Rheology of Bitumen modified by EVA – organoclay nanocomposites

Ternary systems, bitumen/ethylene-vinyl acetate (EVA)/organoclay, were prepared by two mixing methods (physical mixing and melt blending) and then studied in small amplitude oscillations, start-up of shear flow and repeated creep and recovery tests. The effect of mixing method and the role of two organoclays on the rheological properties of the studied systems were investigated. Improved thermomechanical properties of bitumen/EVA/organoclay nanocomposites, prepared by melt blending, were demonstrated by the low accumulated strain/compliance in the repeated creep and recovery tests. Structural differences between the studied systems were reflected in the behavior of the dynamic phase angle, specifically in the shape of the derivative of phase angle w.r.t. the reduced frequency. Similarly, the structural differences between the prepared nanocomposites were reflected by the behavior of the stress growth function gþ in the transient experiments.