Rheological Investigation on the Rutting Characteristics of Nanoclay Modified Asphalt Binders

This study is aimed at evaluating the rutting potential of a conventional viscosity graded (VG-30) binder modified with different percentages (2–6%) of nanoclay. Rheological investigations, including performance grading (PG) of the binder, frequency sweep (FS) test and multiple stress creep recovery (MSCR) were carried out using a dynamic shear rheometer (DSR). FS and MSCR were done at four different temperatures ranging from 40 to 70 °C. Master curves plotted at a reference temperature of 60°C using FS data indicated better performance of nanoclay modified binders, especially at lower frequency range. Increase in percentage recovery (R) and reduction of unrecoverable creep compliance (J_nr) from MSCR test proved the efficacy of nanoclay as a positive reinforcing agent. At the reference temperature, R value for 2, 4 and 6% nanoclay increased from 0.47% (for VG-30) to 1.71, 3.34, and 5.3% respectively. The corresponding reduction in J_nr was about 12, 14, and 29%. Cole-Cole plots for each binder obtained from frequency sweep test at different test temperatures were modelled using a 3rd-order polynomial. The h-parameter calculated using the Cole-Cole plots at different temperatures were found to appreciably correlate with the values of J_nr and R for all the asphalt binders. In addition to the positive effect of nanoclay modification, it is concluded that h-parameter from the frequency sweep test can be used to explain the rutting potential of asphalt binders.