Influence of Evotherm on the thermal equilibrium time of unmodified and modified bituminous binders

Abstract

ABSTRACT The rheological properties of bitumen largely influence the performance of the pavement. Determination of rheological properties of bitumen depends on thermal equilibrium time. The main objective of this study is to evaluate the effect of Evotherm, a chemical warm mix additive on the thermal equilibrium time of bituminous binders. The bituminous binders used for this study included two unmodified binders, a polymer-modified bitumen (PMB) and a crumb rubber-modified bitumen (CRMB). The thermal equilibrium times for bituminous binders with and without Evotherm were measured using a dynamic shear rheometer. The results indicate that the thermal equilibrium time primarily depends on the type of binder, wherein the asphaltene content, presence of polymer and rubber influence thermal equilibrium time. The higher thermal equilibrium times observed for the Evotherm-modified PMB40 binder and Evotherm-modified CRMB60 binder in unaged condition can be attributed to a change in morphology and chemical interaction respectively upon the addition of Evotherm. Lesser thermal equilibrium time exhibited by short-term aged Evotherm binders can be because of the reduced formation of ageing compounds due to reduced short-term ageing temperature and presence of Evotherm. The linear regression model well predicted the thermal equilibrium time based on test temperature and softening point of binders.