fiber reinforced concrete (frc)
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Contents
Introduction
Benefits of FRC
Toughening Mechanism
Factor affecting the properties of FRC
Comparison of Mix Proportion of FRC and Plain Concrete
Type of fibers
Steel Fiber Reinforced Concrete (SFRC)
Structural behavior & Durability of SFRC
Problems with SFRC
Application Of FRC
Conclusion
References
Introduction to Fiber Reinforced Concrete
Concrete containing a hydraulic cement, water ,
aggregate, and discontinuous discrete fibers is
called fiber reinforced concrete.
Fibers can be in form of steel fiber, glass fiber,
natural fiber , synthetic fiber.
Benefits of FRC
Main role of fibers is to bridge the cracks that develop in concrete and increase the ductility of concrete elements.
Improvement on Post-Cracking behavior of concrete Imparts more resistance to Impact load controls plastic shrinkage cracking and drying
shrinkage cracking Lowers the permeability of concrete matrix and thus
reduce the bleeding of water
Toughening mechanism
Toughness is ability of a material to absorb energy
and plastically deform without fracturing.
It can also be defined as resistance to fracture of a
material when stressed.
Contd.
Source: P.K. Mehta and P.J.M. Monteiro, Concrete: Microstructure, Properties, and Materials, Third Edition, Fourth Reprint 2011
Factors affecting the Properties of FRC
Volume of fibers Aspect ratio of fiber Orientation of fiber Relative fiber matrix stiffness
Volume of fiber
Low volume fraction (less than 1%) Used in slab and pavement that have large exposed
surface leading to high shrinkage cracking Moderate volume fraction(between 1 and 2 percent)
Used in Construction method such as Shortcrete & in Structures which requires improved capacity against delamination, spalling & fatigue
High volume fraction(greater than 2%) Used in making high performance fiber reinforced
composites (HPFRC)
Contd.
Source: P.K. Mehta and P.J.M. Monteiro, Concrete: Microstructure, Properties, and Materials, Third Edition, Fourth Reprint 2011
Aspect Ratio of fiber
It is defined as ratio of length of fiber to it’s diameter (L/d).
Increase in the aspect ratio upto 75,there is increase in relative strength and toughness.
Beyond 75 of aspect ratio there is decrease in aspect ratio and toughness.
Orientation of fibers
Aligned in the direction of load Aligned in the direction perpendicular to load Randomly distribution of fibers
It is observed that fibers aligned parallel to applied load offered more tensile strength and toughness than randomly distributed or perpendicular fibers.
Relative fiber matrix
Modulus of elasticity of matrix must be less than of fibers for efficient stress transfer.
Low modulus of fibers imparts more energy absorption while high modulus fibers imparts strength and stiffness.
Low modulus fibers e.g. Nylons and Polypropylene fibers
High modulus fibers e.g. Steel, Glass, and Carbon fibers
Comparison of Mix Proportion between Plain Concrete and Fiber Reinforced ConcreteMaterial Plain concrete Fiber reinforced
concrete
Cement 446 519
Water (W/C=0.45) 201 234
Fine aggregate 854 761
Coarse aggregate 682 608
Fibers (2% by volume) -- 157
The 14-days flexural strength, 8 Mpa, of the fiber reinforced was about 20% higher than that of plain concrete.
Source: Adapted from Hanna, A.N., PCA Report RD 049.01P, Portland cement Association, Skokie, IL, 1977
Types of fiber used in FRC
Steel Fiber Reinforced Concrete Polypropylene Fiber Reinforced (PFR) concrete Glass-Fiber Reinforced Concrete Asbestos fibers Carbon fibers and Other Natural fibers
Contd.
Type of fiber Tensile strength(Mpa)
Young’s modulus
(x103Mpa)
Ultimate elongation
(%)
Steel 275-2757 200 0.5-35
Polypropylene 551-690 3.45 ~25
Glass 1034-3792 ~69 1.5-3.5
Nylon 758-827 4.14 16-20
Source: ACI Committee 544, Report 544.IR-82, Concr. Int., Vol. 4, No. 5, p. 11, 1982
Steel Fiber Reinforced Concrete
Diameter Varying from 0.3-0.5 mm (IS:280-1976) Length varying from 35-60 mm Various shapes of steel fibers
Advantage of Steel fiber
High structural strength Reduced crack widths and control the crack widths
tightly, thus improving durability less steel reinforcement required Improve ductility Reduced crack widths and control the crack widths
tightly, thus improving durability Improve impact– and abrasion–resistance
Structural Behavior of Steel Fiber Reinforced Concrete
Effect on modulus of rupture Effect of compressive strength Effect on Compressive strength & tensile Strength at
fire condition i.e. at elevated temperature
Effect on Modulus of Rupture
Ref: Abid A. Shah, Y. Ribakov, Recent trends in steel fibered high-strength concrete, Elsevier, Materials and Design 32 (2011), pp 4122–4151
Effect on Compressive Strength
Ref: Abid A. Shah, Y. Ribakov, Recent trends in steel fibered high-strength concrete, Elsevier, Materials and Design 32 (2011), pp 4122–4151
Structural behavior at Elevated Temperature
Ref: K.Srinivasa Rao, S.Rakesh kumar, A.Laxmi Narayana, Comparison of Performance of Standard Concrete and Fibre Reinforced Standard Concrete Exposed To Elevated Temperatures, American Journal of Engineering Research (AJER), e-ISSN: 2320-0847 p-ISSN : 2320-0936, Volume-02, Issue-03, 2013, pp-20-26
Contd.
Ref: K.Srinivasa Rao, S.Rakesh kumar, A.Laxmi Narayana, Comparison of Performance of Standard Concrete and Fibre Reinforced Standard Concrete Exposed To Elevated Temperatures, American Journal of Engineering Research (AJER), e-ISSN: 2320-0847 p-ISSN : 2320-0936, Volume-02, Issue-03, 2013, pp-20-26
Durability
Resistance against Sea water (In 3% NaCl by weight of water) Maximum loss in compressive strength obtained was
about 3.84% for non-fibered concrete and 2.53% for fibered concrete
Resistance against acids (containing 1% of sulfuric acid by weight of water) Maximum loss in compressive strength obtained was
found to be about 4.51% for non-fibered concrete and 4.42% for fiber concrete
Problems with Steel Fibers
Reduces the workability; loss of workability is proportional to volume
concentration of fibers in concrete Higher Aspect Ratio also reduced workability
Application of FRC in India & Abroad
More than 400 tones of Steel Fibers have been used recently in the construction of a road overlay for a project at Mathura (UP).
A 3.9 km long district heating tunnel, caring heating pipelines from a power plant on the island Amager into the center of Copenhagen, is lined with SFC segments without any conventional steel bar reinforcement.
steel fibers are used without rebars to carry flexural loads is a parking garage at Heathrow Airport. It is a structure with 10 cm thick slab.
Precast fiber reinforced concrete manhole covers and frames are being widely used in India.
Conclusion The total energy absorbed in fiber as measured by the area
under the load-deflection curve is at least 10 to 40 times higher for fiber-reinforced concrete than that of plain concrete.
Addition of fiber to conventionally reinforced beams increased the fatigue life and decreased the crack width under fatigue loading.
At elevated temperature SFRC have more strength both in compression and tension.
Cost savings of 10% - 30% over conventional concrete flooring systems.
References
K.Srinivasa Rao, S.Rakesh kumar, A.Laxmi Narayana, Comparison of Performance of Standard Concrete and Fibre Reinforced Standard Concrete Exposed To Elevated Temperatures, American Journal of Engineering Research (AJER), e-ISSN: 2320-0847 p-ISSN : 2320-0936, Volume-02, Issue-03, 2013, pp-20-26
Abid A. Shah, Y. Ribakov, Recent trends in steel fibered high-strength concrete, Elsevier, Materials and Design 32 (2011), pp 4122–4151
ACI Committee 544. 1990. State-of-the-Art Report on Fiber Reinforced Concrete.ACI Manual of Concrete Practice, Part 5, American Concrete Institute, Detroit,MI, 22 pp
Contd.
P.K. Mehta and P.J.M. Monteiro, Concrete: Microstructure, Properties, and Materials, Third Edition, Fourth Reprint 2011, pp 502-522
ACI Committee 544, Report 544.IR-82, Concr. Int., Vol. 4, No. 5, p. 11, 1982
Hanna, A.N., PCA Report RD 049.01P, Portland Cement Association, Skokie, IL, 1977
Ezio Cadoni ,Alberto Meda ,Giovanni A. Plizzari, Tensile behaviour of FRC under high strain-rate,RILEM, Materials and Structures (2009) 42:1283–1294
Marco di Prisco, Giovanni Plizzari, Lucie Vandewalle, Fiber Reinforced Concrete: New Design Prespectives, RILEM, Materials and Structures (2009) 42:1261-1281
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