HIGH-TEMPERATURE PROPERTIES AND MODELING OF ASPHALT BINDERS MODIFIED WITH SBR COPOLYMER AND PPA IN THE MULTIPLE STRESS CREEP AND RECOVERY (MSCR) TEST

The main objectives of this paper are to (i) study the rutting performance of asphalt binders modified with styrene butadiene rubber (SBR) copolymer, polyphosphoric acid (PPA) and SBR+PPA, (ii) quantify the percent recoveries R and the nonrecoverable compliances J(nr) in the multiple stress creep and recovery (MSCR) test, and (iii) indicate the best formulations in terms of rutting performance. All these formulations have the same high-temperature performance grade in the Superpave (R) specification (PG (6)(7)-xx). The Burgers model was used to fit the laboratory data and the parameter G(V)was obtained from the model. The degrees of improvement in the R and the Jnr values after binder modification are higher for the AC+SBR+PPA and the AC+PPA than for the AC+SBR and the results are slightly better for the AC+SBR+PPA. The use of longer creep and recovery times led to increases in the stress sensitivity of the modified asphalt binders and in their rutting potential (higher Jnr values and lower R values) and these effects are more pronounced for the AC+SBR. The AC+SBR+PPA was identified as the best formulation in terms of elastic response and susceptibility to rutting, followed by the AC+PPA and the AC+SBR.