Description
Rejuvenation Mechanism of Asphalt Mixtures Modified with Crumb Rubber
Hossein Noorvand1*, Kamil E. Kaloush2, Jose R. Medina1, B. Shane Underowood3
ABSTRACT. Asphalt aging is one of the main factors causing asphalt pavements deterioration. Previous studies reported on some aging benefits of asphalt rubber mixtures through laboratory evaluation. A field observation of various pavement sections of crumb rubber modified asphalt friction courses (ARFC) in the Phoenix, Arizona area indicated an interesting pattern of transverse / reflective cracking. These ARFC courses were placed several years ago on existing jointed plain concrete pavements for highway noise mitigation. Over the years, the shoulders had very noticeable and extensive cracking over the joints; however, the driving lanes of the pavement showed less cracking formation in severity and extent. One hypothesis could be that traffic loads continually manipulate the pavement over time, which causes some maltenes (oils and resins) compounds absorbed in the crumb rubber particles to migrate out leading to rejuvenation of the mastic in the asphalt mixture. To investigate the validity of such a hypothesis, an experimental laboratory testing was undertaken to conditions samples with and without dynamic loads at high temperature. This was followed by creep compliance and indirect tensile strength testing. The results showed higher creep for samples aged with dynamic loading compared to those aged without loading. Higher creep compliance was attributed to higher flexibility of samples due to the rejuvenation of the maltenes. This was also supported by the higher fracture energy results obtained for samples conditioned with dynamic loading from indirect tensile strength testing.
KEYWORDS: Crumb Rubber, Asphalt Mixtures, Rejuvenation, Swelling, Aging, Dynamic Load, Creep Compliance, Indirect Tensile Strength.
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