Investigation Of Concrete Properties With Different Types Of
Transcription
Investigation Of Concrete Properties With Different Types Of
IJSART - Volume 1 Issue 4 –APRIL 2015 ISSN [ONLINE]: 2395-1052 Investigation Of Concrete Properties With Different Types Of Fibers With Their Variation Of Volume Fraction And Different Aspect Ratio Mr. Charkha Kailas 1, Prof. Prashant Awsarmal2 1, 2 MIT Aurangabad Abstract- The present work deals with the literature works of different researcher’s results of their experimental investigations on steel fiber reinforced concrete. Effect of these different types of steel fibers on various strengths of concrete are studied. They are use Fibers at various volume fraction rates like as 0 % to 5 % by weight of cement. Various strengths considered for investigation are compressive strength, flexural strength, split tensile, and bond strength. Results are observe of different researchers and their experimental comparison of results of steel fiber reinforced concrete with that of normal concrete showed the significant improvements in the results of various strengths like as compressive strength, flexure strength, splitting strength, bonding strength of concrete with different types of steel fiber with various constant volume fractions and different aspect ratio. Keywords- Concrete, Steel Fibers, Hook end, Crimped, Straight, Compressive, Flexure, Split Tensile and Bond Strength. metallic and non-metallic fibers. Here, we will mainly discuss Steel Fiber Reinforced Concrete (SFRC). The SFRC is a composite material made of cement, fine and coarse aggregates and discontinuous discrete steel fibers. In tension SFRC fails only after the steel fiber breaks or pulled out of the cement matrix. The composite nature of SFRC is responsible for its properties in freshly mixed and hardened state. The SFRC possess many excellent dynamic performances such as high resistance to explosion and penetration as compared to traditional concrete. When used in structural applications, SFRC should only be used in a supplementary role to inhibit cracking, to improve resistance to impact or dynamic loading and resist material disintegration. The investigation reported in this paper is aimed at studying the behavior of steel fiber reinforced concrete beam under combined loading. The tests conducted on rectangular beams under different combination. The results of tests will be comparing with the theoretical predictions. A good agreement between the theory and experiment will been observed. I. INTRODUCTION 1.1 Objectives Fiber Reinforced Concrete (FRC) is a composite material made primarily from hydraulic cements, aggregates and discrete reinforcing fibers. Fiber incorporation in concrete, mortar and cement paste enhances many of the engineering properties of these materials such as fracture toughness, flexural strength, resistance to fatigue, impact, thermal shock and spalling. It is a type of building material that is increasing in use. New types of concrete develop continuously and the need to update the knowledge on the use of fiber reinforcement in such concrete increases. The use of fiber reinforcement is not a particularly recent idea. During ancient times, fibers extracted from organic material were used. Fiber Reinforced Concrete started to come to its modern industrial use during the 1960‟s. The first applications were mainly defense related where FRC was used in various shelter structures. Research development has led the FRC to increase its use as a building material. Nowadays, it is commonly applied in shotcrete, pavements, industrial floors, bridge decks and precast elements. The fiber reinforced concrete is produced using different types of fibers. The fibers are mainly classified in two groups as Page | 131 The objective of this study is to investigate the mechanical properties like as compressive strength, flexure strength, splitting strength and bond strength of concrete with different types of steel fiber with different volume fractions and different aspect ratio. II. LITERATURE REVIEW 2.1 Fiber Reinforced Concrete Fiber reinforced concrete can be defined as a composite material consisting of a cement matrix containing uniformly or randomly dispersed discrete fibers. The fibers act as crack arrestors that restrict the growth of cracks in the matrix, controlling them from enlarging which under stress eventually causes brittle failure. In the past, attempts have been made to impart improvement in tensile properties of concrete members by way of using conventional reinforced steel bars and also by www.ijsart.com IJSART - Volume 1 Issue 4 –APRIL 2015 applying restraining techniques. Although both these methods provide tensile strength to the concrete members, they however, do not increase the inherent tensile strength of concrete itself. It has been recognized that the addition of small, closely spaced and uniformly dispersed fibers to concrete would act as crack arrester and would substantially improve its static and dynamic properties. This type of concrete is known as Fiber Reinforced Concrete. Fiber is a small piece of reinforcing material possessing certain characteristic properties. They can be circular or flat. The fiber is often described by a convenient parameter called “aspect ratio”. The aspect ratio of the Fiber is the ratio of its length to its diameter. Typical aspect ratio ranges from 30 to 150. Basically fibers are classified asmetallic fibers and polymeric fibers. Different fibers give different effects such as follows: • • • • • • • • • • Metallic fibers: Increase of fracture energy, which subsequently improves ductility Increase of strength such as compressive strength, tensile strength, etc. Reduction of tendency for cracking Polymeric Fibers: Decrease of microscopic crack growth with high loading Gain in fire resistance Decrease of early shrinkage Glass Fibers: Decrease of early shrinkage 2.2 Classification of Fibers Fig-2.1 Classification of Fibers ISSN [ONLINE]: 2395-1052 MPa. The minimum strength specified in ASTM is 345 MPa. The modulus of elasticity for metallic fiber is 200 GPa. The fiber cross section may be circular, square, or irregular. The length of the fiber is normally less than 75 mm even though longer fibers have been used. The length-diameter ratio typically ranges from 30 to 100 or more. 2.4 Polymeric fibers Synthetic polymeric fibers have been produced as a result of research and development in the petrochemical and textile industries. Fiber types that have been tried with cement matrices include acrylic, aramid, nylon, polyester, polyethylene, and polypropylene. They all have a very high tensile strength, but most of these fibers (except for aramid) have a relatively low modulus of elasticity. The quality of polymeric fibers that makes them useful in FRC is their very high length-to-diameter ratios; their diameters are on the order of micrometers. Polymeric fibers are available in single filament or fibrillated form. The length used in FRC range from 12 to 50 mm. The number of studies of FRC containing polymeric fibers is very limited. 2.5 Basic Mechanism of Fiber Reinforcement Fiber influences the mechanical properties of concrete in all modes of failure, especially those that induce fatigue and tensile stresses. The strengthening mechanism of fibers involves transfer of stress from the matrix to the fiber by interfacial shear or by interlock between the fiber and matrix. With the increase in the applied load, stress is shared by the fiber and the matrix. With the increase in the applied load, stress is shared by the fiber and the matrix in tension until the matrix cracks; then the total stress is progressively transferred to the fibers, till the fibers are pulled out, or break, or break in tension. Fiber efficiency and the fiber content are the important variables controlling the performance of FRC. Fiber efficiency is controlled by the resistance to pullout, which depends on the bond at the fiber matrix interface. Pullout resistance increases with fiber length. Since pull out resistance is proportional to the interfacial area, the smaller the diameter, the larger is the interfacial area available for the bond. For a given fiber length, smaller the area, more effective is the bond. The composite effect of these two variables is expressed by the „aspect ratio‟ (length/diameter). Fiber efficiency increases with increase in „aspect ratio‟. 2.3 Metallic Fibers Metallic fibers are made of either carbon steel or stainless steel. The tensile strength ranges from 345 to 1380 Page | 132 The contribution of fiber to the composite depends upon the fiber material and type, Length (L), diameter (d), and www.ijsart.com IJSART - Volume 1 Issue 4 –APRIL 2015 aspect ratio (L/d), and volume concentration of fibers in the matrix. 2.6 Factors Influencing Fiber Reinforced Concrete Fiber reinforced concrete can be defined as a composite material consisting of a cement-based matrix containing an ordered or random distribution of fibers. The fibers act as crack arrestors that restrict the growth of flaws in the matrix, controlling them from enlarging under stress into cracks which eventually cause failure. By inhibiting the propagation of cracks originating from internal flaws, considerable improvements in static and dynamic properties can be obtained andfibers impart to the composite qualities of crack control, toughness, ductility impact resistance. The use of continuous, aligned fibers in a cement matrix is fundamentally not different from conventional reinforced or pre-stressed concrete, where the large diameter reinforcing bars or the smaller diameter pre-stressing wires behave analogously to the continuous aligned fibers. The phenomena of multiple cracking and of composite action in such materials have been well established for over a century. Obviously the highest strength characteristics are obtained when the fibers are aligned to resist the critical stresses, but then the material becomes markedly anisotropic. A more exciting challenge that will find a wider practical application is the use of short, discontinuous fibers that are uniformly in the matrix. It is true that with random orientation not all fibers are equally effective in crack control or in their strengthening and stiffening role: nevertheless, if sufficient strength and crack control improvements could be obtained, the practical advantages of discontinuous fibers will outweigh the strength advantage of continuous aligned fibers. The effective reinforcement of the matrix and the efficient transfer of stress between the matrix and the fiber depend upon many factors. Many of these factors are intimately interdependent, and exercise a profound but complex influence on the properties of the composite. • • • • • • • • • • The relative fiber matrix stiffness Fiber matrix interfacial bond Strain compatibility between fiber and the matrix. Shape of fibers Strength of fibers Fiber orientation Specimen size Span of specimen Spacing of fibers Physical and mechanical properties of fibers Page | 133 ISSN [ONLINE]: 2395-1052 2.7 Steel Fiber Reinforced Concrete Steel fiber reinforced concrete is a composite material made of hydraulic cements, fine and coarse aggregate, and a dispersion of discontinuous, small steel fibers. It may also contain pozzolans and admixtures commonly used with conventional concrete. The addition of steel fibers significantly improves many of the engineering properties of mortar and concrete, mainly impact strength and toughness. Flexural strength, fatigue strength, and the ability to resist cracking and spalling are also enhanced. Similarly, addition of fibers decreases the workability of fresh concrete and this effect is more pronounced for fibers with high aspect ratios. Research and design of steel fiber reinforced concrete began to increase in importance in the 1970s, and since those days various types of steel fibers have been developed. They differ in material as well as in size, shape and surface structure, as shown in figure 2.1. Due to different manufacturing processes and different materials, there are differences in the mechanical properties such as tensile strength, grade of mechanical anchorage and capability of stress distribution and absorption. Figure 2.2: Different Types of Steel Fibers There are drawn wire fibers, cut sheet metal fibers and milled steel fibers. Melt extracted fibers are amorphous and thus stainless. In order to improve anchorage and adhesion with the concrete matrix, the shape can be designed with hooked ends, completely corrugated or provided with end cones. Steel fibers are generally 12.7 - 63.5 mm long, and 0.45 - 1.0 mm in diameter. The usual amount of steel fibers ranges from 0.25% to 2% by volume, or 20 - 157 kg/m¬¬3. A lot of research work has been done and is going on the use of different types of steel fibers in enhancing different properties of concrete. Research work done by different researchers is discussed here in brief. www.ijsart.com IJSART - Volume 1 Issue 4 –APRIL 2015 2.8 Research work by different researchers Banthia and Sappakittipakorn: In the opinion of these two researchers, crimped steel fibers with large diameters are often used in concrete as reinforcement. Such large diameter fibers are inexpensive, disperse easily and do not unduly reduce the workability of concrete. However, due to their large diameters, such fibers also tend to be inefficient and the toughness of the resulting fiber reinforced concrete (FRC) tends to be low. Hence, an experimental program was carried out to investigate if the toughness of FRC with large diameter crimped fibers can be enhanced by hybridization with smaller diameter crimped fibers while maintaining workability, fiber dispensability and low cost. The results showed that such hybridization, replacing a portion of the large diameter crimped fibers with smaller diameter crimped fibers can significantly enhance toughness. The results also suggested that such hybrid FRCs fail to reach the toughness levels demonstrated by the smaller diameter fibers alone. Bayramov, C. Tasdemir and M. Tasdemir: conducted this research to optimize the fracture parameters of steel fiber reinforced concretes to obtain a more ductile behavior than that of plain concrete. The effects of the aspect ratio (L/d ) and volume fraction of steel fiber (Vf ) on fracture properties of concrete in bending were investigated by measuring the fracture energy (GF ) and characteristic length (lch ). For optimization, three-level full factorial experimental design and response surface method were used. The results show that the effects of fiber volume fraction and aspect ratio on fracture energy and characteristic length are very significant. Padmarajaiah and Ramaswamy ; carried out an experimental program for eight fully prestressed beams and seven partially prestressed beams made with high strength fiber-reinforced concrete (plain concrete strength of 65 MPa). These studies mainly attempted to determine the influence of trough-shaped steel fibers in altering the flexural strength at first crack and ultimate, the load–deflection and moment–curvature characteristics, ductility and energy absorption capacity of the beams. The magnitude of the prestress, volume fraction of the fibers ranging from 0% to 1.5% and the location of fibers were the variables in the test program. Analytical models to determine the load– deflection and moment–curvature relationships as a function of the fiber volume fraction were formulated. Empirical relationships for the ultimate strength, first crack load level, load versus deflection and moment versus curvature as a function of fiber content were proposed by making use of force equilibrium and compatibility considerations. A primary finding was that the placement of Page | 134 ISSN [ONLINE]: 2395-1052 fibers over a partial depth in the tensile side of the prestressed flexural structural members provided equivalent flexural capacity as in a beam having the same amount of fiber over the full cross-section. In large scale precast concrete applications it is expected that this would be economical and lead to considerable cost saving in the design without sacrificing on the desired structural performance. The analytical models proposed in this study predicted the test results closely. Rao and SeshuRelatively little research work has been done on the behavioral aspects of SFRC under pure torsion compared to its behavior under flexure or shear or under combined loading. The researchers suggested that the enhanced properties of SFRC in particular the ductility of the matrix can be achieved when a minimum volume fraction of fiber content is maintained. They studied the behavioral aspects of plain SFRC members under pure torsion and derived an empirical formula to predict the ultimate torsional strength of the SFRC members under pure torsion. Wang, Liu and Shen: investigated three types of SRFC specimens with 0.0%, 3.0% and 6.0% (percentage by volume) of ultra short steel fibers subjected to impact compression tests conducted on 74-mm-diameter split Hopkinson pressure bar (SHPB). Based on the stress–strain curves of different strainrates, as well as the random statistical distribution hypothesis for SFRC strength, a dynamic damage constitutive model of SFRC composite under compression was proposed. It was established that both the volume fraction of steel-fiber and strain-rate of loading exert significant influences on the SFRC strength. The theoretical results were in good agreement with experimental data. Kurugo, Tanacan and Ersoy : studied the effect of steel fiber reinforcement and polymer modification on the Young‟s modulus of lightweight concrete aggregates. Through experimental measurements, composite property models that best describe the mixtures in terms of the properties and volume fractions of their constituents were identified. The relationship between various composite properties and the mixtures used to produce the lightweight concrete were also explored qualitatively. Yazici, Inan and Tabak: investigated the effects of aspect ratio (l/d) and volume fraction (Vf) of steel fiber on the compressive strength, split tensile strength, flexural strength and ultrasonic pulse velocity on steel fiber reinforced concrete (SFRC). For this purpose, hooked-end bundled steel fibers with three different l/d ratios of 45, 65 and 80 were used. Three different fiber volumes were added to concrete mixes at 0.5%, 1.0% and 1.5% by volume of concrete. Ten different concrete mixes were prepared. After 28 days of curing, www.ijsart.com IJSART - Volume 1 Issue 4 –APRIL 2015 compressive, split and flexural strength as well as ultrasonic pulse velocity were determined. It was found that, inclusion of steel fibers significantly affect the split tensile and flexural strength of concrete in accordance with l/d ratio and Vf. Besides, mathematical expressions were developed to estimate the compressive, flexural and split tensile strength of SFRCs regarding l/d ratio and Vf of steel fibers. Mohammadi, Singh and Kaushik: studied properties of plain concrete and steel fiber rein- forced concrete (SFRC) containing fibers of mixed aspect ratio. An experimental programme was planned in which various tests such as inverted cone time, Vebe time and compaction factor were conducted to investigate the properties of plain concrete and fiber reinforced concrete in the fresh state. Compressive strength, split tensile and static flexural strength tests were conducted to investigate the properties of concrete in the hardened state. The specimen incorporated three different volume fractions, i.e., 1.0%, 1.5% and 2.0% of corrugated steel fibers and each volume fraction incorporated mixed steel fibers of size 0.6 • 2.0 • 25 mm and 0.6 • 2.0 • 50 mm in different proportions by weight. Complete load deflection curves under static flexural loads were obtained and the flexural toughness indices were obtained by ASTM C-1018 as well as JCI method. A fiber combination of 65% 50 mm + 35% 25 mm long fibers can be adjudged as the most appropriate combination to be employed in SFRC for compressive strength, split tensile strength and flexural strength. They found better workability as the percentage of shorter fibers increased in the concrete mix. Song, Wu, Hwang and Sheu: studied impact resistance variations of high-strength steel fiber-reinforced concrete (HSFRC), versus those of high-strength concrete (HSC). They found that impact resistance of the high-strength steel fiber-reinforced concrete improved satisfactorily over that of the high-strength concrete; the failure strength improved most, followed by first-crack strength and percentage increase in the number of post- first-crack blows. The two concretes resembled each other on the coefficient of variation values, respectively, on the two strengths, whereas the high-strength concrete was much higher in the value on the percentage increase Lu and Hsu: conducted extensive experimental program which showed the behavior of high strength concrete and steel fiber reinforced high strength concrete under uniaxial and triaxial compression. Triaxial stress–strain relations and failure criteria were used to evaluate the effect of steel fiber reinforcement on the mechanical properties of high strength concrete in triaxial compression, which were found to be insignificant. Page | 135 ISSN [ONLINE]: 2395-1052 Lau and Anson: investigated the compressive strength, flexural strength, elastic modulus and porosity of concrete reinforced with 1% steel fiber (SFRC) and changes of color to different elevated heating temperatures, ranging between 105 °C and 1200 °C. The results showed a loss of concrete strength with increased maximum heating temperature and with increased initial saturation percentage before firing. Mechanical strength results indicated that SFRC performs better than non-SFRC for maximum exposure temperatures below 1000 °C, even though the residual strength remains very low for all mixes at this high temperature. The variations with colour, which occurred, were associated with maximum temperatures of exposure. Altun, Haktanir and Ari : studied C20 and C30 classes of concrete produced each with addition of Dramix RC-80/0.60-BN type of steel fibers (SFs) at dosages of 0 kg/m3, 30 kg/m3, 60 kg/m3, and their compressive strengths, split tensile strength, moduli of elasticity and toughness were measured. Nine reinforced concrete (RC) beams of 300 300 2000 mm outer dimensions, designed as tension failure and all having the same steel reinforcement, having SFs at dosages of 0 kg/ m3, 30 kg/ m3, 60 kg/m3 with C20 class concrete, and nine other RC beams of the same peculiarities with C30 class concrete again designed as tension failure and all having the same reinforcement were produced and tested under simple bending. The load versus mid-span deflection relationships of all these RC and steel-fiber-added RC (SFARC) beams under simple bending were recorded. First, the mechanical properties of C20 and C30 classes of concrete with no SFs and with SFs at dosages of 30 kg/ m3 and 60 kg/ m3 were determined in a comparative way. The flexural behaviors and toughness of RC and SFARC beams for C20 and C30 classes of concrete were also determined in a comparative way. The experimentally determined (midsection load)–(SFs dosage) and (toughness)–(SFs dosage) relationships are given to reveal the quantitative effects of concrete class and SFs dosage on these crucial properties. 2.9 Concluding remark It is observed from the literature survey that the use of steel fibers, especially hooked end fibers, crimped fiber and straight fibers are more advantageous as they enhance the overall mechanical properties of plain concrete than other fibers. Thus, one can think of comparison in such steel fibers by putting variation of volume fraction with their difference aspect ratio, and check their engineering properties. www.ijsart.com IJSART - Volume 1 Issue 4 –APRIL 2015 III. EXPERIMENTAL WORK Flow chart of experimental work: ISSN [ONLINE]: 2395-1052 V. RECOMMENDATIONS FOR FUTURE WORK The present work has good scope for future research, some are given below: 1. Behaviour of concrete with different types of steel fibers will be study by changing the volume fraction also aspect ration 2. Check the strength of concrete by adding the Fly ash in same work. 3. Investigation of strength of concrete with same work by addition of Metacoline. 4. Finite Element Analysis. 5. Torsional Strength transfer mechanism in Circular Section. 6. Study of resistant to chemical attack. VI. APPLICATIONS Steel Fiber Concrete is being used widely nowadays. SFC has found number of applications, some of which are listed below: Construction of highway paving and industrial floors with crimped as well as strength fibers. Repairs and new construction on hydraulic structures to provide resistance to cavitations and severe erosion. Repairs and rehabilitation of marine structures. Tunnel as also as Cannel lining. REFERENCES IV. EXPECTED OUTCOME From above study is conclude that, all mechanical properties viz. compressive strength, flexure strength, splitting strength and bond strength will be improved by addition of fibers irrespective of fiber type and aspect ratio. All strength likes compressive strength, flexure strength and splitting strength will be improved with increasing aspect ratio. Also for same aspect ratio the hook ended fibrewill be showing pronounce improvement in all properties of concrete as compare crimped & straight fiber. There might be decrease in the strength with decrease in aspect ratio of same fiber type. The straight fibers will having less strength as compared with hook end and crimped fibers. Also that will be hook end and crimped fibers having because of their shape and anchorage in the matrix resulting in more strength. 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