Asphalt concrete mixtures lightened with expanded clay for high-grip wearing course layers

In this paper the authors describe the results of a volumetric mix design study where the Light Expanded Clay Aggregate (LECA) is used (in addition to natural aggregate) in the surface layers of flexible pavements. The experimental phase has required the prior identification of the optimal particle size distribution of a traditional wearing course asphalt concrete with siliceous inert. Then, after characterization of the mechanical performance of the mixture (called AC1), three further asphalt mixtures were made (AC2, AC3 and AC4), characterized by different percentage volumes of Structural LECA (10%, 15% and 20%). The authors have defined the quantity of LECA to replace AC1 in the mixture in terms of volume and not in weight in order to take into account the considerable difference between the apparent density of LECA and natural stone aggregate, and therefore to ensure the conservation of the particle size distribution of the traditional departure mixture (AC1).