Design, Placement, and Laboratory Evaluation of Rejuvenated Cold Recycled Pavement Mixtures

Abstract

Cold recycled (CR) pavements, the combination of reclaimed asphalt pavement (RAP) and a recycling agent (foamed or emulsified asphalt binder) at ambient temperatures, can provide a sustainable method to rehabilitate, maintain, and construct roadways. However, to utilize a CR pavement as an equal alternative to a hot mix asphalt base or surface course, the addition of a rejuvenating agent may be needed. This thesis focuses on the laboratory formulation, plant production, and placement of one foamed asphalt CR mixture, two CR mixtures containing rejuvenator, and one engineered emulsion CR mixture. These mixtures were subjected to laboratory evaluation via Indirect Tensile Asphalt Cracking Test (IDEAL-CT), High Temperature Indirect Tension Test (HT-IDT) and Dynamic Modulus testing. The influence of laboratory production versus plant production on mixture performance was investigated, as well as the influence of rejuvenators on mixture performance and density. During the mixture design process, all selected designs performed above the required minimums established for CR except for the mixture containing a CR rejuvenator, which failed the dry strength requirement by a small margin. However, this design surpassed the conditioned strength requirements during mixture design, showed improved strength when conditioned versus dry, and passed all minimum strength requirements when plant produced. Test results indicated that the addition of a rejuvenator led to increased dry densities during mixture design, plant production, and laboratory production and decreased moisture susceptibility versus non-rejuvenated CR mixtures. Rejuvenators also increased the CTIndex by at least 35% when compared to other CR mixtures. HT-IDT testing revealed that the rejuvenated mixtures performed slightly below the engineered emulsion mixture, with the foamed asphalt mixture outperforming all others. Dynamic modulus testing showed higher overall moduli in rejuvenated mixtures versus the CR mixture containing foamed asphalt, with the lower modulus of the foamed asphalt CR mixture being indicative of a less temperature and loading susceptible mixture. The engineered emulsion mixture performed between the two rejuvenated mixtures, with the anionic emulsion with bio-based rejuvenator mixture having the highest dynamic modulus values.