Exploration of Pavement Oxidation Model Applications and Field Validation

Abstract

Asphalt paved road is one of the building blocks of the modem world. Flexibility is one of its major advantages; however, this flexibility suffers from asphalt oxidation since the first day of pavement service life. Several elements of binder oxidation have been investigated, such as oxidation kinetics, asphalt hardening in response to oxidation, pavement design, and environmental conditions. Based on understandings on those elements, pavement oxidation models have been developed to predict the oxidation rates in pavements in specific locations. This prediction contributes greatly to reducing the pavement life cost and elongating pavement service life. However, experimental methods to determine required model inputs, values of those oxidation elements, seriously limit the model application. This work focuses on understanding the elements of asphalt oxidation and on exploring applications of the pavement oxidation model.

This dissertation presents a detailed investigation of pavement oxidation, two new test methods to obtain the model inputs, and a study on dynamic diffusion-reaction balance. First, a detailed investigation on pavement oxidation was reported to give some general conclusions about asphalt oxidation rates vary largely in different climate zones, and pavement design defines thickness of the asphalt film and thus controls aging. Secondly, new methods to obtain the model inputs were proposed: (1) Aging tests on laboratory made asphalt concretes have been proven as new information sources on asphalt concretes aging to replace sampling field cores. This method makes a pavement oxidation prediction before construction a reality; (2) Aging on recovered asphalt binders have been proven as new information sources on asphalt kinetics and hardening properties. This method solves the problem that original binders are not available in many cases. With the data obtained from these aging tests, long term oxidation predictions for the pavements were made using the pavement oxidation model and validated their accuracies by field data, including one complicated case, a layer-by-layer prediction on a seal coat treated pavement. To better understand the asphalt aging process, the last topic in this dissertation was to study a dynamic balance between oxygen diffusion and oxidation reaction using the pavement oxidation model.