Different Types Of Steel Fibers Research Articles

Flexural toughness and stress-strain relationship of different types of steel fiber reinforced shotcrete in high geothermal environment

The shape of steel fiber plays a pivotal role in determining the mechanical properties of concrete. In this paper, the impacts of end-hooked, wavy and ultra-fine steel fibers (all with a doping amount of 1.0 %) on the compressive strength, flexural strength, flexural toughness, and strain-strain relationship of shotcrete under curing conditions of 20 ℃, 40 ℃, and 60 ℃ are studied. Furthermore, the flexural toughness of steel fiber shotcrete is evaluated using the energy absorption method, and a constitutive model for steel fiber shotcrete was established based on meso-damage mechanics theory. The results indicate that curing temperatures below 40 ℃ are conducive to enhancing the compressive strength, flexural strength, and flexural toughness of steel fiber shotcrete, while curing temperatures above 60 ℃ are unfavorable for the development of strength and toughness in steel fiber shotcrete. Regardless of the type of steel fiber, its incorporation can alleviate the negative impact of high-temperature curing on the strength and toughness of shotcrete. Under high-temperature curing conditions, the influence of end-hooked steel fibers on the strength of shotcrete is superior to that of corrugated and ultrafine steel fibers, while ultrafine steel fibers are beneficial for improving the flexural toughness of shotcrete. The slope, peak stress, and peak strain of the stress-strain curves of shotcrete cured at 40 ℃ and 60 ℃ with the addition of the three types of steel fibers are greater than those of concrete without steel fibers. Furthermore, the descending segment of the curve is wider and smoother, with a larger surrounding area, demonstrating good toughness, deformability, and ductility. The end-hooked steel fibers and ultrafine steel fibers exhibit superior performance in enhancing the toughness and ductility of shotcrete under high-temperature curing conditions compared to wavy steel fibers. Based on meso-damage theory, the impacts of curing temperature and steel fiber types on the constitutive model of shotcrete under axial compression were established, and the model parameters were discussed. The research results can provide theoretical support for the durability design of tunnel linings in high ground temperature environments.

Experimental Study on Fracture Properties of Self-Compacting Concrete Containing Red Mud Waste and Different Steel Fiber Types

This study aims to investigate the effect of integrating red mud (RM) waste and different types of steel fibers on the fracture toughness characteristics of self-compacting concrete (SCC). A total of 24 specimens consisting of notched SCC beams with various steel fibers (measuring 100 × 100 × 500 mm) are subjected to a three-point bending test. This study examines five various fiber types characterized by varying shapes and aspect ratios. These fiber types include the hook-end fiber with lengths of 60 and 30 mm, the long straight fiber with lengths of 21 and 13 mm, and the flat-end fiber. Six concrete mixtures, each incorporating fibers with 1% of the volume percentage, are examined. RM is used at a replacement rate of 20% of the mass of cement. Another objective of the study is to analyze the mechanical and fresh characteristics of concrete. The findings indicate that the incorporation of steel fiber has an adverse effect on the fresh concrete characteristics of SCC. The presence of steel fiber results in enhanced mechanical properties, peak loads, and deflection at the point of failure, in addition to an increase in the crack mouth opening displacement. The fracture toughness of SCC mixtures is also influenced by the presence of steel fiber.

Selected Mechanical Properties of Concrete with Regard to the Type of Steel Fibers

Not only in the construction industry, but also in other technical areas, efforts are being made to reduce the costs or difficulty of producing a certain product and at the same time to improve some of its properties. With the development of modern technologies come new possibilities in the development and production of such products. Fiber reinforced concrete is one of them. Fiber reinforced concrete does not fully replace reinforced concrete, but even with a reduction in price and production time, it has a certain part of the properties of reinforced concrete, which can be used for structural elements with specifically required properties. The subject of the presented paper is the testing and comparison of compressive and split tensile strength of steel fiber reinforced concrete (SFRC) with steel fibers MasterFiber 482 with dosage 60 kg/m3 and 90 kg/m3 and SFRC with 5 different types of steel fibers with dosage 50 kg/m3, where dosage 0 kg/m3 represents ordinary portland concrete (OPC). Submitted paper is also focused on specific test methods of concrete, such as measurement of resistance to frost and defrosting chemicals and pressure water seepage.

Influence of fiber dosage, fiber type, and level of prestressing on the shear behaviour of UHPFRC I-girders

Ultra-High-Performance Fiber-Reinforced Concrete (UHPFRC) has excellent mechanical and durability properties compared to conventional concrete. It offers lightweight structures compared to reinforced concrete. In this study, the shear behaviour of post-tensioned UHPFRC girders is experimentally studied. The parameters considered in this study are (i) the level of prestressing, i.e., 0%, 35%, and 70% of ultimate tensile strength of strand (fpu), (ii) the volume fraction of fibers (Vf), i.e., 1.0%, and 2.0%, and (iii) different types of steel fibers; straight fibers, hybrid fibers (straight and hooked ended). The principal tension and compression strain of beams along and across the cracks were measured throughout the loading and compared with localization strains from the direct tension test. Due to increase in prestress from 0% to 70% of fpu, the ultimate load-carrying capacity increased from 18% to 39% in girders with a 1% fiber volume fraction. Similarly, it increased from 24% to 50% for 2% fiber reinforced girders. This is due to increased active stress transfer across the concrete cross-section, which reduces the crack angle from 44° to 34°. Similarly, the shear cracking load increased, and the post-cracking reserve capacity reduced with an increase in fiber dosage. Digital image correlation analysis reveals that strain distribution across the crack is uniformly distributed at all loading stages.

Axial strength of fibrous reactive powder concrete circular columns

In this paper, a formula is proposed to calculate the nominal axial strength (Po) of fibrous reactive powder concrete (RPC) columns reinforced with steel fibres of different geometries and volume contents. The formula takes into account the effects of concrete, longitudinal reinforcement, transverse constraints, geometry of steel fibres and their volume content. A comparison is made with existing formulations that consider only for concrete and steel reinforcement. The proposed formula has been verified and validated by the experimental results of different types of steel fibre reinforced concrete (SFRC) columns in the literature. The results show that the current formulation considering only concrete and reinforcement significantly underestimatesPo of fibrous RPC columns. Furthermore, it is found that the proposed formula well predicts the nominal axial strength for fibrous RPC columns with an accuracy of 97–99%.

Pull-out behaviour of steel fibres embedded in ultra-high-performance concrete after exposure to high temperatures

The paper examined the bond-slip behaviour of steel fibres embedded in ultra-high-performance concrete (UHPC) after exposure to elevated temperatures. Different types of steel fibres were cast into the halved UHPC dog-bone-shaped samples, including straight fibres, three types of hooked-end fibres and corrugated fibres. The bond response was investigated through single fibre pull-out tests on the samples unheated and heated to 200, 400 and 600 °C. In addition, the effects of polypropylene (PP) fibre addition and heating rate on steel fibre’s bond behaviour were also investigated. The results revealed an increase in bond strength when the straight and hooked-end fibre samples were heated to 200 °C, while the bond strength of the corrugated fibre decreased at the same temperature. Bond strength reductions were observed at higher temperatures. In addition, the straight fibres led to the lowest pull-out resistance as both the hooked-end and the corrugated fibres significantly enhanced the bond strength. With the hooked-end or corrugated fibres, the failure mode gradually shifted from pull-out failure to fibre rupture. Besides, adding PP fibres increased the bond strength of straight fibres at 400 °C but reduced the bond strengths of hooked-end fibres at ambient and high temperatures. High heating rate also led to a greater bond strength for the straight fibres at 200 °C and 400 °C.

Effect of compounding conductive materials on the mechanical properties of concrete and the microscopic mechanism

After adding conductive materials into the concrete matrix, cracks can be monitored in real-time through the change of concrete resistance when cracking. However, adding conductive materials will affect the working and mechanical properties of concrete. Therefore, this paper studied the influence rule and failure characteristics of the addition of conductive materials such as steel fiber and nanocarbon black on the mechanical properties of concrete. Combined with the performance index of the mix, it comprehensively determined the optimal dosage range of different types of steel fiber and nanocarbon black under the single mixing factor. Then, the orthogonal test method of three factors (different kinds of fiber, different contents of steel fiber, and different contents of nano carbon black) at four levels are used to test and study the mechanical properties of concrete. Through the analysis of the test results, the primary and secondary factors of conductive materials affecting the strength of concrete and the optimal dosage are obtained, and the failure mechanism is analyzed from the microscopic level. Finally, a structural model of the cracking resistance mechanism of conductive materials is proposed.

Enhancing the Behavior of Reinforced Concrete Beams Subjected to Pure Torsion Stresses Using Different Types of Steel Fiber in the Mix

Enhancing the Behavior of Reinforced Concrete Beams Subjected to Pure Torsion Stresses Using Different Types of Steel Fiber in the Mix

Meso-Mechanical Simulation of the Mechanical Behavior of Different Types of Steel Fibers Reinforced Concretes

Introducing steel fibers into traditional concrete can improve its mechanical properties and crack resistance, but few studies have considered how the steel fiber shape and the bond-slip effect between fibers and matrix affect the mechanical behavior of concrete. This paper establishes a three-dimensional representative volume element (3D RVE) of steel fiber-reinforced concrete (SFRC) with random distribution, different shapes, and different interfacial strengths of steel fibers using Python, Abaqus and Hypermesh. Uniaxial tensile behaviors and failure modes of the SFRC are systematically simulated and analyzed. The results show that when the interfacial strength of steel fiber/concrete is changed from 1 to 3 MPa, the tensile strength of the SFRC increases accordingly. When the interfacial strength is greater than 3 MPa, it has no effect on tensile strength. Additionally, if the interfacial strength is 1 MPa, the tensile strength of the SFRC with end-hook steel fibers is increased by 7% when compared to the SFRC with straight steel fibers, whereas if the interfacial strength reaches 2.64 MPa (strength of pure concrete), the fiber shape has little effect on the tensile strength of the SFRC. Moreover, the simulation results also show that interfacial damage dominates when the interfacial strength is less than 1 MPa, and the crack propagation rate in the end-hook steel fiber-modified SFRC is lower than that in a straight steel fiber-modified SFRC. Therefore, this research reveals that using end-hook steel fibers can improve the strength of the SFRC under low interfacial strength, but the ideal strength of the SFRC can be achieved only by using straight fibers when the interfacial strength between steel fibers and concrete is relatively high.

Mechanical Properties of Lightweight Aggregate Concrete Reinforced with Various Steel Fibers

The objective of the present study is to examine the effects of different types and content of steel fibers on the workability, mechanical properties, and ductility enhancement of lightweight aggregate concrete (LWAC). Thirteen LWAC mixtures were prepared using different types of steel fibers including conventional hooked-end macro steel fibers (SF(H)), straight (CSF(S)), crimp-shaped (CSF(C)), and hooked-end (CSF(H)) copper-coated micro steel fibers at the designed compressive strength of 40 MPa. The fiber volume fraction varied from 0% to 1.5% at an interval of 0.5%. Test results showed that CSF(H) type possesses a better potential than the other types in enhancing the tensile resistance and toughness at the post-peak branch of the load–deflection curve of beams. The bond characteristics of fibers with cement matrix were one of critical parameters that needs to be considered in designing the fiber reinforced concrete. Thus, the splitting strength, modulus of rupture, and modulus of elasticity of fiber reinforced LWAC were formulated as a function of volume fraction, aspect ratio, and bond strength of fibers from the regression analysis using the present test data.

Fibre-Reinforced Grout for Micropile Construction

Hollow bar micropiles (HBMP) are increasingly used to support heavy structures owing to their ability to carry considerable axial loads. However, their lateral capacity is relatively small due to their small flexural strength, which could limit their application for structures subjected to large lateral loads. Enhancing the micropile flexural strength by utilizing fibre-reinforced grout in its construction can thus improve its lateral performance. This study investigates the use of four types of fibers in grout mixture with different dosages to enhance the strength of grout used for micropile construction. Plastic, basalt, steel and micro-steel fibers were applied with dosages of 1%, 1.5% and 2%. Based on the obtained results, steel fibers were selected for further investigation. Nine model micropiles 1000 mm long and 76 mm in diameter were casted and tested in a laboratory environment with two different types of steel fibers. The micropiles were subjected to pure bending tests and the moment – curvature curves were extracted. The moment – curvature results indicated that the micropiles moment capacity increased and their post-cracking behaviour improved by adding steel fibers to the grout mix. As part of a large-scale study of lateral performance of single and grouped micropiles installed in cohesionless soil, one micropile was constructed with 1% micro-steel fiber to investigate its effect on its lateral performance. The lateral load test results indicated that the lateral capacity of the reinforced micropile improved by 10% over that of the non-reinforced micropile.

Effects of nano-SiO2 coating and induced corrosion of steel fiber on the interfacial bond and tensile properties of ultra-high-performance concrete (UHPC)

In this study, the effects of nano-silica (SiO2) coating and induced corrosion of steel fibers on the interfacial bond and tensile properties of ultra-high-performance concrete (UHPC) were investigated. Two different types of steel fibers were prepared: plain and nano-SiO2-coated. Corrosion was induced in each of these to two different degrees (2% and 5% by weight) using a 3.5% standard sodium chloride (NaCl) solution. The test results indicate that nano-SiO2 coating increases the bond strengths of steel fibers embedded in UHPC by approximately 50%. Furthermore, more scratches and higher hydrate contents were detected on the surface of nano-SiO2 coated steel fibers after pulling out from UHPC. Under tension, the UHPC containing nano-SiO2-coated steel fibers exhibited double the strain energy density, compared to that containing plain steel fibers. Moderately corroded steel fibers resulted in higher interfacial bond strength and energy absorption capacity owing to the increased surface roughness. In addition, the nano-SiO2 coating enhanced the tensile performance of UHPC even under corrosive environments. This enhancement was however diminished by steel fiber corrosion, so that fiber corrosion needs to be carefully controlled when nano-SiO2-coated steel fibers are used for UHPC.

Теплопроводность сталефибробетона

The article presents the study results of the thermal conductivity of steel fiber reinforced concrete (SFRC) on a matrix of fine-grained concrete with different types of steel fibers and different content of fibers. It is shown, that with an increase in the volume content of steel fiber, the thermal conductivity coefficient of SFRC, depending on the diameter of the fiber, can either increase or decrease compared to the thermal conductivity coefficient of the matrix. The obtained result is explained based on the influence of both the ratio between the wavelength of infrared (thermal) radiation and the diameter of the steel fiber and the conditions of thermal flow passage through the fiber-matrix boundary on the thermal flow propagation.

Electrical Resistivity of Steel Fibre-Reinforced Concrete-Influencing Parameters.

This paper presents a systematic study of the electrical resistivity of different steel fibre-reinforced concretes with fibre contents from 0 kg/m3 to 80 kg/m3 in order to identify possible effects of interactions among concrete composition and fibre type and content regarding electrical resistivity. Based on a literature review, four parameters, w/c ratio, binder content, ground granulated blast-furnace slag (GGBS) and fineness of cement, which show a significant influence on the electrical resistivity of plain concrete, were identified, and their influence on the electrical resistivity as well as interaction effects were investigated. The results of the experiments highlight that the addition of fibres leads to a significant decrease in electrical resistivity, independent of all additional parameters of the concrete composition. Additionally, it was shown that a higher porosity of the concrete, e.g., due to a higher w/c ratio, also results in a lower electrical resistivity. These results are in agreement with the literature review on plain concrete, while the influence of the concrete composition on the electrical resistivity is weaker with the increase in fibre content. The influence of fibre reinforcement is thus not affected by changes in the concrete composition. In general, a higher fibre dosage leads to a decrease in electrical resistivity, but the impact on the electrical resistivity varies slightly with different types of steel fibres. Based on this study, the potential of determining the fibre content using electrical resistivity measurements could be clearly presented.

Probability distribution of bond efficiency of steel fiber in tensile zone of reinforced concrete beams

The applicability of bond efficiency of steel fiber in the flexural bearing capacity calculation of steel fiber reinforced concrete (SFRC) beams was experimentally investigated through tests on 18 SFRC beams and one reinforced concrete (RC) beam. The test results indicated that the flexural bearing capacity of SFRC beams increased significantly with the use of high-strength steel bars, and the bond efficiency of the steel fiber in the tensile zone of reinforced concrete beams according to ACI 544.4R-88 [1] is conservative for the flexural carrying capacity calculation of SFRC beams containing high-strength steel bars. The probability distribution of the bond efficiency of steel fiber in the tensile zone of reinforced concrete beams was analyzed through experimental data collected from relevant literature. The bond efficiency of different types of steel fibers with different guarantee rates was determined. A range of bond efficiency for steel fiber in the tensile zone of reinforced concrete beams was proposed to predict the flexural carrying capacity of SFRC beams.

The interplay of abrasion, impact and salt scaling damage in fibre-reinforced concrete

This investigation aims to study the abrasion and impact resistance of fibre-reinforced concrete before and after exposure to salt scaling. Different types of steel fibre and different mixture compositions were used to improve the strength and resistance of the tested mixtures. The variables were the type of steel fibres, surface condition of steel fibres (coated and uncoated), length of steel fibres (35 and 60 mm), volume of steel fibres in the mixture (0, 0·35 and 1%), end condition of steel fibres (single- and double-hooked ends), coarse aggregate size (10 and 20 mm), coarse aggregate/fine aggregate ratio (0·7 and 2) and cement content (300 and 550 kg/m3). The results indicated that the uncoated steel fibres experienced some rust after the exposure to salt scaling, causing more deterioration and higher surface scaling than coated steel fibres. The results also revealed that the samples that were exposed to salt scaling showed a noticeable reduction in the abrasion and impact resistance compared with samples that were not exposed to salt scaling. Adding steel fibres, however, alleviated this reduction and contributed to enhancing the impact and abrasion resistance of scaled concrete surfaces.

Influence of concrete strength, fiber content and aspect ratio in the residual flexural strength of steel fiber reinforced self-compacting concrete

Abstract Steel Fiber Reinforced Self-Compacting Concrete (SFRSCC) is a material that combines the benefits of self-compacting concrete in the fresh state and the greater durability, with the gains of fiber- reinforced concrete in the hardened state, especially the gains in residual flexural strength. Results are presented in this paper of residual flexural strengths on 48 prenotched prisms conducted in accordance with RILEM TC 162 TDF for the Steel Fiber Reinforced Self-Compacting Concretes (SFRSCC). This article presents equations to estimate residual flexural stresses in SFRSCC. For this, SFRSCC prisms of two compressive strength classes, 20 MPa and 40 MPa, were produced with 3 different types of steel fibers with the contents volume of 0.5% and 1.0%. Based on the test results, equations were proposed to determine the residual flexural stresses established through regression analysis, which were, then, further validated with concretes produced in this work and results available in the literature. The equations found, despite showing an indication of the residual flexural strengths that will be achieved, obtained a relatively high error. In order for the equations to be applied in a technical way, further studies for a larger sample need to be carried out, seeking to optimize the equations.

SIFCON-A High Performance Concrete - Experimental Investigations

This paper addresses the development of High Performance Concrete in the past along with the experimental work on properties of Slurry Infiltrated Fibrous Concrete (SIFCON). Slurry infiltrated fibrous concrete has high strength, large ductility and good performance under seismic excitations. There is an increase in numbers of structures testified by the recent symposiums and conferences held on HPFRC. Now presently investigations are being carried out to suggest recommendations for the design of HPFRC structures. SIFCON consist of cement slurry and different types of steel fibers. It is observed that with the increase in percentage of steel fibers there is an improved static, dynamic and mechanical properties of concrete. Steel fibers also act as crack arrester and improve durability. In the present study, it is observed that at 9% fiber content the compressive strength, split tensile strength and flexural strength is optimum.

LABORATORY TESTING OF STEEL FIBER CONCRETE PRISM FOR TENSION IN BENDING

Abstract. Laboratory bending tests of concrete and steel-fiber-concrete prisms were carried out. The concrete matrix for all prisms is made of a concrete mixture of the same composition with a coarse aggregate size up to 10 mm and a water-cement ratio that allows correct mixing of the ready mixture with fiber, so that the latter is evenly distributed over the sample volume. Fiber reinforcement is 1% for all three types of fiber, a fiber made of the same steel with an ultimate strength of 1335 MPa, fiber length 50 mm, diameter 1 mm is used. Fibers differ only in shape, which makes it possible to compare test results across series without correction factors. Concrete samples without fiber are considered as control samples. As a result of laboratory tests, data sets were obtained and analyzed, which are presented in the form of diagrams. Different types of steel fiber show different increases in the load at the beginning of cracking and load-bearing capacity. The most profitable from this point of view is the addition of anchor fiber to concrete, the least – wave fiber. However, the presence of any of the considered steel fibers in the mixture significantly increases the load-bearing capacity of the sample. In addition, the type of destruction of such a sample changes from brittle to viscous. We also studied the deformability of samples with different fiber reinforcement and plotted the dependence of the relative longitudinal strain on the load. Before the crack formation begins, there is a direct proportionality between the load and the strain with the appearance of cracks, the slope of the graphs changes sharply. When the load-bearing capacity is lost, steel fiber-reinforced concrete samples are restrained from final destruction. The use of steel fiber in concrete on average increases the crack resistance by 40%, and the load-bearing capacity by 64%. Compared with samples without fiber reinforcement, samples with anchor fiber show an increase in load-bearing capacity by 89%, and crack resistance by 61%. When using flattened fiber, these values are 56% and 32%, and for wave fiber – 47% and 25%, respectively. The use of steel fiber in the manufacture of concrete mix avoids the brittle nature of destruction.

Chelate effect on fiber surface morphology and its benefits on pullout and tensile behaviors of ultra-high-performance concrete

To develop optimum engineered steel fibers as reinforcement for ultra-high-performance concrete (UHPC), three different types of steel fibers having various geometries, such as circular straight (C), non-twisted triangular (T0), and singly twisted triangular (T1), were considered. The surface of the steel fibers was also modified using an electrolyte solution comprising ethylenediaminetetraacetic acid (EDTA). The surface morphology was quantitatively evaluated, and the pullout and tensile behaviors of UHPC with the steel fibers were examined. The roughness of the fiber surface increased with the duration of immersion in EDTA electrolyte solution up to 9 h, and the roughness parameter increased by approximately 10 times. The C fiber absorbed the highest pullout energy (632.1 mJ), followed by the T0 and T1 fibers, whereas the T1 fiber most effectively increased the tensile strength and specific energy of UHPC, followed by the C or T0 fiber. The surface treatment efficiently enhanced both the pullout and tensile performance of UHPC with the C and T0 fibers owing to the increased surface roughness, whereas it deteriorated the tensile performance of UHPC with the T1 fibers. Steel fiber types that produced severe matrix spalling at the inclined condition or those that were ruptured in UHPC had a higher possibility of inferior tensile performance than those with minor matrix spalling and nonrupture. As an optimal reinforcement strategy of UHPC, 6-h treatment of C and T0 fibers or the pristine T1 fiber was recommended, which helped to achieve tensile strengths of 17.5–20.4 MPa and specific energies of 106.7–113.0 kJ/m3.