Using Highly Oxidant Gas for Simulating Long-Term Ageing of Asphalt Mix Specimens in the Lab

Abstract

Ageing of bitumen leads to increased stiffness and brittleness. Thus, bituminous bound pavements become more prone to failure by low-temperature and fatigue cracking. Therefore, the ageing behavior of bitumen has a crucial impact on durability, as well as recyclability of pavements. To assess ageing of bitumen, RTFOT and PAV are standardized methods for short-term and long-term ageing in the lab. For lab-ageing of hot mix asphalt (HMA), various methods have been developed in the last decades. This paper presents an optimized lab-aging procedure (Viennese Aging Procedure-VAPro) for compacted HMA specimens to assess mix performance of long-term lab-aged specimens. Thus, it is possible to optimize mix design not only for short-term performance but to take into account effects of oxidative aging during its in-service life. VAPro is based on a triaxial cell with forced flow of a gaseous oxidant agent through the specimen. The oxidant agent is enriched in ozone and nitric oxides to increase the rate of oxidation. It is shown by stiffness tests of unaged and lab-aged specimens, as well as by DSR tests of recovered binder from aged specimens that asphalt mixes can be long-term aged at moderate temperatures (+60 °C) and within 4 days and a flow rate of 1 l/min by applying VAPro. Thus, VAPro can simulate long-term ageing at conditions that are representative of conditions that occur in the field within an efficient amount of time.