Fibre reinforcement of concrete is a superior alternative to traditional methods of reinforcing concrete. Depending on the project, fibre type and dosage, even primary steel reinforcing can be replaced with our fibres. Using fibres can result in faster construction, less risk, better long-term performance, cost savings, etc.
Concrete - why reinforce?
Portland cement concrete is a brittle material made by chemical reactions with primarily water and cement to bind and hold together coarse and fine aggregate. Reinforcement for concrete is not a material, such as steel, but whatever holds broken concrete together and redistributes stresses before and after concrete cracks. Reinforcement allows the concrete to continue to perform when cracked. However, apart from structurally reinforced concrete, uncracked concrete is stronger than cracked concrete with reinforcement. Below we explore ways of improving and reinforcing concrete.
Concrete can be placed unreinforced and this relies on proper placement, sizing, saw cuts/joints, curing, etc to ensure that uncontrolled cracking does not occur. Unreinforced concrete relies on the aggregate interlock to hold any cracks together. However, typically once a crack develops in unreinforced concrete, it will open up thereby significantly reducing the ability of the concrete to carry a load which means failure at some point. Level 1 fibres are recommended for concrete that would traditionally be placed as unreinforced concrete. Applications include:
Traditionally steel is used to reinforce concrete. For slab on ground, this is most commonly wire mesh. However, wire mesh has many disadvantages when compared to fibre reinforcement. These include:
Rusting - wire mesh rusts and when the concrete cracks, the wire mesh is no longer protected within the concrete leading to further rust and failure
Safety - handling and cutting can lead to workplace injuries
Positioning - for wire mesh to work properly as a reinforcement for concrete, it must be correctly placed within the slab. However, all too often, workers place the mesh on the ground and lift it when pouring concrete.
A single plane of reinforcing. Wire mesh only reinforces the concrete near it; all the other concrete is unreinforced.
Does not offer any early age benefits to concrete such as reducing plastic shrinkage cracking.
Doesn't improve impact or abrasion resistance of concrete
Does not interact with the paste of concrete which is where cracking develops
Level 2 and Level 3 fibres are recommended for concrete traditionally reinforced with wire mesh. More information on which fibre system is appropriate for the application can be found on this page and on the Reinforcement Levels page.
Fibres are a means of reinforcing concrete and include steel, synthetic, glass and natural fibres. Fibres are discontinuous as opposed to continuous conventional reinforcement, so the mode of failure is not usually by yield of the materials (for steel that would be the steel snapping) but by pull out of the fibres at the matrix (concrete) – fibre interface. FRC fibres provide significant advantages over traditional steel reinforcement, most notably that the fibres are distributed everywhere throughout the slab to help resist cracking, rather than in one plane only. Conventional steel reinforcement requires cracking some distance through the concrete before it is useful and this cracking leads to issues such as corrosion of the steel and failure of the concrete above the steel. FRC fibres are automatically placed in the correct location (as they are mixed through the concrete) and provide three-dimensional reinforcement throughout the concrete slab. FRC fibres can be divided into 3 levels of reinforcement - Level 1, Level 2 and Level 3.
Level 1 fibres are mostly used for applications requiring enhanced performance over plain unreinforced concrete. They are used to reduce plastic shrinkage cracking (cracking that occurs as soon as concrete is poured and for the first 24 hours) prior to initial set. These fibres have a very low ability to hold cracks together should they occur after the first 24 hours. The high fibre count is designed to reduce or eliminate plastic shrinkage cracking and therefore the potential for hardening shrinkage cracking.
Level 2 fibres are used for applications that need to reduce plastic shrinkage cracking and hardening shrinkage cracking. They can be used as an alternative to wire mesh for many applications and offer a higher level residual strength should a hardening shrinkage crack occur - they can hold the crack tight.
Level 3 fibres are used for applications that need to reduce plastic shrinkage cracking, hardening shrinkage cracking, extend joint spacing, reduce slab curling and to carry more load that Level 1 and Level 2 fibres. Furthermore, Level 3 fibres can replace greater levels of steel reinforcement or be used in conjunction with steel reinforcement to reduce bar thicknesses and spacing.
Fibre Reinforced Concrete Ltd: A division of Stratmore Construction Solutions Ltd