Fiber-Reinforced Concrete: All You Need To Know

Whether you build your dream home or commercial structure, almost every type of construction uses concrete. Concrete is a mixer of cement, sand, coarse aggregate and water. Because of its extreme durability, strength, and versatility, it’s the most widely used building material worldwide. Even under extreme weather conditions and compressive and tensile stresses, the architectural stability of the concrete structure remains intact.

You can use concrete for various structures, including buildings, roads, parking structures, bridges, highways, foundational surfaces, and much more. Concrete gives more strength in compression stress than tensile stress; hence, steel rebar reinforcement is used to construct many concrete structures to improve their tensile strength and capacity to support any other significant loads. Combining the tensile strength of the reinforcement material with the compressive strength of the concrete increases its overall durability. Hence, fibre-reinforced concrete has become popular in the construction industry.

So, in this blog, Brick & Bolt brings a detailed guide on fibre-reinforced concrete, including what it is, the different types of fibers used in it, its uses, benefits and disadvantages.

What is Fiber Reinforced Concrete?

Glass fibers or other fibrous materials, either natural or synthetic, are added to concrete mixtures to create fibre-reinforced concrete. In other words, it’s composition of cement, sand, aggregates, water and discrete, short fibers distributed evenly throughout the material.

Fibers improve the overall energy absorption and structural integrity of concrete and reduce the risk of cracking. However, fibres are weak in flexural strength- the bending capacity of the concrete without breaking, so they are not a substitute for steel reinforcement concrete.

When blending fiber-reinforced concrete, two factors to consider are the fiber size, also known as the aspect ratio, which is the length of the fiber divided by its diameter, and the water-cement ratio. Since the volume of fibers used in the concrete can affect the strength and durability of the structure, it is also important to consider the percentage of fiber you use in the concrete. Fiber-reinforced concrete should be mixed uniformly without separating the mixtures. In order to prevent fibers from balling together, they must be added before the water is mixed in. This should ideally be done with a laboratory mixer and filtered through a wire mesh basket.

Different Types of Fibers Used in Fiber-Reinforced Concrete

The following types of fibers are used in fiber-reinforced concrete. 

• Steel Fibers

Steel fibers are typically added to concrete to increase its strength and ability to support loads after cracks. Steel fibers for concrete are typically loose or bundled, formed into various geometries- such as crimped, hooked-end, or with other mechanical deformations for anchorage in the concrete—and made of carbon or stainless steel. 

• Glass Fibers

The main applications for glass fiber-reinforced concrete (GFRC) are in architecture and the modification of cement-based panel structures. Glass fibers can be used in concrete to create lighter, more contemporary, and aesthetically beautiful structures, such as architectural cladding for buildings or furniture.  

• Natural Fibers

All over the world, natural fibers are utilised in non-commercial applications to strengthen cement-based products. They are made of different natural materials, including sugarcane, coconut, sisal, jute, and other materials, and they have different lengths, shapes, and properties.

• Synthetic Fiber

There are two types of synthetic fibers- micro-fibers and macro-fibers.Micro-fibers, which are often composed of acrylic, polyester, nylon, or polypropylene, among other materials, are used in concrete to minimise shrinkage cracks. However, in concrete structures where high tensile strength is required, macro-fiber is a more affordable reinforcement option than welded wire. Common structures constructed with microfibers added to the mix include sidewalks, curbs, and driveways; common structures constructed with macro-fibers include septic tanks and manholes. 

In the construction industry, fiber-reinforced concrete is also known by different names according to the type of fiber used in concrete, such as steel fiber-reinforced concrete, glass fiber concrete, etc.

Use of Fiber Reinforced Concrete

Fiber-reinforced concrete functions totally rely on how the contractor uses the material's static and dynamic properties. Among the areas it can be used in are:

• Roads

• Bridges

• Runway

• Thin Shell

• Walls

• Pipes

• Aircraft Parking

• Pavements

• Manholes

• Dams

• Tunnel Lining

• Slope Stabilisation

• Hydraulic Structure

• Elevated Decks, etc.

Benefits of Fiber-Reinforced Concrete

The following are the benefits of fiber-reinforced concrete:

1. Fiber-reinforced concrete improves the tensile strength of the concrete.

2. It improves the durability of the concrete.

3. It minimises the water and air voids that contribute to the natural porosity of the gel.

4. Fibres are more resistant to creep; hence, the creep performance of rebars is greatly influenced by the orientation and volume of fibers.

5. It prevents cracks and increases the static and dynamic properties of the concrete.

Disadvantages of Fiber-Reinforced Concrete

The following are the disadvantages of fiber-reinforced concrete:

1. To make fiber-reinforced concrete, the fibers must be evenly and carefully distributed throughout the concrete mixture. If it's mixed incorrectly, there can be a significant margin of error. It’s crucial to ensure that the fibers do not bunch up.

2. Fiber-reinforced concrete is costlier than non-reinforced concrete. 

3. The weight of fiber-reinforced concrete is more than plain concrete, ultimately, it increases the overall weight of the structure.

4. It requires skilled labourers to work with.

Conclusion

In conclusion, concrete continues to be a basic building material because of its strength and durability. Fiber-reinforced concrete has evolved to address specific challenges like energy absorption and cracking by incorporating fibers like steel, glass, and natural and synthetic fibers. Although fiber-reinforced concrete has better durability and tensile strength, it has drawbacks such as heavier weight, more expensive, and specific mixing needs. The best way to use fiber-reinforced concrete in different types of structures will depend on how the construction industry innovations are going forward and how carefully the advantages and disadvantages of the material are evaluated.

Image Source- Image 1 - Civil Engineering Forum