Steel Fibre High Strength Concrete Research Articles

Study on the performance of coal gangue ceramsite steel fiber high strength concrete

Our study aims to use coal gangue ceramsite (CGC) as coarse aggregate and add an appropriate volume fraction of steel fiber to prepare high strength concrete with lighter weight and meeting pumping requirements. The effects of (w/b) ratio, CGC content, the volume fraction of steel fiber, and water reducing agent content on the properties of coal gangue ceramsite steel fiber concrete (CGCSFC) were analyzed by orthogonal test, range analysis, and variance analysis. The optimal mix proportion of CGCSFC was obtained by using the efficacy coefficient method combined with the AHP-CRITIC method. The results showed that the crushing value of CGC was 37.26 % lower than that of coal gangue (CG). The reason for the increase in the strength of CGC was that there were few micro-cracks in CGC and the increase in quartz content. The (w/b) ratio had the most significant effect on the compressive strength of CGCSFC. CGCSFCs with compressive strength of 60–90 MPa and slump of 140–220 mm were prepared. The dry apparent density of CGCSFC with the same strength grade was 18.2–19.4 % lower than that of normal concrete (NC), and the specific strength was increased by 19.7–36.3 %. The average calculation error of Bowromi modified formula considering CGC content and the volume fraction of steel fiber is 3.82 %.

Strength Enhancement and Deformability of Confined High-Strength Steel Fiber Concrete After Burning

This study investigates post-burning steel fibrous concrete that aims to identify the mechanical quantities affecting the behavior of confined steel fibrous concrete after burning. A total of 72 specimens of unconfined concrete and confined concrete were made by reviewing design parameters, namely concrete compressive strength (fc ’), fiber fraction and duration of combustion (1 hour, 2 hours and 3 hours). All specimens were monotonically compressed with a deformation control testing system. The parameters discussed from the experimental results represent the strength of the confined concrete (fccf ’), the peak strain of the confined concrete (εccf ′), and the strain of the confined concrete after the peak stress is exceeded and decreases by 50% (εcc50f ). The experimental results showed that for concrete with higher volume fractions of fiber (0%, 1% and 2%), the relative strength enhancement of confined concrete (K value) indicates an increase in the value of K although it is not significant. On the other hand, in general, the values of εccf′ and εcc50f tend to increase significantly at post peak response, if the confined steel fiber concrete specimen is burned for a longer time and volume fraction of fiber were higher. The increase in the strain of confined concrete is one indication that the specimen is more ductile with increasing burning time.

Deformation parameters of high-strength steel fiber concrete under long-term load application

This article contain an experimental study of the rheological characteristics of high-strength steel fiber concrete (SFRC) that is used for the manufacture of permanent formwork. Permanent SFRC formwork is used in the construction of reinforced concrete structures of new generation nuclear power plants (NPP), where due to improved physical and mechanical characteristics it is used as a load bearing element. As a result, a structure with combined reinforcement is obtained, requiring improvement of existing calculation methods, including continuously acting load. The use of existing models of concrete behavior under conditions of continuous loading using SFRC is limited and requires experimental refinement. Studies in the field of nonlinear creep, where, according to a number of studies, the use of steel fibers is most effective are of a particular interest. The high labor intensity and duration of creep tests limited the research to two compositions of SFRC recommended for the manufacture of formwork and fine-grained matrix. Based on the established rheological characteristics at loading levels 0.3, 0.8, 0.85 and 0.9, analytical dependences that allow predicting the values of creep strain at different loading levels are obtained. The presented dependences are recommended for the calculation of reinforced concrete structures with non-removable formwork made of SFRC under a long-term load.

Investigation of the properties of high-strength steel fiber concrete with a minimum effective fiber content under loads of various durations

The authors review the results of complex theoretical studies of the physico-mechanical and rheological properties of high-strength steel-fiber concrete in comparison with non-reinforced fine-grained high-strength concrete made of self-compacting mixtures under short-term and long-term load exposure. Based on the data of extensive experimental studies, methods of Mathematical description of concrete properties depending on the key factors of influence have been selected and developed. A steel fiber concrete with a minimum content of the selected type of fiber is studied, at which the positive effect of fiber reinforcement begins to manifest itself. The theoretical approach of V.M. Bondarenko to the description of creep measures of steel fiber concrete has been developed. The developed methods can be used to calculate structures made of high-strength steel-fiber concrete using the modern diagram method.

A Comparative Study on the Confinement Models of High-Strength Steel Fiber Concrete

Since the last four decades, the behavior of concrete contains of steel fiber, or often called steel fiber concrete, with a wide range of compressive strength has been carried out. Generally, the results of the experimental program produced a material which has a more ductile compared with normal concrete or concrete without fiber. Due to the ductility properties of the material, it is very suitable for use as an earthquake-resistant structural material. At the same time, the behavior of high-strength steel-fiber concrete has also investigated, one of which is about confined high-strength steel-fiber concrete. Analytical models of confined high-strength steel fiber concrete have been developed in various preliminary studies, with their characteristics derived based on the experimental results. Therefore, this research evaluated the models of confined high-strength steel-fiber concrete proposed by Mansur et al., Hsu and Hsu, and Paultre et al. The evaluation includes stress-strain behavior, strength enhancement of confined concrete (f'cc/f'co) or K value, the increase in confined concrete strain (ε'cc/ε'co), and strain of confined concrete when the stress has dropped by 50 percent against its unconfined strain (εcc50/εc50). The comparison method was carried out using a statistical approach and stress-strain simulation. Evaluation results showed significant predictive differences in confinement models in terms of post-peak behavior and parameters ε'cc/ε’co and εcc50/εc50. Prediction of confinement models on the value of f'cc/f’co to the experimental results has a coefficient of variation above 10%. The result further showed that a modified model of confined high-strength steel-fiber concrete was proposed and able to simulate the stress-strain behavior.

Seismic performance of HSS reinforced interior beam-column joints with high-strength steel fiber concrete and enhanced reinforcements

Reinforced concrete moment frame structures in high seismicity regions were often faced with complicated reinforcement details in the joint resulting in construction difficulty. High-strength steel (HSS) bars were used as longitudinal reinforcements in beams and columns to reduce the bar amount and alleviate steel congestion. High-strength steel fiber concrete (HSSFC) was adopted in the joint to enhance the bonding performance of HSS bars. Meanwhile, an enhanced detail of X-shaped reinforcement was proposed to enhance the shear strength. This study investigated the effect of adopting a hybrid method, including HSSFC and X-shaped enhanced reinforcement, on the seismic behavior of interior beam-column joints (BCJs) with HSS bars. Eight full-scale HSS-reinforced interior BCJs were tested under reversed cyclic loading to examine the seismic performance and evaluate the influences of enhanced reinforcement, shear compression ratio, and HSSFC usage. Seismic performance was evaluated in terms of cracking patterns, loading capacity, energy dissipation, and ductility. Test results showed that HSS-reinforced interior beam-column joints with HSSFC exhibited excellent seismic performance with less concrete damage, enhanced ductility, and increased energy dissipation capacity. Similar results were achieved for HSS-reinforced BCJs with X-shaped enhanced reinforcements. Moreover, slippage of beam longitudinal reinforcements and shear deformation were also decreased due to improved bond performance between HSS bars and HSSFC, resulting in less occurrence of bond-slip at the beam end. A suggested equation was proposed for regulating the diameter of high-strength beam bars through the joint section and the height of the column section.

Experimental Study on the Mechanical Properties of Perfobond Rib Shear Connectors with Steel Fiber High Strength Concrete.

Perfobond rib (PBL) shear connectors, made up of the perforated steel plates with the penetrating rebars passing through the holes, are extensively adopted in steel-concrete composite structures for their excellent performance. The adequate understanding of mechanical properties for PBL connectors is of great significance for their reasonable design. In this study, a push out experiment, including 12 specimens with the parameters of concrete strength, diameter of penetrating rebars and the number of holes on perforated steel plate, was performed to explore the mechanical behavior of PBL connectors with steel fiber high strength concrete (SFHSC). The experimental results showed that the shear capacity of the PBL connectors increased with the increase in concrete strength, diameter of the penetrating rebars and the number of holes. Furthermore, a general prediction formula for the shear capacity of PBL connectors was developed, which considers the shear contribution of concrete dowels, concrete end-bearing, interfacial bonding between the perforated steel plates and concrete and the penetrating rebars as well as the enhancement effect of steel fibers. The prediction results of the equation are in good agreement with the experimental data and could provide a reference for the design of PBL connectors.

КРУЧЕНИЕ С ИЗГИБОМ СТАЛЕФИБРОЖЕЛЕЗОБЕТОННОЙ БАЛКИ ПРЯМОУГОЛЬНОГО СЕЧЕНИЯ

The article provides information about the tests of rectangular cross-section reinforced concrete beams made of high-strength steel-fiber concrete on combined torsion and bending. Given information contains the main results: a diagram of the cracks with an indication of their opening width, the values of support reactions at the moment of cracking and at the moment before destruction. It was found that as the load is applied in beams made of high-strength steel-reinforced concrete, in the case of several cracks at the first stage, there is one crack increases. The beams are modeled in the design complex and given description of the main design parameters. The results of the calculation are presented and a comparative analysis of the results obtained with the experiments results. It is noted that the adopted models in the computational complexes require the development of subroutines and refinement.

МЕТОД ПОСТРОЕНИЯ ДИАГРАММ-ИЗОХРОН ВЫСОКОПРОЧНОГО СТАЛЕФИБРОБЕТОНА И ЕГО МАТРИЦЫ

High-strength steel fiber concrete, made on the basis of fine-grained high-strength concrete, is a quite promising building material, in particular, for the construction of high-rise buildings and structures of increased massiveness. The introduction of steel fiber into the concrete matrix can significantly reduce the influence of such shortcomings of fine-grained concrete as increased fragility and explosive nature of fracture, and also positively affects the tensile properties of concrete. However, the widespread use of high-strength steel fiber concrete is currently limited, among other things, by the lack of an experimentally relied normative framework for this material. The proposed article aims to bridge this gap. Modern engineering trends are aimed at introducing into practice diagram methods of calculation based on real diagrams of material deformation under load. This article describes the technique of constructing isochron diagrams for fine-grained high-strength concrete and steel fiber concrete with disperse reinforcement in the amount of 1.5% by weight, made from Russian-made components. Isochron diagrams allow you to calculate the deformation of the material depending on the level of load at any time, including during prolonged loading. There have been made changes to the existing methodology, allowing to take into account the nonlinearity of both current and ultimate creep characteristics depending on the level of loading. The proposed theoretical dependences give good convergence with the experimental data.

Changes in the Prismatic Strength and Elastic Modulus of High-Strength Steel Fiber Concrete and its Matrix Depending on the Age

Changes in the Prismatic Strength and Elastic Modulus of High-Strength Steel Fiber Concrete and its Matrix Depending on the Age

ДИАГРАММЫ ДЕФОРМИРОВАНИЯ МЕЛКОЗЕРНИСТОГО ВЫСОКОПРОЧНОГО БЕТОНА И ВЫСОКОПРОЧНОГО СТАЛЕФИБРОБЕТОНА ПРИ СЖАТИИ

The unique properties of high-strength steel fiber concrete, such as reduced fragility, high crack resistance, increased tensile strength, and others, make this material quite attractive for using in various areas of construction. However, at present, our knowledge of the properties of this material is not yet supported by a sufficient amount of experimental data. The article aims to eliminate this gap. In our work is compared the behavior of the steel fiber concrete with rational fiber content and its matrix, fine-grained high-strength concrete under compression. The method used in the described experiments with the inclusion of a metal pipe acting as a force sensor and receiving a part of the load at stresses close to the design resistance of concrete allows to obtain the relative deformation values corresponding to prism strength. So, we get the opportunity to construct full strain diagrams of steel fiber concrete. As a result of the tests, the effect of a “clip” was confirmed: introduction of steel fiber into the concrete matrix causes a decrease in transverse deformations, increases crack resistance. The nature of the destruction also changes and becomes smoother. As a result of theoretical data processing, the dependences were corrected for calculating the characteristics of high-strength steel fiber concrete under the short-term action of a compressive load.

Experimental investigation of continuous two-layer reinforced concrete beams

Models and full-scale statically determinate two-layer beams (TLBs) made of steel-fiber high-strength concrete (SFHSC) in the compression zone and normal-strength concrete (NSC) in the tensile zone have been tested by the authors. The present study is a further stage of these investigations, focused on testing a continuous, two-span TLB with optimal steel/fiber ratio as in the previous stages. This is the first experimental investigation of continuous TLBs (CTLBs). The study is aimed at testing the CTLB behavior under positive and negative bending moments in the span and above the middle support. An additional issue that is studied in the course of this work is the influence of bending moment redistribution on the behavior of a CTLB. As in the previous research stages, interaction of the concrete layers in a CTLB was studied to demonstrate the efficiency of such beams for real structures. No cracks between the SFHSC and NSC layers were observed up to the ultimate limit state of the tested beam, which demonstrates proper interaction between the layers. The results obtained in the present study enable the recommendation of CTLBs for practical application as effective and economical continuous bending elements.

Performance evaluation of high strength concrete and steel fibre high strength concrete columns reinforced with GFRP bars and helices

This study presents the results of an experimental investigation on high strength concrete (HSC) and steel fibre high strength concrete (SFHSC) circular column specimens reinforced longitudinally and transversely with Glass Fibre-Reinforced Polymer (GFRP) bars and helices, respectively. The Influence of the type of the reinforcement (steel and GFRP), the pitch of the transverse reinforcement, the addition of the steel fibres and the loading condition (concentric, eccentric and four-point loading) on the performance of the specimens was investigated. The study showed that the GFRP bar reinforced HSC (GFRP-HSC) specimen is as efficient as the steel bar reinforced HSC (steel-HSC) specimen in sustaining concentric axial load. However, the maximum load sustained by the GFRP-HSC specimens under eccentric axial load was 10–12% lower than the maximum load sustained by the steel-HSC specimens. GFRP bar reinforced SFHSC (GFRP-SFHSC) specimens sustained 3–13% higher axial load and 14–27% greater ductility than GFRP-HSC specimens under different loading conditions. Furthermore, reducing the pitch of the GFRP helices in GFRP-SFHSC specimens resulted in a significant improvement in the ductility and the post-peak axial load-axial deformation behaviour of the specimens.

Strength and Energy Absorption of High-strength Steel Fiber-concrete Confined by Circular Hoops

Strength and Energy Absorption of High-strength Steel Fiber-concrete Confined by Circular Hoops

The Effects of Steel Fibre on the Mechanical Strength and Durability of Steel Fibre Reinforced High Strength Concrete (SFRHSC) Subjected to Normal and Hygrothermal Curing

This paper presents the experimental investigation into the mechanical strength and durability of steel fibre high strength concrete (SFHSC). In the experimental investigation, the properties of the steel fibre high strength concrete were assessed through two types of curing regimes, the normal water curing and the hygrothermal curing treatment, with the results of the tests being taken at 7 days and 7 days + 24 hours. The steel fibres were added at volume fractions of 0.5%, 1.0%, 1.5%, 2.0% and 3.0%. The tests that were performed for the mechanical strength and durability were the compressive and flexural strength test, the modulus of elasticity test, the ultrasonic pulse velocity test, the water absorption test, the air permeability test and the porosity test. The compressive and flexural strength of the steel fibre high strength concrete reached their maximum of 70.7 MPa and 11.45 MPa, respectively during normal curing for the 3.0% volume fraction of steel fibre. The experimental results of this study indicate that the inclusion of steel fibres enhances the mechanical strength of high strength concrete cured in normal water curing as compared to the hygrothermal curing treatment.

Compressive Properties of High Strength Steel Fiber Reinforced Concrete with Different Fiber Volume Fractions

This paper describes the experimental results of 70 MPa high strength steel fiber reinforced concrete (SFRC) with different steel fiber volume fractions in compression. The effect of steel fiber on fresh properties, compressive strength, toughness index, cracking procedure of high strength steel fiber concrete is also investigated. The steel fibers were added as the volume fractions of 0%, 0.5%, 1.0%, 1.5% and 2.0%. The cylindrical specimens with Φ100 x 200 for compressive tests were manufactured in accordance with ASTM C 39[. The experimental results showed that the slump of fresh SFRC was inversely proportional to the fiber volume fraction added to high strength concrete. As the addition of steel fiber increased, compressive strength of SFRC decreased. Inclusion of steel fiber improves compressive toughness of high strength SFRC.

Pseudo-Plate Method of High-Strength Steel Fiber Concrete Multi-Ribbed Slab

Basing on the disadvantages of multi-ribbed slab in practice, a new high-strength steel fiber concrete (HSFC) composite multi-ribbed slab structure is introduced. Because adding steel fibers can improve the capacity of the concrete, it also can make some influence on the mechanic performance of HSFC multi-ribbed slab, such as elastic module, shear module, flexural rigidity, and torsion rigidity and so on. So by the analysis of the material and mechanic capacity and considering the influence of steel fiber, the formulas to calculate flexural rigidity, torsion rigidity, deflection and internal force of the new composite slab are given, in which the multi-ribbed slab is equivalent to orthotropic slab by the principle of stiffness coincidence. The study in this paper can provide some valuable theory references for further study and application of multi-ribbed slab.

Experimental Research on Physical and Mechanical Properties of Steel Fiber High-Strength Concrete

Based on experiment, the mix proportion matching with the design and construction requirements is obtained. It meets with the requirement of pump structure on the basis of meeting the strength requirement. On this basis, the basic physical and mechanical performance is studied and the conclusion is that steel fiber high-strength concrete has excellent resistance to splitting, bending and drying shrinkage. The splitting strength and bending strength of steel fiber high-strength concrete named CF60-2 is respectively 38.7% and 56.8% higher than that of plane concrete named C60. The drying shrinkage rate of CF60-2 is 45.5% lower than that of C60 in three days. The results have an important guiding significance to steel fiber high-strength concrete in theoretical and engineering practice.

Combined effect of silica fume and steel fiber on the mechanical properties of high strength concretes

In this experimental study, the changes on some mechanical properties of concrete specimens produced by using silica fume and steel fiber were investigated. The main objective of this work is to obtain a more ductile high strength concrete produced by using both silica fume and steel fiber. Two types of steel fibers with aspect ratios (fiber length/fiber diameter) of 65 and 80 were used in the experiments and volume fractions of steel fiber were 0.5% and 1%. Additions of silica fume into the concrete were 0%, 5%, 10% and 15% by weight of cement content. Water/cement ratio was 0.38 and the reference slump was 120 ± 20 mm. Slump test for workability, air content and unit weight tests were performed on fresh concretes. Compressive strength, splitting tensile strength and flexural strength tests were made on hardened concrete specimens. Load–deflection curves and toughness of the specimens were also obtained by flexural test performed according to ASTM C1018 standards. Flexural tests on beam specimens were achieved using a closed loop deflection-controlled testing machine. The use of silica fume increased both the mechanical strength and the modulus of the elasticity of concrete. On the other hand, the addition of steel fiber into concrete improves toughness of high strength concrete significantly. As the steel fiber volume fraction increases, the toughness increases, and high values of aspect ratios give higher toughness. The toughness of high strength steel fiber concrete depends on silica fume content, the fiber volume fraction and the fiber aspect ratio.

Compressive Stress-Strain Behavior of Small Scale Steel Fibre Reinforced High Strength Concrete Cylinders

An experimental investigation was carried out to generate the complete stress-strain curves of steel fibre reinforced high strength concrete under axial compression. The experimental program consisted of testing 100 x 200 mm concrete cylinders. The experimental variables of the study were concrete strength levels (58.03 MPa and 76.80 MPa), volume fractions (0.5% to 2.0%) and aspect ratios (20 and 40) of flat crimped steel fibres. The effect of the mixed aspect ratio of fibres on the stress-strain behavior of steel fibre high strength concrete was also studied by blending short and long fibres. The effects of these variables on the stress-strain curves are presented and discussed. The results indicate that high strength concrete can be made to behave in a ductile manner by the addition of suitable fibres. It is concluded that short fibres are more effective in controlling early cracking, thereby enhancing the strength of the composite, whereas long fibres are more effective in providing post peak toughness. Concrete strength seemed to have an adverse effect on the deformability of fibre reinforced high strength concrete. Based on the test data obtained, a simple model is proposed to generate the complete stress-strain relationship for steel fibre reinforced high strength concrete. The proposed model has been found to give a good representation of the actual stress-strain response.