Nanomodified Asphalt Binders Aging Study and Predicted Performance under Different Climatic Conditions Using AASHTOWare

Abstract

Nanomaterials have shown great potential in improving the mechanical and rheological properties of asphalt binders based on laboratory examination. Some nanomaterials were reported to improve asphalt binders’ resistance to aging. This paper investigates the effect of adding different contents of nanoclay and nanosilica to asphalt binders on short-term aging and simulated pavement performance using AASHTOWare Pavement ME Design. The rheological properties of a conventional asphalt binder as well as modified asphalt binders with different percentages of two different nanomaterials, namely, nanoclay and nanosilica, were measured in the laboratory. An aging index based on Superpave rutting parameter was calculated. A matrix of 84 simulations was developed to evaluate the effect of these nanomaterials on the predicted flexible pavement distresses under three different climate conditions and two asphalt concrete (AC) thicknesses with different percentages of two types of nanomaterials. The simulated performance results were analyzed using statistical tools to determine the most significant parameters and the significance of the interaction between these parameters. Results showed that both nanomaterials can significantly improve the pavement resistance to aging, permanent deformation, fatigue cracking, and roughness. The results of the simulations showed that there is no unique nanomaterial content that can be considered optimum for all climatic conditions. All the investigated nanomaterials have shown extended simulated pavement life for different pavement structures and climatic conditions except the case of nanosilica for thin AC under moderate climatic condition. Finally, both nanomaterials’ content and type were found to have significant effects on the investigated distresses with the nanomaterial content ranked higher than the nanomaterial type in rutting and fatigue prediction and the opposite for international roughness index (IRI). Recently, the well-known AASHTOWare Pavement ME Design software has been used by many engineers, contractors, and highway agencies to perform pavement structural design based on a mechanistic-empirical pavement design approach. Comparing the laboratory testing results for nanomodified asphalt binders with conventional asphalt binder can help decision makers translate the laboratory results to actual field performance in terms of known pavement distresses such as rutting, fatigue cracking, and international roughness index (IRI). Several scenarios were investigated in this study varying the structure (thin and thick sections), material properties (control asphalt and nanoclay- and nanosilica-modified asphalts), nano content (0%, 3%, 5%, and 7%), climate (cold, moderate, and hot), and binder grading system (conventional and Superpave) in the software with 84 computer simulation runs. Nanoclay and nanosilica were found to improve the pavement resistance to asphalt concrete (AC) rutting, bottom-up fatigue cracking, and IRI. Both nanoclay- and nanosilica-modified asphalts extended the pavement life in most of the studied scenarios with one scenario achieving up to 9 and 13 years more life than the unmodified asphalt, respectively.