Effects of water activation of crumb rubber on the properties of crumb rubber-modified binders

Hot water activation of crumb rubber has been suggested as a method of improving compatibility between crumb rubber and asphalt binder. This procedure removes light oil fractions present in the crumb rubber particles, thus decreasing segregation occurring between rubber particles and binder. For this research, a PG 64-22 binder was modified with four different crumb rubber sources at concentration of 15% by weight of binder. Binder properties were evaluated for virgin binders, water-activated crumb rubber-modified (CRM) binders, and for non-activated CRM binders. CRM surface morphologies were studied using a scanning electron microscope, molecular size distributions of modified binders were determined using gel permeation chromatography, while storage stability was evaluated by cigar tube testing. Rheological properties of the CRM binder were investigated; improved phase separation properties were observed following water activation, however, these improvements did not result in improved rheological properties of the activated CRM binder.