Federal Highway Research Institute

OBAS

Optimizing the surface design of asphalt pavements

Demonstrating the application of an optimised type of paver screed.

Installation of asphalt pavement

Background

During the paving process of asphalt surface layers chippings are applied to enhance the initial skid resistance. Usually the chippings are applied by rollers and integrated into the layer during compaction. At that rather late point in time the integration of the chippings could be unsatisfactory. In addition the applied rate of material could vary depending on the technique used, or the applied material overlaps due to the limited width of the roller drums.

Concept

The picture shows a roadsurface while fabrication Application of the asphalt surface layer at duraBASt

After a basic study on the influence of chippings on the structure of a road surface (texture), the OBAS project designed a new type of paver screed which applies the chippings in the paver and integrates them into the hot non-compacted asphalt by the screed. The design of a paver screed allows different positions: before, within or after the screed. After basic considerations three positions were designed and constructed. The supply of the chippings to the screed had also to be designed and is carried out, comparable to the hot mix, from the front with an additional hopper. Likewise the feeding components were designed and built.

Objectives

Besides the reduction of the chippings used, the advantages of this new type of construction are the homogenous application and integration of the chippings near an optimum. In addition the precise application of the material allows influencing surface characteristics like brightness.

Conclusion

On the duraBASt a first practical test was carried out with the optimized screed and the material transfer system for the chippings, which consists of a hopper and the feeding components. As suggested by initial tests, the position directly behind the screed was chosen to apply the chippings.

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