White Topping: fibre concrete over asphalt

White Topping is a renovation technique in which a thin layer of (fibre) concrete is applied over an existing asphalt pavement. It is a lesser-known but promising technique for extending the lifespan of ageing asphalt. This article explains how it works and where fibre reinforcement fits in.

What is White Topping?

With White Topping, a layer of concrete — often relatively thin, sometimes only a few centimetres — is applied directly over an existing, ageing asphalt pavement. Rather than fully removing and replacing the old asphalt, the asphalt layer functions as the foundation for the new concrete layer. This makes the technique particularly attractive for renovation projects where full replacement would be costly or time-consuming.

Why fibre reinforcement with White Topping?

• Thin layer thicknesses call for crack control. Because White Topping layers are often thinner than a regular concrete pavement, the structure is more susceptible to cracking from shrinkage and temperature fluctuations. Fibre reinforcement (particularly synthetic or basalt fibre) helps control this cracking without needing to reserve space for traditional reinforcement mesh, which is difficult to position in a thin layer.

• No separate reinforcement work step at a limited layer thickness. With a thin layer there is little room to position reinforcement mesh with sufficient concrete cover. Fibres, which are distributed homogeneously throughout the (thin) volume, do not have this problem.

• Faster execution on renovation projects. White Topping is often applied precisely because it is a faster renovation method than full replacement. Fibre reinforcement fits well here because no extra work step is needed for reinforcement.

Where is White Topping applied?

White Topping is applied, among other things, in the renovation of ageing industrial estates, car parks and specific road sections where the underlying asphalt structure still has sufficient bearing capacity, but the surface (rutting, ravelling) is due for replacement.

Points of attention

• Bond between the concrete and the underlying asphalt layer is a crucial point of attention with White Topping, regardless of the reinforcement type chosen.

• Assessment of the residual bearing capacity of the existing asphalt structure is needed before White Topping is applied — after all, the asphalt layer must continue to function as the foundation.

• Fibre type and dosage must be matched to the specific layer thickness and loading, preferably in consultation with a structural engineer.

In conclusion

White Topping with fibre reinforced concrete offers a promising, lesser-known renovation technique for ageing asphalt pavements, where the crack-controlling effect of fibres fits well with the limited layer thicknesses that characterise this technique.