Biomodification of rubberized asphalt and its high temperature properties

Asphalt rubber has been commonly used in the United States for modifying asphalt binder. There have been several studies on improving the interaction and adhesion between rubber and asphalt matrix. The modification of asphalt binder with crumb rubber (CR) is mainly controlled by the exchange equilibrium between components of asphalt binder and CR. This phenomenon increases the size of rubber particles (swelling) up to three times their original size and leads to a significant increase in the viscosity of the resulting asphalt. Swelling and increased viscosity not only promote separation of the modified matrix into two distinguishable phases but also increase the difficulty of pumping and application of rubberized asphalt. This study investigated the effectiveness of treating rubber with an amide-enriched biomodifier to facilitate breakage of disulfide bonds in rubber polymer while promoting interactions between free radicals and amide groups of biomodifier. Promoting interactions between rubber polymer and asphalt aromatic compounds by adding a biomodifier could alleviate phase separation while enhancing overall matrix elasticity. This modification enhanced the rheological properties of rubberized asphalt, including high-temperature properties as well as its palpability. The rotational viscometer and dynamic shear rheometer were used to evaluate the effect of biomodifier on the rheological properties of asphalt rubber at high and intermediate temperatures. Fourier transform infrared spectroscopy was used to examine the presence of rubber polymer compounds inside the asphalt matrix. The results showed that introduction of biomodifier facilitated the application of higher CR percentages while improving the overall rheological properties of the asphalt rubber.