Effects of Aging on Physicomechanical and Chemical Properties of Chemically Modified Binders

Abstract Asphalt binders and their chemical compositions vary widely based on their crude sources. Chemical modifications are often implemented to attain certain rheological and chemical superiorities over neat (unmodified) binders. These modifications involve complex chemistries. The crude specific behavior of asphalt binders keeps pavement professionals from perceiving the underlying concept of binder modifications. This study was intended to predict the effects of aging on physicomechanical and chemical properties of chemically modified asphalt binders and thereby determine the dosages that would yield optimal benefits of chemical modifications. Asphalt binders from two crude sources (Canadian and Arabian) were primarily modified with Polyphosphoric Acid (PPA). A commonly used polymer, styrene butadiene styrene, was also investigated to compare the results of PPA-modified binders. These binders were analyzed using a column chromatography technique to observe any significant changes in chemical fractions (saturates, aromatics, resins, and asphaltenes) along with colloidal stability. One of the crude sources was also evaluated after its modification with different percentages of a Reclaimed Asphalt Pavement (RAP) binder containing PPA. There were two different optimum levels of chemical modification for two different crude binders. Binders were tested at unaged, short-term, and long-term aging conditions in the laboratory. Two binders demonstrated two different patterns of aging escalation; the Arabian crude binder was found to be more colloidally stable that the Canadian crude binder. Finally, an effort was made to find any correlation between selected physicomechanical properties and chemical compositions of the tested asphalt binders. Some of the mechanical properties were found to be linearly correlated with binders’ chemical compositions. A high amount (over 40 %) of RAP binder modification in neat binders induced some instability in the colloidal structure of the Canadian crude binders.