Increase Of Steel Fiber Content Research Articles

Bond Stresses between Reinforcing Bar and Reactive Powder Concrete

A good performance of reinforced concrete structures is ensured by the bond between steel and concrete, which makes the materials work together, forming a part of solidarity. The behavior of the bond between the reinforcing bar and the surrounding concrete is significant to evaluate the cracking control in serviceability limit state and load capacity in the ultimate limit state. In this investigation, the bond stresses between reinforcing bar and reactive powder concrete (RPC) was considered to compare it with that of normal strength concrete (NSC). The push-out test with short embedment length is considered in this study to evaluate the bond strength, bond stress-slip relationship, and bond stress-crack width relationship for reactive powder concrete members. The compressive strength of concrete, the nominal diameter of reinforcement, concrete cover, and amount of steel fibers and embedded length of reinforcement were considered as variables in this study.
 The test results show that the ultimate bond stress increased with increasing of the compressive strength of concrete, decreasing the nominal diameter of the reinforcing bar, increasing the concrete cover and increasing steel fiber content. In a bond stress-slip relationship, the NSC specimen shows a very short softening zone after reaching the peak point in comparisons with RPC specimen. In RPC, bond stress-slip relationship shows stiffer behavior when the steel fiber content was increased. RPC shows stepper softening zone due to the presence of steel fiber, and the absence of steel fiber cause push-out failure without descending part after peak point. Using NSC instead of RPC in anchorage between reinforcement and concrete, decrease the crack width produced due to radial tensile stresses through the push-out of reinforcing bar. In RPC, the absence of steel fiber, decrease the nominal diameter of the reinforcing bar, increase the concrete cover, decrease the embedded length of reinforcing bar cause push-out failure and vice versa cause splitting failure.

Effects of steel fiber and strain rate on the dynamic compressive stress-strain relationship in reactive powder concrete

Three types of steel fiber-reinforced reactive powder concrete (SFRPC) with steel fiber contents of 0%, 2%, and 5% by volume are tested under dynamic compression by using a 40-mm-diameter split Hopkinson pressure bar (SHPB) apparatus. Data from SHPB experiments are employed to analyze the influence of critical parameters on the dynamic compressive stress-strain relationship of SFRPC at high strain rates. Test results show that steel fiber has a significant effect on the stress-strain relationship and energy absorption of RPC. Peak strain and peak stress increase with the increasing steel fiber content at the identical strain rates. A dynamic compressive damage-softening model for SFRPC at high strain rates is put forward on the basis of the Weibull distribution of SFRPC strength. A theoretical formula for Ed was established in order to ascertain Ed for the proposed constitutive model. The ratio of Ed to static elastic modulus Es increases with increasing strain rate and decreasing steel fiber content. The proposed constitutive model captures the dynamic compressive stress-strain relationship of SFRPC, and theoretical results are in agreement with measured data.

STUDY ON ANTI-CRACKING PERFORMANCE EVALUATION METHOD OF STEEL FIBER REINFORCED CERAMSITE CONCRETE (SFRCC) BASED ON PARTLY-RESTRAINED SHRINKAGE RING

In the study of crack resistance of steel fiber reinforced concrete in steel fiber on concrete deformation ability and prevent the Angle of the micro cracks, and the lack of overall evaluation on the performance of steel fiber reinforced concrete crack. By tinder barrier-free restrain some experimental research on steel fiber ceramsite concrete shrinkage ring crack resistance, and use the test results within the definition of steel ring strain from expansion to contraction cut-off age for early and late ages, and the ages of the cut-off point for the early and the late steel fiber ceramsite concrete anti-cracking performance evaluation. The results show that the anti-cracking properties of the steel fiber ceramic concrete are improved with the increase of steel fiber content.

Compressive behavior of steel fiber reinforced recycled coarse aggregate concrete designed with equivalent cubic compressive strength

This paper presents the experimental results related with the compressive behavior of steel fiber reinforced-recycled coarse aggregate concrete (SFRCAC). Compressive strength, Young’s modulus and stress-strain curves were carried out on more than 100 specimens. Emphasis was placed on the combined effect of steel fibers (SFs) and recycled coarse aggregate (RCA) on the axial compressive behavior of SFRCAC with equivalent compressive strength. Test results indicate that with the addition of SFs, Young’s modulus and stress-strain curves of SFRCAC are similar to those with natural coarse aggregate (NCA) concrete, but the critical strain has a significant increase with the increase of steel fiber content and RCA replacement ratio. Regression formula of compressive strength, Young’s modulus, critical strain and constitutive model of SFRCAC are proposed.

Mechanical properties of steel fiber reinforced high strength lightweight self-compacting concrete (SHLSCC)

With addition of steel fibers to concrete, its properties are altered from brittle to ductile. Using lightweight concrete enables decrease in additional loads while self-compacted concrete avoids use of vibrators for concrete compaction, in case of renovation or/strengthening of existing structures. This study is aimed at investigating the effect of change in micro steel fiber content on the properties of steel fiber reinforced high strength lightweight self-compacting concrete (SHLSCC). Slump flow test was conducted to find the workability of fresh concrete mixture. Further compressive strength, splitting tensile strength, modulus of elasticity and flexural strength of hardened concrete were tested. Five concrete mixes of SHLSCC with different fiber contents (0%, 0.5%, 0.75%, 1% and 1.25%) were prepared to study the change in its fresh and hardened properties. Results show that there is strong influence on the workability of SHLSCC with steel fiber content of 1% or more. There is around 12% reduction in compressive strength, 37% and 110% increase in splitting tensile strength and flexural strength respectively, with increase of steel fiber content from 0% to 1.25%, while the modulus of elasticity remains unchanged.

Effect of Change in Micro Steel Fiber Content on Properties of High Strength Steel Fiber Reinforced Lightweight Self-Compacting Concrete (HSLSCC)

As known, with addition of fibers to concrete, the properties of concrete are altered. Steel fiber is one of the common fiber used in concrete. Using lightweight concrete is extremely important for reducing the self-weight of structures, especially in heavy ones, like high rise buildings. It enables to decrease additional loads in case of renovation or/strengthening of existing structures. Moreover, self-compaction avoids using vibrations for compaction of concrete in existing structures. Therefore the present study is aimed at investigating the effect of change in micro steel fiber content on the properties of high strength steel fiber reinforced lightweight self-compacting (HSLSCC). For this reason slump flow test was conducted to find workability of the fresh concrete mixture. Further compressive strength, splitting tensile strength, modulus of elasticity and flexural strength of the hardened concrete were tested. Four concrete mixes of HSLSCC with different fiber contents were prepared to study the change in its fresh and hardened properties. Results show that there is strong influence on workability of SCC with steel fiber content of 1% or more. There is around 7% reduction in compressive strength, 18% and 70% increase in splitting tensile strength and flexural strength respectively, with increase of steel fiber content from 0.5% to 1.25%, while the modulus of elasticity remains almost the same.

Stress–Strain Characteristics and Elastic–Plastic Damage Constitutive Equation of Steel Fiber Reinforced Concrete Under Cyclic Compression at Medium Strain Rate

Abstract An experimental investigation was performed on dynamic compressive stress–strain relationships for steel fiber reinforced concrete (SFRC) with various steel fiber volumetric contents under cyclic compression at a medium strain rate. Results indicate that the mechanical properties of SFRC are not only affected by strain rates but are also influenced by loading modes. The envelope curves of unconfined SFRC are different from those of specimens under monotonic compression. Dynamic compressive strength presents a non-monotonic enhancement with increasing steel fiber content. On the basis of the experimental results of cyclic compression at a medium strain rate, the elastic–plastic damage constitutive equations are proposed to describe the dynamic compressive stress–strain relationships of SFRC under cyclic compression at a medium strain rate. These equations match the test results well.

Flexural toughness of steel fiber reinforced high performance concrete containing nano-SiO2 and fly ash.

This paper aims to clarify the effect of steel fiber on the flexural toughness of the high performance concrete containing fly ash and nano-SiO2. The flexural toughness was evaluated by two methods, which are based on ASTM C1018 and DBV-1998, respectively. By means of three-point bending method, the flexural toughness indices, variation coefficients of bearing capacity, deformation energy, and equivalent flexural strength of the specimen were measured, respectively, and the relational curves between the vertical load and the midspan deflection (P V-δ) were obtained. The results indicate that steel fiber has great effect on the flexural toughness parameters and relational curves (P V-δ) of the three-point bending beam specimen. When the content of steel fiber increases from 0.5% to 2%, the flexural toughness parameters increase gradually and the curves are becoming plumper and plumper with the increase of steel fiber content, respectively. However these flexural toughness parameters begin to decrease and the curves become thinner and thinner after the steel fiber content exceeds 2%. It seems that the contribution of steel fiber to the improvement of flexural toughness of the high performance concrete containing fly ash and nano-SiO2 is well performed only when the steel fiber content is less than 2%.

Effects of silica fume and steel fiber on chloride ion penetration and corrosion behavior of cement-based composites

This project was aimed to evaluate the chloride permeability and corrosion behavior of cement-based composites which comprised fibers and silica fume in the mixes. Resistivity, polarization resistance, ponding and rapid chloride penetration results of specimens were obtained through tests. Test results indicate that resistivity, open circuit potentials and direct current polarization of specimens with w/b ratio of 0.35 are higher than those of specimens with w/b ratio of 0.55. For length-diameter ratio of 65, resistivity and direct current polarization of specimens with fiber length of 35 mm were similar to those of 60 mm. In addition, the open circuit potentials of specimens with fiber length of 60 mm were slightly higher that those of 35 mm. The resistivity decreased with increasing steel fiber content, and the open circuit potential and direct current polarization increased with increasing steel fiber content. The specimens containing silica fume were found to provide higher resistivity, open circuit potentials and direct current polarization than the control specimens. The incorporation of steel fiber and silica fume in composites achieved more significantly decreases in resistivity and increases in direct current polarization than steel fiber composites or silica fume composites. The penetration depth and six-hour total charge passed of specimens for w/b ratio of 0.35 were lower than those for w/b ratio of 0.55. For length-diameter ratio of 65, the penetration depth of specimens for fiber length of 35 mm was similar to that of 60 mm. The penetration depth decreased with increased steel fiber content in the composites. By regression analysis, a good correlation between open circuit potential and direct current polarization, and chloride penetration depth and direct current polarization.

The Effect of Steel Fiber on Some Mechanical Properties of Self Compacting Concrete

Self compacting concrete (SCC) is compacting itself alone due to its self-weight and is filled almost completely while flowing in the formwork. In structural members with high percentage of reinforcement ,it fills also completely all voids and gaps. The purpose of presented research is to investigate, the fresh properties of Steel Fiber SCC and the hardened properties. Fresh properties comprising flow ability, passing ability, and viscosity related segregation resistance. Hardened properties comprising compressive strength, splitting tensile strength, flexural strength, modulus of elasticity, and Ultrasonic pulse velocity. The results indicated of the fresh properties of SCC with steel fiber , reduction in workability with increase of steel fiber content. Also the Steel fibers had effect on compressive & tensile strength , modulus of elasticity and ultrasonic pulse velocity of steel fiber self compacting concrete, there was an optimum content of steel fiber at which higher performance obtained at the both mentioned characteristics ,the content was(0.75- 1)% . All fiber mixes demonstrated higher splitting tensile strength, and flexural strength relative to plain mix at all curing ages. The strengths increased as the fiber content increased. The fibers slightly decrease the U.P.V followed the same behavior as in compressive strength of SCC.

Assessment of fiber distribution in steel fiber mortar using image analysis

A new test method was introduced to measure fiber distribution in steel fiber reinforced mortar by using image analysis technique. Through specimen preparation, image acquisition, fiber extraction, and measurement of related fiber parameters, quantitative analysis of fiber distribution could be obtained by two parameters, namely dispersion coefficient and orientation factor. Effect of boundaries, size and steel fiber content on fiber distribution was discussed. Results showed that, steel fiber distribution was affected by boundary effect, which would be weakened with the increase of specimen size. If the length and width remained constant, the specimen height had a significant effect on orientation factor of fiber, while its influence on dispersion coefficient was not so obvious. With the increase of steel fiber content, dispersion coefficient decreased slightly, and orientation factor deviated from 0.5.

Research on Mechanical Properties of Steel Fiber Reinforced High Performance Recycled Concrete

In this paper, high-quality mineral admixtures and superplasticizer double mixing technology is used to produce high performance recycled concert (HPRC), and then steel fibers are used to modify the characteristics of HPRAC. The compressive strength, splitting tensile strength, ultimate bending load and fracture energy of HPRC with different content of steel fiber. Experiments suggest that with the increase of steel fiber content, the compressive strength doesn’t change too much, but the splitting tensile strength, ultimate bending load and facture energy increase dramatically. Therefore it can be concluded that increasing the content of steel fiber properly can improve the ductility and resistance to crack propagation of HPRC and enhance the ultimate load of HPRC bending member.

Influences of fiber content on properties of self‐compacting steel fiber reinforced concrete

This paper deals with the mix design and mechanical properties of self‐compacting steel fiber reinforced concrete (SFRC). By using superplasticizers and mineral admixtures such as slag and fly ash, three SFRC of different fiber contents (0.5, 1.0 and 1.5%) and one plain concrete with high fluidity (slump ≈250mm) have successfully been developed without bleeding or segregation. The compressive and flexural strengths, flexural toughness as well as shrinkage and creep of the four mixes of concrete were studied. It has been shown that increasing steel fiber content can improve the flexural strength and toughness of self‐compacting SFRC even though its compressive strength could be reduced due to the increase of air content. It has also been found that the addition of steel fibers can efficiently reduce both the autogenous and drying shrinkages of the self‐compacting SFRC. The models of ACI Committee 209 accurately predicted the autogenous shrinkage of the plain self‐compacting concrete but they overestimated its drying shrinkage and creep.

Steel Fibers as Shear Reinforcement in Beams

Steel fibers of various shapes (round, flat and crimped), size, and volume concentration replaced the vertical stirrups in conventional reinforced beams loaded in flexure. Shear failures were prevented by various types of fibers. The shear span ration, A/D, decreased with increasing steel fiber content. /Author/