THE RECENT ITALIAN EXPERIENCE ON POROUS ASPHALT. THE "DDL" PAVEMENT. (DOUBLE DRAINING LAYER)

The application of porous asphalt pavements on the Italian motorway network has interested more than 10,000,000 mq, in the last 5 years. A new porous asphalt pavement, named "DDL" (Double Draining Layer), has been recently developed by "Autovie" Road Research Center with the following goals: to increase the durability and drainage performance; to increase the skid resistance and the sound absorbing characteristics; to facilitate the periodical cleaning of the pavement; to reduce the production cost of a porous pavement. To this purpose, after the laboratory research for the optimization of asphalt mixes, a new pavement has been realized, with the application of two draining layers: the under layer of 3 cm thickness, with calcareous low cost aggregates (0-12 mm); the surface layer of 1.5 cm, with basaltic aggregates (0-6 mm). For both layers a hard modified bitumen is used (5% weight on the mix). At the base of the pavement a type SAMI layer (1.5-2.0 Kg/mq) with modified asphalt is employed. The pavement has been applied for the first time on the AUTOVIE VENETE (Venice-Trieste Motorway) network in September 1995. A more extensive application has been realized in 1996. For the mix design a special attention was paid, in order to increase the drainage and sound absorbing properties, in comparison with traditional porous asphalt pavements. (A) For the covering abstract see IRRD 890329.