PERFORMANCE OF POLYMER AND MODIFIED ASPHALT FIELD TRIALS IN MISSISSIPPI BASED ON GTM AND SUPERPAVE TESTS, MECHANISTIC ANALYSIS, AND FIELD EVALUATION

The Mississippi Department of Transportation (MDOT) is carrying out contruction of new highways and reconstruction of existing ones using Superpave hot mix asphalt mix design as recommended by FHWA (Federal Highway Administration) for improved and longer lasting pavements. Performance-based Superpave characterization measures of asphalt binders and mix design have been adopted for asphalt overlay pavement construction in Mississippi. This paper gives results of I-55 highway polymer-asphalt study near Grenada, Northern Mississippi. Nine pavement sections built of control asphalt and 8 different kinds of modified asphalt binders were subjected to detailed evaluation. The study used nondestructive falling weight deflectometer (FWD) testing, coring, lab creep compliance testing, and determining kneading resilient modulus through the Gyratory Testing Machine. Several newly acquired pieces of Superpave asphalt binder lab testing equipment have been acquired through a grant from MDOT and implemented in civil engineering materials courses and graduate research at the University of Mississippi. The Superpave binder equipment has been used to determine binder material properties for asphalt and modified asphalt binder samples collected in the prior I-55 research study. Mechanistic analysis was conducted using layer modulus values backcalculated from FWD deflection data and considering seasonal effects. The study shows: 1) the predominant mode failure is rutting and 2) the modified asphalt sections out perform the unmodified asphalt section. The field evaluation indicates that controlled sections constructed with the original asphalt binder showed more rutting than all other polymer- and modified-asphalt pavement sections.