Effect of nanosilica morphology on modification of asphalt binder

Based on a literature review, modification of asphalt binder with nanosilica (NS) has been the topic of several research studies, but hardly any published research concerning structural aspects is available. This research investigates the modification effect of two morphologically different NS materials: (i) a synthesised fibrous with porous structure and (ii) a commercial spherical with nonporous structure, on asphalt binder. The fibrous NS was synthesised using a low surfactant concentration synthesis method. Morphological and structural characterisations were carried out using the SEM, TEM, XRD and BET techniques. High and low temperature performance characterisations were conducted using physical and rheological determinations including conventional test parameters, dynamic shear rheometer, multiple stress creep recovery and bending beam rheometer evaluations. Results indicate that due to the porous structure and extremely high specific surface area, the synthesised fibrous NS provides a higher performance-related enhancement to the asphalt binder comparing to the spherical NS, thus providing more beneficial effects on the high temperature rutting resistance of asphalt binder at lower dosages, without detrimental effect in its low temperature grade. This reveals that the effectiveness of NS materials could be highly dependent on the morphological and structural properties of the NS particles, which strongly influence the performance characteristics of asphalt binder.