Evaluation of linear viscoelastic properties of low energy asphalt mixtures modified with crumb rubber

Considering the important economic and environmental benefits of low energy asphalt mixture and the need to know and study more about this asphalt due to little research, in this article, the linear viscoelastic properties of this type of asphalt are evaluated using dynamic modulus test. Due to the mechanical weakness of this asphalt mixture and considering its environmental nature, an additive compatible with the environment was selected to modify it. Therefore, crumb rubber in three levels of 10, 15 and 20% by weight of asphalt binder was used to modify the samples. Controlled and modified asphalt samples were designed and compacted according to the superpave method and were tested to determine the dynamic modulus and their viscoelastic properties at different temperatures and frequencies. The master curve of asphalt mixtures showed that at high temperature (low frequency) the highest dynamic modulus belongs to low energy asphalt mixtures with 15% rubber powder. Therefore, this mixture has the highest rutting strength compared to other mixtures. On the other hand, comparison of the master curve of asphalt mixtures at low temperature (high frequency) showed low stiffness of low energy asphalt samples without additive and low energy asphalt with 15% additive and their resistance to cracking, respectively. Evaluation of the viscoelastic properties of the test specimens also confirmed the fact that the highest elasticity belonged to the low-energy asphalt sample modified with 15% crumb rubber and the most viscous mixture was the hot asphalt sample.