Development of New Methodologies for Prediction of Performances of Asphalt Mixtures

This thesis proposes the use of new methodologies for prediction of performances of asphalt mixtures. Recent improvements in technology make it possible to adopt new methods of investigation with the dual objective of improving the performance in the survey of the parameters and investigate new properties so far not analyzed. In particular, the image analysis and the tyre/surface interaction belong to an innovative framework, which is next to flank, if not replace, the classic measurements so far employed. The thesis deals with the use of these technologies for the analysis of three rubberized stone mastic asphalts, which were laid on a stretch of road close to Bologna, Italy. Three different surveys were carried out on site during the first year of service. The surveys included the change in texture and skid resistance due to the traffic, along with the acoustic properties of the pavement. Local as well as dynamic continuous measurements were carried out, involving the use of a profilometer and a skiddometer. A second phase involved the prediction of the surface parameters with different stages of simulated trafficking on Road Test Machine. At each stage change in macrotexture, skid resistance, adhesion between bitumen and aggregates, contact pressures and areas were assessed. The image analysis is used for the assessment of the adhesion between the bitumen and the aggregate. The images are then processed in order to create 3D models of the asphalt specimens and investigate the surface and volume properties. The tyre/pavement interaction is another fundamental phenomena that received little considerations from the research, given its importance. A final discussion summarizes these investigations by separately review three different simulated periods, i.e. the early life, the in-service equilibrium and the end of life. In order to accelerate the distress, one slab was subjected to Immersion Wheel Track test.