Rheological Behaviour and Rutting Resistance of Asphalt Modified with SBS and Nano-silica

This study is conducted to enhance the performance of bitumen at high temperatures. To do so, styrene-butadiene-styrene (SBS) and Nano-silica polymer additives were used. Initially, pure bitumen versus bitumen 60/70 samples with 2.5%, 3.5%, 4.5%, and 5.5% SBS polymer, and modified bitumen samples with 4.5% SBS polymer and 1%, 2%, 3%, and 4% Nano-silica were prepared using a high shear mixer. Polymer separation tests, rolling thin film oven tests, dynamic shear rheometer tests, and rotational viscosity tests were performed on the modified bitumen samples. Preliminary results of the dynamic shear rheometer test showed that SBS polymer improved the high-temperature performance of bitumen and increased its resistance to permanent deformation. However, Nano-silica had a more significant effect than SBS in improving the high-temperature performance of bitumen. The combination of 4.5% SBS and 4% Nano-silica enhanced the high-temperature performance of bitumen. Additionally, the results of the bitumen separation test showed that combining bitumen with SBS polymer caused the polymer to separate from the bitumen. Nevertheless, adding 1% Nano-silica resolved this issue. Asphalt mixture samples for the above compounds were then prepared based on the Superpave mix design method, and a dynamic creep test was performed. The results of this test showed that the combination of SBS and Nano-silica polymers significantly increases the resistance of the mixture at high temperatures. The combination of 4.5% SBS polymer and 4% Nano-silica, compared to the control sample with pure bitumen at 50 °C and 60 °C, reduces the cumulative strain by 51% and 41%, respectively, demonstrating the best performance. Therefore, the combination of Nano-silica with SBS polymer can be widely used in places with hot weather.