Steel Fibre Reinforced Self-compacting Concrete Research Articles

Application of Self-Compacting Steel Fiber Reinforced Concrete for Pervious Frames Used for River Revetment

Aimed at improving the production efficiency of tetrahedron-like pervious frames for the river revetment, self-compacting steel fiber reinforced concrete (SFRC) was applied to strengthen the tensile resistance of concrete to remove conventional steel bars used as reinforcement. The workability and mechanical properties of self-compacting SFRC were experimentally studied with the volume fraction of steel fiber changed from 0.4% to 1.2%, and the rational volume fraction of 0.8% was determined for producing the pervious frames. Based on the flow-induced orientation of the steel fibers in the fresh mix, the casting process of self-compacting SFRC was optimal from one inclined rod to other two inclined rods and the horizontal rods of the pervious frame. The loading capacities of pervious frames during lifting and stacking were respectively detected by the simulation tests on the testing machine, which ensure the safety of pervious frames lifted six layers together and stacked for nineteen layers. By testing groups of pervious frames throwed in and then salvaged from the river, the quality of pervious frames without any damage was observed. Finally, the pervious frames were successfully applied in an engineering project for the river revetment.

Fracture Mechanical Properties of Steel Fiber Reinforced Self-Compacting Concrete under Dry–Wet Cycle Sulfate Attack

Sulfate attack is the most common form of the durability damage of hydraulic concrete, and the performance degradation of cracked structural components is more significant at the position of water level change. Fly ash, a widely utilized supplementary cementitious material, can effectively improve the durability of concrete. In this paper, fly ash was used to partially replace Portland cement at 0 w%, 40 w%, 50 w%, 60 w%, and 70 w%, respectively. Through the three-point bending beam test with notch and the dry–wet cycle of sulfate attack, the change law of the fly ash content on the fracture mechanical properties of steel fiber reinforced self-compacting concrete (SFSCC) and its degradation mechanism under sulfate attack was studied. The results show that the load–crack mouth opening displacement curve of SFSCC changed from a steamed bread peak to a sharp peak under 30 dry–wet cycles of sulfate attack. The fracture toughness, peak load, and fracture energy of SFSCC with a high-volume fly ash increased with the increase in the fly ash content, while they reversed after sulfate attack. When the percentage of fly ash was 70 w%, the retention ratio of the fracture parameters was lower than that of SFSCC without incorporating fly ash, and when the percentage of fly ash was 50 w%, SFSCC had good bearing capacity, fracture mechanical properties, and corrosion resistance. The corrosion product of the reference SFSCC with 30 dry–wet cycles of sulfate attack was ettringite, whereas the SFSCC with a high-volume fly ash had no obvious corrosion products and the microstructure became looser.

A BRIEF REVIEW OF STEEL FIBER SELF-COMPACTING CONCRETE IN RIBBED SLAB

The use of Steel Fiber Reinforced Self-Compacting Concrete (SCFRC) as structural elements is seen as favorable alternative to solve typical issues of complex reinforcing spacing and compaction in normal reinforced concrete. The primary benefit of SCFRC is that it can be easily poured in-situ, filling corners of formwork and gaps between bars of reinforcement with its own weight. SCFRC's structural performance is constantly being investigated because of its superior engineering and mechanical properties. Steel fibers added to the mix improved the hardened properties of self-compacting concrete in terms of tensile strength, ductility, toughness, energy absorption capacity, and cracking resistance. This study reviews previous research on SCFRC performance in slab structures with an emphasis on flexural performance. Thus, the knowledge could provide guidelines for academia and industry players on the structural and materials behavior of the slab elements.

Effect of Fibre Aspect-Ratio on the Fresh and Strength Properties of Steel Fibre Reinforced Self-Compacting Concrete

This paper presents the findings of investigation, which was instigated to assess the effects of fibre aspect-ratio on the fresh and mechanical properties of SCC. The investigational parameters were aspect-ratio of the fibre and fibre addition rate. Two different aspect-ratios (64 and 73) of steel fibre were used and the fibre addition rate was between 0.2% and 1.0% with the increment of 0.2% and the fibres were added to the SCC in volume fraction. A series of tests were performed to determine the impact of fibre aspect-ratio and fibre inclusion rate on the engineering/mechanical properties of SCC. The presence of steel fibre in the SCC lessened the workability; furthermore, the upsurge in the inclusion rate of steel fibre abridged the workability further. The inclusion of fibre boosted the compressive strength of the SCC moderately, and conversely, an overwhelming increase in flexural and tensile strength was observed. The rise in the fibre aspect-ratio caused a 2.53% augmentation in the compressive strength of the SCC. Nevertheless, more than 11% improvement in tensile strength was observed, because of the bridging/anchorage established by the fibre. From the obtained results, it can be inferred that the impact of fibre aspect-ratio on the compressive strength of the SCC is not substantial; however, the tensile strength properties of the SCC can be enhanced moderately by increasing the fibre aspect-ratio.

Mechanical Properties and Axial Compression Deformation Property of Steel Fiber Reinforced Self-Compacting Concrete Containing High Level Fly Ash.

The cement industry has brought serious environmental pollution problems. In the background of ecological civilization, accelerating rational use of waste resources plays an important role in protecting the environment. In this study, self-compacting concrete (SCC) is prepared using fly ash and lime powder as supplementary cementitious materials by replacing 50%, 60%, and 70% of ordinary Portland cement. By systematically analyzing the influence of the fly ash replacement rate on the workability and mechanical properties of SCC, steel-fiber-reinforced SCC containing 60% fly ash is chosen for further study, and steel fiber is added at the percentages of 0.25%, 0.50%, 0.75%, and 1.00%. The performances in fresh and hardened states are investigated in terms of workability, compressive strength, splitting tensile strength, flexural strength, and axial compression deformation property. The obtained outcomes indicate that although the incorporation of fly ash can improve the workability of the mixture, there is a negative correlation between the mechanical properties of SCC and the fly ash replacement rate. For steel-fiber-reinforced SCC containing 60% fly ash, when the content of steel fibers exceeds 0.75%, the workability decreases sharply, and even when the volume fraction is 1.00%, the passing ability cannot meet the requirements of the technical specifications for applications of self-compacting concrete. The analysis results for mechanical properties show that compressive strength is not changed significantly with increasing percentage of steel fibers. The steel fibers strengthen splitting tensile strength and flexural strength significantly, and compared with that of without steel fibers, they increased by 22% and 58%, respectively, with steel fibers up to 1.00%. Additionally, the parameters of the axial compression deformation property are improved by introducing steel fibers, especially the strain energy () and relative toughness () of steel-fiber-reinforced SCC containing a high level of fly ash.

Probabilistic Assessment of the Dynamic Viscosity of Self-Compacting Steel-Fiber Reinforced Concrete through a Micromechanical Model.

This article develops a probabilistic approach to a micromechanical model to calculate the dynamic viscosity in self-compacting steel-fiber reinforced concrete (SCSFRC), which implies a paradigm shift in the approach of the deterministic models used. It builds on a previous work by the authors in which Bayesian analysis is applied to rheological micromechanical models in cement paste, self-compacting mortar, and self-compacting concrete. As a consequence of the varied characteristics of the particles in these suspensions (in terms of materials, shapes, size distributions, etc.), as well as their random nature, it seems appropriate to study these systems with probabilistic models. The Bayesian analysis, thorough Markov Chain Monte Carlo and Gibbs Sampling methods, allows the conversion of parametric-deterministic models into parametric-probabilistic models, which results in enrichment in engineering and science. The incorporation of steel fibers requires a new term in the model to account for their effect on the dynamic viscosity of SCSFRC, and this new term is also treated here with the Bayesian approach. The paper uses an extensive collection of experimental data to obtain the probability density functions of the parameters for assessing the dynamic viscosity in SCSFRC. The results obtained with these parameters’ distributions are much better than those calculated with the theoretical values of the parameters, which indicates that Bayesian methods are appropriated to respond to questions in complex systems with complex models.

Experimental evaluation on punching shear resistance of steel fibre reinforced self-compacting concrete flat slabs

Steel fibre reinforced self-compacting concrete (SFRSCC) consolidates under its own weight and has been shown to have the ability to provide an efficient reinforcement mechanism. The concrete with an adequate amount of steel fibre might increase the load and deformation capacities of the structural elements, particularly the tension dominant members. In this study, eight square slab specimens of the same size and reinforced with an identical and sufficient amount of flexural reinforcement were tested. The variables considered included types of concrete, slab thickness, types of shear reinforcement, and the limiting area of SFRSCC around the column. The results show that SFRSCC flat slabs performed well in terms of punching shear strength, ductility, and crack control. The results also reveal that slabs with SFRSCC within a square area around the column can be as efficient in resisting the punching shear as the ones with the SFRSCC cast over the entire slab.

Mechanical and physical characterisation of steel fibre reinforced self-compacting concrete: Different aspect ratios and volume fractions of fibres

This study investigates the effect of steel fibres on the physical and mechanical properties of Self-compacting concrete (SCC). Six mixes of steel fibre reinforced self-compacting concrete (SFR-SCC) were prepared with two different steel fibre aspect ratios (l/d) of 60 and 80 at three-volume fractions (Vf) of 0.35%, 0.45% and 0.55%, in addition to a control mix. All specimens were cast with a constant water-binder ratio of 0.34 and 2% silica fume (SF) of cement content as additive. The performance of different SCC specimens was characterized for compressive strength, ultrasonic pulse velocity, rebound hammer, permeability, flexural strength, toughness, splitting tensile strength and impact resistance of SCC. With the increase of steel fibre aspect ratio, (1) the workability and rheology decrease; (2) the compressive strength of different SCC mixes shows slight variations; (3) the flexural strength increases the toughness, split tensile strength and impact resistance; (4) the ultrasonic velocity results increase (5) the permeability results decrease.

Experimental study on steel fiber reinforced self-compacting concrete

The aim of this research is to produce high-strength Self-Compacting Concrete (SCC) by using industrial wastes such as GGBFS and fly ash as partial replacements for cement. Additionally, the research aims to investigate how the proportions of steel fibers should be selected to produce Steel Fiber Reinforced Self-Compacting Concrete (SFRSCC) mixes with the appropriate flow ability, passing capability, and segregation resistivity. To produce self-compacting concrete, GGBFS and fly ash are used as partial replacements for cement in proportions of 5%, 10%, 15%, 20%, 25%, and 30% by weight of cement. Furthermore, the impact of steel fibers on the characteristics of SCC is analyzed by utilizing steel fibers in different proportions ranging from 0.5%, 1.0%, 1.5%, and 2%. The research methods used to determine the concrete workability include the slump flow test and L-box test.

The effect of recovered demolition debris as aggregates to check sulphate resistance of steel fiber reinforced self-compacting concrete

In the Present study major goal is to determine the effects of swapping NAs with rDWAs on Sulphate resistance of steel fibre-reinforced self-compacting concrete (FRSCC). Instead, 13 experiments were performed and evaluation was done using RSM and CCD. In a 28-day, 90-day, and 120-day pattern, Sulphate resistance (SR) of these FRSCC samples was assessed in terms of the percent reduction in compressive strength (CS). The percent drop in compressive strength was 97%, 14.85%, and 8.6% more than other samples after 28, 90, and 120 days respectively. Percentage loss in compressive strength of FRSCC samples developed a linear relationship between the process parameters, such as the percentage replacement of NAs with rDWAs and the percentage content of steel fibres. The results of this study will almost certainly endorse the utilization of recovered demolition waste aggregates in FRSCC-based constructions.

Mathematical model for the impact strength of triple-blended steel fiber self-compacting concrete based on the experimental study

This technical research paper deals with the study on the impact strength behavior of steel fiber reinforced self-compacting concrete (SFRSCC) with a triple blended technique. The triple blended means the partial replacement of cement by Fly ash (FA) and condensed silica fume (CSF) by mass. The replacement of cement by FA and CSF were 20and 10 percentages respectively to fulfill the rheological requirements of the Self-compacting concrete (SCC). Steel fibers having 1 mm diameter, 20, 30, and 40 as aspect ratios are used. The steel fibres are added to the volume of the concrete were at 0%, 0.2%, 0.4%, 0.6% and 0.8%. From which the result benefits of the impact strength are studied. The specimens are tested for impact as per ACI specifications. The regression equation is carried out based on experimental values. A mathematical model developed and verified the validity of the equation from the experimental results.

Numerical simulation of the casting process of steel fiber reinforced self-compacting concrete: Influence of material and casting parameters on fiber orientation and distribution

The orientation and distribution of fibers immersed in the self-compacting concrete (SCC) are affected by various material and casting parameters, and knowledge of the variation of fiber orientation is important for improving the mechanical properties of steel fiber reinforced self-compacting concrete. Therefore, a computational fluid dynamics (CFD) based method that can monitor the fiber orientation and distribution during concrete flow is developed in this work. In this method, the flow of fresh concrete and the movement of fibers are calculated by a CFD software (ANSYS CFX) and MATLAB code respectively. Through comparisons with the results in two experiments, the accuracy of this method was verified. Furthermore, the influence of rheological properties of fresh concrete, casting point location, formwork height, formwork width and formwork length on the variation of the fiber orientation and distribution was investigated. The numerical results regarding concrete flow state, fiber distribution state, probability density distribution of fiber orientation, average fiber orientation angle, the change of fiber orientation with the casting time, and fiber distribution along the length of the beam were analyzed, which can provide a reference for optimizing the casting process and mechanical performance of steel fiber reinforced self-compacting concrete (SFRSCC). Among these material and casting parameters, formwork length was shown to be the most significant parameter affecting fiber orientation and distribution during the flow of steel fiber reinforced self-compacting concrete.

Impact of using Recycled Demolition waste as Aggregates in Steel Fiber Reinforced Self-compacting Concrete on its Sulphate Resistance

The objective of performing this study was to estimate the impact of replacement of natural aggregates (NAs) with the recycled demolition waste aggregates (rDWAs) on the sulphate resistance of steel fiber-reinforced self-compacting concrete (FRSCC). In this regard, 13 laboratory experiments were conducted and analyzed using central composite design (CCD) in combination with response surface methodology (RSM). The sulphate resistance was evaluated in the form of % reduction is compressive strength (CS) of the FRSCC samples after 28 days, 90 days and 120 days. It was revealed that after 28 days, 90 days and 120 days the % reduction in CS was 97%, 14.85% and 8.6% more than the control samples, respectively. Also, the % reduction in CS of the FRSCC samples showed a linear relation with both the process parameters i.e., % replacement of NAs with rDWAs and % dosage of steel fibers. The findings of this study are expected to encourage the reuse of rDWAs in FRSCC-based structures.

Study on Quasi-Static Mechanical Property of SFRSCC

Steel fiber reinforced self-compacting concrete (SFRSCC) inherits the advantages of self-compacting concrete (SCC) characterized by sound fluidity and self-compaction. Meanwhile, the addition of steel fiber has enhanced the roughness and ductility of substratum. This paper designs SCC of two different strength grades, including C40 and C60, and conducts SFRSCC quasi-static mechanical property test and split tensile test. Uniaxial tensile test is carried out through the design of a dedicated damper to obtain SFRSCC quasi-static uniaxial tensile strength and relational expressions about SFRSCC uniaxial tensile strength and eigenvalue of steel fiber content. It is discovered from SFRSCC split tensile test that, for the concrete with strength grade of C40, its split tensile strength rises by about 36% when the fiber content increases from 0.5% to 2%. For the concrete with strength grade of C60, in addition to the concrete with 1% fiber, the overall variation trend of split tensile strength is the same as that of C40 concrete, but the variation range is relatively small. The damage morphology of specimens indicates that steel fiber can effectively improve the tensile strength and roughness of SFRSCC and help it fully take in the energy before being damaged.

Study on Adaptability of Test Methods for Workability of Fresh Self-Compacting SFRC

To ensure the quality of concrete construction, the workability of fresh mix measured by rational test methods is critical to be controlled. With the presence of steel fibers, whether the test methods and evaluation indices of fresh self-compacting concrete (SCC) are adaptable for self-compacting steel fiber reinforced concrete (SFRC) needs to be systematically verified. In this paper, seven groups of self-compacting SFRC, referenced with one group SCC, were prepared by using the mix proportion design method based on the steel fiber-aggregates skeleton packing test. The main factors included the volume fraction and the length of hooked-end steel fiber. Tests for filling ability, passing ability, and stability of fresh self-compacting SFRC and SCC were carried out. Results indicate that the adaptability was well for the slump-flow test with indices of slump flow and flow time T500 to evaluate the filling ability, the J-ring flow test with an index of PA level to evaluate the passing ability, and the static segregation test with an index of static segregation resistance to evaluate the stability of fresh self-compacting SFRC. By the repeated tests and measurements, the slump cone should be vertically lifted off to a height of 300 mm within 3 s at a constant speed, the spacing of the rebar in the J-ring test should be adjusted to be two times the fiber length. If the table jumping test is used, the dynamic segregation percent should be increased to 35% to fit the result of the static segregation test. Good workability of the self-compacting SFRC prepared in this study is presented with the general evaluation of test results.

Development of a coupled numerical framework of steel fiber reinforced self-compacting concrete

A coupled numerical framework comprised of a computational fluid dynamics (CFD) based method and a finite element method is presented in this paper to model the steel fiber reinforced self-compacting concrete (SFRSCC). The computational fluid dynamics based method is applied to simulate the casting process of fresh SFRSCC to determine the coordinates of the steel fibers, which are used as input to the finite element model of hardened SFRSCC specimens. In the finite element model, SFRSCC is assumed to be a heterogeneous medium consisting of a homogeneous phase (concrete matrix) and a discrete phase (steel fibers). The nonlinear behavior of the concrete matrix is modelled by the continuum damage plasticity model, while the steel fibers are explicitly modeled as discrete truss elements. In order to take into account the fiber pull-out response, the equivalent stress–strain laws derived from an analytical load-slip curve are assigned to the steel fibers depending on their orientation angles. To verify the numerical framework, the casting process and four-point bending tests of the SFRSCC beam specimens were numerically simulated. The good agreement with the simulated and experimental results proves the feasibility of the proposed numerical framework.

Strength And Durability Properties Of Steel Fiber Reinforced Self Compacting Concrete

In this present study the durability characteristics of Steel fiber reinforced Self compacting concrete (SFRSCC) is determined for M30 and M40 grade concrete mixes. Along with durability strength and sorptivity is carried out and comparison is made with Plane self-compacting concrete (SCC) by chemical resistances, Initial Surface Absorption Test (ISAT).
 In the present study, the rational mix design procedure for self-compacting concrete is used. SCC mixes contains large quantity of powder (material whose parcel size is 0.125 mm) to maintain the plastic yield of the properties of fresh concrete as per the general guidelines for design of SCC mixes given in the EFNARC (2005). The present project consists of two phases. In the first phase, SCC mixes for different grades are developed without steel fibers and with steel fibers. The mechanical properties like compressive strength of the different grades were studied. In the second phase, based on the experimental results, durability properties were studied with the using of specimens of size 100 mm × 100 mm × 100 mm. Durability studies like Acid attack factors, Acid-Durability factors, Sulphate attack factors, Sorptivity are studied for the Plain SCC and steel Fiber Reinforced SCC and a comparison is made.

Seismic behaviour of precast sandwich wall panels of steel fibre reinforced concrete layers and fibre reinforced polymer connectors

In recent past, the authors developed an innovative modular system for low rise building made by structural sandwich panels. This system was conceived with the focus on the rationalization of the construction process and on the thermal efficiency of the building. Thus, the precast panels comprise two outer Steel Fibre Reinforced Self-Compacting Concrete (SFRSCC) layers, a thermal insulation material and Glass Fibre Reinforced Polymer (GFRP) connectors. Studies previously made by the authors have proved the viability of the proposed solution when subjected to flexural loads (out-of-plane loads). However, the in-plane biaxial cyclic behaviour of these type of panels has not yet been assessed. Therefore, to investigate the response of these panels to loading conditions that can occur in a seismic event, an experimental program was carried out. This program was composed of almost real-scale panels (2.0 m by 2.0 m), with and without openings, which were subjected to a constant vertical load representative of the load transferred by the slab to the panel, while horizontal reversed cyclic loading was imposed to the top of the panel. The in-plane cyclic behaviour of the panels was evaluated in terms of strength, stiffness, ductility and energy dissipation. The results have shown that the tested prototypes were able to withstand high values of lateral loads, namely 212kN and 155kN in the prototypes without and with opening, respectively.

Crack Detection and Localisation in Steel-Fibre-Reinforced Self-Compacting Concrete Using Triaxial Accelerometers.

Cracking in concrete structures can significantly affect their structural integrity and eventually lead to catastrophic failure if undetected. Recent advances in sensor technology for structural health monitoring techniques have led to the development of new and improved sensors for real-time detection and monitoring of cracks in various applications, from laboratory tests to large structures. In this study, triaxial accelerometers have been employed to detect and locate micro- and macrocrack formation in plain self-compacting concrete (SCC) and steel-fibre-reinforced SCC (SFRSCC) beams under three-point bending. Experiments were carried out with triaxial accelerometers mounted on the surface of the beams. The experimental results revealed that triaxial accelerometers could be used to identify the locations of cracks and provide a greater quantity of useful data for more accurate measurement and interpretation. The study sheds light on the structural monitoring capability of triaxial acceleration measurements for SFRSCC structural elements that can act as an early warning system for structural failure.

Tensile Behavior of Self-Compacting Steel Fiber Reinforced Concrete Evaluated by Different Test Methods

Due to the mechanical properties related closely to the distribution of steel fibers in concrete matrix, the assessment of tensile strength of self-compacting steel fiber reinforced concrete (SFRC) is significant for the engineering application. In this paper, seven groups of self-compacting SFRC were produced with the mix proportion designed by using the steel fiber-aggregates skeleton packing test method. The hooked-end steel fibers with length of 25.1 mm, 29.8 mm and 34.8 mm were used, and the volume fraction varied from 0.4% to 1.4%. The axial tensile test of notched sectional prism specimen and the splitting tensile test of cube specimen were carried out. Results show that the axial tensile strength was higher than the splitting tensile strength for the same self-compacting SFRC, the axial tensile work and toughness was not related to the length of steel fiber. Finally, the equations for the prediction of tensile strength of self-compacting SFRC are proposed considering the fiber distribution and fiber factor, and the adaptability of splitting tensile test for self-compacting SFRC is discussed.