FIBRE REINFORCED CONCRETE

Historical development Materials used in fibre reinforced concrete Contents: Definitions Historical development Materials used in fibre reinforced concrete Engineered Cementitious Composite (ECC) Advantages and Disadvantages of Fiber Reinforced Concrete. Ongoing projects using FRC

Fibre reinforced concrete (FRC) is concrete containing fibrous material which increases its structural integrity. It contains short discrete fibres that are uniformly distributed and randomly oriented. Fibres include steel fibres, glass fibres, synthetic fibres and natural fibres. Within these different fibres that character of fibre reinforced concrete changes with varying concretes, fibre materials, geometries, distribution, orientation and densities.

HISTORICAL DEVELOPMENT

HISTORICAL DEVELOPMENT 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.

HISTORICAL DEVELOPMENT 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.

Volume percent of fiber(vf =o.1 to 3%) 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

THE MAIN PROPERTIES INFLUENCING TOUGHNESS AND MAXIMUM LOADING OF FIBRE REINFORCED CONCRETE 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 Glass fibres Steel fibres

POLYPROPYLENE 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

FREEZE -THAW

SPALLING OF CONCRETE

POLYPROPYLENE FIBRES

Polypropylene Fiber Reinforced Precast Concrete Blocks for Roads and Pavements

TEMPORARY WALL MADE BY PFRC

GLASS FIBER REINFORCED CONCRETE

GLASS FIBER REINFORCED CONCRETE (GFRC) 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. 

GLASS FIBER REINFORCED CONCRETE (GFRC) 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.

CLADDING PANNEL

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.

STEEL FIBER REINFORCED CONCRETE (SFRC) 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.

STEEL FIBRES

PROPERTIES OF STEEL FIBRE Length:6-60mm Diameter:0.2-1.0mm Appearance: Clear and Bright Tensile Strength:800-2500mpa

Steel fibres can: Improve structural strength Reduce steel reinforcement requirements Improve ductility Reduce crack widths Improve impact & abrasion resistance Improve freeze-thaw resistance

HALF JOINT STRUCTURE MADE BY SFRC

Engineered Cementitious Composite (ECC)

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.

Engineered Cementitious Composite (ECC) 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.

Engineered Cementitious Composite (ECC) 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

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.

ADVANTAGES AND DISADVANTAGES OF FIBER REINFORCED 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.

ADVANTAGES AND DISADVANTAGES OF FIBER REINFORCED CONCRETE When used in bridges it helps to avoid catastrophic failures. Also in the quake prone areas the use of fiber reinforced concrete would certainly minimize the human casualties. In addition, polypropylene fibers reduce or relieve internal forces by blocking microscopic cracks from forming within the concrete(20)

ADVANTAGES AND DISADVANTAGES OF FIBER REINFORCED CONCRETE GRC products do not contain mild steel reinforcement and the problems associated with corrosion of reinforcement do not apply. GRC has a wide flexibility in design and manufacture, which enables it to reproduce most architectural styles and features. The main disadvantage associated with the fiber reinforced concrete is fabrication. The process of incorporating fibers into the cement matrix is labor intensive and costlier than the production of the plain concrete. The real advantages gained by the use of FRC overrides this disadvantage.

ONGOING PROJECTS USING FIBRE REINFORCED CONCRETE

BARCELONA METRO In Spain, construction of the 43km long extension to the Barcelona Metro has made extensive use of precast tunnel lining-segments incorporating steel reinforcement fibres. When completed, it will be the longest and one of the deepest lines in Europe and the longest metro line in the world of entirely new construction. It will also be the most expensive enterprise the Catalan government has ever undertaken. The final projected costs are thought to be close to €6.5 billion, when the project is completed in 2012.

BARCELONA METRO Here, Joint Venture Construction Consortia, UTE Gorg, UTE Linea and UTE Aeroport, used precast FRC segments for the lining to three individual sections of the 12.0m diameter tunnel, totalling some 11.7 km in length. At the 3.8km long, Sagrera TAV-Gorg section, construction work began in 2003. An earth pressure balance, tunnel boring machine [TBM] was used to excavate the tunnel, with the precast lining segments placed ring by ring behind the machine, using a robotic arm.

BARCELONA METRO

OLYMPIC HEIGHTS TOWER, PHILIPPINES

COMPLETED PROJECTS USING FRC

CITY GARDEN HOTEL, MAKATI The entire facade of this 22-Storey hotel along Makati Avenue was designed and built using Precast Concrete (PC) for construction efficiency and uniformity.Each item was fabricated at LARC’s plant and installed simultaneously with the building’s ascent.

CITY GARDEN HOTEL, MAKATI

DOÑA SOLEDAD PEDESTRIAN OVERPASS, PHILIPPINES

RESIDENTIAL APARTMENT IN LOS ANGELES, 2008

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