14 - A new approach for aggregate grading optimization for mixtures

Abstract

Aggregate packing concepts developed in the field of high-performance cement concrete, were transposed to the field of asphalt concrete. These concepts, associated with the use of the gyratory compactor on aggregates only, enabled the development of a new laboratory design procedure of dense high-modulus asphalt concretes (HiMAs). These mixes are characterized by single- or double-gap-graded curves, great coarse aggregate interlock, and no need for low-penetration-grade bitumens to fulfill the European EME2 (enrobé à module elevé 2) specification requirements, in particular the 14,000MPa stiffness modulus value at 15°C. In addition, the use of polymer-modified binders (PMBs), at a content of about 4–4.5%, combined with such an optimized aggregate packing leads to the design of HiMA, which are characterized by great compactability, very high stiffness modulus, and high fatigue resistance in a single formulation, allowing for reduced pavement thickness and increased longevity. Moreover, the proposed mix design and the 4–4.5% binder content make the use of PMBs affordable in base courses. Laboratory assessment of such materials consists of the evaluation of compactability, moisture resistance, rutting resistance at 60°C, complex stiffness modulus at 15°C, and fatigue resistance at 10°C. Apart from these results, the chapter also addresses the successful application of this new material on different job sites, located mainly in France. The proposed HiMA material may be potentially considered as a relevant solution for sustainable long-life pavements that do not deteriorate structurally, needing only timely surface maintenance.