Investigating Low-Temperature Properties of Nano Clay-Modified Asphalt through an Energy-Based Approach

摘要

Significant effort has been given by researchers in recent years to explore the potential use of nanomaterials such as nano clay (NC) for asphaltic pavement applications. The effect of NC on fatigue and rutting performance of asphalt binder has been reported by many researchers; however, limited information is available regarding its effect on the low-temperature performance of asphalt binder. Besides that, reported work reflects inconsistent conclusive remarks about the influence of NC on low-temperature performance parameters of asphalt binder. Therefore, this study examines the effects of NC on low-temperature properties of asphalt binder not only through a conventionally adopted approach (on the basis of creep stiffness and creep rate) but also a dissipated energy-based approach. NC dose was selected as 0, 2, 4 and 6 % by the weight of the asphalt binder. Initially, creep stiffness and relaxation rate were evaluated as per the recommendation of ASTM D6648, Standard Test Method for Determining the Flexural Creep Stiffness of Asphalt Binder Using the Bending Beam Rheometer (BBR). Although the creep stiffness value was found to increase, the creep rate was found to decrease only by a marginal amount with incremental dosages of NC. A master curve was subsequently drawn for creep stiffness, relaxation modulus, and creep rate, and the curve indicated their strong dependency on the level of creep period. Furthermore, various energy parameter components were evaluated with the help of viscoelastic modeling of creep compliance response using the Burgers model. Although both the energy components were found to decrease with NC addition, the rate of decrease in the dissipated energy component was higher compared with the corresponding decrease in stored energy with incremental dosages of NC. Such a response indicated a decrease in overall stress relaxation rate and hence degradation of low-temperature properties of control binder with the addition of NC to asphalt binder.