The Effect of Zinc Stearate Modification on Aging Characteristics of Asphalt Binder

Abstract

Different types of modifiers have been investigated to improve aging characteristics of asphalt binders. In this research, the effect of zinc stearate modification has been studied on aging resistance of asphalt binder. For this purpose, viscous flow properties and other rheological characteristics of neat and modified asphalt binders have been evaluated by using conventional experimental tests and superpave protocol test. In order to evaluate rheological behavior of asphalt binder in presence of zinc stearate, a neat asphalt binder sample with three modified samples containing 0.5, 1 and 2 wt% of zinc stearate were aged by means of the Rolling Thin Film Oven Test (RTFOT). The Brookfield rotational viscosity (RV) was implemented at six different temperatures from 100 to 200 degree of centigrade. Furthermore, the dynamic shear rheometer (DSR) was used for evaluating complex modulus (G*) and phase angle (δ) of all neat and modified samples at 10, 20, 30, 40, 50 and 60°C in frequency sweep mode. To evaluate effect of adding zinc stearate by using viscosity results, proportion of asphalt binder’s viscosity after aging to its viscosity before aging was defined as viscosity aging index (VAI). Results showed that adding zinc stearate to neat asphalt binder reduces the viscosity aging index. Results of frequency sweep test indicated that zinc stearate causes the values of complex shear modulus in aging asphalt binder approach to neat state which means the effect of zinc stearate modification is positive for improving aging resistance of asphalt binder.