Development of criteria for durability of modified asphalts

A laboratory investigation was conducted to evaluate the effects of a few promising modifiers on the temperature susceptibility and long-term aging characteristics of typical asphalt cements and asphalt concrete mixtures used in Florida. The seven types of modifiers evaluated in this study include (1) gilsonite, (2) carbon black, (3) fine ground tire rubber (GTR-80), (4) coarse ground tire rubber (GTR-40), (5) styrene-butadiene rubber (SBR), (6) ethylene vinyl acetate (EVA), (7) styrene-ethylene-butylene-styrene (SEBS). These modifiers were blended with an AC-30, AC-20 and AC-5. These modified and unmodified asphalts were subjected to the thin film oven test (TFOT) to simulate the short-term aging effect that occurs in the hot-mix plant process. Eleven of these modified asphalts were subjected to the thin film oven test (TFOT) and rolling thin film oven test (RTFOT) at higher oven temperatures to simulate the long-term aging effects on these modifiers. All these asphalts and asphalt blends were evaluated by rheological and chemical tests.; The eleven modified asphalt blends and unmodified AC-30 were also used to make Florida type S-1 structural course and type FC-2 friction course mixtures. These mixtures were compacted into Marshall specimens for age-hardening and subsequent testing. These aged and unaged asphalt blend mixtures were evaluated by resilient modulus, indirect tensile strength, and fracture energy tests at two different temperatures. Asphalt residues were recovered from the broken samples and evaluated by consistency tests.; The test results indicate that the modified asphalt mixtures appear to have a more pronounced delayed elastic behavior as compared with that of the unmodified asphalt mixture. The laboratory RTFOT aging process performed at a temperature of 185{dollar}spcirc{dollar}C can simulate a one-year field aging effect, while the California tilt oven process for a duration of 168 hours can simulate an eight-year field aging under typical Florida conditions. In addition, the SHRP pressure aging vessel (PAV) at 100{dollar}spcirc{dollar}C for a duration of 40 hours could simulate an aging effect of over 8 years of service under typical Florida conditions.