Influence of warm mix additive and loading rate on rutting of warm mix asphalt pavement

Abstract

Two major types of warm mix asphalt (WMA) technologies exists and they are wax-based and chemical-based. The wax-based additive melt completely in the binder at the mixing and compaction temperatures and hence enable construction at lower temperature. The chemical-based additives facilitate similar results during construction, however, by reducing the friction between the aggregates and binders. As it is well known, WMA technologies exhibit tendencies for increased rutting due to reduced ageing during construction, however, the wax-based additives exhibit better performance in laboratory trials since at pavement service temperatures, the wax crystallise and provide increased stiffness to the mastic. The presence of the wax and the associated temperature sensitive properties (crystallisation and melting) influence the viscoelastic response of the WMA at pavement service temperatures. This investigation focuses on such issues for one wax-based additive and one chemical-based additive along with a control hot mix asphalt (HMA) binder. This paper presents three important results. In the first, the rheological response of the binders are characterised and in the second the rutting and the mechanical properties of mixtures are quantified. It was seen that bituminous mixture with wax-based additives exhibited better rutting resistance characteristic at temperature below 40 C, identical response in the temperature range of 40–50 C and more prone to rutting at the temperature above 50 C when compared to HMA mixture. It was also seen that WMA mixture with chemical additives consistently exhibited higher rutting. Taking into account the temperature sensitive response of WMA, the final result relates to simulation for rut resistance for pavements constructed with WMA mixtures for 16 different locations in India.