Thermal Segregation Influence on Current Asphalt Mixtures

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Thermal segregation during the construction of asphalt mixtures can result in the formation of low-density areas and a subsequent decrease in pavement life. Although the methods for measuring thermal segregation have remained largely unchanged, significant advancements have been made in asphalt mixture types and design methods over the past decade. This study assessed the significance of thermal segregation with current asphalt mixes, validated existing criteria, and established modified criteria as necessary. The study also resulted in guidance on identifying and addressing recurring thermal segregation issues, ensuring that thermal profile requirements align with modern asphalt mixes and construction practices. Results from this study showed that based on current practices, more than two thermal profiles with severe thermal segregation could be considered recurring. This study also showed that thermal segregation does induce higher air voids in current mixes, which results in poorer rutting and reduced crack life properties. Analysis suggested that the influence of thermal segregation-induced air voids could take as much as 10 years off the pavement life, although the actual influence of thermal segregation on field performance can vary significantly depending on many factors. In practice, thermal segregation-induced air voids may impact performance but may allow the pavement to still reach its design life. Results from this study showed that the current 25°F temperature differential is still valid as a threshold to define thermal segregation. Results from this study also revealed that the current methods for evaluating thermal profile need further development to include affected area and absolute placement temperature.