Effect Of Hybrid Fibers Research Articles

Mechanical properties and damage modeling of hybrid fiber reinforced concrete under freeze-thaw cycles

This study aimed to investigate the mechanical properties of steel-polyacrylonitrile hybrid fiber reinforced concrete and its durability under freeze-thaw damage. Firstly, the mechanical properties of hybrid fiber reinforced concrete were studied by compressive strength and flexural strength tests. Secondly, with the help of rapid freeze-thaw test, the variation rules of mass loss rate and relative dynamic elastic modulus were characterized. Based on the test results and freeze-thaw damage theory, the evolution equation of freeze-thaw damage of hybrid fiber reinforced concrete based on Weibull distribution was established. The results show that the enhancement effect of hybrid fiber on the mechanical strength of concrete is better than that of single mixed fiber, especially in the improvement of flexural strength; Accordingly, compared with the single mixing of steel fibers or single mixing of polyacrylonitrile fibers, hybrid fibers are more effective in improving the durability of concrete against freezing and this improvement effect increases with the increase of steel fiber content; The freeze-thaw damage model of Weibull distribution can better reflect the freeze-thaw damage process of hybrid fiber reinforced concrete .Through the freeze-thaw damage evolution curve, it can be found that after 500 freeze-thaw cycles, the freeze-thaw damage degree of the hybrid fiber reinforced concrete with different steel fiber content has been very close, which means that the influence of steel fiber content on the freeze-resistant performance of hybrid fiber reinforced concrete will be limited. This study provides a theoretical basis and technical basis for the design of concrete structures in alpine regions.

Fracture performance of fiber reinforced geopolymer: Synergetic perspective

It is well-known the hybridization of different types of fibers exaggerates the contribution of mono fiber reinforcement on the mechanical and/or fresh properties of the concrete. Despite this fact, very few researchers have pointed out the synergetic effect of hybrid fibers on the fracture response of the geopolymer concretes. Hence, the present work seeks to extend the current knowledge of material science to cover the synergetic effect of hybrid fibers. To this end, a total of 15 mixtures, including plain matrix were manufactured. Steel, carbon, and glass fibers were incorporated into the mixtures at varying ratios. For the fracture evaluations, the rectangular prisms with the central notches were exposed to a three-point static bending test. Crack formations on the specimen surfaces were recorded through the 2D digital image correlation (DIC) method. Test results were examined in terms of some mechanical and fracture properties of geopolymer composites. Accordingly, the compressive strength, Young's modulus, flexural strength, limit of proportionality, and residual strengths were evaluated as the mechanical properties, while the fracture energy, characteristic length, effective crack length, initial stress intensity factor, and unstable stress intensity factor were considered as the fracture properties. Based on the experimental results, carbon fiber was found to be capable of increasing pre-peak mechanical response, while the steel and glass fibers were useful in improving the post-peak fracture properties of geopolymer concretes. In most cases, similar results were also attained for the hybrid fiber-reinforced concretes.

Experimental Investigation of the Impact of Blended Fibers on the Mechanical Properties and Microstructure of Aeolian Sand Concrete.

To investigate the effect of hybrid fibers on the compressive strength of aeolian sand concrete, compressive strength tests were conducted on aeolian sand concrete with single polypropylene fibers and aeolian sand concrete with mixed polypropylene fibers and calcium carbonate whisker, and their variation rules were studied. Using scanning electron microscopy and nuclear magnetic resonance, the microstructure and pore structure of specimens were analyzed, and a mathematical model of the relationship between compressive strength and pore structure was established with gray entropy analysis. The results show that the compressive strength of hybrid fiber aeolian sand concrete first increases and then decreases with an increase in whisker content. When the replacement rate of wind-accumulated sand is 80% and the fiber content is 0.1%, the optimal volume content of whisker is 0.4%, and the 28 d compressive strength of whisker is 24.8% higher than that of aeolian sand concrete. The average relative errors of compressive strength at 7 d and 28 d are 8.16% and 7.48%, respectively, using the GM (1,3) model. This study can provide effective theoretical support for the application of calcium carbonate whisker and polypropylene fibers in aeolian sand concrete.

Effect of hybrid fibres on mechanical behaviour of magnesium oxychloride cement-based composites

Magnesium oxychloride cement (MOC) as a green cement has superior mechanical properties such as high strength and quick gain of early strength, however the inherent brittleness has limited its applications where ductility is crucial. To enhance the strength and ductility, a novel hybrid fibre-reinforced MOC-based composite (FRMOC) is developed for the first time using polyethylene (PE) fibres and basalt fibres (BF) to reinforce the MOC. A systematic investigation of the effect of fibre dosage on the flowability, rheological properties, compressive strength, and tensile properties of the developed FRMOC is conducted in this study. The results revealed that the addition of fibre reduces flowability while increasing the yield stress and plastic viscosity. The 1-day compressive strength of the FRMOC reached 68.2–85.4% of the corresponding value at 28 days, demonstrating its high early strength characteristic. The mix with 1.25% PE and 0.75% BF exhibited the maximum compressive strength at all curing ages. All the mixes consistently demonstrated excellent tensile strength and tensile strain capability (ductility), with the tensile strength and tensile strain capacity of 10.95 MPa and 4.41% achieved for the mix of 2% PE fibre, and 8.49 MPa and 2.43% for the mix of 1.25% PE and 0.75% BF respectively. Moreover, a decline in strength characteristics and strain capacity was observed as BF percentages increased. Scanning electron microscope (SEM) analysis was further employed to investigate the morphological changes in the FRMOC matrix at the microscale to discover the fibre reinforcing mechanism.

Combined Effects of Steel and Glass Fibres on the Fracture Performance of Recycled Rubber Concrete

As an environmentally friendly construction material, recycled rubber concrete (RRC) is commonly used as a road material owing to its excellent flexural strength and crack resistance. Previous studies have shown that the addition of fibres is an effective method for improving the crack resistance of concrete. The purpose of this study is to investigate the fracture performance of RRC reinforced with steel fibres (SFs) and glass fibres (GFs). A total of 28 RRC mixtures were prepared. The results of the fracture test showed that the addition of SFs and GFs significantly enhanced the RRC fracture performance. The maximum increases or decreases in flexural strength, brittleness coefficient, fracture energy, initial fracture toughness, and unstable fracture toughness were 64.9, −34.6, 775.6, 92.0, and 118.4%, respectively. The ideal GF content is usually in the range of 0.4–0.6% and decreases with increasing SF content. In addition, scanning electron microscope (SEM) tests were conducted to explore the mechanism of the effect of hybrid fibres on RRC at a microscopic level. The results show that SFs were always pulled out, while GFs were pulled apart at the initial defects. At the same time, excessive GFs caused more initial defects. These results are expected to provide theoretical direction and experimental support for the practical application of hybrid fibre-reinforced recycled rubber concrete (HFRRRC).

Ballistic impact resistance of ultra-high-performance concrete (UHPC): A comprehensive experimental investigation and parametric analysis

This study explores the ballistic impact resistance of Ultra-High Performance Concrete (UHPC) through an extensive and detailed experimental investigation. This study will address various gaps related to the impact performance of UHPC. This investigation focused on understanding the ballistic resistance performance of UHPC based on (a) the influence of projectile/bullet parameters (hardness, velocity/energy, diameter, and nose shape), (b) the effect of hybrid fibers, (c) comparative analysis of the use of steel mesh and reinforcement bars and (d) effect of sub-zero temperature. In this parametric investigation, different types and shapes (flat, conical, and ogive) of hardened steel projectiles (diameter 12 and 18 mm) with impact velocities ranging from 103 to 182 m/s or impact energy ranging from 674 to 2103 J and UHPC slabs with thickness ranging from 36 to 100 mm was considered. Steel mesh and reinforcement bars at different spacing (with and without fiber UHPC) were also assessed, along with the effect of sub-zero temperature of −30 °C. The impact energy of the projectile and thickness of UHPC targets were statistically significant parameters affecting penetration depth in UHPC compared to other parameters with a p-value much less than 0.001. The Artificial Neural Network (ANN) model developed in the study could predict the penetration depth with reasonable accuracy (MAPE and RMSE were observed to be 7.69 and 12.12, respectively). The experimental results of this study will provide insights into the development of guidelines for using UHPC as a protective material, which can help ensure the safety and resilience of infrastructures in the face of potential threats.

Experimental study on flexural toughness of fiber reinforced concrete beams: Effects of cellulose, polyvinyl alcohol and polyolefin fibers

Flexural toughnesses of concrete reinforced by cellulose fibers (CTFs), polyvinyl alcohol fibers (PFs) and polyolefin fibers (VSs) are studied through notched beam tests. Flexural strength, ultimate strength, residual flexural and tensile strength, fracture energy, the relationship between crack mouth opening displacement and deflection, as well as the synergistic effect of hybrid fibers are investigated. The results show the following. (1) With the increase of fiber dosage, CTFs enhance the flexural strength and ultimate strength of concrete, while high dosages of PFs and VSs weaken the flexural and ultimate strengths. (2) CTF-PF hybrid fibers have a positive synergistic effect on the flexural strength and ultimate strength of concrete. (3) With the increase of fiber dosage, CTFs firstly strengthen and then weaken the fracture energy of concrete, while PFs weaken and then strengthen the fracture energy, and VSs strengthen the fracture energy. CTF1.2PF2.0VS2.0 is considered the optimal combination of hybrid fibers. (4) It is significant that there is a three-stage linear functional relationship between the crack mouth opening displacement and deflection of fiber reinforced concrete.

The effect of hybrid fiber and shear stud on the punching performance of flat-slab systems

In this paper, for the first time, the binary/ternary hybrid fiber and/or shear stud reinforcement as a measure was used to improve the punching performance of flat-slab systems by innovative self-compacting concrete (SCC). Because in these slab systems, sudden and brittle punching failure can be seen due to application and design errors, early removal of formwork, changes in the purpose of use of the building, earthquakes, etc. Besides, numerous studies investigated the punching performance of the single fiber and/or shear stud reinforced flat-slab systems, but research into the measures of the hybrid fiber or the combined use of hybrid fiber and shear stud reinforcement, which were the variable parameters of this study, was quite lacking. For this purpose, the half-scale slab-column connection elements were produced from SCC containing different punching measures (binary/ternary hybrid and/or shear stud) and tested to investigate the punching performance of flat-slab systems. In conclusion, it was found that hybrid fiber reinforcement was the best punching measure to improve the punching performance of slab-column connection elements with/out shear stud. Besides, 3D graphs were drawn so that designers and researchers could estimate the punching strength and energy absorption capacity for flat-slab systems with/out shear stud based on the parameters of micro fiber type and total volume fraction. On the other hand, empirical formulas were developed to predict the punching strength of binary/ternary hybrid fiber reinforced flat-slab systems with/out shear stud by compressive strength, fiber reinforcement index, the slab useful height, and the punching perimeter parameters.

Effect of hybrid fibers on the flexural performance of high‐strength recycled aggregate concrete beams

AbstractFibers are mixed within reinforced high‐strength recycled aggregate concrete (RHRAC) beams to improve their flexural performance. This study experimentally and analytically investigates the effect of using RAC combined with polyvinyl alcohol fiber (PVAF) and steel fiber (SF) on the flexural performance of RHRAC beams. A total of 11 RHRAC beams (150 × 300 × 2600 mm3) are manufactured and subject to four‐point flexural testing. The parameters of the concrete are investigated, including the volume content of the PVAF and SF. The experimental results show that SF increases the flexural strength of RHRAC beams more than PVAF does. Conversely, the effect of PVAF on deformability is more significant than that of SF. In addition, the positive influences of hybrid fiber (PVAF and SF) on the crack load, flexural capacity, and deformation capacity are superior to those of single‐mixed PVAF or SF. Three different specifications are used to calculate the flexural capacity of the test beams, among which, JGJ/T465‐2019 is the most reliable.

Multicriteria performance assessment of sustainable recycled concrete produced via hybrid usage of basalt, polypropylene and glass fiber

Fiber hybridization is a new and effective way of altering the inherent low mechanical properties and durability issues of recycled concrete by using a multi-fiber approach. Research conducted thus far is majorly focused on studying the effects of hybrid fibers on the basic mechanical properties of recycled concrete and no attention is given to the multicriteria-based performance assessment, which is highly important from the perspective of practical applications. The current study is an effort in this regard that intends to evaluate, compare, and rate the multicriteria-based performance of a total of eleven mix formulations prepared with a single and hybrid usage of basalt fiber (BF), polypropylene fiber (PPF) and glass fiber (GF). In addition, two mineral admixtures namely pulverized flyash (PFA) and ground granulated blast furnace slag (GGBFS) were used. From the results of mechanical properties, it is determined that mix formulations comprising hybrid 0.75 %BF-0.25 %PPF and 0.5 %BF-0.5 %GF had the highest strength improvement of 16–21% in compressive strength, 36–49% in splitting tensile strength, and 54–71% in flexural strength. The freeze–thaw assessment revealed that the use of hybrid fibers together with PFA and GGBFS resulted in superior durability performance of recycled concrete specifically in terms of lower length variation (0.055%), lower mass loss (0.39%) and higher UPV (4137 m/s) after 300 cycles. From the cost analysis, it is observed that MRC-1BF had the highest net cost increase of 121.7% of all mixes. Lastly, the multicriteria analysis revealed that the hybrid BF-GF and BF-PPF based MRC had the best performance score and ranking of all formulations, thus implying that their practical use would be highly beneficial in terms of mechanical performance as well as cost-effectiveness.

Cyclic tensile behavior of ultra-high performance concrete with hybrid steel-polypropylene fiber: Experimental study and analytical model

The present study deals with the effect of steel-polypropylene hybrid fiber on the tensile stress–strain behavior of ultra-high performance concrete (UHPC) subjected to monotonic and cyclic loading. Eight batches of UHPC samples with hybrid fibers were tested, with the failure process monitored by acoustic emission (AE) technique synchronously. The failure mechanism of UHPC and reinforcing mechanism of hybrid fibers were analyzed based on the combination of AE source location and scanning election microscope (SEM) observation results. The results indicated that the inclusion of hybrid steel-polypropylene fibers in UHPC matrix contributes to the enhancement of tensile mechanical performance with respect to the tensile strength, peak strain and especially the tensile toughness. Moreover, the relationship between plastic strain accumulation and envelope unloading strain during cyclic tension presents a linear pattern and appears insensitive to the variation of fiber parameters. However, the hybrid fibers significantly contribute to alleviation of the elastic stiffness degradation of UHPC during the cyclic tension. Based on the stiffness degradation process, a damage evolution law characterized by an exponential equation associated with fiber reinforcement indexes is proposed. Notably, the failure of UHPC specimen stems from concurrent macro-crack propagation and multiple cracking behavior throughout the whole loading process, which is improved due to the multi-scale reinforcement effect of hybrid fibers. Finally, in consideration of the effect of hybrid fibers, an analytical constitutive model is developed to generalize the tensile behavior of UHPC, and the comparisons yield a close estimation with test results in current research and literature.

Effects of hybrid fibers on properties of desulfurized gypsum-based composite cementitious materials

Basalt fiber (BF) and polyvinyl alcohol fiber (PVAF) were mixed into desulfurized gypsum-based composite cementitious material (DGCCM) by an orthogonal test to prepare hybrid fiber-reinforced DGCCM, whose mechanical properties, water resistance, and durability were studied using visual, range, variance, and microstructure analyses. The results show that combining the two fibers improved the mechanical properties, water resistance, and durability of DGCCM. In terms of mechanical properties, the maximum absolute dry flexural strength and compressive strength increased by 70.05% and 64.52%, respectively, compared with the blank group. PVAF played a better role than BF in crack resistance and toughening, hence contributing more. When the content of PVFA and BF increased to 0.5% and 0.75%, respectively, the water resistance of hybrid fiber-reinforced DGCCM was better. The enhancement showed that BF had a more significant effect on the softening coefficient of DGCCM than PVAF. The incorporation of fibers inhibits the generation of a large number of cracks during the dry-wet and freeze–thaw cycles of DGCCM, which greatly improves its durability. When the content of PVAF and BF were both increased to 0.5%, the durability of hybrid fiber-reinforced DGCCM was better.

Experimental analysis of torsional behavior of hybrid fiber reinforced concrete beams

This experimental study intended to compare the effect of hybrid fiber between carbon fiber (CF), basalt fiber (BF), and steel fiber (SF) on the torsional behavior of reinforced concrete (RC) beams. Thirteen RC beams were tested under pure torsion and loaded until failure. Beams were divided into four series: A, B, C, and D. Series A consisted of four beams: one without fibers, and others with one type of fiber (CF, BF, and SF). Each one of series B, C, and D contain two types of fibers: (CF and BF), (BF and SF), and (CF and SF) with a varying fiber content of 0.25%, 0.50%, and 0.75% in term of volume. This paper represented the results of the torsional moment, twisting angle, crack pattern, fracture modes, ductility, and energy absorption of specimens. Experiments showed that the use of a hybrid of SF and CF enhanced torsional moment, angle of twist, and energy absorption more than the hybrid of BF and CF or BF and SF. Conversely, the positive effect of the hybrid of BF and SF on ductility was greater than other hybrids. Therefore, the maximum torsional strength increased by 22.3%, 28.6%, and 65.2% when a hybrid fiber of (0.75% BF and 0.75% CF), (0.75% BF and 0.75% SF), and (0.75% CF and 0.75% SF) added, respectively. Moreover, the ultimate torsion was predicted by different theories and code provisions and a formula was developed to take the effect of hybrid fiber on the ultimate torsion of hybrid fiber reinforced concrete (HFRC) beams.

Cyclic bond behavior and bond stress-slip constitutive model of rebar embedded in hybrid fiber reinforced strain-hardening cementitious composites

In this study, direct pullout tests were conducted to illustrate the influences of fiber types (polyethylene (PE) fiber, steel (ST) fiber and hybrid PE/ST fiber), rebar diameter (20 mm, 25 mm, 32 mm), matrix strength (50 MPa and 70 MPa), and loading procedure (monotonic and cyclic loading) on the bonding performance between rebar and strain-hardening cementitious composites (SHCC). The effects of design parameters on bond behavior under monotonic loading, as well as degradation laws of bond strength, bond stiffness, and energy dissipation capacity under cyclic loading are discussed in detail. Experimental results indicate the synergic effect of hybrid fiber is beneficial to crack arrest, bond strength, and bond strength and bond stiffness retention. Compared with those under monotonic loading, SHCC specimens under cyclic loading exhibit similar ascending behavior while an obvious performance degradation at descending. Additionally, ST fiber behaved more effectively than PE fiber in improving the energy dissipation capacity. Furthermore, a cyclic bond stress-slip constitutive model with acceptable accuracy is developed to predict the cyclic bond behavior of rebar embedded in SHCC.

In Situ Formation of Soft–Rigid Hybrid Fibers Decorated by Sparse Lamellae of PLLA: Achieving Ductile and Heat-Resistant Materials with High Strength

Constructing an oriented crystalline structure with high crystallinity in poly(l-lactide) (PLLA) is one efficient way to improve its mechanical strength, but flexibility is sacrificed because orderly arrangement restricts molecular mobility seriously. In this work, a unique hierarchical structure of soft–rigid hybrid fibers decorated by sparse lamellae of PLLA is in situ constructed successfully to improve mechanical strength and flexibility simultaneously. Through interfacial stereocomplexation between the PLLA matrix and poly(3-hydroxybutyrate-co-3-hydroxyvalerate)–poly(d-lactide) (PHBV-PDLA) copolymers, followed by a strong flow field during the multistage stretching extrusion (MSE), soft–rigid hybrid fibers of PHBV/interfacial stereocomplex crystallites (i-SCs) are formed to not only act as a reinforcement filler but also favor energy-dissipating deformation mechanisms. Moreover, under the coupling effect of hybrid fibers and intense flow field, the sparse PLLA lamella with a stiff shish is obtained. Consequently, nanofibrillar PLLA/PHBV-PDLA composites with a highly oriented structure exhibit high strength (94.1 MPa), considerable ductility (65.7%), and excellent heat resistance (E′140 °C > 310 MPa), compared to sea–island structured PLLA/PHBV-PDLA composites with an isotropic structure (59.3 MPa, 11.7%, and E′140 °C > 60 MPa). Furthermore, nanofibrillar PLLA/PHBV-PDLA composites can maintain ductility (57.7%) and strength (98.3 MPa) for 886 days at ambient temperature. The strengthening and toughening mechanisms based on the unique structure are proposed by investigating the microstructural changes before and after a tensile test. This work provides significant guidance for strong, ductile, and heat-resistant PLLA-based materials for durable applications.

Mechanical properties of hybrid fiber reinforced ternary-blended alkali-activated materials

This study employed fly ash, blast furnace slag and steel slag to synthesize ternary-blended alkali-activated materials (AAMs) in order to make full use of the industrial solid wastes and improve the mechanical performance by synergistic effects of the precursors. However, peudo-brittle nature is still the main problem of ternary-blended AAMs. To solve this problem, the effect of hybrid fibers consisting of high-modulus steel (ST) fiber and low-modulus Polyvinyl Alcohol (PVA) fiber on the mechanical properties of the ternary-blended AAMs was evaluated by testing their setting time, flowability, uniaxial compressive strength (UCS), indirect tensile strength (IDT), uniaxial tensile strength (UTS), and three-point bending strength (3PBS). Also, the microstructure of the matrix and fibers were analyzed using a scanning electron microscope. The results show that the flowability and setting time increased with the increasing replacement of PVA fiber by ST fiber. At the PVA/ST fiber volume ratio of 1:1, the AAMs cured for 28 days achieved the highest UCS, IDT, UTS, and 3PBS, which were 32 %, 91 %, 80 % and 114.7 % higher than the AAMs without fiber reinforcement, respectively. The fracture pattern and microstructure illustrated that the best synergistic effect of hybrid fibers was achieved at the PVA:ST fiber ratio of 1:1, at which the small-sized PVA fibers and large-sized ST fibers can inhibit the propagation of micro- and macro-cracks at early and late deformation processes. Furthermore, the ultimate elongation of the composite was improved from 2.62 % to 4.21 % and 5.3 % by modifying the PVA fiber with acrylic polyurethane copolymer and replacing the PVA fiber with polyethylene fiber, respectively, implying the significance of surface hydrophilicity of low-modulus fiber on the ductility of AAMs. This study provided a guide for synthesizing and tailoring the mix design of hybrid-fiber-reinforced ternary AAMs with better strength and ductility.

Dynamic splitting tensile behaviour of engineered geopolymer composites with hybrid polyvinyl alcohol and recycled tyre polymer fibres

Partial replacement of the widely used polyvinyl alcohol (PVA) fibre in engineered geopolymer composites (EGC) with recycled fibres can reduce the material cost and improve sustainability. This study investigates the effect of hybrid PVA and recycled tyre polymer (RTP) fibre content on the quasi-static and dynamic splitting tensile behaviour and microstructure of ambient-cured fly ash-slag based EGC through split Hopkinson pressure bar, scanning electron microscopy and X-ray computed tomography tests. Results indicate that the presence of PVA or RTP fibres can considerably improve the quasi-static and dynamic splitting tensile behaviour of geopolymers. All investigated mixtures are characterised by remarkable strain rate sensitivity within the considered test range, which can be well described using the proposed relationship between dynamic increase factor and strain rate for predictions of dynamic properties. Replacing PVA fibre with 0.25–0.5% RTP fibre can lead to better dynamic splitting tensile properties of EGC compared to that with 2.0% PVA fibre, which can be mainly ascribed to the improved synergistic effect of hybrid fibres in controlling the cracks. The microscopic images reveal that the failure mode of RTP fibres is not sensitive to the strain rate due to its hydrophobic surface feature, which could benefit the energy absorption capacity of EGC under dynamic loading. EGC containing hybrid PVA and RTP fibres holds promise as a cost-effective and sustainable material for applications against dynamic loadings.

RETRACTED: Evaluation of pseudo-strain hardening behavior of hybrid fiber reinforced ultra-high performance concrete containing coarse aggregates by using micromechanical principles

In this study, pseudo-strain hardening (PSH) behavior of hybrid fiber reinforced ultra-high performance concrete containing coarse aggregates (UHPC-CA) and the synergistic effect of hybrid fibers were investigated. First, three types of fiber hybrid samples, namely, 2% short steel fiber (SSF2), 1.5% short steel fiber + 0.5% long steel fiber (SSF1.5 + LSF0.5) and 1.5% short steel fiber + 0.5% PE fiber (SSF1.5 + PE0.5), were designed and tested for their tensile properties. The results showed that the tensile strength and peak tensile strain of SSF1.5 + LSF0.5 were 19.9% and 183.3% higher than the corresponding values of SSF2, respectively. The tensile strength of SSF1.5 + PE0.5 was 3.6% lower than that of SSF2, but its ductility was 4.5 times higher than that of SSF2. Next, three-point bending tests on notched beams and single-crack tensile tests were conducted to evaluate the PSH behavior of hybrid fiber reinforced UHPC-CA by using micromechanical principles. The results showed that all groups met the strength and energy criteria with PSH index values of 5.86, 11.28, and 14.66 for SSF2, SSF1.5 + LSF0.5, and SSF1.5 + PE0.5, respectively. The higher the PSH index of the specimens, the greater the tensile ductility, which is consistent with the tensile test results. These results suggest that it is reasonable to evaluate the PSH behavior of hybrid fiber reinforced UHPC-CA by using micromechanical principles. Third, mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM) analyses were performed to clarify the potential micromechanical properties of the hybrid fibers in improving the tensile properties of UHPC-CA. The MIP results showed that the total porosity was closely related to the initial cracking strength of the matrix; The smaller the total porosity, the higher the initial cracking strength of the matrix. The SEM results showed the characteristics of the PE fibers and the matrix. The bond strength between the PE fibers and the matrix was found to be high, leading to various damage patterns during the pull-out process of the PE fibers. Moreover, the combination of PE fibers and steel fibers showed a good synergistic effect, which explains the reason for the significant improvement in the ductility of the specimens when 1.5% steel fibers and 0.5% PE fibers were mixed.

Evaluation of Strength Parameters of PCC and Hybrid FRC

Abstract: The present trend in concrete technology is towards increasing the strength and durability of concrete to meet the demands of modern construction. The aim of this paper is to study the effect of hybrid fiber (steel & polypropylene) in concrete and compare its properties with that of plain cement concrete. The findings showed that the addition of hybrid fibers to plain cement concrete improved its mechanical properties.

An investigation on the effect of hybrid fiber reinforced on the flexural behavior of RC beams having different lap‐spliced lengths

AbstractThere are only a few studies related to the effect of the hybrid fiber reinforcement on the flexural behavior of full‐scale beam specimens having lap‐spliced length. Thus, this study will ensure important experimental data about the effect of macro steel fibers blended with micro steel fibers on lap‐spliced length. The aim of this study was to investigate the influence of hybrid steel fiber reinforcement on the flexural behavior of full‐scale reinforced concrete beams having different lap‐spliced bars. A sum of three traditional concrete mixtures including a total of 1% fiber by volume fraction was adopted: control mixture without steel fiber, only macro steel fiber and hybrid steel fiber reinforced mixtures. For this purpose, 18 full‐scale beams (200 × 300 × 2000 mm) having three different lap‐spliced length (15, 25, and 35Ø) as tension steel bars were produced and tested under four‐point bending to examine flexural behavior, mode of failure, ductility, and energy absorption capacity properties. In conclusion, the hybrid fiber reinforcement caused the highest increase in the load carrying capacity of the beam specimens. Besides, the hybrid fiber reinforced beam specimens exhibited excellent ductility and energy absorption capacity compared to single fiber reinforced beam specimens. On the other hand, it can be addressed that the hybrid fiber reinforced structural elements had a vital important to compensate the application errors and carelessness in steel bar workmanship, inadequate the lap‐spliced length as per the codes. It can be emphasized that the lap‐spliced length as per the building codes can be reduced in 40% by containing hybrid steel fiber (0.8% macro‐0.2% micro) reinforced concrete without a reduction in load carrying capacity, ductility, and energy absorption capacity compared to control beam specimens without fiber.