This is a report on the state of the art of research on the phenomenon of the aging of asphalt-aggregate mixtures. Compared to research on the aging of asphalt cement, there has been little research on the aging of asphalt mixtures. Binder studies are considered as well as mixture sutdies, the relationship between laboratory aging tests and field performance, and the relationship between chemical composition and field performance. Recommendations are made for aging procedures which show promise for laboratory investigation. Test methods to evaluate aging are also considered. It is noted that extended heating procedures show the most promise for short-term aging and pressure oxidation and/or extended heating the most promise for long-term aging.

The level of research activity in the highway sector as a whole has declined precipitously in recent decades, whilst the challenges facing US state highway agencies have escalated. As a result, a Strategic Highway Research Program - SHRP) was initiated to establish collaboration with research bodies tackling similar highway problems in countries worldwide. This collection of reports from around the world presents SHRP`s progress towards providing research-based new products from which the international highway engineering community may benefit. SHRP concentrates on six high-priority research areas: asphaltic materials; pavement performance; cement and concrete; maintenance cost effectiveness; concrete bridge component protection systems and the chemical control of snow and ice.