Influence of dosage of warm mix additives on the rheological behavior of asphalt binders in the mixing and compaction temperature regime

In Warm Mix Asphalt (WMA), the reduction in mixing and compaction temperatures of asphalt mixtures is achieved by the addition of additives to the conventional binder. Such addition of WMA additives can change the rheological behavior of the binder at high temperature regime. In this investigation, a Viscosity Graded (VG30) base binder was added with two types of WMA additives. One of them was EVOTHERM, a chemical based additive and the other was SASOBIT, a wax based additive. To understand the influence of dosage on the rheological behavior, Evotherm was added to VG30 binder at four dosages of 0.2, 0.4, 0.8 and 1.2% and Sasobit was added at four dosages of 0.5, 1.5, 2.0 and 2.5%. All the samples were subjected to shear rate sweep tests in a rotational viscometer at four different temperatures of 100, 120, 135 and 155°C. It was seen that while all the materials exhibited Newtonian response at 135 and 155°C, the manner in which the materials exhibited non-Newtonian response at other temperatures was different and such difference was influenced by the type and dosage of the additive.