Desempenho à deformação permanente de ligantes com diferentes origens e misturas asfálticas preparadas com CAP puro e modificado por polímero

Abstract

The participation of the road modal in the Brazilian transportation matrix is significant, and it refers to more than 60% of the total freight transportation in the country. Despite such an importance, more than 50% of the paved road network does not show an excellent or good conservation status, especially in the less developed states. Within the group of main distress mechanisms found in Brazilian asphalt pavements, rutting (or permanent deformation) deserves a special attention. To counteract this pavement distress mechanism, modification of the asphalt binder – or Asphalt Cement (AC) – constitutes an interesting option to increase rutting performance of the asphalt mixture. In this manner, the present research study mainly aims at evaluating rutting performance of asphalt binders and mixtures and by considering three different crude sources for the binder (Russia, Brazil and Colombia), three modification types with the styrene-butadiene-styrene (SBS) copolymer and materials typically used in pavement construction in the southern region of Brazil. Two of these binders are unmodified – AC 50/70 (64S-22) and AC 60/70 (64H-22) – and the three remaining materials are SBS-modified (SMB): SMB 65/90 (76S-28), SMB 60/85 (70H-22) and highly-modified binder, HiMA (82V-22). The rheological tests in the binder scale include multiple stress creep and recovery (MSCR) at temperatures between 64 and 82°C and oscillatory shear for the determination of the complex modulus (G*) and the phase angle (δ), as well as master curves at 25°C. The mechanical tests in the mixture scale include flow number at 60°C (FN) and the Hamburg Wheel Tracking Device (HWTD) at 50°C and with mixtures immersed in water. The nonrecoverable creep compliance at 3,200 Pa (Jnr3,2) and at 64°C may be interpreted as a promising parameter to predict the rutting resistance of the asphalt mixture due to the excellent correlations with the parameter FN and HWTD. The ratio of Jnr3,2 to the original SUPERPAVE rutting parameter G*/senδ is described as combined elastic plastic parameter CEP3,2, and such an parameter showed results and correlations with mixture data that are comparable to the ones of Jnr3,2. The AC 60/70 depicted a better rutting performance than the AC 50/70, as based on the outcomes of the mixture and the binder. In a general context, both FN and HWTD can be used in studies about rutting in the asphalt mixture, and the final choice depends on the user. Construction and monitoring of pavement test sections may collaborate with a more detailed analysis of the susceptibility of each of the above-mentioned formulations to rutting.