Evaluation of Chemical, Physical and Fatigue Properties of Modified Asphalt Binder with Nanosilica and Synthesized Polyurethane

Asphalt pavement roads are composed of bitumen, aggregates and filler. Asphalt binder plays an important role in the properties of asphalt mixtures, and it is therefore important to identify its behavior. Asphalt concrete is still the most used material in the construction of roads. Fatigue failure is one of the most common failures in roads, and repairing such failures is very costly. Bitumen correction is one of the important methods to increase the strength of the pavement against failure. In this research, nanosilica and synthesized polyurethane with 3, 5 and 7 asphalt binder percentage were used. Due to the instability of thermoplastic polyurethane in asphalt binder, synthesized polyurethane was used. Polyurethane was synthesized by using a combination of polyol and isocyanate. To test the fatigue, a time sweep test was used. Results showed that synthesized polyurethane and nanosilica have improved the fatigue life. The effect of synthesized polyurethane on fatigue life was much greater than that of nanosilica. The fatigue life was increased 3.7 and 4.5 times for nanosilica and synthesized polyurethane in low strain, respectively. Results of the chemical test of Fourier-Transform Infrared Spectroscopy and physical tests showed that the physical changes which were made in the bitumen are not reliable for prediction of fatigue. In fact, changes in the chemical composition and creation of various bonds are influential on the fatigue behavior.