Rheological Investigation on the Rutting Characteristics of Nanoclay Modified Asphalt Binders

Abstract

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 (Jnr) 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 Jnr 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 Jnr 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.