Advantages of Fibre-Reinforced Concrete

Concrete is an integral part of any construction project, whether you are building roads, a a ground floor in your private home, or a power plant. This is because concrete is very durable, but it can be susceptible to fractures as subsoil frosts and thaws, if it shifts, or if tree roots press upward on the concrete. This can be a major problem for construction projects, as fractures lead to costly repairs and could spell disaster. The solution to this problem is the introduction of reinforced concrete.

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What Does It Mean for Concrete to Be Reinforced?

Concrete is reinforced when it has suitable fibres in the mix to increase its toughness and ductility. Unlike non-reinforced concrete that is likely to break down when it fractures and cracks, reinforced fibre concrete will maintain its structural integrity, as it is held together by these fibres when a crack develops.

Suppose you are looking to embark on a construction project. In that case, you must analyse the advantages and disadvantages of using fibre-reinforced concrete, and the different types of fibres used. Trusted professionals like SB Civil Engineering would take this burden off you and ensure your project is completed hitch-free.

The advantages of fibre-reinforced concrete include the following:

• Fibre-reinforced concrete has more tensile strength when compared to non-reinforced concrete.
• It increases the concrete&#;s durability.
• It reduces crack growth and increases impact strength.
• Fibre-reinforced concrete improves resistance against freezing and thawing.
• Reinforcing concrete with fibre increases fatigue strength.

The disadvantages of fibre-reinforced concrete include the following:

• Rain might expose the fibres.
• Fibres randomly orient in the concrete and could result in poor quality concrete, if not uniform.
• Reinforced concrete is about 10% to 15% costlier than non-reinforced concrete.

Types of Fibre-Reinforced Concrete

There are several types of fibres used in reinforced concrete. Descriptions of the most common types follow.

Cellulose Fibres. These fibres are made with esters of cellulose or ethers obtained from plant leaves, wood, tree barks, or other plant material. The mechanical properties of these fibres can be altered by introducing lignin and hemicellulose in varying proportions. Cellulose fibres are majorly used in the textile industry as fibre reinforcement composites and chemical filters.

Natural Fibres. This fibre type is efficient and cost-effective; it is highly recommended as it is easy to source locally and readily available. Natural fibres can be obtained from a mineral source, animals, or vegetables, and processed into nonwoven fabric. The use of fibre in construction is not a new development, as horsehair and straws have been used in making plaster and bricks.

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Carbon Fibres. This type of fibre is composed mainly of carbon atoms with a diameter of 5 micrometres to 10 micrometres. There are many advantages to using carbon fibres; they include, but are not limited to, the following:

• It has a low thermal expansion.
• It has high chemical resistance.
• Carbon fibres have a high temperature tolerance.
• They are stiff, low weight, and have a high tensile strength.

Polyester Fibres. Polyester fibres are the preferred choice for warehouse and other industrial floors, pavements, and precast products. Polyester macro and microfibres are mixed with concrete to ensure structural integrity, toughness, and to protect against plastic shrinkage cracks.

Glass Fibres. Glass fibre shares many mechanical features and properties with other fibres like carbon fibre and polymer fibre. This type of fibre is less brittle when used in composites but not as rigid compared to carbon fibre. As a result, glass fibres are used as reinforcing agents for many polymer products, an example of glass-reinforced plastic, also known as fibreglass.

Polypropylene Fibre. Polypropylene, or PP, is a type of fibre used in concrete because it is resistant to drying shrinkage and plastic shrinkage. This fibre helps reduce water bleeding in concrete and reduces the concrete&#;s permeability significantly. Polypropylene fibre is a synthetic white rugged material with good insulating properties and has high resistance against chemicals like organic solvents, acids, and alkalis.

Steel Fibre. The right amount of steel fibre in concrete can change the concrete&#;s physical properties qualitatively. Adding steel fibre to the mix significantly increases the concrete&#;s durability, resistance to cracking, resistance to bending, strength, and toughness.

&#;This article was contributed to POWER by SB Civil Engineering.

tradesman said:

Hello guys, I am having my shop built this week, the size is 24' by 40' by 14 '. The floor spec is 6" thick with fiber and psi mix, my question is should I be using some sort of steel reinforcement also or is just the fiber as good. I will be install a Automotive lift and will be bring vehicle in and out a lot, any help would be appreciated.

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There are a number of threads that get into the technicalities of this, but:

- You are fine as-is. Your lift instructions don't tell you that you need rebar. They also don't tell you that you need fibers. The engineers who work for the lift manufacturer know something. (So you don't need to sweat too much or worry about analyzing too much. BTW - There are some members here who have done a great job with their slabs. There are also some members who have made some very poor choices with good intentions. Concrete is a heterogeneous material and does not behave like wood or steel.)

- As pointed out below, fiber and rebar - in the type of slab we are talking about here in a garage - are just for different types of crack width control. This time of year in PA, you don't need to worry about the type that fiber goes after. At 6" of depth, you are making a heavy investment in concrete and the slab will be very strong. So, you really don't "need" the rebar, either - if you do your control joints properly. (And you have a properly prepared base.)

So, rebar would just be a shrinkage crack insurance policy for you OR it would allow you to space your control joints further apart. If your concrete finisher has a rebar "formula" for a 4" slab, you would need to beef up the quantity of steel by 50% of you go to 6", etc. (The need is proportional to the thickness.) There are also engineering formulas for this if you want to get exotic on the spacing of the joints.


In the end, your time is most worthwhile to be spent on figuring out what your control joint cut plan is going to be. You'll want to work this out with your finisher. ALL slabs crack. (Generally, even when rebar is used.) The trick is to get the cracking to happen in your control joints.

So, you will want these control joints spaced properly away from your posts. (Your lift instructions will give you parameters for how far you need the posts to be away from joints or cracks.) This is the most important thing!

There are a number of threads that get into the technicalities of this, but:- You are fine as-is. Your lift instructions don't tell you that you need rebar. They also don't tell you that you need fibers. The engineers who work for the lift manufacturer know something. (So you don't need to sweat too much or worry about analyzing too much. BTW - There are some members here who have done a great job with their slabs. There are also some members who have made some very poor choices with good intentions. Concrete is a heterogeneous material and does not behave like wood or steel.)- As pointed out below, fiber and rebar - in the type of slab we are talking about here in a garage - are just for different types of crack width control. This time of year in PA, you don't need to worry about the type that fiber goes after. At 6" of depth, you are making a heavy investment in concrete and the slab will be very strong. So, you really don't "need" the rebar, either - if you do your control joints properly. (And you have a properly prepared base.)So, rebar would just be a shrinkage crack insurance policy for you OR it would allow you to space your control joints further apart. If your concrete finisher has a rebar "formula" for a 4" slab, you would need to beef up the quantity of steel by 50% of you go to 6", etc. (The need is proportional to the thickness.) There are also engineering formulas for this if you want to get exotic on the spacing of the joints.In the end, your time is most worthwhile to be spent on figuring out what your control joint cut plan is going to be. You'll want to work this out with your finisher.(Generally, even when rebar is used.) The trick is to get the cracking to happen in your control joints.So, you will want these control joints spaced properly away from your posts. (Your lift instructions will give you parameters for how far you need the posts to be away from joints or cracks.) This is the most important thing!

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