Ground tire rubber and bitumen with wax and its application in a real highway

Abstract

This research shows results over the structure-property relation of Ground Tire Rubber (GTR) modified after a high shear mixing process using wax as rejuvenator agent in a product under the environmental and technical regulations. The GTR was used after a milling process which produced a mean particle size of 1.19 mm. Bitumen 60/70 type was mixed with the rubber waste at 4000 rpm at 190 °C. A set of 15 formulations with rubber waste ranging from 10 to 20 wt% were prepared by following the Box-Behnken experimental design. Gradation tests were conducted over the GTR. Penetration, softening point, elastic recovering and viscosity tests were conducted over all formulations. Scanning electron microscopy with energy dispersed spectroscopy was used to analyze the microstructure and the chemical composition of samples. The effects of the main variables and their combinations over the properties have been analyzed. Using the desirability criterion, three different formulations were found to follow the specifications, and the best composition of them was the sample with GTR 15 wt%, 40min agitation time, and 3 wt% of rejuvenator, with a coefficient of determination of R2 = 0.9924. Results were successfully scaled up in a large manufacturing process by a road construction company and applied in a heavy traffic road at Colombia.