Selection of Laboratory Aging Procedures for Asphalt-aggregate Mixtures

Two major effects dominate aging of asphalt-aggregate mixtures: 1) loss of volatile components and oxidation in the construction phase (short-term aging) and 2) progressive oxidation of the in-place mixture in the field (long-term aging). Aging results in hardening (stiffening) of a mixture, which alters its performance both positively and negatively. This report presents the results of a preliminary investigation to evaluate aging methods for asphalt-aggregate mixtures. Short-term methods included oven aging and extended mixing, while long-term methods included oven aging and oxygen enrichment. The effects of temperature and aging duration are presented. The effects of aging were determined using the diametral resilient modulus test. Recommendations for short- and long-term aging are provided.