Fibre Reinforced Concrete

Fiber-reinforced concrete is a construction material produced from cement and cementations materials such as fly ash, slag materials, aggregate, water, and chemical mixtures.

This concrete exhibits many desirable properties such as high compressive strength, hardness and durability.

Here we’ll learn about fibre reinforced concrete, kinds of fibre reinforced concrete & what are applications of fiber reinforced concrete?

Introduction to fibre reinforced concrete:

Fibre-reinforced concrete (FRC) is concrete by which small and discontinuous fibers are uniformly dispersed.

Fiber reinforcement is one of the efficient methods to enhance the properties of concrete, the addition of fiber to the concrete makes it homogeneous and isotropic materials.

Fibers used in fiber reinforced concrete might be various materials such as metal, G.I., carbon, asbestos, polypropylene, jute, etc

Fibre Reinforcement Concrete consists of any of the following four types of fibres:

1. Steel Fibers consisting of stainless steel, alloy steel, or carbon steel fibres.
2. Glass Fibers consisting of alkali-resistant (AR) glass fibres.
3. Synthetic Fibers consisting of polyethene, polypropylene, nylon or carbon fibres.
4. Natural Fibers consisting of cellulose fibre.

Type of Fiber Reinforced concrete:

1.Natural fibres:

The oldest forms of fiber-reinforced composites had made with naturally found fibers such as straw and horsehair.

Modern technology has made it possible to economically extract fibers from various crops such as jute and bamboo in cement composites.

A unique aspect of those fibers is the low amount of energy required to remove these fibers, the defect of mixing and uniform dispersion can be solved by adding a superplasticizer.

A natural fiber are bamboo fiber, coconut fiber and jute fiber.

2.Glass fibre:

Glass fiber is especially used for glass fiber reinforced concrete sheets, common e-glass fibers had been found in concrete.

This observation led to the development of alkali-resistant AR-glass fibers.

However, the use of glass fibre in Portland cement products has two primary issues, i.e., the breakdown of the fibre by the excessive alkalinity of the hydrated cement paste and the degradation of the glass floor.

3.Carbon fibres:

Carbon fiber has a higher modulus of elasticity with 2 to 3 times stronger than steel.

They are also very light with particular gravity and also inactive for many chemicals.

4.Polymeric fibres:

Artificial polymer fibers have been produced because of the research and development of the petrochemical and textile industries.

The forms of fiber which have been strained with cement matrices include acrylic, aramid, nylon, polyester, polyethylene, and propylene.

All these fibers have excessive tensile strength, besides that aramid fibers have a decrease modulus of elasticity.

The first limitations that include Aridum fibers are their high cost.

5.Metallic fibres:

Metallic fibers are made from metal, the tensile strength of fibers ranges from 345MPa to 1380MPa, the modulus of elasticity is about 200GPa.

Fibers could also be rectangular, square or irregular, the length of the fiber is generally lower than 75 mm.

The aspect-ratio varies from 30 to 100.

Mechanical properties of fibre reinforced concrete:

Compressive Energy:

The presence of fibres can change the failure mode of the cylinder, but the impact of the fiber on the improvement of compressed strength values (0 to 15 %) will be minor.

Modulus of elasticity:

The modulus of elasticity of FRC will increase slightly with increase in fiber content.

It was found that for every 1 % increase in fiber content by quantity, the modulus of elasticity increased by 3 %.

Flexure strength:

Flexural strength was reported to increase 2.5-fold using 4 % fiber.

Splitting Tensile Strength:

The presence of 3% fiber by volume was reported to increase 2.5 times the tensile mortar splitting without any negotiation.

Toughness:

For FRC, toughness is about 10 to 40 times that of plain concrete.

Fatigue Strength:

Addition of fibers will increase fatigue by about 90 %.

Impact resistance:

Depending on the amount of fiber, the impact strength for fibrous concrete is typically 5 to 10 times that of plain concrete.

difference between fibre reinforced concrete and normal reinforced concrete:

Fibre Reinforced Concrete	Normal Reinforced concrete
High Durability.	Lower Durability.
Protect steel from Corrosion.	Steel potential to corrosion.
Lighter materials.	Heavier materials.
With the same volume, the strength is greater.	With the same volume, the strength is less.
More expensive.	Economical.
Much less workability.	High workability as compared to FRC.

Advantages of fibre reinforced concrete:

• FRC will increase the tensile strength of the concrete.
• This reduces air and water content that prevents the underlying opening of the gel.
• Also increases the durability of the concrete.
• The primary function is to bond the cracks that develop in concrete and enhance the ductility of concrete elements.
• This improves the post-cracking behavior of concrete.
• This supplies greater resistance to impact load.
• In addition, controls plastic shrinkage cracking and drying shrinkage cracking.
• This reduces the permeability of concrete matrix, thus decreasing water bleeding.
• It has the ability to reduce CO2.
• This concrete increased fire resistance.

Disadvantages of fibre reinforced concrete:

• This concrete enhances in specific gravity of concrete.
• It proportions the exact amount of fibre in a batch of concrete.
• It has a higher price due to its control issues as well as higher raw materials costs.
• Additionally, there is corrosion of steel fibre.

Application of fibre reinforced concrete:

Tunnel lining and slope:

Stabilization Metal fiber reinforced concrete is used to line underground openings and rock slope stabilization.

This eliminates the need for mesh reinforcement and scaffolding.

Dam and Hydraulic:

Construction FRCs are used in construction repairs and other hydraulic structures to provide resistance to cavities and severe erosion due to the impact of large particles.

Thin shells, walls, pipes and manholes:

Fibrous concrete permits the use of thin flat and curved structural components.

Metal fibrous shotcrete is used within the construction of hemispherical domes.

Agriculture:

It’s used in animal storage constructions, walls, silos, paving, etc.

Precast Concrete and Merchandise:

It’s used in architectural panels, tilt-making, walls, fencing, septic tanks, oil mesh structures, vaults and sculptures.

Commercial:

It is used in exterior and interior floorings, slabs, parking areas, roadways, etc.

Warehouse / Industrial:

It is used in the light to heavyweight flooring.

Residential:

It is used in driveways, sidewalks, pool construction, cellars, foundation, coloured concrete, drainage, etc.

Blast resistant structures:

When plain concrete slabs are traditionally reinforced, tests show that there is no reduction within the velocity of the piece or the number of items under explosion and shock waves.

Similarly, reinforced slabs of fibrous concrete, however a 20% relaxation in velocity greater than 80% within the fragments.

Tunnel lining and slope stabilization:

It is used for underground openings and rock slope stabilization that eliminates the need for mesh reinforcement and scaffolding.

Also read: Concrete Screed, Concrete forms & Concrete Spalling

Conclusion:

The efficient use of fibrous concrete has various properties such as tensile strength, impact strength, and fatigue strength.

At elevated temperatures, SFRC has greater strength in both compression and tension.