High Performance Steel Fiber Reinforced Concrete Research Articles

Tensile behavior and failure modes of expansion anchors in High-Performance Steel Fiber Reinforced Concrete (HPSFRC)

To investigate the tensile(pullout) behavior of expansion anchors in High-Performance Steel Fiber Reinforced Concrete(HPSFRC), 30 valid unconfined tension(pullout) tests on expansion anchors, studying the effects of different steel fiber content(0.0 %, 0.5 %, 1.0 %, and 1.5 %), embedment depths(25 mm, 35 mm, and 45 mm), and anchor diameters(10 mm and 12 mm) on the tensile behavior of anchors. A total of seven failure modes, including different types of mixed modes, are observed. The incorporation of fibers reduces the anchorage stiffness, increases the ductility, and improves the post-peak performance of the tensile behavior of anchors. Effective embedment depth(Hef)exerts a great influence on the failure mode; as Hef increases, the dominant failure mode transits from the concrete breakout to the pull-through and mixed failure modes, and finally the steel failure mode. The increase in Hef also leads to increases in the ultimate tensile strength of the anchor(Nu) and the anchorage ductile. For the same Hef and fiber content, compared to the smaller diameter(D), Nu for the larger diameter is larger but the pullout ductility is weaker. A modified model considering the influence of steel fibers is proposed to predict Nu of CB mode in HPSFRC, and it results in more accurate predictions compared to the existing prediction models(CCD model, Toth model). An existing prediction model for PT mode in normal concrete has been proven to be applicable for anchors HPC/HPSFRC.

Mechanical properties, flexural behavior, and chloride permeability of high-performance steel fiber-reinforced concrete (SFRC) modified with rice husk ash and micro-silica

To improve the fiber-matrix bond and enhance the macro-mechanical performance of SFRC, this study is focused on the modification of the cement matrix by using two eco-friendly supplementary cementitious materials (SCMs), rice husk ash (RHA) and micro-silica (MS). The modification effects of SCMs on the steel fibers were observed and characterized by conducting several macro-mechanical tests i.e., compressive strength, splitting tensile strength, and load-deflection behavior. Besides that, ultrasonic pulse velocity, water absorption, and chloride migration tests were performed to characterize the durability of modified SFRC mixes. The results showed that the incorporation of RHA and MS at low levels notably enhanced the efficiency of steel fibers under splitting tensile and flexural strength testing. SFRC made with 7.5% MS and 7.5% RHA showed 79% and 96% more flexural strength than plain concrete (PC), respectively. Whereas SFRC experienced 14% and 26% further improvement in flexural toughness with the addition of 7.5% RHA and 7.5% MS, respectively. The addition of 7.5% and 12.5% RHA showed a beneficial effect on the resistance of SFRC against the penetration of chloride ions and water. The results of this study confirmed the synergistic interaction of steel fiber and SCMs.

Mechanical performance and numerical simulation of high-performance steel fiber reinforced concrete

This paper presents the outcome of the investigation of high-performance steel fiber reinforced concrete (HP-SFRC) with water to binder ratio (w:b) of 0.30- 0.40. The binder included cement replacement of 10 and 15% by silica fume. Fiber volume fractions (Vf) of 0, 0.5, 1.0 and 1.5% with aspect ratios of 80 and 53 were used. The study aims to present the effect of the inclusion of micro-silica and steel fibers on the mechanical performance of HP-SFRC. Experimental results show that moderate increase in compressive strength and significant improvement in flexural strength of HP-SFRC at Vf = 1.5% (reinforcing index = 3.88) with 15% micro-silica replacement. Empirical expressions were developed for compressive and flexural strength of HP-SFRC as a function of steel fiber volume fraction. The power relation between flexural tensile and compressive strengths was developed with an integral absolute error of 6.39. Further, the validity of the proposed models was tested against published data. A machine learning framework was established based on an adaptive neuro-fuzzy inference system (ANFIS) to predict the compressive strength of HP-SFRC mixes with higher accuracy. Finally, a multiple linear regression (MLR) model is proposed for the strength of HP-SFRC mixes and tested against published data. The validity of the MLR model is checked with experimental results and it is shown that the model has good prediction capability.

Experimental and numerical study on tensile strength and failure pattern of high performance steel fiber reinforced concrete under dynamic splitting tension

High performance steel fiber reinforced concrete (HPSFRC) is widely used in structural engineering due to its excellent performance. It is necessary to study its dynamic mechanical properties for making full use of the material, reducing the engineering cost and optimizing the structural design. Firstly, the dynamic splitting tensile tests of HPSFRC with different fiber contents (0%, 1%, 2%) were conducted by using a 74 mm-diameter splitting Hopkinson pressure bar (SHPB) system under different strain rates (70/s ~ 190/s). Then, according to failure pattern of the specimen and test data, the enhancement mechanism of strain rate and steel fiber on tensile stress of HPSFRC is analyzed, relationship between strain rate and dynamic splitting tensile strength increase factor (DIFft) is also discussed. Furthermore, the enhancement mechanism of steel fiber and strain rate on HPSFRC is verified based on energy conversion during failure process. Finally, the dynamic failure process of HPSFRC is simulated by LS-DYNA, and failure patterns of HPSFRC with different fiber contents are compared from the perspective of crack development. The results indicate that the energy dissipation ratio increases with the ascending steel fiber content and decreases with the ascending strain rate. The steel fiber can increase tensile stress of HPC, and the enhancement degree under quasi-static loading is better than that under dynamic loading. In addition, steel fiber reinforced factor and DIFft have strain-rate effect. Steel fiber reinforced factor decreases as strain rate increases. On the contrary, DIFft increases as strain rate increases, and the increasing trend gradually slows down. These results can provide a basis for improving the dynamic tensile properties of HPSFRC.

Mechanical Properties of High-Performance Steel-Fibre-Reinforced Concrete and Its Application in Underground Mine Engineering.

In order to economically and reasonably solve the problem of mineshaft support in complex geological conditions, the mechanical properties of high-performance steel-fiber-reinforced concrete (HPSFRC) and its application in mineshaft lining structures were investigated in this study. Firstly, the mix proportion of HPSFRC for the mineshaft lining structure was obtained through raw material selection and preparation testing. Then, a series of mechanical property tests were conducted. The test results showed that the compressive, flexural, and tensile strengths of HPSFRC were 9%, 71%, and 53% higher than that of ordinary concrete, respectively. The fracture toughness of HPSFRC was 75% higher than that of the ordinary concrete and the fracture energy of HPSFRC was 16 times that of the ordinary concrete. Finally, the model test results of the HPSFRC shaft lining structure showed that the crack resistance, toughness, and bearing capacity of the shaft lining structure had been significantly improved under a non-uniform confining load because of the replacement of ordinary concrete with HPSFRC. HPSFRC was proved to be an ideal material for mineshaft support structures under complex geological conditions.

Variation of the Pore Morphology during the Early Age in Plain and Fiber-Reinforced High-Performance Concrete under Moisture-Saturated Curing.

In this paper, two concrete mixtures of plain concrete (PC) and steel fiber-reinforced high-performance concrete (SFRC) have been scanned in order to analyze the variation of the pore morphology during the first curing week. Six cylinders of 45.2-mm diameter 50-mm height were performed. All of the specimens were kept in a curing room at 20 °C and 100% humidity. A computed tomography (CT) scan was used to observe the internal voids of the mixtures, and the data were analyzed using digital image processing (DIP) software, which identified and isolated each individual void in addition to extracting all of their geometrical parameters. The results revealed that the SFRC specimens showed a greater porosity than the PC ones. Moreover, the porosity increased over time in the case of SFRC, while it remained almost constant in the case of PC. The porosity increased with the depth in all cases, and the lowest porosity was observed in the upper layer of the specimens, which is the one that was in contact with the air. The analysis of the results showed that the fibers provided additional stiffness to the cement paste, which was especially noticeable during this first curing week, resulting in an increasing of the volume of the voids and the pore size, as well as a reduction in the shape factor of the voids, among other effects.

Experimental study of the punching shear behavior of high performance steel fiber reinforced concrete slabs considering casting directions

This paper presents the results of an experimental study on the punching shear behavior of high performance steel fiber reinforced concrete (HPFRC) slabs without shear reinforcement, particularly considering the effect of fiber orientation. In recent decades, high performance steel fiber reinforced concrete (HPFRC) has been a new achievement in concrete technology. Due to its superior mechanical properties, civil engineers can address the problem of punching shear of thin slabs that are currently widely used in buildings. By processing some studies, researchers have found that the strength capacity of the material before cracking and the post-cracking resistance strongly depend on the orientation of the fibers, which heavily rely on the casting direction and casting method. While most previous studies focused on the effect on the behavior of beams, this research particularly considers how the casting procedures as well as the volume content of the fiber affect the punching shear behavior of flat slabs.

Correlation of Compressive Strength and Other Engineering Properties of High-Performance Steel Fiber–Reinforced Concrete

AbstractIn this paper, correlations among the compressive, flexural, and splitting tensile strengths of high-performance steel fiber-reinforced concrete (HPSFRC) were analyzed. For the investigation, a large amount of data was collected from the published papers with water/binder ratio in the range of 0.25–0.48, steel fiber volume fraction of 0.5–2.0% with aspect ratio of 40–80, and specimens of 150 mm O cylinders and 100×100×500 mm size prisms. Results on the evaluation of the published empirical relations using the collected data indicate a large variation and inapplicability to steel fiber reinforced concrete, which necessitates the determination of empirical relations between the mechanical properties of SFRC. Through a statistical analysis on the data collected, power relations for flexural and splitting tensile strengths as a function of compressive strength, and the relation between flexural and splitting tensile strengths of HPSFRC with r=0.94, were obtained. The validity of the proposed models w...

Stress-strain behavior and toughness of high-performance steel fiber reinforced concrete in compression

The complete stress-strain behavior of steel fiber reinforced concrete in compression is needed for the analysis and design of structures. An experimental investigation was carried out to generate the complete stress-strain curve of high-performance steel fiber reinforced concrete (HPSFRC) with a strength range of 52-80 MPa. The variation in concrete strength was achieved by varying the water-to-cementitious materials ratio of 0.40-0.25 and steel fiber content (Vf = 0.5, 1.0 and 1.5% with l/d = 80 and 55) in terms of fiber reinforcing parameter, at 10% silica fume replacement. The effects of these parameters on the shape of stress-strain curves are presented. Based on the test data, a simple model is proposed to generate the complete stress-strain relationship for HPSFRC. The proposed model has been found to give good correlation with the stress-strain curves generated experimentally. Inclusion of fibers into HPC improved the ductility considerably. Equations to quantify the effect of fibers on compressive strength, strain at peak stress and toughness of concrete in terms of fiber reinforcing index are also proposed, which predicted the test data quite accurately. Compressive strength prediction model was validated with the strength data of earlier researchers with an absolute variation of 2.1%.

High-velocity impact of large caliber tungsten projectiles on ordinary Portland and calcium aluminate cement based HPSFRC and SIFCON slabs -Part I: experimental investigations

Impact experiments have been carried out on concrete slabs. The first group was traditionally manufactured, densely reinforced concrete targets, and the next were ordinary Portland and calcium aluminate cement based HPSFRC (High performance steel fiber reinforced concrete) and SIFCON (Slurry infiltrated concrete) targets. All specimens were hit by anti-armor tungsten projectiles at a muzzle velocity of over 4 Mach causing destructive perforation. In Part I of this article, production and experimental procedures are described. The first group of specimens were ordinary CEM I 42.5 R cement based targets including only dense reinforcement. In the second and third groups, specimens were produced using CEM I 42.5 R cement and Calcium Aluminate Cement (CAC40) with ordinary reinforcement and steel fibers 2 percent in volume. In the fourth group, SIFCON specimens including 12 percent of steel fibers without reinforcement were tested. A high-speed camera was used to capture impact and residual velocities of the projectile. Sample tests were performed to obtain mechanical properties of the materials. In the companion Part II of this study, numerical investigations and simulations performed will be presented. Few studies exist that examine high-velocity impact effects on CAC40 based HPSFRC targets, so this investigation gives an insight for comparison of their behavior with Portland cement based and SIFCON specimens.

Service Performance of HPSFRC Suitable for Super-High Vertical Pumping

A type of small-scale fibers with dumbbells on two ends and notches in the middle was first designed to improve the workability and crack resistance of fresh high performance steel fiber reinforced concrete (HPSFRC). By using the fiber, the HPSFRC was continuously pumped to 306 meter high Sutong bridge tower. To ensure crack resistance of HPSFRC, tests concerning both non-loaded crack and structural crack were systematically performed, respectively. Then, the mechanisms behind the macro-behaviors were explored. Finally, life assessment method of HPSFRC that focused on the fatigue loading coupled with chloride and carbonation environment was presented by considering the effects of different fatigue degree on concrete durability. The results demonstrate that the steel fiber has the remarkable ability to restrain shrinkage and resist structural crack. It was also shown that the small-scale steel fiber can greatly improve the fracture toughness and fatigue property. In addition, the increased degree of damage due to fatigue loading would shorten the service life of concrete and the service life of HPSFRC under the multi-damage of fatigue loading and environmental loading would be longer than that of plain concrete.

Free Shrinkage of High Performance Steel Fiber Reinforced Concrete

Abstract The paper deals with the results of an experimental investigation into the free shrinkage of high performance steel fiber reinforced concrete (HP-SFRC). The development over time of the autogenous, total, and drying shrinkage of HP-SFRC, with a steel fiber content of between 0.25 % and 2 % by volume and that of a comparable high performance concrete (HPC) without fibers, was studied. The laboratory investigations were also concerned with the effect of the length of steel fibers on the shrinkage of the composites. The results of measurements of the autogenous shrinkage of the investigated concretes, at an early age, are also shown. From the results of the experimental investigation, it can be seen that both the autogenous shrinkage and the total shrinkage of HP-SFRC are less than the values corresponding to the comparable HPC. By gradually adding longer steel fibers (l=30 mm) up to 1 % of the composite volume, the shrinkage of the HP-SFRC can be significantly reduced, whereas if the fiber content is further increased, only a relatively small reduction in the composite shrinkage can be achieved. When using shorter steel fibers (l=16 mm), the shrinkage of the composite can, with an increase in the fiber content, be noticeably reduced only up to a fiber content of 0.75 % by volume of the composite. When the volume content of the steel fibers is higher than 1 %, the workability of the composite becomes significantly poorer, especially when longer fibers are used.

Use of high performance concrete on rigid pavement construction for exclusive bus lanes

This study presents a case study to introduce the application of rigid pavement on the exclusive bus lanes in Taipei City. Specifically, the jointed reinforced concrete pavement (JRCP), in which high performance concrete (HPC) and high performance steel fiber reinforced concrete (HPSFRC) are used, is adopted in the construction of the intended rigid pavement. The properties of HPC and HPSFRC, including compressive and flexural strengths at 3, 28, and 56 days, workability, and durability, are specially designed. The performances of HPC and HPSFRC are further evaluated and the results show that the designed HPC and HPSFRC can reach the design requirements. This successful case study provides a basis to draw up a transportation policy in Taipei City that the rigid pavement is strongly recommended to substitute for the conventional flexible pavements of exclusive bus lanes in the bus stops.

Modeling the cyclic response of fiber reinforced concrete joints

A nonlinear static (pushover) procedure (NSP) was used to model the behavior of interior beam–column (B–C) joints under lateral cyclic loading. The results of the analytical and numerical solutions were compared with the results obtained from experimental tests. Ten 1/3-scale interior beam–column joints, part of a prototype building designed according to the existing practice in Jordan, were tested under cyclic reverse loading. Most of these joints lacked transverse reinforcement, column lap splices and continuous bottom beam reinforcement. They were strengthened using high performance steel fiber reinforced concrete (HPFRC) in place of ordinary concrete in two types of joint region, extending 200 and 300 mm from the face of the column. The experimental results were found to be in good agreement with the results of the applied modeling technique and assumptions made. The static pushover analysis appears to be a viable tool for predicting the load–deflection and moment–curvature responses of beam–column joints.

프리스트레스트 이중 콘크리트 보의 휨 거동 해석

Cracks due to low tensile strength in prestressed concrete (PC) beams may decrease rigidity and structural performance, resulting in excessive deflection. In an effort to solve this problem, in this research, prestressed dual concrete (PDC) has been proposed, consisting of normal strength concrete in compression zone, and high performance steel fiber reinforced concrete(HPSFRC) with a partial depth in tensile zone. Three PDC beams with different depths of HPSFRC and two PC beams were cast for experiments. Analytical models at each stage, i.e., precracking, postcracking, and ultimate, were proposed for analysis of flexural behavior in PDC beams. The experimental results agree well to the analytical ones. Crack formation and its propagation are controlled by the HPSFRC in PDC beams. The initial cracking and service limit loads are increased along with the load carrying capacity and flexural stiffness.

Lateral load response of high performance fiber reinforced concrete beam–column joints

Six beam–column (B–C) joints were constructed according to the existing practice in Jordan and tested under cyclic lateral loading to determine the effect of using high performance steel fiber reinforced concrete (HPFRC) in place of conventional concrete in the joint region. The properties of ultimate strength, ductility, energy dissipation capacity, and joint stiffness of the reference concrete specimens were compared with those containing different amounts of brass-coated (BCSF) or hooked steel fibers (HSF). It was determined that the steel fiber concrete specimens exhibited three times higher load levels, 20 times larger energy dissipation, and two times slower stiffness degradation compared to the reference concrete specimens. Using hooked steel fibers showed a significant increase (three times) in the maximum load carrying capacity and in the initial secant stiffness compared to reference specimens.

Effect of axial compressive damage on gas permeability of ordinary and high-performance concrete

Abstract Gas permeability is commonly used to evaluate durability characteristics of concrete. However, these values are often achieved using never stressed or damaged specimens. The objective of this study is to examine experimentally the effect of axial compressive loading on the permeability of three different types of concrete: ordinary concrete (OC), high-performance concrete (HPC), and high-performance steel fiber-reinforced concrete (HPFC). Monotonic and cyclic loads are applied on 220×110-mm diameter specimens. Stress levels vary between 60% and 90% of the ultimate strength. At the end of the loading phase, a disc is extracted from the middle part of the cylinders and is dried in a ventilated oven. Four different gas permeability tests are conducted during the drying procedure. The results show that, for each drying stage, the gas permeability of the discs increases with the load-induced strain. A correlation is worked out between the increase in permeability and the applied-strain/yield-strain ratio. Finally, a relationship between mechanical damage indicators and the increase in permeability is also discussed.

Steel fiber reinforced high-performance concrete: a study on the mechanical properties and resistance against impact

Steel fiber reinforced high-performance concrete (SFRHPC) was prepared by fluidized mortar and steel fibers; the manufacturing process was a combination of mortar infiltrating and vibration. With increase in fiber volume fraction (Vf), mechanical properties of SFRHPC were significantly improved. The peak compressive and flexural strength of SFRHPC reached 140 MPa and 80MPa respectively, increasing by 61% and 774% compared with those of the hardened mortar without fiber reinforcement. The peak flexural-to-compressive strength ratio was 0.6. Failure pattern of SFRHPC was in a pseudo plastic manner with multiple cracking. In simulation test, targets made of SFRHPC were subjected to high velocity impact by projectiles and compared with those targets made of reinforced high strength concrete (RHSC). Test results showed that RHSC targets were smashed up while SFRHPC targets kept intact with several radial cracks in the front faces and some minor cracks in the side faces. The projectiles were either embedded in or rebounded from SFRHPC targets. Relationship between the impact resistance and characteristics of SFRHPC targets was discussed.

Characteristics of high-performance steel fiber-reinforced concrete subject to high velocity impact

Targets made of high-performance steel fiber-reinforced concrete (HPSFRC), which was produced by fluidized mortar, steel fibers and casting process of mortar infiltrating and vibrating, were subject to high velocity impact of projectile and compared with those targets made of reinforced high strength concrete (RHSC). Test results show when impacted by projectiles at high speed, the RHSC targets exhibited smash failure, while HPSFRC targets remained intact with several radial cracks in the front faces penetrated by projectiles and some minor cracks in the side faces. The projectiles were either embedded in or rebounded from HPSFRC targets. Relationship between the resistance of the targets against impact and the parameters concerned was analyzed. Based on the dimensional analysis, it is possible to predict the penetration performance in a real situation by using the test results from a simulation test. Besides, the relationship between penetration depth in CZ targets and the dimensionless speed of projectile was built by regressing the test results.