Why is cold milling such an important part of the rehabilitation process?

"One thing is certain – paving thin layers hot only works if the base is sealed. It is important that the emulsion is applied uniformly over the entire surface and that the emulsion film is not damaged, i.e. torn open, before being covered with asphalt. Spray pavers are perfect for this. They make it possible to pave the asphalt directly after the emulsion has been sprayed on. This prevents the emulsion film from being “rolled up” by the tires of the transport vehicles, the feeder, or the paver. The amount of emulsion can be precisely controlled. This is extremely important because the amount of emulsion required is highly dependent on the condition of the layer that needs to be covered and the quality of the asphalt. This is what Vögele’s spray paver technology does to perfection. With VÖGELE’s spray pavers, you can set spray rates from 0.3 kg/m² to over 1.6 kg/m². And this is exactly what counts in everyday use."

What role does the asphalt mixture play?

"A major role. In 90% of the cases in Germany, the asphalt mix DSH-V 5 is used, an asphalt mixture that lies between stone mastic asphalt and asphalt concrete on the grading curve. It has a higher void content than conventional asphalt. The bituminous emulsion is sprayed onto the surface to seal it beforehand."

What needs to be kept in mind during final compaction?

"The binder accumulates artificially on the underside of the asphalt layer. The asphalt mixture itself only contains enough binder to ensure that the surface of the DSH-V layer doesn’t have to be roughened after paving, as is otherwise the case with all other rolled asphalt layers. The surface immediately exhibits the necessary grip. Spreading sand on the surface should be avoided. We recommend dynamic compaction with oscillation or static compaction. We don’t recommend using vibration. In order to retain the noise-reducing properties of the mixture, pneumatic tire rollers shouldn’t be used during final compaction. Admittedly, noise reduction is not quite as high as with OPA (open-pored asphalt), but it is significantly higher than with classic, dense asphalt surface layers."

What are the SmartSynergies benefits for the customer in this process?

"Our customers benefit from the expert advice we provide at our locations. Together, the WIRTGEN GROUP can supply perfectly compatible technologies for this process’s entire value chain – from the cold milling machine with fine milling drum to the mixing plant and spray paver to the right compaction technology. We are pioneers in all of these technologies, so our customers always receive leading products, reliable service solutions, and expert application consulting from a single source."