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VIGNESH POLYTECHNIC COLLEGE THIRUVANNAMALLAI NATIONAL LEVEL TECHNICAL SYMPOSIUM Topic: FIBER REINFORCED CONCRETE & IT’S RECENT DEVELOPMENT BY S. DAMODARAN S.SUDHARSAN Department of Civil Engineering Sri Ramakrishna Mission Vidyalaya Polytechnic College Coimbatore

CONTENTS  INTRODUCTION - FIBRE REINFORCED CONCRETE. (FRC)  PROPERTIES AND TYPES OF FIBRES USED.  CLASSIFICATION OF FRC.  APPLICATIONS OF FRC  RECENT DEVELOPMENT IN FRC.  CONCLUSION.

FRC INTRODUCTION  PCC has low tensile strength, limited ductility, little resistance to cracking. In pcc,cracks develops due to self weight and drying shrinkage. The width of the crack will increase to few microns in few days,but length and height will increase in larger extent. It will reduce the total strength of the structures.  To rectify these defects research studies have revealed that addition of small closely spaced uniformly dispersed Fibers to concrete acts as a crack arrestor and this concrete with Fibers is known as “FIBRE REINFORCED CONCRETE.”  In RCC, fibers are mainly used to have a good bond between steel and concrete. It will attract it’s surrounding concrete towards itself.  FRC is mainly used in place where water tightness is required, earthquake resistant structures, roads, bridges, water decks etc.

PROPERTIES AND TYPES OF FIBRES USED STEEL FIBRES:  Only few Fibres are suitable for concrete they are steel fibres, polypropylene, asbestos, nylon, glass and carbon. They reduce micro cracks.  Fibres can be circular or flat. They can be expressed in “ASPECT RATIO”. Aspect ratio ranges from 30 to 150. up to 75 increase in aspect ratio increase in ultimate strength beyond 75 strength reduced.  Steel fibre is most commonly used, it’s diameter varies from 0.25 to In steel fibres corrosion will takes place only at surface but the core remains unaffected. SYNTHETIC FIBRES:  Polypropylene and nylon fibres are increase the impact strength. Polypropylene fibres are hydrophilic  Asbestos, a mineral fibre, is a most successful of all the fibres. Tensile strength varies between 560 to 980N/mm2.  Glass fibre is a recent introduction. Tensile strength varies between 1020 to 4080 N/mm2. STEEL FIBRES POLYPROPYLENE FIBRES

WHAT MADE FRC UNIQUE? It is advisable because  Increase in flexural strength and toughness  Increase in impact resistance  Reduction in shrinkage and cracking  Fiber Reinforced concrete can be easily placed, cast, sprayed in site

FRC Major classification FRC Fibre Reinforced Concrete SNFRC ( Synthetic FRC ) SFRC ( Steel FRC )

 Steel fiber-reinforced concrete is basically cheaper.  Easier to use in the form of rebar reinforced concrete.  Having greater structural strength and reduces cracking  SFRC is mainly used in place where there is increased in static and dynamic tensile strength and better fatigue strength.  The uniform dispersion of fibres provides isotropic properties not common to conventional methods STEEL FIBRE REINFORCED CONCRETE Cracking in Tensile Zone Uniformity of Dispersion

Features and Benefits of SFRC in final state FeatureBenefits 1.Controls cracking which occurs in the hardened state. 2. Even distribution of fibres throughout the concrete. 3. A tougher surface with fewer bleed holes. 4.Increase in impact and abrasion resistance. 1.Enhanced load bearing capability 2. Improved flexural properties. 3. Reduced absorption of water, chemicals etc. 4.Increase durability and reduction in maintenance cost.

SYNTHETIC FIBRE REINFORCED CONCRETE  The dosage of super plasticizer in concrete has to be adjusted to get the desired slump.  General dosage per cum is 0.9 Kg.  The water demand is nil for polypropylene fibre reinforced concrete.  FRC mixes usually contain a high mortar volume as compared to conventional concrete mixes  SNFRC reduce the plastic shrinkage crack area due to their flexibility and ability to conform to form.  The vapor pressure In SNFRC is released in newly formed voids and explosive sapling is significantly reduced

APPLICATIONS OF FIBRE REINFORCED CONCRETE

FRC IN ROAD AND FLOOR CONSTRUCTION INDUSTRIAL FLOORING LANDING OF PLANE PLAYGROUND

FRC IN BRIDGE AND WATER TANK CONSTRUCTION Bridges in water Rail way bridges in water WATER TANK

FRC IN DAM CONSTRUCTION POURING OF CONCRETE IN DAMS CONSTRUCTION OF WALS SIDE WALL CONSTRUCTION OF DAMS

HOME APPLICATION OF FRC ARCHITECTURAL ELAVATION SUN SHADE ARCHES IN HOMES

Glass Fibre Reinforced Concrete  Design freedom since GFRC is able to be molded into almost any shape and color  Installation is quick and cost effective and economical.  It has the feature of being applied on all kinds of architectural form and in sliding application.  Weather and fire resistant and is highly durable and safe  It is used for fabricating concrete products having section of 3 to 12 mm in thickness. It is used in the name of(CEM FIL)  These are applied by spraying, casting, spinning, pressing…. Among these spraying is the most advanced method. Mortar slurry is fed into the gun and is atomized by compressed air along with the glass fed in chopper unit.

SLURRY INFILTRATED CONCRETE  Slurry Infiltrated concrete (SIFCON) was invented in steel fibre bed is prepared first and cement slurry is infiltrated. With this technique macro fibre contents about 20% by volume can be achieved.  It increase both flexural load carrying capacity and toughness. A very high compressive strength is also achieved.  (SIFCON) can be used for blast resistant structures and burglar proof safe vaults in banks and residential buildings.

HANDLING OF FRC  A fibre with double end hooks as anchorage elements gives the right optimization of performance and workability.  The maximum drum rotating speed should be revolutions per minute.  Each truck mixer should be rotated at full speed for minutes after adding the fibres  The concrete with steel fibres can be pumped, with some adjustments to the mix design may be necessary depending on the fibre dosage requirements.  Recommended slump SFRC pumping is 150mm to avoid balling.  The concrete can be compacted and finished normally. Toweling will help to embed the fibres in to the concrete surface. Hence, Toweling after laying is advisable.  The fibers should not float to the surface nor sink to the bottom in the fresh concrete.  Synthetic fibres are commercially available in water disposable bags.

EXISTING MONUMENTS  Roman Coliseum was built with fiber reinforced concrete in 80 AD, they used horse-hair as fibers. Tipu Sultan’s palace at Srirangpattnam has been built with Sheep's wool. A Pueblo house built in 1540 with straw reinforcement adobe brick is believed to be the oldest house in USA

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