DEVELOPMENT AND USES OF HARD-GRADE ASPHALT AND OF HIGH-MODULUS ASPHALT MIXES IN FRANCE

Hard-grade paving asphalts, i.e., those having a penetration at 25 deg C lower than 25 mm/10, have experienced in France a significant development over the past 20 years. A brief review of the evolution of asphalts in France is provided, mentioning the current recommendations for the selection of asphalts and the rheological characteristics of the different hard asphalts produced in France. Data on the effect of rolling thin-film-oven and pressure-aging-vessel tests are given. Then high-modulus asphalt mixes are discussed. The different types of application of hot-mix asphalt concrete (HMAC) are indicated. Information is given about the composition of HMAC together with the current specifications in Association Francaise de Normalisation standards. Results are presented with respect to compactibility with the gyratory shear compactor, stiffness, resistance to rutting and to fatigue cracking, and about field performance. Two examples illustrate the potential economical benefit when making use of HMAC in new pavements instead of conventional base asphalt concrete.