PREDICTING ASPHALT PERFORMANCE

Further statistical analyses of data on mixture properties and asphalt binder properties that had been available for a previous study "Changes in Fundamental Properties of Asphalts During Service in Pavements" indicated the following: 1. Pavements should be sampled at several random sites to obtain meaningful estimates of the existing levels of mixture properties. 2. Because significantly lower sampling plus testing variability of the bulk specific gravity measurement is obtained in 8-inch (203 mm) core smaples than for the 6-inch (152 mm) or 4-inch (102 mm) core samples, the 8-inch (203 mm) core should be used whenever possible. 3. Lower variabilities of some mixture properties were significantly characteristics of "surviving" pavement projects and higher variabilities of some mixture properties were significantly associated with "non-surviving" or poorly performing pavement projects. 4. Lower project variability of bituminous mixture properties such as percentages of asphalt, air voids, mineral voids, mineral voids filled, bulk specific gravity, and aggregate percent passing the 3/8 inch (9.5 mm), Nos. 4, 8, 16, 30, 100, and 200 sieves were significantly characteristic of higher rated "surviving" pavements. 5. Long-term hardening of asphalt binder in a pavement is essentially dependent on the asphalt content and air voids in the pavement mixture. 6. Regression equations are reported for predicting consistencies of binders in aged "surviving" pavements from the consistencies of the original asphalts or their laboratory aged residues, the percentages of asphalt and air voids in the pavement mixtures, and the percentages of certain chemical fractions in the original binder. /FHWA/