Enhancing the viscoelastic properties of bituminous binders via thiourea-modification

Although added in a very low concentration, bitumen controls the final properties and performance of the resulting asphalt mixture. As an alternative to classic bitumen modification with polymers, we herein propose the use of thiourea, which has proved to efficiently enhance the binder thermo-rheological properties in a broad temperature interval. As revealed by thermogravimetric and chemical analysis, benefits above may derive from new structures, probably formed by the interaction between ammonium thiocyanate and bitumen most polar fraction. Thus, flexural DMTA and dynamic shear tests demonstrated an improvement in the binder flexibility and an increase in its elasticity, at low and medium/high in-service temperatures, respectively. In addition, this research emphasizes the use of isothermal frequency sweep tests (and frequency/temperature-dependence conversion) as a means of achieving glass transition temperature values which, in contrast to isochronal temperature sweep tests, do not depend on the selected heating rate.