Ultra thin white topping

Thin white toppings (TWT), as originally developed in the USA in 1918 as a quick, cost-effective and long-lasting rehabilitation solution are, in majority, placed as an overlay on deteriorated asphalt pavements. Usual thicknesses were 150 – 225 mm but since the last 30 years also ultra thin white toppings (UTWT) with thicknesses of 75 – 150 mm are used as an overlay on both asphalt- and cement concrete. Applications are not always successful; the problems are often related to the imperfect bonding to the layer underneath and to the thickness of the TWT or UTWT. A high shrinkage, curling, debonding, crack distribution and large crack widths are the most common problems. Load distribution is based on the effective thickness of the concrete layer placed and the stiffness and quality of the sub layers. Steel reinforcement and/or steel fiber reinforcement contribute only little to this.

The development of High Performance Concrete and Ultra High Performance Concrete made it possible to reduce the cover on the reinforcement and to utilize the reinforcement much more efficiently. The Contec Ferroplan® as developed by Contec ApS makes new applications for UTWT possible. The Contec Ferroplan® not only functions as an independent overlay regardless the type, quality and condition of the sub base but can also give an additional strength to the underlying structure due to the very high stiffness and thus load spreading capacities in combination with bonding (anchors, intermediate layer, etc.). We recommend a fully bonded Contec Ferroplan® on the sub base. Bonding can be obtained by a mechanical bonding with anchors, by creating a rough interface (cold milling, shot blasting, etc.) between the Contec Ferroplan® and sub base or to apply a thin (20 - 30 mm) new asphalt layer on the sub base. In some cases it will be necessary to make special edge details at the joints between the Contec Ferroplan® and other material and at the sides to avoid peel stresses. 


Application of the Contec Ferroplan® is possible with traditional equipment like for instance: slipform paver, laserscreed and vibration screed.