Perfectly bonded layers withstand traffic loads.

Replacing the entire pavement at full depth is not necessary when damages are limited to the road surface. Paving thin layers in hot application is a viable option for rehabilitating such roads. How does the method work? What are the advantages of paving thin layers in hot application?

Rehabilitation methods that can be carried out both quickly and with economic efficiency are becoming increasingly important worldwide. Paving thin layers in hot application is such a method, offering an exceptionally economical alternative to full pavement rehabilitation. Paving thin layers in hot application is eminently suitable for roads in need of rehabilitation but with damages limited to the surface, or poor grip, or pronounced surface irregularities. The surface properties of worn-out roads, such as grip, evenness and noise reduction, can be improved significantly for extended periods of time.

Perfect bond between layers is vital

In a preliminary operation, surface deformations are removed by cold milling machines fitted with fine milling drums to create an even, slightly roughened road surface. The road texture produced by fine milling offers an ideal base which ensures an excellent bond with the thin pavement layer to be applied. Paving thin layers in hot application is typically carried out by a road paver with an integrated spray module.

Spraying the tack coat

When using a paver with integrated spray module, the paver seals the base by spraying a tack coat of polymer-modified bitumen emulsion with a minimum bitumen content of 60% in an automated operation, and then applies a 1.2 cm to 2.0 cm thin asphalt surface course in a second operation immediately afterwards, but all in one single pass. When a conventional road paver is used, the bitumen emulsion needs to be sprayed in a separate operation prior to applying the new, thin pavement layer.

Rollers create an even road surface

Compaction is a big challenge when paving thin layers in hot application, as it requires the layers to be compacted uniformly but without causing irregularities in the surface. Moreover, the specified density needs to be achieved without damaging the underlying, cold pavement layers. These prerequisites require the use of high-quality rollers. Dynamic compaction with oscillation is the ideal compaction method. Alternatively, such layers can be compacted using static rollers, whereas compaction with vibration is not allowed.

Economical use of material saves costs

The small layer thickness of the new surface course helps to keep the costs of this method of rehabilitation fairly low. Paving thin layers in hot application uses 30 kg to 50 kg of asphalt mix per m² of the new surface course, which is up to 50% less when compared to conventional “mill and fill” measures. Because it helps to save natural resources, paving thin layers in hot application is also beneficial to the environment.