In this paper, the authors present the experimental results obtained in the laboratory by using the ASTRA interface shear test for the performance-related characterisation of tack coat emulsions. The test focuses on the failure properties of bituminous multi-layered systems and yields results which may be modelled by means of a straightforward theoretical approach based on the identification of various strength components due to cohesion, pure friction and dilatancy. It was found that the latest version of the testing apparatus may be conveniently used to evaluate temperature-related effects. This was done in a research project in which test conditions were obtained by combining test temperatures and normal stress levels comprised within wide variation ranges.

Crumb rubber (CR) derived from grinding of end-of-life tyres (ELTs) may be successfully used as a bitumen modifier or as a supplementary component in the production of bituminous mixtures employed for the construction and maintenance of road pavements. However, CRs deriving from different sources and production processes yield effects on performance of corresponding paving mixtures under traffic loading and on gaseous emissions produced during laying on site which may change considerably depending upon their physical and chemical properties. In order to quantitatively assess the possible variability of CR characteristics, 16 samples were taken from 9 Italian and 2 foreign ELT processing plants. Investigation activities included field surveys, during which plants were examined in detail, and laboratory tests, which focused on physical and chemical characterization of CR. Based on the analysis of available technical information and experimental data, it was possible to find relationships between the peculiar characteristics of treatment cycles and corresponding CR properties.