Temperature sensitivity of foamed asphalt mix stiffness: field and lab study

Abstract

Knowledge of the temperature sensitivity of foamed asphalt stiffness is very important in mix and structural design, field non-destructive testing and advanced research. However, this subject has not been studied extensively, especially the effects of the stress state on the temperature sensitivity, which is essential to understand the behavior of weakly bonded granular materials. This paper first presents triaxial resilient modulus testing results of foamed asphalt treated materials with various asphalt contents at various temperatures. General observations are made in terms of the effects of the bulk stress, deviator stress, temperature and their interactions. Based on these observations, the temperature sensitivity coefficient of foamed asphalt stiffness is defined and a simplified model to predict foamed asphalt mix stiffness at any triaxial stress state and temperature is proposed and validated. A procedure to normalize back-calculated resilient modulus to a standard temperature is also presented. The essential step of this procedure is to estimate the temperature sensitivity coefficient based on the field test results at various temperatures. Finally, an example is presented comparing the stiffness of a foamed asphalt material over two years. It was found that the stiffness did not change significantly over the two years period, despite the accumulation of traffic loading.

Keywords:

• Foamed asphalt
• Stiffness
• Temperature susceptibility
• Deep in situ recycling
• Falling weight deflectometer
• Triaxial

Acknowledgements

The work presented in this paper was sponsored by the California Department of Transportation, Division of Research and Innovation, for which the authors are grateful. The authors also wish to thank their collaborators in the California Department of Transportation. The results presented in this paper do not represent any standard or specification of the California Department of Transportation, and the opinions expressed are those of the authors alone.