Modeling of Oxidative Aging Behavior of Asphalts from Short-Term, High-Temperature Data as a Step toward Prediction of Pavement Aging:

The oxidative aging data collected during the Strategic Highway Research Program have been analyzed in terms of kinetics of viscosity change with time and temperature. Changes in viscosity have been used as the measure of the progress of aging. The objective is to model viscosity increases accurately enough to be able to predict aging (in terms of viscosity changes) at pavement temperatures from short-term test data acquired at high temperature. This involved constituting a mathematical model, based on oxidative reactions, and a nonlinear regression of the data to test predictability of the proposed model. Clearly, there is a point beyond which viscosity change becomes independent of time, but no data were collected to that extent. Separately, it has been shown that oxidation of aliphatic sulfide to sulfoxide and oxidation of benzylic carbon to carbonyl are the principal chemical reactions that contribute to an increase in viscosity. The data fit the proposed equation sufficiently well to allow calculatio...