Characterization of Aging and Foaming Properties for Asphalt Mixtures
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Economic, environmental, and engineering benefits have motivated the implementation of warm mix asphalt (WMA) in the United States. While asphalt foaming has become the most popular method for producing WMA, concerns remain about the performance of foamed asphalt mixtures due to the use of water in the foaming process. Along with the advent of WMA, recent changes in asphalt mixture components and production parameters have raised the need to review the current design practices and evaluation methods for asphalt mixtures, including the effects of aging. Therefore, the main objectives of this study were to evaluate the aging characteristics of asphalt mixtures and to explore asphalt foaming technology for WMA applications. Aging of asphalt mixtures occurs during production and construction and continues throughout the service life of pavements. In this study, laboratory short-term aging protocols were evaluated in terms of simulating the asphalt aging and aggregate absorption that occurs during plant production and pavement construction. In addition, the concepts of cumulative degree-days and mixture property ratios were proposed to quantify field aging and to explore its correlation with laboratory long-term aging protocols in terms of mixture properties. Furthermore, the effects of various mixture components and production parameters on the aging characteristics of asphalt mixtures were investigated. Finally, post-construction cores obtained from several field projects were measured to explore mixture stiffness and binder property gradients in order to characterize the non-uniform field aging of asphalt pavements with depth. Asphalt foaming technology was also explored in this study via a comprehensive laboratory experiment. A non-contact test method consisting of a laser device and a digital camera was developed to measure the asphalt foaming process in terms of volume expansion and collapse and evolution of asphalt foam bubbles. In addition, novel test methods were proposed to evaluate the workability and coatability for foamed asphalt mixtures. The proposed test methods were then utilized to investigate the effects of foaming water content and laboratory foamer type on asphalt foaming characteristics and foamed mixture properties. Finally, a mix design procedure for foamed asphalt mixtures was proposed and validated with field and laboratory data.
Yin, Fan (2015). Characterization of Aging and Foaming Properties for Asphalt Mixtures. Doctoral dissertation, Texas A & M University. Available electronically from