Fiber Reinforced Concrete (FRC)

Fiber reinforced concrete (FRC) is a special type of concrete that is made of hydraulic cement and special aggregates by incorporating discrete and discontinuous fibers. The fibers used in concrete helps to provide greater resistance to plastic shrinkage cracking and other service related concrete. The fibres are added to concrete during the production of concrete.

Fiber Reinforced Concrete (FRC)

FRC posses widespread use in shotcrete and in thin overlay structures where it is difficult to accommodate reinforcing bars ( less thick structures) and for good resistance to impact, vibration and blast.

Fiber Reinforcement and Steel Reinforcement in Concrete

Plain concrete is a brittle material, whose low strength and strain capacities is managed by the addition of steel reinforcement. With the existing successful and major use of steel reinforcement in concrete, there has been widespread studies conducted in the use of fibers in concrete. Hence, fibers in concrete is not intended to increase the strength of concrete, instead its role is to control cracking and alter the material behavior when it undergoes any form of cracking.

Note : Conventional reinforcing bars are used to increase the load-bearing capacity of concrete. Fibres are used to have effective crack control in concrete structures.

When plain or unreinforced cementitious materials  (Brittle materials) require reinforcement other that normal steel rebars to improve the cracking resistance, fibers are used as a solution. Fiber reinforcement unlike conventional or steel reinforcement bars are discontinuous and are randomly distributed throughout the cementitious matrix. 

Hence, it must be recognized that fiber reinforcement is not a substitute for conventional reinforcement bars. Both have different roles to play in influencing the concrete behavior. There are many applications where, fibres are used alone or along with conventional reinforcement. 

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Applications of Fiber Reinforcement in Concrete

The applications of FRC can be more precisely explained through the applications of fibers in concrete. Generally, fibers can be used either as a primary reinforcement or as a secondary reinforcement. Let us explains different applications where the fibers are used as primary and secondary reinforcement.

1. Fiber Reinforced Concrete (FRC) for Thin Sheet Components

The construction of thin sheet components using conventional reinforcing bars is not possible. In which, fibers are used in a relatively high amount in a range exceeding 5% volume of the concrete. Hence, the fibers used act as primary reinforcement which takes the objective to increase both the strength and toughness of the composite. Such fiber rich concrete is called as High Performance FRC.

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2. Fiber Reinforced Concrete (FRC) for High load or Deformation Withstanding Structures

Structures like tunnel linings, blast resistant structures or precast piles that are required to be hammered to the ground are best constructed using FRC.

3. FRC to Control Cracking in Concrete Slabs and Pavements

Fibers can be added into components to control cracking induced in concrete elements caused due to humidity and temperature variations in slabs and pavements. Here, FRC is added along with conventional steel reinforcement. Hence, here fibers forms secondary reinforcement. These fibers helps to provide post-cracking ductility. This type of composite material is called as conventional FRC.

Typical Stress-Strain Curves for Conventional and High-Performance FRC as per ACI 544
Fig.1. Typical Stress-Strain Curves for Conventional and High-Performance FRC as per ACI 544

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