Rheological Investigations on Warm Mix Asphalt Binders at High and Intermediate Temperature Ranges

Warm mix asphalt (WMA) technology is used to reduce mixing and compaction temperature of the binder; however, such addition is also expected to influence the rheological response of the binder during pavement service. This investigation is focused on WMA binders produced using Evotherm (Evotherm-VG30) and Sasobit (Sasobit-VG30) with a base binder (VG30). Shear rate sweep tests and steady shear tests conducted in the temperature range of 100-155 degrees C indicate that the addition of Evotherm and Sasobit consistently reduce the viscosity of binder. This change in viscosity is found to be temperature and aging dependent. Short-term aged Evotherm-VG30 and Sasobit-VG30 binders exhibited increased shear thinning in the compaction temperature regime. Oscillatory shear tests and repeated creep and recovery tests were conducted in the temperature range of 15-75 degrees C. The relationship between dynamic modulus and phase angle of WMA and VG30 binders followed Kramers-Kronig relations. Addition of Sasobit and Evotherm did not change the temperature regime associated with viscoelastic solid-fluid transition. From the creep and recovery test, addition of Evotherm and Sasobit resulted in increased strain during creep at higher temperatures. The influence of additives, especially Sasobit, on the base binder was found to be strongly temperature dependent.