Abstract:
Although many research works are available on evaluating the effect of carbon nanotube (CNT) on intermediate and high temperature performance of asphalt binder, limited studies have been reported for its effect on low temperature properties. Moreover, reported research work showed inconsistent conclusive remarks about its influence on the low temperature properties of asphalt binder. Therefore, along with the conventionally adopted technique, this study aimed at investigating the effect of CNT on low temperature properties of asphalt binder using the dissipated energy-based approach to make an appropriate conclusive remark. CNT content was varied as 0%, 0.75%, 1.5%, and 2.25% by the weight of asphalt binder. Initially, creep stiffness and creep rate corresponding to 60 s creep period were evaluated. Although CNT addition changed the creep stiffness and creep rate, the impact was not statistically significant at 0.75% CNT. However, a subsequently higher dose of 1.5% CNT significantly increased the creep stiffness and decreased the creep rate. A master curve for creep stiffness, relaxation modulus, creep stiffness rate, and creep relaxation rate was drawn to understand the effect of prolonged creep period on low temperature properties. The detrimental effect of CNT on low temperature properties of asphalt binder was found to be apparent, especially in a higher creep period zone. Subsequently, viscoelastic modeling of creep compliance data obtained from a bending beam rheometer (BBR) test was carried out using the Burgers model. Different energy components (stored and dissipative) were subsequently evaluated based on model parameters. Stored, as well as dissipated energy components, were found to be decreasing with an increase in CNT content to 1.5%. However, the degree of decrease in the dissipated energy component was found to be relatively higher compared to the corresponding decrease in the stored energy component. As a result, the dissipated energy ratio (DER), which is expected to be higher for better low temperature performance, was found to be decreasing with the incremental dosages of CNT. Although CNT addition decreased the DER value, the impact was not statistically significant at 0.75% CNT. However, a subsequently higher dose of 1.5% CNT showed a significant decrease in DER value. Such a response further reinforced that CNT addition may have a negative impact on low temperature properties of asphalt binder.