Concrete is a tension-weak building material, which is often crack ridden connected to plastic and hardened states, drying shrinkage, and so on. The cracks generally develop with time and stress to penetrate the concrete, thereby impairing the waterproofing properties and exposing the interior of the concrete to the destructive substances containing moisture, bromine, acid sulphate, etc. The exposure acts to deteriorate the concrete, with the reinforcing steel corrosion. To counteract the cracks, a fighting strategy has come into use, which mixes the concrete with the addition of discrete fibres. Plain cement concrete has some shortcomings like low tensile, limited ductility, little resistance to cracking, high brittleness poor toughness, and so on that restrict its application. The cracking of concrete may be due to economic structural, environmental factors, but most of the cracks are formed due to inherent internal micro cracks and the inherent weakness of the material to resist tensile forces. Drying shrinkage in the concrete may also results in the formation of cracks. To overcome these deficiencies, extra materials are added to improve the performance of concrete.
Based on the results presented and discussed, it is evident that the combinations of kenaf fibres and steel fibres have the potential to serve as part of shear reinforcement in reinforcedconcrete beams. The increase in strength of the reinforcedconcrete beams was not consistent during the testing as the beams with fibres were not fully dried and hardened. Therefore, the full capability and capacity of the fibrereinforcedconcrete in increasing the strength consistently with the increase in the fibre content was not observable. However, for the case of three beams with reduce in shear reinforcement, it can be clearly seen that the fibres improved the load carrying capacity of the beam up to 29% and 25% for KFSF-RC beams with V f
Concrete is acknowledged to be a relatively brittle material when subjected to normal stresses and impact loads, where tensile strength is only approximately one tenth of its compressive strength. As a result of these characteristics, concrete member could not support such loads and stresses that usually take place, majority on concrete beams and slabs. Historically, concrete member reinforced with continuous reinforcing bars, withstand tensile stresses and compensate for the lack of ductility and strength. Furthermore, steel reinforcement is adopted to overcome high potentially tensile stresses and shear stresses at critical location in concrete member. The additional of steel reinforcement significantly increase the strength of concrete, but to produce concrete with homogenous tensile properties, the development of micro cracks is a must to suppress. The introduction of fibres was brought in as a solution to develop concrete in view of enhancing its flexural and tensile strength, which are a new form of binder that could combine Portland cement in the bonding with cement matrices. Fibres are most generally discontinuous, randomly distributed throughout the cements matrices. The term ‘FibreReinforcedConcrete’ (FRC) is made up with cement, various sizes of aggregates, which incorporate with discrete, discontinuous fibres.
techniques for flexural and shear strengthening of concrete beams using CFRP laminates. The author investigated the influence of reinforcement ratio and spacing of FRP strips on the efficiency of flexural strengthening technique. A total of 24 beams in two series were cast and tested under four-point bending for this study. The effectiveness of NSM and EBR techniques for flexural and shear strengthening of reinforcedconcrete beams was compared. Nadeem (2010) presented the results of an experimental study made on beams wrapped with CFRP. Ehsan Ahmed et al. (2011) studied the flexural strengthening of reinforcedconcrete beams with CFRP laminates attached to the soffit by epoxy adhesive.A total of six reinforcedconcrete beams having different degrees of strengthening scheme weretested under transverse bending over an effective span of 1900 mm. Habibur Rahman Sobuz et al. (2011) investigated theflexural behaviour of reinforcedconcrete beams strengthened with CFRP laminates. A total of five beams were cast for this study. One beam served as the control beam and the rest were strengthened by changing the level of CFRP laminates. All the beams were tested under four- point bending over a clear span of 1900 mm. Sena Cruz et al. (2012) investigated the effect of two different techniques in flexural strengthening of beams under monotonic and fatigue loading. One was externally bonded reinforcement (EBR) and the other was near surface mounted (NSM) FRP. Both the strengthening techniques were applied on the cover concrete, which was normally the weakest region of the element to be strengthened. Magda Musa (2015) evaluated thefactors affecting the bond strength between fibrereinforced polymer laminates and concrete surface.A total of 17 plain concrete beams were cast in three groups with concrete strengths 33.5, 40.7 and 67 MPa for this study. The beams were simply supported and had a length of 1110 mm with 120 × 250 mm cross-section. Carbon fibrereinforced polymer (CFRP) sheet of uni-directional type was bonded to the tension face of beams.
This research work focuses on the steel-polyester hybridfibrereinforced system. In this system, steelfibre, which is stronger and stiffer, improves the first crack strength and ultimate strength, while the polyester fibre, which is more flexible and ductile, leads to improved toughness and strain capacity in the post - cracking zone 7-8 . Information
---------------------------------------------------------------------***---------------------------------------------------------------------- Abstract – In conventional concrete, micro-cracks develop before the structure is loaded because of drying shrinkage and other causes of volume change. When the structure is loaded, the microcracks open up and propagate because of the development of such microcracks, results in inelastic deformation in concrete. Fiber reinforcedconcrete (FRC) is cementing concretereinforced mixture with more or less randomly distributed small fibers. In the FRC, several small fibers are dispersed and distributed randomly in the concrete at the time of mixing and thus improve concrete properties in all directions. The fiber shell transfer load to the internal microcracks. FRC is a cement based composite material that has been developed in decent years. It has been successfully used in construction with its excellent flexural-tensile strength, resistance to spitting, impact resistance and excellent permeability and frost resistance. It is an effective way to increase toughness, shock resistance and resistance to plastic shrinkage cracking of the mortar. These fibers have many benefits. Steel fibers can improve the structural strength to reduce the heavy steel reinforcement requirement. Freeze the resistance of the concrete is improved. The durability of the concrete is improved to reduce in the crack widths. Polypropylene and Nylon fibers are used to improve the impact resistance. Many developments have been made in the fiber reinforced concert.
Majority of the studies were conducted with a combination of metallic fibre with non-metallic fibres. From tables 4-6, it is evident that hybrid combination of metallic and non-metallic fibres have significant effect on the compressive, tensile and flexural strength. Strength parameters are found to increase with respect to increase in percentage volume fraction of steel fibres in both geopolymer and geopolymer fibreconcrete. The combination of steel and polypropylene fibre has better performance than combination of steel with glass fibresbecause of the high elastic modulus of steelfibre and the low elastic modulus of polypropylene fibre. Improved tensile strength can be achieved by increasing the percentage of steel fibres. The higher number of fibres bridging the diametric ‘splitting’ crack, the higher would be the spilt tensile strength. The easy availability of PP fibres, combined with the high stiffness of steel fibres, resulted in the enhancement of the split tensile strength (6). Heat cured hybridfibrereinforced geopolymer concrete had high strength parameters than ambient cured hybridfibrereinforced geopolymer concrete.
A/c to Manisha M(6th International Conference on Recent Development in Engineering Science Humanities Management,May 2017 ):-From the review of research articles mentioned in this paper, the HFRC is an innovative engineering material. Both the tensile and compressive strength of hybrid fiber reinforcedconcrete decreases with increasing temperature. The workability/ rheological properties of concrete mixtures are found to depend on types, dosages, geometry of fiber, and in cases of hybrid mixtures, interaction and synergic properties between different fiber types also play a critical role. The enhancements in modulus of rupture, deflection capacity and energy absorption capacity were different according to the types of macro fiber as the amount of micro fiber blended increased. High performance hybrid fiber concrete should first possess good capacity on compaction and static properties, such as compressive strength, MOR, and splitting strength. The main reasons for adding steel fibers to concrete matrix is to improve the post- cracking response of the concrete i,e.to improve its energy absorption capacity and apparent ductility, and to provide crack resistance and crack control.Use of hybrid fibers in specimens increases significantly the toughness indices and thus the use of hybrid fibers combinations in reinforced
Olivito.R.S., 2007, the failure mode is affected by the presence of fibers, while concrete elements usually fails suddenly and break in their middle section, steel fiber reinforced specimen started micro-cracking symmetrically on their side and fiber bridging effect abounded the sudden failure. From that, the steel fibers can improve the tensile strength of the concrete.
A820, Type I, and Standard Specification for Steel Fibers for Fiber ReinforcedConcrete. These steel macrofibers will also improve impact, shatter, and fatigue and abrasion resistance while increasing toughness of concrete.BananaFiber ReinforcedConcrete The capability of durable structure to resist weathering action, chemical attack, abrasion and other degradation processes during its service life with the minimal maintenance is equally important as the capacity of a structure to resist the loads applied on it.. Recently, however the development of Banana fiber-reinforcedconcrete has provided a technical basis for improving these deficiencies. Quartz, most common of all minerals is composed of silicon dioxide, or silica, SiO₂. Specimens are transparent; others are translucent. In pure form, quartz is colourless, but it is commonly coloured by impurities. Rock crystal is a colourless form of quartz occurring in distinct crystals. This paper presents an overview of the effects of hybrid fibres (banana fibre and steelfibre) and hybridfibre with partial replacement of silica fume and quartz powder on various properties of concrete in fresh and hardened state such as workability, compressive strength, tensile strength, flexural strength. The main objective of this study as follows
Cement concrete is the most extensively used construction material in the world. The reason for its extensive use is that it provides good workability and can be moulded to any shape. Ordinary cement concrete possesses a very low tensile strength, limited ductility and little resistance to cracking. Internal micro cracks lead to brittle failure of concrete. In this modern age, civil engineering constructions have their own structural and durability requirements. Every structure has its own intended purpose and hence to meet this purpose, modification in traditional cement concrete has become mandatory. It has been found that different type of fibers added in specific percentage to concrete improves the mechanical properties, durability and serviceability of the structure. It is now established that one of the important properties of Steel Fiber ReinforcedConcrete (SFRC) is its superior resistance to cracking and crack propagation. In this paper effect of fibers on the strength of concrete for M20 and M40 grade have been studied by varying the percentage of fibers in concrete. Fiber content were varied by 0.50%, 1% and 1.5% by volume of cement. Cubes of size 150mmX150mmX150mm to check the compressive strength and beams of size 500mmX100mmX100mm for checking flexural strength were casted. All the specimens were cured for the period of 7, 28 and 56 days before crushing. The results of fiber reinforcedconcrete for 3days, 7days and 28days curing with varied percentage of fiber were studied and it has been found that there is significant strength improvement in steel fiber reinforcedconcrete. The optimum fiber content while studying the compressive strength, flexural strength cube is found to be 1%. Also, it has been observed that with the increase in fiber content up to the optimum value increases the strength of concrete. Slump cone test was adopted to measure the workability of concrete. The Slump cone test results revealed that workability gets reduced with the increase in fiber content.
Samer et al. (2010) investigate the viability of extending beams length usingsteelfibrereinforcedconcrete. The experimental was conducted with sixteen large scale welded beams and four control beams under three points loading. Totally thirty six prismatic concrete elements were designed the volume of fraction of steelfibre was 2% and 3%. Two different welded beams were tested. One welding joint at mid span of the beam and two welding joint At third point of the beam. Cyclic loading was applied on all the specimens. Load-deflection curve, failure and cracking behaviour and ultimate flexural capacity of the beams were monitored. Finally the test results suggested that increase in strength and ductility of the welded beam and the behaviour of moment-curvature capacity of the welded beams with curved joints were better than those with the zigzag joints.
Abstract: This paper discusses the experimental results on the mechanical properties of hybridfibrereinforced composite concrete (HyFRCC) containing different proportions of steelfibre (SF) and polypropylene fibre (PPF). The mechanical properties include compressive strength, tensile strength, and flexural strength. SF is known to enhance the flexural and tensile strengths, and at the same time is able to resist the formation of macro cracking. Meanwhile, PPF contributes to the tensile strain capacity and compressive strength, and also delay the formation of micro cracks. Hooked-end deformed type SF fibre with 60 mm length and fibrillated virgin type PPF fibre with 19 mm length are used in this study.
The amount of fibers added to the concrete mix is expressed as a percentage of total volume of the composite (concrete and fibers), termed volume fraction (Vf). Vf typically ranges from 0.1 to 3%. Aspect ratio (l/d) is calculated by dividing fiber length (l) by its diameter (d). Fibers with a non-circular cross section use an equivalent diameter for the calculation of aspect ratio. If the modulus of elasticity of the fiber is higher than the matrix (concrete or mortar binder), they help to carry the load by increasing the tensile strength of the material. Increase in the aspect ratio of the fiber usually segments the flexural strength and the toughness of the matrix. However, fibers which are too long tend to ―ball‖ in the mix and create workability problems. Some recent research indicated that using fibers in concrete has limited effect on the impact resistance of the materials. This finding is very important since traditionally, people think that the ductility increases when concrete is reinforced with fibers. The results also indicated out that the use of micro fibers offers better impact resistance compared with the longer fibers.
numerous micro-cracks. On application of the load, the micro- cracks begin to propagate in the concrete matrix. The addition of randomly spaced discontinuous fibres help in restricting the propagation of the micro-cracks and macro-cracks. Fibres also improve the mechanical properties of plain concrete such as, resistance to impact, resistance to fracture and resistance to dynamic loads . In the modern era, hybridization technology has also been an area of interest to researchers. Hybridization is the process of combining fibers with different characteristics, such as, length, diameter, and aspect ratio, modulus of elasticity, material type and tensile strength, to produce a unique composite that derives benefits from each of the individual fibers . In this study, hybridfibrereinforcedconcrete is prepared by combining basalt and steel fibers together according to different volume fraction and aspect ratio. Different experiments were carried out to determine the flexural strength, toughness index and load deflection behaviour of hybridfibrereinforced beams. For comparison steelfibrereinforcedconcrete beams and basalt fibrereinforcedconcrete beams were also casted. All these beams were compared with control beam consisting of no fibres. Key Words: Hybridfibrereinforcedconcrete beam, Steelfibre, Basalt fibre.
All cementitious materials are based on having cement as their main binding constituent being also responsible of providing some of the most relevant properties such as their compressive strength and modulus of elasticity. These two properties are highly recommended for construction applications, but some other properties conferred by the cementitious matrix are not as beneficial as the two previous ones. For instance, the flexural strength and the tensile strength of the cementitious materials are limited and consequently might be enhanced if possible. This situation appears in concrete which boasts a remarkable compressive strength and a tensile strength that as a rule of the thumb can be estimated in a tenth of such value. Thus, when constructing structural elements that are subjected to bending moments the stresses that appear would crack the material and even fracture it if the tensile strength is surpassed. Obviously, such event would cause an economic impact on society and might also create a situation where physical damage on humans is inflicted. The traditional solution to such situations has been the use of steel bars placed inside the concrete element section forming reinforcedconcrete. This approach has been used in a wide variety of applications both in civil engineering and architecture. However, in the nineteenth century the possibility of creating a continuous reinforcement in concrete by adding fibres appeared. From that moment onwards the use of fibres became an option to be considered based on the positive effect of the randomly distributed fibres in the mechanical properties of concrete.
Fuat Ko Ksal et al (2007) experimentally investigated on the mechanical properties of concrete specimens produced by using silica fume and steelfibre. The main objective of this work was to obtain a more ductile high strength concrete produced by using both silica fume and steelfibre. Two types of steelfibre with aspect ratios (fibre length/fibre diameter) of 65 and 80 were used in the experiments and volume fractions of steelfibre were 0.5% and 1%. Additions of silica fume into the concrete were 0%, 5%, 10% and 15% by weight of cement content. Water/cement ratio was 0.38 and the reference slump was 120 ± 20 mm. Slump test for workability, air content and unit weight tests were performed on fresh concretes. Compressive strength, splitting tensile strength and flexural strength tests were made on hardened concrete specimens. Load–deflection curves and toughness of the specimens were also obtained by flexural test performed according to ASTM C1018 standards. Flexural tests on beam specimens were achieved using a closed loop deflection-controlled testing machine. The use of silica fume increased both the mechanical strength and the modulus of elasticity of concrete. On the other hand, the addition of steelfibre into concrete improves toughness of high strength concrete significantly. As the steelfibre volume fraction increases, the toughness increases, and high values of aspect ratios give higher toughness. The toughness of
The promotion of steelfibrereinforcedconcrete (SFRC) as a construction material for tunnel linings has prompted a number of researchers to focus on methods of evaluating their flexural strength and stiffness. This thesis presents the results of an experimental and numerical investigation of the flexuralbehaviour of full-scale steelfibrereinforcedconcrete tunnel lining segments. A series of a three-point flexure tests were performed to evaluate the maximum load carrying capacity, the load-deformation behaviour and crack propagation characteristics of these segments. The material properties of the steelfibrereinforcedconcrete were also studied, using both destructive and non-destructive methods. Element compression and tension tests were conducted to characterize the compressive and tensile strength properties of the SFRC. Additionally, computed tomographic scanning was conducted to analyse and estimate the density fraction and fibre orientation of the fibres in SFRC cores. Three-dimensional finite element analyses were conducted to calibrate a concrete damage plasticity constitutive model and provide better understanding of the segment flexuralbehaviour. The experimental program indicated that the variation in structural performance of the segments was likely due to an inhomogeneity of fibre distribution and orientation. Modifying the numerical model to account for these variations resulted in a more accurate analysis. Furthermore, from the numerical finite element analysis it was found that the non-linear elasto-plastic concrete damage plasticity model in the crack zone of the beam was mesh dependent. Parametric analyses also revealed that the model was particularly sensitive to small changes to the tensile material property input parameters.
strength, splitting tensile strength, modulus of rupture, modulus of elasticity of normal concrete (NC), steelfibrereinforcedconcrete (SFRC) and hybrid fiber reinforcedconcrete have been obtained from standard tests and compared. A total of 36 specimens were tested for determining the mechanical properties. The grade of concrete used was M25. The total volume of fibers was fixed as 0.5% of total volume of concrete. Six concrete mixes were selected for study. Which include control mix without fibers, steel fiber reinforcedconcrete (SFRC) with 0.5% steel fibers and four hybrid fiber reinforced (HFRC) concrete of steel and polyester fibers with total volume fraction as 0.5%. In general, the addition of fibres improved the mechanical properties. However the increase was found to be nominal in the case of compressive strength (8.51%), significant in the case of splitting tensile strength (61.63%), modulus of rupture (24%), modulus of elasticity (64.92%) at 0.35% steel fibers and 0.15% polyester fibers. An attempt was made to obtain the relation between the various engineering properties with the percentage of fibers added.
The main intention of this paper is to estimate the flexural fatigue strength/endurance limit of concrete containing blends of LP and SF. The fatigue behavior of concrete is generally be characterized by the so called S-N curve, which allows the mean fatigue life of concrete under a given fatigue stress level to be predicted. The fatigue behavior of the fibrereinforcedconcrete is most meaningfully expressed in terms of its strength under static loading. To reach conclusions regarding the comparative relationships between stress and number of cycles to failure, commonly called S-N relationships, a linear regression was performed on each set of data. For fibrereinforcedconcrete, previous investigators have shown that S-N relationships are linear up to at least two million cycles, and have usually summarized their results in terms of a two million cycle endurance limit. Accordingly, to permit comparison with the trend of the S-N relationships in this investigation, two million cycle limits were predicted. The predicted range of the two million cycles limits of load application for CLS and CL are 74% and 71% of the static flexural strength respectively. The two- million cycles fatigue strength/endurance limit of plain concrete (plotted for the purpose of comparison) has been reported to be 58% of its static flexural strength [8, 26, 28] where as for control concrete and SFRC containing comparable steel fibres in terms of shape and size, the two million cycles endurance limit at 1.0% fibre content is 73%. The fatigue strengths or endurance limits for various concretes evaluated from the S-N curve as shown in Figure 5 depicts comparatively higher fatigue performance of CLS concrete and lower fatigue performance of CL concrete as compared to control concrete at two million cycles when