Interlayer Shear Effects of Grid Reinforcements

It is well known that cracking in asphalt pavements and its related degradation processes can be caused by traffic loading and temperature variations. Moreover, the increasing traffic, higher axle loads and reduced road maintenance budget, force engineers to seek alternative materials and/or working methods for the design and rehabilitation of asphalt pavements. In this context there is an increasing interest in the use of reinforcement systems to provide higher durability of asphalt pavements. In fact, they could extend service life preventing pavement cracking with a reduction in maintenance costs. In order to improve our knowledge of pavement reinforcement applications, the present study focuses on the analysis of bonding at the interface between asphalt concrete layers and reinforcements. In fact, geosynthetics could not act as a reinforcement product if they are a cause of separation between the layers at the interface. The aim of this study concerns a better understanding of reinforcement systems behaviour and their effects on mechanical properties of the interface. To this purpose the interlayer direct shear test ASTRA (Ancona Shear Testing Research and Analysis) is used to provide more details regarding the comprehension of the interlayer shear resistance. In particular, this paper presents the results obtained using four types of reinforcements at the interface, with both conventional and porous wearing course for the upper layer of laboratory samples. Our experimental program considers the effects of various test parameters, among which temperature and normal stress, in order to investigate the influence of the reinforcement properties (stiffness, geometry, size, coating, etc.) on the interlayer shear strength and stiffness.