Crimped Steel Fibres Research Articles

SFRHPC interior beam-column-slab joints under reverse cyclic loading

Beam-column joints are highly vulnerable locations which are to be designed for high ductility in order to take care of unexpected lateral forces such as wind and earthquake. Previous investigations reveal that the addition of steel fibres to concrete improves its ductility significantly. Also, due to presence of slab the strength and ductility of the beam increases considerably and ignoring the effect of slab can lead to underestimation of beam capacity and defiance of strong column weak beam concept. The influence of addition of steel fibres on the strength and behaviour of steel fibre reinforced high performance concrete (SFRHPC) interior beam-column-slab joints was investigated experimentally. The specimens were subjected to reverse cyclic loading. The variable considered was the volume fraction of crimped steel fibres i.e., 0%, 0.5% and 1.0%. The results show that the addition of steel fibres improves the first crack load, strength, ductility, energy absorption capacity and initial stiffness of the beam.

Experimental Study on Seismic Performance in Beam-Column Joint Using Hybrid Fibers

An experimental investigation was carried out to study the effect of hybrid fibers on the strength and behavior of High performance concrete beam column joints subjected to cyclic load. A total of 12 reinforced concrete beams column joints were casted and tested. Design mix of M25 is chosen which is widely used in residential. Crimped steel fibers and Glass fibers were used in hybrid form. From cube tests, the volume fraction of (i) crimped steel fibers 0.75% (ii) glass fibers viz. 0.33% gives best results. Addition of fibers in hybrid form improved many of the engineering properties such as the crack pattern, ultimate load and ductility factor of the composite. The combination of 0.75% volume fraction of steel fibers and 0.33% volume fraction of Glass fibers gave better performance with respect to energy dissipation capacity and stiffness degradation than the other combinations. This project proposed that beam column joint is the weak zone where failure occurs and crack pattern is linear form. To resist the cracks, different types of fibers in linear form are introduced in the joint and also to improve the ductility property in the weak zone of the Beam-Column joint.

X-ray computed tomography of fibre reinforced self-compacting concrete as a tool of assessing its flexural behaviour

The aim of the presented research programme was to investigate the flexural behaviour of steel fibre reinforced self-compacting concrete beams. The tested beams were reinforced with two types of crimped steel fibres. Fibres were added in volumes of 0.5, 1.0 and 1.5 %. The experimental tests were conducted on specimens cut from 1.2 m long elements. Before destructive mechanical testing the specimens were subjected to medical X-ray computed tomography (XCT) procedures. Results of XCT allowed to determine the distribution of fibres. The flexural behaviour of the beams was tested according to the RILEM TC 162-TDF recommendation. A comparison of non-destructive results and mechanical behaviour of tested specimens proved a very strong dependence. XCT also made it possible to assess the uniformity of fibre distribution throughout the tested elements. The influence of the location of concrete casting on fibre distribution was determined. The influence of mixture flow on fibre orientation was also analysed.

Mechanical Properties of Self Compacting Concrete using Crimped Steel Fiber

Mechanical Properties of Self Compacting Concrete using Crimped Steel Fiber

Effect of hybrid fibres on the shear and durability behaviour of high performance concrete

An attempt has been made to investigate the effect of hybrid fibres on the shear strength and behaviour of high performance concrete (HPC). A total of 24 reinforced concrete beams of size 100 × 150 × 1,200 mm were cast and tested under two–point loading. No shear reinforcement was provided in the shear span to ensure shear failure. The main variables considered were the volume fraction of: 1) crimped steel fibres viz. 0.5% and 1.0%; 2) polypropylene fibres viz. 0.1%, 0.15% and 0.2%. Test results indicate that addition of fibres in hybrid form significantly improves the first crack load (about 48%) and ultimate shear strength (about 37%). Prior to the beam testing, the basic mechanical properties and durability characteristics of hybrid fibre reinforced high performance concrete (HFRHPC) were also evaluated. The material test results showed that the HFRHPC has excellent performance in terms of mechanical and durability properties.

Bond behaviour of reinforcing bars embedded in steel fibre reinforced geopolymer concrete

An experimental investigation was carried out to study the influence of steel fibres on the bond strength of geopolymer concrete (GPC). Pull-out tests under monotonic loading were carried out. A total of 30 concentrically reinforced concrete cubes were cast and tested. Of these, six were made of GPC and the remainder were made from steel fibre reinforced geopolymer concrete (SFRGPC). High yield strength deformed bars of 10 mm, 12 mm and 16 mm diameter were used as reinforcement, the grade of concrete was M40 and different volume fractions (0·25% (16·62 kg/m3), 0·50% (39·25 kg/m3), 0·75% (58·87 kg/m3) and 1% (78·50 kg/m3)) of crimped steel fibres were used. The test results indicate that the addition of steel fibres to GPC significantly enhances the bond strength.

De-Icing Salt Scaling Damage Kinetics of Fibre Reinforced Concretes Made with High Bond Crimped Steel Fibres

Durability of steel fibre reinforced concrete (SFRC) specimens is tested and evaluated. Concrete is mixed with moderately sulphate resistant CEM I 42.5 cement and does not contain airentraining agent. The aim of the research is to study how the dosage of high bond crimped steel fibre influences the durability damage kinetics of SFRC; freeze-thaw resistance, de-icing salt scaling resistance and resistance to water penetration are studied, completed with basic mechanical performance tests (compressive strength, modulus of elasticity, flexural tensile strength, splitting tensile strength, flexural toughness, fracture toughness, apparent porosity and vacuum water absorption). Results reveal the importance of the increased volume of the interface transition zone (ITZ) around the steel fibres in the first freeze-thaw cycles and the importance of the internal restrain activated by the steel fibres during later freeze-thaw cycles.

Determination of 3D porosity in steel fibre reinforced SCC beams using X-ray computed tomography

The conducted research programme was focused on air voids in fibre reinforced SCC. There were used two types of crimped steel fibres. Properties of fresh mix were checked. The specimens in a form of beams with fibre volumes ranging from 0% to 1.5% have been non-destructively tested using X-ray computed tomography. Total volume of air, its distribution and spacing analysis have been performed. The air voids number and their volume were evaluated along the beam main axis. The amount of air trapped in the upper and lower beam halves has been analyzed. The uniformity of spacing of air voids was assessed and discussed as well as volume distribution.

Influence of steel fibres on tension stiffening and cracking of reinforced geopolymer concrete

An experimental investigation was conducted to study the influence of steel fibres on the tension stiffening effect and cracking behaviour of geopolymer concrete (GPC). A total of ten concentrically reinforced concrete prisms (60 × 60 × 600 mm) were cast and tested under uniaxial tension. Out of these, two were made of GPC and the remainder were of steel-fibre-reinforced GPC. The grade of concrete was M40. Different volume fractions of 0·25% (16·62 kg/m3), 0·50% (39·25 kg/m3), 0·75% (58·87 kg/m3) and 1% (78·50 kg/m3) of crimped steel fibres of aspect ratio 66 were used. The test results indicate that the incorporation of steel fibres improves the tension stiffening effect and reduces the spacing and width of cracks. A method was also proposed to predict the width of cracks.

Performance and modeling of high-performance steel fiber reinforced concrete under impact loads

Impact performance of high-performance concrete (HPC) and SFRC at 28-day and 56-day under the action of repeated dynamic loading was studied. Silica fume replacement at 10% and 15% by mass and crimped steel fiber (<TEX>$V_f$</TEX> = 0.5%- 1.5%) with aspect ratios of 80 and 53 were used in the concrete mixes. Results indicated that addition of fibers in HPC can effectively restrain the initiation and propagation of cracks under stress, and enhance the impact strengths and toughness of HPC. Variation of fiber aspect ratio has minor effect on improvement in impact strength. Based on the experimental data, failure resistance prediction models were developed with correlation coefficient (R) = 0.96 and the estimated absolute variation is 1.82% and on validation, the integral absolute error (IAE) determined is 10.49%. On analyzing the data collected, linear relationship for the prediction of failure resistance with R= 0.99 was obtained. IAE value of 10.26% for the model indicates better the reliability of model. Multiple linear regression model was developed to predict the ultimate failure resistance with multiple R= 0.96 and absolute variation obtained is 4.9%.

Experimental Study on Axial Tensile Performance of Low Volume Fraction of Ternary Hybrid Fiber Reinforced Concrete

In order to acquire axial tensile stress-strain curve of HFRC, specimens of equal cross-sections with embedded screw and pasted with carbon fiber cloth in corresponding length were tested on closed-loop electro-hydraulic servo testing machine which a subsidiary rigid frame was attached to. The effect of fiber volume, steel fiber slenderness ratio, steel fiber type and active admixture on the tensile properties of HFRC with low volume fraction was studied. The results indicate that when total volume proportion is less than 1% the first crack strength and ultimate tensile strength of HFRC can increase more than 15% and about 40% , respectively, the difference of effect of arched steel fiber and crimped steel fiber on the tensile behavior is small. The tensile behavior of HFRC is the best with a combination of slenderness ratio of 80 and 47.1kg/m3 arched steel fiber, 2.6kg/m3 macro-polypropylene fiber and1.0kg/m3 dura fiber and 10% .

STEEL FIBER CURVATURE IN CONCRETE COMPOSITES: MODULUS PREDICTIONS USING EFFECTIVE STEEL FIBER PROPERTIES

Results in the literature demonstrate that substantial improvements in the mechanical behavior of concrete have been attained through the addition of steel fibers as a reinforcing phase. We have developed a model combining finite element results and micromechanical methods to determine the effective reinforcing modu-lus of hook-ended steel fibers. This effective reinforcing modulus is then used within a multiphase micro-mechanics model to predict the effective modulus of concrete reinforced with a distribution of fibers. We found that fiber curvature effect is negligible when compared to straight fibers. Then mechanical properties of concrete reinforced with crimped steel fibers are predicted using Weng and Huang schemes. The predic-tions are in excellent agreement with experimental results.

EXPERIMENTAL AND PREDICTIVE MECHANICAL STRENGTH OF FIBER REINFORCED CEMENTITIOUS MATRIX (FRCM)

Fiber Reinforced Cementitious Matrix (FRCM) are sustainable building materials as it uses lesser quantities of natural resources as raw materials for production, when compared to conventional concrete. This study is an attempt to explore the possibility of using crimped mild steel (MS) fibers (12.5 mm length) as reinforcement in cementitious matrix, with sand-cement and water-cement ratio in line with the ACI Codes. From the experimental results, it was found that when the percentage of MS fibers is increased in cement-based mortar from 0.5% to 2.5% of volume of specimens (with 0.5% interval), there is a corresponding increase in the cylinder compressive strength and splitting-tensile strength at 7 and 28 days, and flexural strength at 28 days. There was an increase in compressive strength of 74%, splitting-tensile strength of 38% and flexural strength of 35% at 28 days, when MS fibers of 2.5% was used, when compared to control mortar specimens (with no fibers). Also, the predictive strength models were developed from the experimental data using statistical regression analysis. It was observed that the experimental results of FRCM highly correlate with the predicted values, with minimum prediction error.

An Experimental Investigation on Strength Properties of Metakaolin Based Light Weight Aggregate Concrete Reinforced With Steel Fibers

At present all the constructions are executed with conventional granite aggregate concrete. If the granite aggregate is reduced by replacing it partially and fully by Metakaolin pellets as aggregate, the behavior and strength properties are interesting to be investigated. In this study an attempt has been made to use the Metakaolin as the basic ingredient in preparation of artificial pelletized metakaol in aggregate using lime and cement as binders. In the present experimentation, addition of Metakaolin pellets replacing the conventional granite aggregate in percentages of 0, 25, 50, 75 and 100% by volume of concrete and also adding the crimped steel fibre in percentages of 0.50, 1.00, 1.50 and 2.00% by weight. The properties such as compressive strength, split tensile strength, modulus of elasticity and flexural strength are studied by casting and testing around 240 samples consisting of 60 numbers of plain cube specimens of size 150x150x150 mm, 120 numbers of cylinders of size 150mm diameter and 300mm height and 60 numbers of plain beams of size 500x100x100 mm for testing after 28 days of curing.

Experimental Study on Crimped Steel Fiber Reinforced Concrete Deep Beam in Shear

Experimental Study on Crimped Steel Fiber Reinforced Concrete Deep Beam in Shear

Experimental Study on Crimped Steel Fiber Reinforced Concrete Deep Beam in Shear

The experimental work is carried out to evaluate the shear strength of steel fiber reinforced concrete deep beams without stirrups. For this 18 beams are cast. The beams are tested under two-point loading as per IS after 28 days curing. Fiber fraction is varied as 0%, 1.5% and 3%. The shear span-to-depth ratio (a/d ratio) for beams is kept as 0.60 for specimen series-I and 0.74 specimen series-II. The cube compressive strength is estimated. The experimental results are compared with theoretical results obtained from empirical equations and design codes. Also the experimental results are compared with the equations put forth by the other researchers and codes to estimate the shear strength of the steel fiber reinforced concrete deep beams without stirrups.

Effect of Steel Fibres and Low Calcium Fly Ash on Mechanical and Elastic Properties of Geopolymer Concrete Composites

Effect of steel fibres and low calcium fly ash on mechanical and elastic properties of geopolymer concrete composites (GPCC) has been presented. The study analyses the impact of steel fibres and low calcium fly ash on the compressive, flexural, split-tensile, and bond strengths of hardened GPCC. Geopolymer concrete mixes were prepared using low calcium fly ash and activated by alkaline solutions (NaOH and Na2SiO3) with solution to fly ash ratio of 0.35. Crimped steel fibres having aspect ratio of 50 with volume fraction of 0.0% to 0.5% at an interval of 0.1% by mass of normal geopolymer concrete are used. The entire tests were carried out according to test procedures given by the Indian standards wherever applicable. The inclusion of steel fibre showed the excellent improvement in the mechanical properties of fly ash based geopolymer concrete. Elastic properties of geopolymer concrete composites are also determined by various methods available in the literature and compared with each other.

Bond stress slip response of bars embedded in hybrid fibre reinforced high performance concrete

Pullout tests were carried out to study the effect of steel-polypropylene hybrid fibres on the bond strength and bond stress–slip response of deformed reinforcement bars embedded in high performance concrete. A total of 96 specimens were cast and tested in the present investigation. The main variables considered were the volume fraction of crimped steel fibres, volume fraction of polypropylene fibres and the diameter of reinforcement bars. The combination of 1% volume fraction of steel fibres and 0.10% volume fraction of polypropylene fibres gave better performance with respect to bond strength than the other combinations considered in this study.

Behaviour of hybrid fibre reinforced concrete beam–column joints under reverse cyclic loads

An experimental investigation was carried out to study the effect of hybrid fibres on the strength and behaviour of High performance concrete beam column joints subjected to reverse cyclic loads. A total of 12 reinforced concrete beams column joints were cast and tested in the present investigation. High performance concrete of M60 grade was designed using the modified ACI method suggested by Aïtcin. Crimped steel fibres and polypropylene fibres were used in hybrid form. The main variables considered were the volume fraction of (i) crimped steel fibres viz. 0.5% (39.25kg/m3) and 1.0% (78.5kg/m3) and (ii) polypropylene fibres viz. 0.1% (0.9kg/m3), 0.15% (1.35kg/m3), and 0.2% (1.8kg/m3). Addition of fibres in hybrid form improved many of the engineering properties such as the first crack load, ultimate load and ductility factor of the composite. The combination of 1% (78.5kg/m3) volume fraction of steel fibres and 0.15% (1.35kg/m3) volume fraction of polypropylene fibres gave better performance with respect to energy dissipation capacity and stiffness degradation than the other combinations.

Tension Stiffening and Cracking of Hybrid Fiber-Reinforced Concrete

An experimental program has been carried out to study the effect of hybrid fibers on the tension stiffening and cracking characteristics of high-performance concrete (HPC). A total of 24 axially reinforced concrete tension members were cast and tested under uniaxial tension. The main variables considered were the volume fraction of: 1) crimped steel fibers (0.5 and 1.0%); and 2) polypropylene fibers (0.1, 0.15, and 0.2%). Load-deformation response was recorded and analyzed. Crack width and crack spacing were also measured at all stages of loading. Test results indicate that the addition of fibers in hybrid form significantly improves the tension stiffening effect and resistance to cracking. The combination of 1% steel fiber and 0.1% polypropylene fiber showed better performance than the other combinations considered in this study. A method is proposed to predict the crack width of hybrid fiber-reinforced, high-performance concrete tension members, and the computed values compared satisfactorily with the test results.