Abstract. To avoid traffic congestion, due to road works, a continuous research into asphalt pavement and especially its durability is of great importance. This research focuses on improving the mechanical performance and the durability of asphalt mixtures by nanoclay modified bitumen. This promising technique of introducing nanoclays or nano particles into bitumen could offer an significant improvement on the fatigue properties and rutting performance and thus the durability of the asphalt top layer.
IntroductionFor the heavely used "congested" Belgian road network, a continuous research into asphalt pavement and especially its durability is of great importance to avoid traffic congestion, due to road works.This research focuses on improving the mechanical performance and the durability of asphalt mixtures by nanoclay modified bitumen. A specific asphalt mixture type for base layers in Flanders, AC 14 base 35/50 (EN 13108-1), using a relatively hard bitumen was modified. Both physical and rheological properties of the modified binder were evaluated. This included the determination of the penetration and softening point and the characterization of dynamic rheological parameters, by using a Dynamic Shear Rheometer (DSR).The prefix 'nano' indicates the occurrence of a material that measures less than 100 nm, in at least one dimension. From literature, general trends on organic montmorillonite nanoclay (OMMT) modified bitumen can be derived. It is indicated that the penetration decreases and the softening point increases by adding nanoclays [1,2,3,4,5,6]. An explanation can be found by the reinforcement effect of the silicate layers on the bitumen [7]. Based on tests with a DSR, the bitumen seems to become more elastic and stiffer [2,8,9,10,11]. This effect is more pronounced at high temperatures and/or low frequencies. The viscosity increases also after the OMMT modification [2,6,8,9,12]. The indirect tensile strength does not change at 5°C and 25°C but does improve at 40°C [1,2,5,12]. In addition, nanoclay can form a barrier in bitumen through which penetration of oxygen and water is prevented [2]. The effects of the modification by nanoclay are more pronounced by increasing the amount or when using soft bitumen. Nevertheless, there is still a need for sufficient research on the use of nano-modified bitumen in asphalt. Especially as there are almost no research publications regarding the application of nanoclay in harder bitumen, a type which is preferably used in Belgian mixtures to provide rutting, though cracking must be avoided. This exploratory study will evaluate physical and rheological properties of a harder bitumen modified with nanoclay. Additionally, the