Use Of Hybrid Fibers Research Articles

Axial compression behavior of hybrid fiber reinforced concrete filled steel tube stub column

Previous studies indicate that the use of hybrid fiber has the potential to improve the properties of concrete. This paper investigates the effect of steel-polypropylene hybrid fiber on the axial compression behavior of concrete-filled steel tube (CFST) columns. Sixteen hybrid fiber reinforced concrete filled steel tube (HFRCFST) stub columns are tested under axial load. The variables considered in the tests are the steel fiber volume percentage and polypropylene fiber quality percentage. The failure mode, ultimate capacity, ductility and energy dissipation capacity of HFRCFST column are investigated. Experimental results show that hybrid fiber has negligible effect on the failure mode and ultimate capacity, delays the failure process and improves the energy dissipation capacity. The fiber hybridization has a favourable reinforcement effect on the ductility over the sum of the individual single fibers. Therefore, using hybrid fiber reinforced concrete is a more effective method to improve the ductility of the CFST columns than single fiber.

Performance of self-compacting concrete containing hybrid fibers in aggressive environment

Self-compacting concrete can be used in many concrete applications some of it susceptible to acid attacks. The aims of this study are to investigate the resistance of different SCC mixture designs to sulphuric acid attacks. The test variables included the type of hybrid fibers (steel, plastic and polypropylene fibers). The powder content of the mixes was kept constant. (500)Kg/m3. The slump flow, L-box, and V-funnel were performed for mixes in their fresh state. In the present work, the specimens were immersion in sulphuric acid solution at concentration of (0.5%) up to 289 days after normal curing for 28 days. After concrete has hardened, two types of test are performed before and after immersion in sulphuric acid solution. Firstly destructive tests are conducted including (compressive strength, splitting tensile strength, and modulus of rupture). Secondly non-destructive tests are performed including (mass loss). The result obtained from this work, shows that the use of hybrid fiber was significant in improving the resistance to sulphuric acid solution in the case of splitting tensile strength, mass loss and modulus of rupture on the other hand, the use of hybrid fibers was insignificant in reducing the concrete compressive strength loss.

Mechanical Properties of Hybrid Fiber Reinforced Concrete

Objectives: To evaluate the suitability of short coconut and PP fiber as a reinforcing agent in cement concrete. Mixing and casting of untreated coconut and PP fiber in RCC check the mechanical properties of HFRC. The experimental background is cited in the literature. Methods/Statistical Analysis: From the basic tested data a mix design for M20 grade concrete at a weight of cement fraction is 1%.For this work 12nos of cube (150 mm * 150 mm * 150 mm) and 12nos of beam (700mm *150 mm*150 mm) were casted by using different fiber proportion of polypropylene fiber & coconut fiber in the laboratory; along with one set of control sample were examined and compared with the HFRC. Findings: All the cube specimens were tested by UTM and beam specimens were tested in UTM by using two points loading as per IS 516-1959. The test result shows that the weight fraction of 1% with Polypropylene 0.75 – coconut coir 0.25 combination specimens improves compressive strength and flexural strength as compared with control specimen. Applications/Improvements: The use of hybrid fiber reinforced concrete in non-structural components like Walls & Surfaces of Septic Tank, Water Storage Tanks and Dams, Sports Grounds, Industrial, Residential Floors & Warehouses etc. The major contribution of fibers in crack resistance and crack control, improve ductility of concrete.

Load-Deflection Characteristics Of Steel, Polypropylene And Hybrid Fiber Reinforced Concrete Beams

AbstractConcrete is the most widely used construction material because of its specialty of being cast into any desired shape. The main requirements of earthquake resistant structures are good ductility and energy absorption capacity. Fiber reinforced concrete possesses high flexural and tensile strength, improved ductility, and high energy absorption over the conventional concrete in sustaining dynamic loads. The aim of this paper is to compare the properties of concrete beams in which three types of fibers are added individually. Steel fibers, polypropylene fibers and hybrid fibers were added to concrete in the weight ratio of four percentages in the preparation of four beam specimens. The fourth specimen did not contain fibers and acted as a control specimen. The dimensions of the beam specimens were 150 mm × 150 mm × 700 mm. The reinforced concrete beams of M30 grade concrete were prepared for casting and testing. Various parameters such as load carrying capacity, stiffness degradation, ductility characteristics and energy absorption capacity of FRC beams were compared with that of RC beams. The companion specimens were cast and tested to study strength properties and then the results were compared. All the beams were tested under three point bending under Universal Testing Machine (UTM). The results were evaluated with respect to modulus of elasticity, first crack load, ultimate load, and ultimate deflection. The test result shows that use of hybrid fiber improves the flexural performance of the reinforced concrete beams. The flexural behavior and stiffness of the tested beams were calculated, and compared with respect to their load carrying capacities. Comparison was also made with theoretical calculations in order to determine the load-deflection curves of the tested beams. Results of the experimental programme were compared with theoretical predictions. Based on the results of the experimental programme, it can be concluded that the addition of steel, polypropylene and hybrid fibers by 4% by weight of cement (but 2.14 % by volume of cement) had the best effect on the stiffness and energy absorption capacity of the beams.

Experimental and Theoretical Study on the Seismic Performance of Corroded Rc Circular Columns Strengthened with Hybrid Fiber Reinforced Polymers

Corroded RC columns do not possess necessary ductility to dissipate seismic energy during a major earthquake, the study investigates the use of hybrid fiber reinforced polymer (HFRP) wrapping as a method of retrofitting non-ductile corroded RC columns, the seismic performance of corroded RC circular columns strengthened with HFRP are tested under cyclic load and constant axial, and a model to determine the envelope response of RC corroded columns strengthened with HFRP are presented based on cross-section analysis for undamaged RC element. Results show that the rebar corrosion may introduce the reduction of seismic performance for RC columns in some extent, and the technique of strengthening corroded RC column with HFRP is quite effective, ductility and energy dissipation are improved significantly, but the bearing capacity can be only increased within limits. The envelope curve estimated using the linear plane assumption with modification by rebar slip model, may still be used as the envelope curve of RC corroded columns strengthened with HFRP, a good agreement between analytical and experimental results is observed.

Effects of the fibers on the properties of high strength flowing concrete

This study first investigates the optimization of different percentages of steel fiber (0–2%) and the hybridization of the steel fiber and palm fiber as 2% volumetric fractions on the high strength flowing concrete and determine the density, compressive strength, flexural strength and toughness indices for the mixes. The results show that the use of 1.0% mono steel fiber increases the compressive strength by about 10%, while the inclusion of more than 0.5% of palm fiber in hybrid fiber mixes reduces the compressive strength. The hybrid fibers can be considered as a promising concept and the replacement of a portion of steel fiber with palm fiber can significantly reduce the density, enhance the flexural strength and toughness. The results also indicates that the use of hybrid fiber (1.5 steel fiber + 0.5% palm fiber) in specimens increases significantly the toughness indices and thus, the use of hybrid fiber combinations in reinforced concrete would enhance their flexural toughness & rigidity and enhance their overall performances.

하이브리드 섬유로 보강된 콘크리트 포장의 역학적 특성 실험연구

Cement concrete pavement offers long-term service life and excellent applicability for heavy traffic. It is easier to purchase and more durable and economical than the asphalt pavement. However, it is difficult to repair and rehabilitate compared to the asphalt pavement when it comes to the maintenance problem. Since the crack is the main reason of the damage of concrete pavement, it is necessary to control the early and long-term crack in the concrete pavement. In this experimental study, the basic performance tests have been carried out to investigate the effect of hybrid fibers which were composed of micro fibers with small diameter and high aspect ratio and macro fibers with large diameter and low aspect ratio on the concrete pavement, in which lower water ratio and larger aggregates were used compared to the general concrete mixture. The test results showed that the flexural strength and toughness of concrete pavement mixture have been increased with the use of hybrid fibers in the concrete pavement mixture, even though they were less effective compared to the normal concrete mixture. It was found that the hybrid fibers were effective to control the early shrinkage of the concrete pavement which is one of the main reasons of the damage in the concrete pavement.

퍼포본드 FRP-콘크리트 합성보의 휨거동에 관한 매개변수 연구

최근 영구거푸집과 보강재 역할을 동시에 하는 FRP-콘크리트 합성부재에 관한 연구가 많이 진행되고 있으며, 일부에서는 실제 교량바닥판에 적용되고 있다. 본 연구에서는 파괴실험으로 평가한 퍼포본드 FRP 콘크리트 합성보에 대해 비선형 유한요소해석 프로그램을 활용하여 검증해석을 실시하고, 이를 이용하여 FRP 보강재 형상에 따른 매개변수 해석을 수행하였다. 퍼포본드 FRP 보강재의 경우 다우웰 영향으로 내력이 증가하는 양상이 나타났고, 본 해석모델을 중심으로 판단하면 웨브의 높이를 고려하여 25~35mm 범위에서 구멍직경을 결정하는 것이 바람직하다고 판단된다. In recent years, the use of hybrid fiber reinforced polymer(FRP)-concrete members with a dual purpose of both formwork and reinforcement, has been considered in some structures and has been applied in a small number of bridge decks. Numerical simulations of the beam failure tests were performed using nonlinear finite element program and a parametric study was performed with variables of perfobond shape. The ultimate strength was increased with perfobond shape because of dowel action. It was showed a good performance in case of approximately perforate diameter 25~35mm in this case.

Characteristic Evaluation of UHPC Flexural Behavior with Mixed-Use Hooked and Straight Type Fiber

This study, in order to identify the effects that the mixed-use of long and short fiber has on the mechanical characteristics of UHPC, we used a steel fiber of 65, 82 and 98 in a shape ratio (l/d) alternating from the length of 13, 16,3 and 19.5 mm respectively in the short fiber with a diameter of 0.2 mm and used the hooked-type high-elasticity steel fiber with a diameter of 0.375 and the length of 30 mm of the long fiber. As a result, it was found that, in constructability and compressive behavior in the same fiber mixing ratio, the more the mixed amount of short fiber, the higher the compressive strength, but it was analyzed that the increase of width was very narrow. According to the results from the review on the flexural tensile behavior of UHPC to make a hybrid from the straight-short and hooked-long fiber, it was analyzed that the use of hybrid fiber does not significantly contribute to the enhancement of the flexural strength of UHPC, however, it greatly contributes to the enhancement of the flexural toughness. In the case of using the fiber in this method, it was analyzed that it would be possible to manufacture UHPC which is superior in workability and mechanical characteristics and economically feasible.

Influence of Hybrid Fibers on Toughness Behavior of High Strength Flowing Concrete

Abstract This study investigates the use of steel fibers and hybrid composite with a total fibers content of 2% on the high strength flowing concrete and determines the density, compressive strength, static modulus of elasticity, flexural strength and toughness indices for the mixes. The results show that the inclusion of more than 0.5% of palm fibers in hybrid fibers mixes reduces the compressive strength. The hybrid fibers can be considered as a promising concept and the replacement of a portion of steel fibers with palm fibers can significantly reduce the density, enhance the flexural strength and toughness. The results also indicates that the use of hybrid fibers (1.5 steel fibers + 0.5% palm fibers) in specimens increases significantly the toughness indices and thus the use of hybrid fibers combinations in reinforced concrete would enhance their flexural toughness & rigidity and enhance their overall performances

Envelope Response of Corroded RC Circular Columns Strengthened with Hybrid Fiber Reinforced Polymers

Corroded RC columns do not possess necessary ductility to dissipate seismic energy during a major earthquake, the study investigates the use of hybrid fiber reinforced polymer (FRP) wrapping as a method of retrofitting non-ductile corroded RC columns, and a model to determine the envelope response of RC corroded columns strengthened with hybrid FRP are presented based on cross-section analysis for undamaged RC element. The results show that the technique of strengthening corroded RC column with hybrid FRP is quite effective, the envelope curve estimated using the linear plane assumption with modification by reinforcement slip model, may still be used as the envelope curve of RC corroded columns strengthened with hybrid FRP, a good agreement between analytical and experimental results is observed.

Contribution of Hybrid Fibers on the Properties of High Strength Concrete Having High Workability

The hybridization of different types of fibers may play important roles in arresting cracks and thus achieve high performance of concrete. Therefore, this study was conducted to investigate the use of different percentages of steel fiber (0, 1.0, 1.25, 1.5, 1.75 & 2%) as vol. %. Consequently, the hybridization of the steel fiber and palm fiber as 2% volumetric fractions on the high strength concrete was applied and determine the density, compressive strength, flexural strength and toughness indices for all the mixes. The results show that the use of 1.0% of steel fibers increases the compressive strength by about 13%. The hybrid fibers can be considered as a promising concept and the replacement of a portion of steel fiber with palm fiber can significantly reduce the density, enhance the flexural strength and toughness. The results also indicates that the use of hybrid fiber (1.5% steel fiber+0.5% palm fiber) in specimens increases significantly the toughness indices and thus the use of hybrid fiber combinations in reinforced concrete would enhance their flexural toughness & rigidity and enhance their overall performances.