Laboratory evaluation of nano-silica modification on rutting resistance of asphalt Binder

Rutting is identified and used as the first failure mechanism in most important design conditions of flexible pavements. Bitumen can play a decisive role as one of the main materials used in asphalt mixtures, and modifying the properties of bitumen can greatly delay these failures and minimizing them in some cases. In this study, the PG 64-22 bitumen was modified using 2, 4 and 6% weight percentage of nanosilica and the effect of this modifier on reducing rutting failure was evaluated compared to the control sample. The rutting parameters including non-recoverable creep compliance (J(nr)) and the recovered creep (R%) were also evaluated, and then the effect of nano-silica on the improvement of these parameters at high temperatures was evaluated by simulating dynamic loading using Dynamic Shear Rheometer (DSR) and performing the MSCR test at 3 temperatures of 58, 64 and 70 degrees C. After investigating the bitumen behavior in the non-linear viscoelastic state, a significant effect was observed in the rutting parameters. So that, as a result of nano-silica addition, the cumulative strain decreased compared to the control sample and this decrease became more by increasing the modifier percentage, resulting from increasing the creep recovery at the end of each creep cycle. It was also concluded that, the increase in temperature in high and low stresses, has a negative effect on decreasing deformation recovery percent (R%) and the non-recoverable creep compliance (J(nr)), both in unmodified and modified bitumen samples, but importantly, the amount of nano-silica effect on the improvement of these parameters was negative, which was discussed in detail in this study. Also, at a certain temperature, increasing the percentage of nano-silica modifier significantly increased R%, and also significantly decreased the J(nr). In the following, the difference of creep recovery in high and low stresses of R-diff and the difference of the non-recoverable creep compliance in high and low stresses of J(nr)diff significantly improved, indicating a reduction in the sensitivity of asphalt samples to the applied stress and also a significant increase in resistance of the samples against rutting. (C) 2019 Elsevier Ltd. All rights reserved.