Effect of crumb rubber on viscosity of rubberized asphalt binders containing wax additives

• Wax additives are effective to reduce the binder viscosities at both testing temperatures.
• Rubberized mixes with wax additive are expected to have better haul management.
• The higher the rubber contents, the steeper the viscosity changes over time.

Viscous properties of rubberized asphalt binders containing wax additive were evaluated through the rotational viscometer at 135 °C and 120 °C. Rubberized binders were produced with three percentages (10%, 15%, and 20% by the weight of binder), and then mixed with two commercial wax additives. Three different periods of 30, 120, and 240 min were applied to the rotational viscosity test to evaluate the viscous properties depending on testing time. The viscosity changes by different time periods were drawn in time versus viscosity curve. From the results, it is concluded that (1) the addition of crumb rubber significantly increases the binder viscosity, (2) the wax additives are effective to reduce the binder viscosities at both testing temperatures, (3) all the viscosity values of rubberized binders are observed to increase after certain time, regardless of the addition of wax additives, (4) the higher the rubber contents, the steeper the viscosity change over time, and (5) the rubberized mixes with wax additive are expected to have a better haul management, based on the less viscosity increase over time.