A performance comparison between mechanical and superficial characteristics of a draining bituminous wearing course and a twin-layer

The necessity for safer wearing courses drove, in the last years, many researchers to bring to perfection the development of draining and noise reducing asphalt pavements. This kind of bituminous road surface, indeed, can significantly reduce the risks for users in case of rainfalls, thanks to the rapid superficial water removal, the reduction of noise due to vehicle movement being also involved, as well as an overall improvement in the grip performances. During this research, the Authors compared the mechanical and superficial performances of two draining and noise reducing bituminous pavements laid in the city of Potenza, thanks to the help of the Provincial Administration. In particular, a typical draining wearing course was considered, the overall performances being compared to the corresponding characteristics of an innovative twin-layer made of two bituminous layers one on the other. The grading curve of both road typologies were chosen in order to fulfil the requirements of the sieve analysis of SITEB (Italian Association of Bitumen Workers). Apart from the usual tests for the assessment of mechanical performances, some measurements were performed so as to evaluate the real improvements of the superficial features of these solutions, compared to a traditional bituminous binder. As a matter of fact, micro and macro-texture, porosity and permeability of the materials were measured. The outcomes showed that, thanks to a careful choice of materials, the safety level for users can be dramatically improved: furthermore, there are some circumstances for which the use of twin-layer draining pavements is to be considered an optimal solution, compared to typical bituminous binder draining road superstructures.