fiber reinforced concrete
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09-04-2010, 04:08 PM
Fiber Reinforced Concrete can be defined as a composite material consisting of mixtures of cement, mortar or concrete and discontinuous, discrete, uniformly dispersed suitable fibers. Continuous meshes, woven fabrics and long wires or rods are not considered to be discrete fibers.
Fiber is a small piece of reinforcing material possessing certain characteristics 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.
Fiber reinforced concrete (FRC) is concrete containing fibrous material which increases its structural integrity. It contains short discrete fibers that are uniformly distributed and randomly oriented. Fibers include steel fibers, glass fibers, synthetic fibers and natural fibers. Within these different fibers that character of fiber reinforced concrete changes with varying concretes, fiber materials, geometries, distribution, orientation and densities.
Fibre-reinforcement is mainly used in shotcrete, but can also be used in normal concrete. Fibre-reinforced normal concrete are mostly used for on-ground floors and pavements, but can be considered for a wide range of construction parts (beams, pliers, foundations etc) either alone or with hand-tied rebars
Concrete reinforced with fibres (which are usually steel, glass or plastic fibres) is less expensive than hand-tied rebar, while still increasing the tensile strength many times. Shape, dimension and length of fibre is important. A thin and short fibre, for example short hair-shaped glass fibre, will only be effective the first hours after pouring the concrete (reduces cracking while the concrete is stiffening) but will not increase the concrete tensile strength
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02-09-2010, 10:53 PM
pls give the full seminar and presentation report of this fiber reinforsed concrete for contect a seminar and presentation
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Joined: Feb 2011
12-03-2011, 12:56 PM
FIBRE REINFORCED CONCRETE.pptx (Size: 1.87 MB / Downloads: 724)
The concept of using fibres as reinforcement is not new. Fibres have been used as reinforcement since ancient times. Historically, horsehair was used in mortar and straw in mud bricks
In the early 1900s, asbestos fibres were used in concrete, and in the 1950s the concept of composite materials came into being and fibre reinforced concrete was one of the topics of interest.
There was a need to find a replacement for the asbestos used in concrete and other building materials once the health risks associated with the substance were discovered.
By the 1960s, steel, glass (GFRC), and synthetic fibres such as polypropylene fibres were used in concrete, and research into new fibre reinforced concretes continues today.
THE MAIN PROPERTIES INFLUENCING TOUGHNESS AND MAXIMUM LOADING OF FIBRE REINFORCED CONCRETE
Type of fibers used
Volume percent of fiber(vf =o.1 to 3%)
Aspect ratio (the length of a fiber divided by its diameter)
Orientation of the fibers in the matrix
Shape, dimension and length of fiber is important. A thin and short fiber, for example short hair-shaped glass fiber, will only be effective the first hours after pouring the concrete (reduces cracking while the concrete is stiffening) but will not increase the concrete tensile strength.
A normal size fibre (1 mm diameter, 45 mm length—steel or "plastic") will increase the concrete tensile strength.
MATERIALS USED IN FIBRE REINFORCED CONCRETE
POLYPROPYLENE FIBRE REINFORCED CONCRETE
Polypropylene fibres can:
Improve mix cohesion
Improve freeze-thaw resistance
Improve resistance to explosive spalling in case of a severe fire
Improve impact resistance
Increase resistance to plastic shrinkage during curing
SPALLING OF CONCRETE
Polypropylene Fiber Reinforced Precast Concrete Blocks for Roads and Pavements
TEMPORARY WALL MADE BY PFRC
GLASS FIBER REINFORCED CONCRETE
Glass fiber reinforced concrete is most popular fiber that is being successfully used since the last 25 years for concrete reinforcement, in addition to steel.
Glass Fiber Reinforced Concrete is similar to concrete in its characteristics, but it is 80% lighter.
Although GRC has a similar density to concrete the products made from it are many times lighter due to the thin 10-15mm skin thickness used.
A cladding panel manufactured from 100mm thick precast concrete would weigh 240kgs per m2 compared to a similar GRC panel of 40-50kgs/m2.
GFRC is finished in a wide selection of colors and textures, eliminating finishing costs and reducing the maintenance cost since there is no need for painting.
GFRC is easily molded into desired shapes with clean lines and sharp details.
FUNCTIONS OF GFRC
Impervious to chloride ion and chemical attack
Tensile strengths greater than steel
Modulus approaching that of steel and three times that of GFRP Rebar
1/5th the weight of steel reinforcing
Surface treatment to enhance bond to portland cement
GLASS FIBRE REINFORCED POLYMER
LOCATING PRESTRESSED GFRC
STRUCTURES MADE BY GFRC
STEEL FIBER REINFORCED CONCRETE
STEEL FIBER REINFORCED CONCRETE (SFRC)
Steel fiber reinforced concrete is a composite material that can be sprayed. It consists of hydraulic cements with steel fibers that are dispersed randomly.
The steel fibers reinforce concrete by withstanding tensile cracking.
The flexural strength of fiber reinforced concrete is greater than the un-reinforced concrete.
Reinforcement of concrete by steel fibers is isotropic in nature that improves the resistance to fracture, disintegration.
Steel fiber reinforced concrete is able to withstand light and heavy loads.
PROPERTIES OF STEEL FIBRE
Appearance: Clear and Bright
Steel fibres can:
Improve structural strength
Reduce steel reinforcement requirements
Reduce crack widths
Improve impact & abrasion resistance
Improve freeze-thaw resistance
HALF JOINT STRUCTURE MADE BY SFRC
Engineered Cementitious Composite (ECC)
A fiber reinforced concrete has been developed recently that is called Engineered Cementitious Composite (ECC).
It is claimed that this concrete is 40 % lighter than normal concrete, resistance to cracking exceeds 500 times, and strain hardening exceeds several percent strain.
Thus, the ductility is significantly greater than normal concrete. It is also known as bendable concrete since it can easily be molded and shaped.
It can self repair minor cracks by the reaction with carbon dioxide and rainwater making the concrete stronger.
The Mitaka Dam near Hiroshima was repaired using ECC in 2003.
The surface of the then 60-year old dam was severely damaged, showing evidence of cracks, spalling, and some water leakage.
A 20 mm-thick layer of ECC was applied by spraying over the 600 m2 surface.
ECC was intended to minimize this danger, after one year only microcracks of tolerable width were observed.
ADVANTAGES AND DISADVANTAGES OF FIBER REINFORCED CONCRETE
Concrete is quite brittle; it has very good compressive strength but comparatively little tensile strength, which makes it likely to crack under many conditions. Cracking leads to further damage. Fiber reinforced concrete is less likely to crack than standard concrete.
Concrete reinforced with fibers while still increasing the tensile strength many times than ordinary concrete.
Fiber reinforced concrete has started to find its place in many areas of civil infrastructure applications where the need for repairing, increased durability arises.
Also FRCs are used in civil structures where corrosion can be avoided at the maximum. Fiber reinforced concrete is better suited to minimize cavitation /erosion damage in structures such as sluice-ways, navigational locks and bridge piers where high velocity flows are encountered.
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29-07-2011, 04:20 PM
Fibre-Reinforced-Concrete1.ppt (Size: 1.77 MB / Downloads: 318)
Fiber Reinforced Concrete
What is a Fiber…?
Small piece of reinforcing material possessing certain characteristic properties.
Can be circular or flat.
Parameter used to describe fiber – “Aspect ratio”.
Aspect ratio is ratio of its length to its diameter.
Typical aspect ratio for fibers ranges from 30 to 150.
What is Fiber Reinforced Concrete (FRC)?
Fiber reinforced concrete (FRC) is concrete containing fibrous material which increases its structural integrity.
It contains short discrete fibers that are uniformly distributed and randomly oriented.
Fibers include steel fibers, glass fibers, synthetic fibers and natural fibers.
Within these different fibers that character of fiber reinforced concrete changes with varying concretes, fiber materials, geometries, distribution, orientation and densities.
Although every type of fiber has been tried out in cement and concrete, not all of them can be effectively and economically used. Each fiber has some characteristic properties and limitations.
Fibers used are-
Steel Fiber Reinforced Concrete…
Most commonly used fiber.
Round fiber of diameter 0.25 to 0.75mm.
Enhances flexural, impact and fatigue strength of concrete.
Used for-overlays of roads, airfield pavements, bridge decks.
Thin shells and plates have also been constructed using stell fibers.
Polypropylene/Nylon Fiber Reinforced Concrete…
Suitable to increase impact strength of concrete.
Possess high tensile strength but their low modulus of elasticity and higher elongation do not contribute to the flexural strength.
Asbestos Fiber Reinforced Concrete…
Mineral fiber, most successful of all as it can be mixed with portland cement.
Tensile strength of asbestos varies between 560 to 980 N/mm2.
Asbestos cement paste has considerably higher flexural strength than portland cement paste.
For unimportant concrete work, organic fibers like coir, jute and canesplits are also used.
Glass Fiber Reinforced Concrete…
Very high tensile strength 1020 to 4080 N/mm2.
Alkali resistant glass fiber has been developed.
Shows comparable improvement in durability to conventional E-glass fiber.
Carbon Fiber Reinforced Concrete…
Posses very high tensile strength 2110 to 2815 N/mm2 and Young’s modulus.
Cement composite consisting of carbon fibers show very high modulus of elasticity and flexural strength.
Used for cladding, panels and shells.
Factors affecting properties of Fiber Reinforced Concrete…
Transfer of stress between matrix and fiber.
Type of fiber.
Orientation and distribution of fibers
Mixing and compaction technique of concrete.
Size and shape of aggregates.
Relative Fiber Matrix Stiffness
Modulus of elasticity of matrix must be much lower than that of fiber for efficient stress transfer.
Nylon and propylene fiber impart greater degree of toughness and resistance to impact.
Steel, glass and carbon impart strength and stiffness to the composite.
Interfacial bonds also determine the degree of stress transfer.
Bonds can be improved by larger area of contact, improving frictional properties and degree of gripping and by treating steel fibers with sodium hydroxide or acetone.
Volume Of Fiber
Strength largely depends upon the quantity of fibers used.
Tensile strength and toughness of the composite linearly increase with increase in volume of fibers.
Higher percentage of fibers is likely to cause segregation and harshness of concrete and mortar.
Aspect Ratio Of Fiber
One of the important factor affecting the properties and behavior of composite.
Increase in aspect ration upto 75, increase the ultimate strength of concrete linearly.
Beyond 75 relative strength and toughness is reduced.
Orientation Of Fibers
One of the major difference in conventional reinforcement and fiber reinforcement.
Specimens with 0.5% volume of fiber were tested and it showed that when fibers were aligned parallel to the load applied, more tensile strength toughness was seen as compared to randomly distributed and perpendicular fibers.
Workability and Compaction of Concrete…
Use of steel fibers decrease the workability.
External vibration fails to compact the concrete.
Poor workability is also result of non uniform distribution of fibers.
Fiber volume at which this situation is reached depends on the length and diameter of fiber used.
Workability and compaction standard can be improved with help of water reducing admixture.
Size Of Coarse Aggregates
Maximum size of aggregates should be restricted to 10 mm.
Fibers also act as aggregate.
The interparticle friction and between fibers and between fibers and aggregates controls the orientation and distribution of fibers which affect the properties of composite.
Friction reducing admixtures and admixtures improving the cohesiveness can significantly improve the mix.
Mixing is important to avoid balling of aggregates, segregation and to obtain uniform composite.
Increase in aspect ration, volume percentage, size and quantity of aggregates intensify the balling tendencies.
A steel fiber content in excess of 2% by volume and an aspect ratio of more than 100 are difficult to mix.
Addition of fibers before addition of water is important to get uniform dispersion of fibers in concrete mix.
Typical Proportions For FRC…
Advantages Of FRC Over Conventionally Reinforced Concrete…
Increased static and dynamic tensile strength.
Energy absorbing characteristics and better fatigue strength.
Uniform dispersion of fibers throughout the concrete provides isotropic properties.
Overlays of air-fields.
Explosive resistant structure.
Fabrications of precast products like pipes, boats, beams, staircase steps, wall panels, roof panels, manhole covers etc.
Manufacture of prefabricated formwork moulds of “U” shape for casting lintels and small beams.
Current development in FRC:-
High fibre volume micro-fibre system.
Slurry infiltrated fibre concrete(SIFCON).
Compact reinforced composites.
High fibre volume micro-fibre system:-
Can replace asbestos fibre.
Improves toughness and impact strength.
These properties make it attractive for thin precast products such as roofing sheets ,cladding panels.
Cement composites are useful for repair & rehabilitation works.
Slurry infiltrated fibre concrete:-
SIFCON was invented by Lankard in 1979.
Steel fibre bed is prepared and cement slurry is infiltrated.
Micro-fibre contents up to about 20% by volume can be achieved.
Increase in both flexural load carrying capacity and toughness.
High compressive strength is achieved.
Used for blast resistant structures & burglar proof safe vaults.
Compact reinforced composites(CRC):-
Consist of an extremely strong ,dense cement matrix.
Exhibits flexural strength up to 260Mpa & compressive strength of about 200Mpa.
As strong as structural steel.
Can be moulded and fabricated at site.
Joined: Apr 2012
11-08-2012, 10:27 AM
to get information about the topic "fiber reinforced concrete" full report ppt and related topic refer the link bellow
seminar and presentationproject and implimentationsshowthread.php?mode=linear&tid=28550
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14-11-2013, 07:17 PM
plzzz send me detail project and implimentation report of fibre reinforced concrete
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05-02-2014, 10:58 AM
plese provide me the detial thesis and the papers on the topic fibre reinforced concrete and its strength