Preparation And Properties Of Asphalt/layered Silicate Nanocomposites

Asphalt has been widely used as the binder of aggregate in road pavement due to its good viscoelastic properties. Unfortunately, asphalt is a form of liquid at high temperatureand, which can cause high temperature rutting and limit its application. Accordingly, enhancing the high temperature rutting resistance of asphalts is an emergent and valuable work.Asphalt/layered silicate nanocomposites were prepared by melt blending with normal layered silicates and organo-modified layered silicates. The effects of montmorillonite and rectorite on physical properties, dynamic rheological properties, stability properties were investigated. The effect of clay on the physical properties before and after aging, such as viscosity, retained penetration and increment in softening point, were investigated. SEM was used to analyse the microstructures of layered silicates, and XRD was used to characterize the dispersing states of nanocomposites. The chemical structures of asphalts were evaluated using Fourier Transform Infrared spectroscopy (FTIR).SEM photos show that the organic modifier made the interlayer space wider which may lead to the morphologic change of layered silicates.The XRD results show that the asphalt/normal layered silicates composites may form the intercalated structure and exfoliated structure. The addition of layered silicates to asphalt increases the softening point and viscosity, the storage stability was enhanced either. Furthermore, the modified asphalts exhibited higher complex modulus, lower phase angle. As a consequence, the asphalt/layered silicate nanocomposites displays enhanced dynamic rheological properties, which improve its rutting resistance at high temperatures. Compared with normal layered silicates, organo-modified layered silicates show better effect in improving softening point and rutting resistance of asphalt, which contributes to the formation of exfoliated structure in asphalt.The viscosity aging index and the increment in softening point decrease significantly with increasing clay contents. The retained penetration increased after the introduction of layered silicates. Moreover, OMMT are more effective than MMT for enhancing the aging resistance of asphalts. FTIR spectrums show that areas of the C=O and S=O stretch bands are increased after aging. It can be concluded that the aging resistances of the asphalt nanocomposites are much better than that of base asphalt. MMT and OMMT as the modifiers can efficiently reduce the oxidation of asphalt due to their prevention of oxygen.