Pouring fibre reinforced concrete: the complete guide

Considering fibre reinforced concrete for your project? This guide walks step by step through the process, from initial orientation through to the pour itself, so you know what to expect.

Step 1: Determine the objective

Before choosing a fibre type, it is important to be clear about what you want to achieve:

• Structural strength (for example, to replace reinforcement mesh in an industrial floor) → steel fibre or macro synthetic fibre.

• Shrinkage crack control during early curing → micro synthetic fibre.

• Corrosion resistance in a damp or chemically exposed environment → synthetic or basalt fibre.

• A combination of requirements → often a hybrid solution using multiple fibre types.

Step 2: Ask for advice on fibre type and dosage

The right dosage depends on the load, the slab thickness and the desired result. For steel fibre the usual dosage is typically between 25 and 50 kg/m³; for synthetic fibre it is usually between 0.5 and 2.5 kg/m³. For structural applications (where fibres replace traditional reinforcement), a reinforcement study or calculation is often required — this can be carried out by the fibre supplier together with a structural engineer.

Step 3: Consult your structural engineer

For non-structural applications (yard pavements, light foundations, screeds), fibre reinforcement is often directly applicable. For primarily structural elements — such as heavily loaded floors, foundations under buildings, or bridges — consultation with a structural engineer is essential to determine whether, and how much, traditional reinforcement is still required alongside the fibres.

Step 4: Order the right mix from the concrete plant

Fibres are added during mixing at the concrete plant — this is a standard order, not a separate operation. When ordering, clearly state the desired fibre type and dosage, and check whether the concrete plant has experience with the specific fibre type for your application.

Step 5: Prepare the formwork

Because no reinforcement mesh needs to be positioned, formwork preparation time is shorter than with traditional reinforcement. Do pay attention to a sound substrate: when pouring onto sand, for example, water from the concrete mix drains away through the sand layer, which can lead to premature crack formation — an intermediate layer (such as sheeting) is then advisable, regardless of the chosen reinforcement type.

Step 6: The pour itself

Fibre reinforced concrete, when correctly dosed, can be poured and worked easily — including with a concrete pump. At higher dosages, a slightly wetter (more fluid) consistency may be needed to safeguard workability; discuss this with the concrete plant beforehand.

Step 7: Curing

Curing (protecting against overly rapid drying, frost or excessive loading during hardening) does not differ fundamentally from traditional concrete. Fibres do help limit shrinkage cracks during this phase, but they do not remove the need for careful curing.

Common mistakes to avoid

• Too low a dosage for the intended load — always have this calculated.

• No consultation with the structural engineer for structural applications.

• The wrong fibre choice for the environment (for example, steel fibre in an environment with a lot of moisture and chlorides, where corrosion is a concern).

• Insufficient coordination with the concrete plant on the desired consistency and workability.

In conclusion

Pouring fibre reinforced concrete is, at its core, a standard concrete pour, with the main difference being that the reinforcement is already in the mix rather than placed separately. Good preparation — the right fibre type, the right dosage and timely consultation with your structural engineer — is the key to a successful result.