Performance Evaluation of Asphalt Binder Modified with Nanomaterials

This study explores the optimization of hot mix asphalt (HMA) performance through the incorporation of nano clay (NC) and carbon nano tubes (CNTs) into the asphalt binder. Through a systematic evaluation, the research determines the optimal proportions of these nanomaterials by assessing their impact on crucial asphalt properties, including viscosity, shear modulus, shift angle, stiffness, the slope of the stiffness-time curve, nonrecoverable shear compliance, and percent recoverable strain. The results reveal that an NC content exceeding 0.8% surpasses the Superpave rotational viscosity limit, thereby adversely affecting the workability of the asphalt mixture. Consequently, further testing on NC-modified binder is halted, with the focus redirected to CNTs-modified binder. The optimal CNT content is identified as 1%. At this concentration, the highest rutting parameter ratio (G*/sinδ) is achieved, along with the lowest nonrecoverable shear compliance and highest percent recoverable strain. On the other hand, this CNT content caused a minimal adverse effect from a small increase in rotational viscosity, creep stiffness at low temperature, and fatigue parameter (G*sinδ) at an average service temperature. Additionally, this CNT concentration results in the stiffness-time curve having a steeper slope, indicating less susceptibility to low-temperature cracking. These findings demonstrate that 1% CNTs substantially enhance the rutting and low-temperature cracking resistance without significantly compromising fatigue crack resistance and workability during mixing and compaction. They offer valuable insights into tailoring asphalt binder compositions for enhanced HMA performance.