Aggregate Coated with Carbon Nanotube–Polymer Composites for Smart Asphalt Mixtures with Different Aggregate Gradations

Abstract

The introduction of carbon-based nanomaterials (CNMs) such as graphite powder, carbon nanotubes (CNTs), and graphene directly into asphalt mixtures offers a theoretical feasibility for increasing their electrical and thermal conductivity. This approach enables the preparation of a conductive asphalt mixture, which can be considered a promising smart material for healing microcracks in pavement, snow and ice removal, traffic information detection, and energy harvesting. However, it is still a challenge to disperse CNMs in asphalt efficiently and cost-effectively. This study develops a novel type of CNT/polymer-coated functional aggregate, which can be mixed with asphalt and mineral filler to produce smart asphalt mixtures. To account for the significant impact of aggregate gradation on the properties of asphalt mixtures, three distinct types of plain and smart asphalt mixture formulations, namely, AC-13, PA-13, and SMA-13, are prepared. Then, the effect of functional aggregate gradation on the performance of smart asphalt mixture is evaluated and compared comprehensively by testing the mechanical strengths, water stability, electrical resistivity, and microwave heating properties. The experimental results show that the electrical resistivities of the smart PA-13 and SMA-13 significantly decrease by eight orders of magnitude relative to the plain group, which is also two orders of magnitude lower than that of the smart AC-13. The good skeleton structure and uniformly distributed functional aggregates enable PA-13 and SMA-13 to demonstrate outstanding heating efficiency and uniformity under microwave radiation. Simultaneously, their mechanical strengths and water stability slightly decrease as compared with the plain group, with insignificant influence on its practical applications.