite

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Strain-Hardening Cement-Based Composites (SHCCs) exhibit high toughness and durability, allowing the design of resilient structures. Despite the exceptional properties of SHCC and the current modeling techniques, the widespread use of the composite is limited. One limiting factor is developing and validating analytical models that could be used for optimizing mixes and designing structural elements. Furthermore, the composite mechanical response is complex and depends on several phenomena, such as fiber pullout, fiber orientation and distribution, size effect, fiber content, group effect, embedding length, fiber dimensions, and matrix strength. In this context, this research presents the state-of-the-art on the micro- and mesomechanisms occurring in SHCC during cracking and robust techniques to predict its tensile behavior accounting for such phenomena already proved experimentally. The study is relevant for designers and the scientific community because it presents the gaps for the research groups to develop new investigations for consolidating SHCC, which is a material to produce resilient structures.

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Effect of curing age on pullout behavior of aligned and inclined steel fibers embedded in UHPFRC

Cited by 30 publications

References 31 publications

Bond Behaviors of Steel Fiber in Mortar Affected by Inclination Angle and Fiber Spacing

Bond Behaviors of Steel Fiber in Mortar Affected by Inclination Angle and Fiber Spacing

Influence of fiber orientation on the behavior of macro synthetic fiber in short- and long-term pullout tests

Modeling the Tensile Behavior of Fiber-Reinforced Strain-Hardening Cement-Based Composites: A Review

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