Analysis of the porous asphalt viscoelastic behaviour

In the latest years porous asphalt concrete has been largely used as it reduces the noise and avoids aquaplaning phenomena. The use of modified bitumen has allowed to obtain porous asphalts with remarkable mechanical characteristics. Therefore, it can be useful to carry out a right characterization of porous asphalt, starting from the evaluation of a reliable complex modulus under both performance and provisional regard. After this, we can examine the representative rheological model and finally study the resistance to fatigue and rutting. The mix asphalt mechanical behaviour is normally characterized by using the components of complex modulus: absolute value and phase angle. These components are both important for a right analysis of pavement performances. In the first part of this work we realized a study about the applicability of the test method EN 12697-26 to porous asphalts. An extensive campaign of tests (four point bending test) was carried out, at different temperatures and frequencies. We analyzed: 1. The measure repeatability and the numerousness of the sample, in order to obtain a reliable complex modulus characterization in both absolute value and phase angle for a fixed error; 2. The linear behaviour and the stiffness modulus variability with the strain, in order to choose the test conditions (referred to in situ strain conditions); 3. The influence of compaction variability on the complex modulus, in order to give directions about the specimen preparation. In the second part of the work the adaptability of the predictive formula proposed by Witczak et al. for the stiffness modulus and of the rheological models more in use was evaluated.