Evaluating the Suitability of Nanoclay-Modified Asphalt Binders from 10°C to 70°C

Abstract

This study presents the results of laboratory experiments and analyses carried out to evaluate the rheological performance of nanoclay (NC) modified asphalt binders from 10°C to 70°C. A viscosity graded binder, VG-30, was modified using 2%, 4%, and 6% NC by weight of the base binder. The suitability of the NC modification was ascertained using a series of rheological evaluations, including a frequency sweep test (10°C–70°C), linear amplitude sweep (LAS) test (10°C, 20°C, and 30°C), and multiple stress creep and recovery (MSCR) test (40°C, 50°C, 60°C, and 70°C). Scanning electron microscopy (SEM) was carried out on the unmodified and modified asphalt binders to assess the microscopic dispersion of NC in the base asphalt binder. The SEM images demonstrated that with an increase in the percentage of NC, the physical dispersion of the modifier in the base asphalt binder changes. Six percent of the NC was found to form an interlocked phase within the composite asphalt binder matrix. It was found that the h-parameter obtained from Cole-Cole plots at individual temperatures offers a better and clearer comparison between the asphalt binders in comparison to the master curves and combined Cole-Cole plots. The analysis using h-parameter indicated a higher elasticity and lower temperature susceptibility offered by the NC modified binders. With an increase in the percentage of nanoclay, both the fatigue and rutting performance improved. The value of the Jnr decreased while the value of the percentage recovery (R) increased with an increase in the percentage of the NC. At the temperature of 70°C, only a 6% NC modified asphalt binder was found to be suitable for standard traffic conditions. The LAS test resulted in a higher value of A and an insignificant increase in the value of B for NC modified binders in comparison to the values obtained for VG-30. No specific trend was observed in the value of A at different CSRs, and it suggested from this study that an average value may be used. The number of cycles to failure for NC modified binders was found to be higher than VG-30. A statistical analysis carried out for different parameters revealed that the NC modification has a significant effect on the performance parameters of asphalt binders at all the test temperatures. A simple framework for the cost-benefit analysis has been proposed in this study, which revealed a 6% NC modification to be the optimum dosage for attaining a higher benefit in comparison to the cost.