The main characteristic of double draining layer flexible pavements is touse different gradation aggregates for the different layers, according tothe specific task that each layer has to perform. Particularly strong basaltic aggregates, which are able to resist the stresses produced by traffic, are used for the top layer mixture, while calcareous aggregates, which are ideal for open mixtures with good draining characteristics, are used for the bottom layer. The function of the top layer, which has a higher density, is to filter surface dust and impurities, protecting the bottom layer which truly performs the draining action. The paper presents the resultsof an experimental study of such a kind of mixture. In particular, the analysis of the permeability test results shows that a double layer system provides excellent permeability coefficient values K and performances whichare very similar to those shown by a traditional mono-draining layer mixture. Also the mechanical characteristic tests carried out have provided excellent resistance values for bottom and top layers.
Abstract