Steel Fiber Concrete Research Articles

Erratum for “Fatigue Behavior of Steel Fiber Concrete in Direct Tension” by Bernard Isojeh, Maria El-Zeghayar, and Frank J. Vecchio

Erratum for “Fatigue Behavior of Steel Fiber Concrete in Direct Tension” by Bernard Isojeh, Maria El-Zeghayar, and Frank J. Vecchio

Influence of Axial Load on Electromechanical Impedance (EMI) of Embedded Piezoceramic Transducers in Steel Fiber Concrete.

With the advantages of high tensile, bending, and shear strength, steel fiber concrete structures have been widely used in civil engineering. The health monitoring of concrete structures, including steel fiber concrete structures, receives increasing attention, and the Electromechanical Impedance (EMI)-based method is commonly used. Structures are often subject to changing axial load and ignoring the effect of axial forces may introduce error to Structural Health Monitoring (SHM), including the EMI-based method. However, many of the concrete structure monitoring algorithms do not consider the effects of axial loading. To investigate the influence of axial load on the EMI of a steel fiber concrete structure, concrete specimens with different steel fiber content (0, 30, 60, 90, 120) (kg/m3) were casted and the Lead Zirconate Titanate (PZT)-based Smart Aggregate (SA) was used as the EMI sensor. During tests, the step-by-step loading procedure was applied on different steel fiber content specimens, and the electromechanical impedance values were measured. The Normalized root-mean-square deviation Index (NI) was developed to analyze the EMI information and evaluate the test results. The results show that the normalized root-mean-square deviation index increases with the increase of the axial load, which clearly demonstrates the influence of axial load on the EMI values for steel fiber concrete and this influence should be considered during a monitoring or damage detection procedure if the axial load changes. In addition, testing results clearly reveal that the steel fiber content, often at low mass and volume percentage, has no obvious influence on the PZT’s EMI values. Furthermore, experiments to test the repeatability of the proposed method were conducted. The repeating test results show that the EMI-based indices are repeatable and there is a great linearity between the NI and the applied loading.

Study of Steel Scrap Reinforced Concrete with Partial Replacement ofCement with Bagasse Ash

According to the report published by United Nations Food and Agricultural Organization in 2017, it is estimated that India presently produces 341.2 million metric tonnes of sugarcane, proving the fact that India is the second largest sugarcane producer on the globe. Sugarcane bagasse is a fibrous waste product recovered from the Sugar milling industry. There is an increasing threat of disposing the bagasse ash, as it causes serious environmental hazards. Hence, there is an immediate need to find an alternative solution to use the waste product in the form of bagasse ash, in an effective manner. Thus, this paper dealt with the replacement of cement using the bash in concrete. Furthermore, there has been numerous research made, into using steel fibre in concrete. Similar to steel fibre is steel scrap, which is a waste material from Lathe machines. Thereby, this paper will also deal with addition of steel scrap to the concrete, as the latter is much cheaper than steel fibres, which are normally used. Hence, a comprehensive study is made in the research, where concrete is prepared by partially replacing cement by bagasse ash and adding steel scrap to the volume of concrete, as a whole. Here, cement is partially replaced by bagasse ash by 0%, 5%, 10% and 15% by weight of cement in concrete. Similarly, steel scrap is added at dosage of 0%, 1% and 2% to the volume of concrete. The studies were conducted on 12 different combinations of bagasse ash and steel scrap being used in M20 grade of concrete. The parameters studied include compressive strength, split tensile strength and flexural strength of concrete. The results are compared with conventional concrete and, the optimum combination of using both bagasse ash as a partial replacement material for cement and addition of steel scrap to the concrete, is determined.

P-value significance level test for high-performance steel fiber concrete (HPSFC)

Statistical analysis has found useful application in the design of experiments (DOE) especially optimization of concrete ingredients however, to be able to apply the concept properly using computer aided applications there has to be an upper and lower limits of responses fed to the system. In this study, the production of high-performance steel fiber concrete (HPSFC) at five different fiber addition levels by volume with two aspect ratios of 60 and 83 were studied under two curing methods completely dry cured (DC) and moist cured (MC) conditions. In other words, this study was carried out for those limits based on material properties available in North Cyprus. Specimens utilized were cubes 100 mm size casted and cured for 28 days and tested for compressive strength. Minitab 18 statistical software was utilized for the analysis of results at a 5 per cent level of significance. Experimentally, it was observed that, there was fluctuation in compressive strength results for the two aspect ratios and curing regimes. On the other hand P-value hypothesis evaluation of the response showed that at the stated level of significance, there was a statistically significant difference between dry and moist curing conditions. Upper and lower limit values were proposed for the response to be utilized in DOE for future studies based on these material properties. It was also suggested that for a narrow confidence interval and accuracy of the system, future study should increase the sample size.

Rehabilitation of Beam Column joint using Steel Fibrous Concrete

An experimental study was conducted to compare the structural behavior of beam column joint before and after rehabilitation by using fibrous concrete with steel fibers as a strength enhancer material. Two specimens were examined in this study out of which one was designed according to IS 456: 2000 (control specimen) codal provision and another one was designed according to IS 13920:2016(ductile specimen). Both the supports at top and bottom faces of the column were hinged, and the load was applied on the edge of the beam. The parameter observed during the experiment was Load- deflection response for both control and rehabilitation specimens. The ultimate load carrying capacity for rehabilitated controlled specimen increased by 36.6% in comparison with controlled specimen, and the ultimate load carrying capacity for rehabilitated ductile specimen increased by 62.3% in comparison with ductile specimen. It has been observed that steel fiber reinforced concrete can enhance flexural strength, ductility and crack arrest.

MECHANICAL PROPERTIES OF CONCRETE CONTAINS WASTE TIRES EXPOSED TO HIGH TEMPERATURE

Concrete contains crumb rubber and steel fiber from waste tires has recently gained interest among researchers as an alternative material to be used in the construction field. Mechanical properties of the concrete containing crumb rubber replacement and steel fiber at high temperature was investigated experimentally. The waste crumb rubber was chemically treated by using sodium hydroxide (NaOH). Water cement ratio of Treated Rubberized Steel Fiber Concrete (TRSF-Con) was modified to get similar strength as Normal Concrete (NC). A microstructure analysis using Scanning Electron Microscopy (SEM) test was conducted to investigate the bonding of crumb rubber in the concrete mix at ambient and high temperature. The TRSF-Con has performed satisfactory on reducing the growth and crack width compared with normal concrete when exposed to high temperature. The concrete containing crumb rubber and steel fiber have high potential to be utilized as insulating or reinforcement materials for non-structural composite member, which ensure the elements of the structure will not collapse for a prescribe period of time.

Evaluation of mechanical properties of steel fiber reinforced concrete with different strengths of concrete

Concrete has high brittleness along with low tensile strength and tensile strain capacities. Such unsatisfactory performance can be improved with the addition of steel fibers in concrete. Steel fiber reinforced concrete (SFRC) has gained popularity in the last decades because of its superior performance. Its main advantages include hindrance in macro crack propagation, prevention of growth of micro cracks to macroscopic level, improvement in ductility and residual strength after formation of the first crack, and high toughness. This study investigates the effect of adding steel fibers with different lengths and diameters on the mechanical properties of concrete for three values of concrete strength. In this study, hooked ended fibers of three lengths (40, 50, and 60 mm) and two diameters (0.62 and 0.75 mm) were used with three water-to-cement ratios (0.25, 0.35, and 0.45). Steel fibers were added with three volume fractions, 0.5%, 1.0%, and 1.5%. Thirty concrete mixes were prepared and investigated. The results indicated that the addition of different content and lengths of steel fibers with increasing water-to-cement ratios caused significant change in the mechanical properties of concrete, with an increase of about 10–25% in compressive strength and about 31–47% in direct tensile strength. The increase in the fiber content from 0.5% to 1.5% increased the flexural strength from 3% to 124% for fiber with the smaller aspect ratio of 65, whereas, for the higher aspect ratio of 80, a 140% increase in the flexural strength was observed compared to the concrete without any fibers. With the consideration of steel fibers of different lengths and diameters, an analytical model for stress strain relationship of fiber reinforced concrete under compression is proposed. There is good agreement between the proposed model and the experimental results.

Influence of long-term compressive stresses on strength of concrete and steel-fiber concrete prismatic element

The strength and deformation characteristics of concrete and steel-fiber concrete on prisms and cubes are determined. Short-term and long-term tests of the samples were carried out taking into account the recommendations of the regulatory documents for the testing of concrete. Loading of samples with a long load was carried out in force installations (stands) consisting of four metal rods to which rigid loading plates were fixed at certain levels with threaded connections. To cover the entire operational spectrum of the stress state of real reinforced concrete elements, levels of 0.3; 0.4; 0.5; 0.67 and 0.8 from the short-term destructive load were adopted as long-term loading levels. All samples, which were more than a year under the action of a long-acting load, increased their bearing capacity. Prisms from steel-fiber concrete, which were under the influence of a long-acting load during 370 days, increased the bearing capacity, depending on the level of load, by 30-50%. The higher load level, the higher the creep rupture strength. When the loading was repeated before the destruction, the deformations of steel-fiberconcrete prisms changed linearly.

Influence of steam curing on properties of fiber-reinforced concrete during hardening

To increase the efficiency of steel-fiber concrete production, the existing technological operations that could reduce the costs should be optimized. This process requires scientific research and analysis of the existing results to improve the efficiency of each production stage. One of the important stages in the steel-fiber concrete production is steam curing, which is responsible for forming the cementitious matrix structure. To increase the efficiency of this production stage, a study was conducted to develop the steam curing conditions according to the rules of steel-fiber concrete structure formation and the methods of improving durability indicators. Tests on several steel-fiber concrete compositions were conducted, and the relations between its thermal conductivity and the reinforcement coefficient of concrete were revealed. The results of the tests let us conclude that with the increase of the reinforcement coefficient its thermal capacity decreases. The temperature gradient charts along the cross-section of samples with different cement/sand ratios and reinforcement coefficients were built. According to the data obtained, the optimal industrial conditions of steam curing were discovered. The dependences determining the increase of mechanical performance of steel-fiber concrete due to the formation of prestressed fiber structure in the material were revealed.

Impact Resistance of High-Performance Steel Fiber Concrete under Long Term Exposure to Environmental Conditions

An investigation is presented here that studied the influence of long-term environmental conditions exposure on cylindrical specimens after initial 28 day moist curing. The specimens were tested after six months subjected to Mediterranean weather elements in North Cyprus. Specimens with 150 mm diameter by 60 mm long cylinders were tested under impact load using a modified version of the testing equipment described in ACI 544.2R. Numbers of blows to create first and damage cracks were determined, and subsequently the impact energies calculated. It was seen that there is as much as twenty times improvement in impact energy of fibered concretes at fiber volume of 2% when compared with plain concrete. This will goa long way to improve the impact resistance of industrial floors and slabs on grade.

The impact of the reinforcement percentage on the stress-strain state of the bending steel fiber reinforced concrete elements

The use of concrete with traditional reinforcement pose the problem of finding ways to increase the crack resistance, impact strength, frost resistance and other characteristics, which in turn depend on the strength properties of the material. One of the solution is the use of dispersion reinforced concrete steel fiber concrete (with short steel fibers of 30-50mm). The combination of rigid fibers with significant strength reserves and the concrete could increase the crack resistance of the matrix and other strength characteristics. The paper presents the results of theoretical studies of the reinforcement percentage effect on the stress-strain state of the rectangular cross-section elements of steel fiber reinforced concrete (SFRC) in bending from at repeated loads with levels of application η = 0.5 and η = 0.7 . It is found that the limit deformations of the SFRC cross-section in bending is recommended to calculate using a polynomial function, which gives the greatest convergence between the true values and approximations in comparison with the logarithmic and exponential functions.

Investigation on dynamic performance of concrete column crumb rubber steel and fiber concrete

In general the Normal Concrete (NC) are by quasi-brittle failure, where, the nearly complete loss of loading capacity, once failure is initiated especially under dynamic loadings. The significance of this study is to improve the damping properties of concrete structure by utilization of the recycled materials from waste tires to be used in concrete as structural materials that improve seismic performance. In this study, the concrete containing 10% of fine crumb rubber and 1 % volume fraction of steel fiber from waste tires is use to investigate the dynamic performance (natural frequency and damping ratio).A small scale column were fabricated from Treated Crumb Rubber and Steel Fiber Concrete (TCRSFC) and NC were cast and cured for 28 days to investigate the dynamic performance. Based on analysis, dynamic modulus, damping ratio and natural frequency of TCRSFC has improved considerably by 5.18%, 109% and 10.94% when compared with NC. The TCRSFC producing concrete with the desired properties as well as to introduce the huge potential as dynamic resistance structure from severe damage especially prevention on catastrophic failure.

Design of steel fiber reinforced concrete beams for shear using inverse analysis for determination of residual tensile strength

The behavior of steel fiber reinforced concrete (SFRC) has been extensively investigated in the last four decades. For the most part, however, existing design models for shear are based on empirical equations where fiber–concrete is considered as a unique material and fibers and concrete components to shear are considered collectively, or where the concrete and fiber components to shear are considered separately and each are derived independently. As demonstrated in this paper, the problem with this latter approach is that the influence of the concrete and the fiber components are each affected by the other—that is, they are coupled. In this paper, a rational model is outlined for determining one‐way shear strength of SFRC beams and slabs. The model is developed from the modified compression field approach with due consideration given to the inter‐relationship between the concrete–steel–fiber components to the shear resistance. Introduced into the model is an inverse analysis method for determining the post‐cracking residual tensile strength of SFRC from prism bending tests, a core materials property needed for design. In determining this strength, due attention is provided to the influences of notches, specimen boundaries and bias in fiber orientation that occurs as part of the casting process. The results of the design model predictions are compared with a dataset of test specimens collected from the literature, with very good correlation observed.

Stray current induced corrosion of steel fibre reinforced concrete

Stray current induced corrosion is a major technical challenge for modern electric railway systems. The leakage of stray current to surrounding reinforced concrete structures can lead to steel reinforcement corrosion and the subsequent disintegration of concrete. Steel fibre reinforced concrete has been increasingly used as the railway tunnel lining material but it is not clear if discrete steel fibres can still pick up and transfer stray current in the same way as conventional steel reinforcement and lead to similar corrosion reactions. The corrosion behaviour of steel fibres was investigated through voltammetry tests and electrochemical impedance spectroscopy. The presence of high concentration chloride ions was found to increase the pitting corrosion tendency of steel fibres in simulated concrete pore solutions and mortar specimens. The chloride threshold level for corrosion of steel fibres in concrete is approximately 4% NaCl (by mass of cement) which is significantly higher than that of conventional steel reinforcement.

Fracture characteristics of plain and steel fibre reinforced rubberized concrete

This study investigates the effect of recycled crumb rubber aggregates on the fracture characteristics of both plain concrete (PC) and steel fibre concrete (SFC) as a potential solution of the problem of discarded tires and due to the capacity of rubber aggregates to absorb high fracture energy. The variables considered in the experimental work are the concrete type (i.e., plain and steel fibre concrete) and the crumb rubber aggregate content as replacement ratios (i.e., 5%, 10%, 15%, 20%, and 25%) by volume of sand. The steel fibre used is a hooked-end fibre with an aspect ratio of 80 and a diameter of 0.75mm with a constant volume of 0.5%. The mechanical properties, fracture energy, stress intensity factor, critical strain energy release rate, elasticplastic fracture toughness parameter, and characteristic length of plain and steel fibre reinforced rubberized concrete are considered herein. Results show enhanced fracture characteristics induced by the crumb rubber inclusion in plain concrete. Further enhancement was observed by combination of steel fibre and crumb rubber aggregate in concrete. In addition to promote healthy environment using recycling waste tires.

INVESTIGATION ON THE MECHANICAL PROPERTIES OF RUBBERIZED STEEL FIBER CONCRETE

Researchers investigated the utilization of crumb rubber aggregate recycled from waste tire in concrete to solve the problem of discarded tire and to produce a green sustainable concrete. However, a reduction in the mechanical properties due to crumb rubber inclusion occurs. Steel fiber rubberized concrete used in this study to provide a balance between the strength loss and sustainable issue. An investigation on the mechanical properties of rubberized concrete combined with hooked – end steel fiber is presented. Rubberized concrete with different replacement ratios of crumb rubber was incorporated in plain and steel fiber concrete mixes via partial replacement of fine aggregate. Four replacement ratios (17.5%, 20%, 22.5%, and 25%) were used to investigate the effect of the partial replacement of fine aggregate by crumb rubber on the mechanical properties of plain and steel fiber concrete. In both mixes, reduction in mechanical properties was observed to be proportionate with the increment of crumb rubber. Finally, a successful combination of steel fiber and crumb rubber was obtained due to improvement of strain capacity under flexural loading.

Experimental Analysis of the Proposed Watertight Steel Fibre Concrete

This report deals with the description of development of waterproof steel fibre reinforced concrete (suitable for concrete lining of tunnel constructions in particular) in cooperation with the concrete supplier. With regard to newly released documents, two formulas of waterproof concrete supplemented with steel and polypropylene fibres were suggested. The formulas were designed according to different approaches (standards / Austrian Directive), and they differ only in various weight doses of the individual components. With regard to the general requirements for the tunnel lining (fire resistance tests, chemical stability, strength, impermeability and adhesion), strength and plastic properties, durability parameters (depth of penetration of water under pressure, depth of penetration of standing water, frost resistance, resistance of cement concrete surface to water and defrosting chemicals, depth of penetration of chloride) and the resistance to extreme thermal stress were determined in both the formulas. Standardized tests and non-standard testing have been completed.

Fatigue Behavior of Steel Fiber Concrete in Direct Tension

AbstractAn investigation was conducted to study the behavior of plain concrete and steel fiber reinforced concrete under direct tension fatigue loading. Tests were conducted on dogbone specimens wi...

Influence of steel fibers extracted from waste tires on shear behavior of reinforced concrete beams

The accumulation of worn‐out tires creates health and fire hazards, and researchers are busy to incorporate waste tire rubber in concrete instead of burning or dumping. After shredding of waste tires, steel beads were separated by magnetic separator. The potential utilization of wasted steel fibers in concrete was investigated in this experimental work; fresh and hardened properties of fiber‐reinforced concrete (RC) were evaluated and compared with the conventional concrete. Shear behavior was investigated by conducting a four‐point bending test on RC beams. Five types of RC beams were cast; two control specimens were cast, with and without stirrups, by using conventional concrete. Three types of beams were cast by using 0.40, 0.65, and 1.00% fibers by volume. Workability of fiber RC was lower than the conventional concrete. Linear increase in failure load was observed with an increase in the dosage of fibers, and a 64.3% increase in failure load was observed after 1% addition as compared to control specimen. Mid‐span deflection, crack initiation load, and ultimate shear load were also increased with the addition of fibers. Crack spacing was reduced by 64.2% of specimen, with 1% dosage of fibers as compared to a control specimen without any stirrups, and a reduction in crack width was also observed with the addition of fibers.

Dynamic Constitutive Model of Steel Fiber Concrete

The paper studies the dynamic compressive strength of steel fiber reinforced concrete. ZWT constitutive model was choose as the basic framework, and the introduction of forms of damage factor Weibull function optimization, combined with M-6 and M-10 groups the experimental data determined parameters, and with the experimental obtained stress-strain curves were compared. The constitutive equation can more accurately reflect the constitutive relation of steel fiber reinforced concrete under three strain rate, and in the form of a shape parameter and scale parameter to distinguish different types of content and steel fiber concrete area, relatively simple parameters, to be close and convenient.