Fibre Reinforced Concrete
Need?
PCC has low tensile strength, limited ductility and little resistance to cracking. PCC develops micro-cracks, even before loading. Addition of small, closely spaced and uniformly distributed fibres act as crack arresters.

Fibre Reinforced Concrete is a composite material consisting of mixtures of cement, mortar or concrete and discontinuous, discrete, uniformly dispersed suitable fibres.
Factors Affecting The Properties Of Fibre Reinforced Concrete
- Relative Fibre Matrix Stiffness
- Volume of Fibres
- Aspect Ratio of the Fibre
- Orientation of Fibres
- Workability and Compaction of Concrete
- Size of Coarse Aggregate
- Mixing
Relative Fibre Matrix Stiffness
Modulus of elasticity of matrix must be much lower than that of fibre. E.g. steel, glass, carbon
Fibres with low modulus of elasticity- nylon, polypropylene
Interfacial bond between the matrix and the fibres determine the effectiveness of stress transfer
Orientation of Fibres
The effect of randomness, was tested using mortar specimens reinforced with 0.5% volume of fibres, by orienting them:
- parallel to the direction of the load
- perpendicular to the direction of the load
- in random
Workability and Compaction of Concrete
Fibres reduce workability
Size of Aggregate
Size of CA is restricted to 10mm
Mixing
Cement content : 325 to 550 kg/m3
W/C Ratio : 0.4 to 0.6
% of sand to total aggregate : 50 to 100%
Maximum Aggregate Size : 10 mm
Air-content : 6 to 9%
Fibre content : 0.5 to 2.5% by vol of mix
- Steel -1% – 78kg/m3
- Glass -1% – 25 kg/m3
- Nylon -1% – 11 kg/m3
Introduction of steel fibres modifies:
1.Tensile strength
2.Compressive strength
3.Flexural strength
4.Shear strength
5.Modulus of Elasticity
6.Shrinkage
7.Impact resistance
8.Strain capacity/Toughness
9.Durability
10.Fatigue
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