Omslagstitel: Optimization of reclaimed asphalt plant mixing

Asphalt mixtures are commonly used for surface layer on the European roads. At the end of the service lifetime of a road or even when maintenance works are performed, surface layers are first removed from the road. Asphalt surface layers are often the most expensive part of road construction and represent useful secondary raw materials. The most proper way of recycling asphalt removed surface layers is to reuse it again in new surface layer. Due to different step of technological development and public awareness asphalt recycling rate in Europe vary from 90% to less than 10%. Selection of case studies in this Deliverable reflects different step of recycling in Europe. In Belgium Denmark, Germany, Netherland and Sweden practically all asphalt plants are equipped to perform "mix in plant" recycling often applying a separate heating of RA and hot mix stone fractions. With this technology content of reclaimed asphalt in a freshly produced asphalt mix is usually round 45% for batch plants and a bit more drum mixer plant. In Denmark and Germany asphalt plants were commonly equipped with parallel drum dryer for heating the reclaimed asphalt, but nowadays some of the asphalt plant had recently been through a general refitting which resulted in a new configuration so that the virgin drum dryer had been modified with the high speed conveyor belt for throwing in the RA material into the last part of the drum dryer and the parallel drum dryer that formerly heated the RA for reaching high percentages of addition had been dismantled. In Sweden the usage of technology of half-warm and cold asphalt recycling at a central plant is determined by National Road. For hot recycling the Swedish administration allows the blending of RA materials in accordance with TBV-coating 99 as follows: - max 20 % for wearing courses, - max 30 % for binder and base courses. Interesting are technologies of cold and half-warm recycled asphalt at a central plant. Produced asphalt mixtures are mostly used for roads with low traffic loads. In Portugal and Slovenia only some asphalt plants recycle asphalt. The asphalt plants that use reclaimed asphalt (RA) are not equipped with additional technology such as parallel drum enabling usage of more than 30% RA in new asphalt mixture. So case studies in these countries are oriented more to increase of RA percentage in new asphalt with minor adaptations of existing technology. In UK capability of batch plants to add RA to the mixture varies considerably from less than 10 % up to 50 % depending on the methods available to add RA to the mixture. With studies they found out that asphalt plant tended to be the limiting factor in addition of RA to the mixture rather than the grading compatibility in cases where surfacing materials were planed off and stored separately from the lower layers. Best Practice guide was produced from further research undertaken into surface course recycling.