Accelerated aging study on rheological properties of synthetic bitumens

For this work, the binder's formulations were made using recycled polypropylene and post-consumed paraffinic oil. The samples were made on IKA Eurostar 20 mechanical stirrer with mixing biade with four propellers. A heating bath was used at 170ºC. The samples were mixed up at 500 rpm and the mixing time was 2 min. The proportions of the mixtures were 5, 1 O and 20 % (m/v). The accelerated aging test was carried out in the QUV aging chamber of the company Q-lab, according to ASTM G-154 cycle 1. The rheological analyzes were performed on Rheometer oscillating disc Haake Mars li (Thermo Scientific), viscosity curves were performed in ascending-descendants ramp with shear rate from O to 200 s-1 for 3 min. The analyzes were performed at 150ºC. Frequency sweep curves were performed with controlled stress of 1 Pa with variation of oscillation frequency of 0.1 to 100 rad/s, the temperature used was 25 and 125 ºC. Observing the values obtained in the flow curve analysis, it is possible to observe an increase in viscosity values at low shear rates in the samples with 15% and 20% polymer mass in the composition of the synthetic bitumen, the sample with 15% PP obtained an increase of 3.5 Pas, while the 20% sample obtained an increase of 1 Pas, however these samples obtained a slight decrease in the viscosity values when the shear rate was increased; the aged samples showed a more pronounced pseudo-plastic characteristic. Observing the results obtained for the frequency sweep test of the samples before aging and after aging, the aged samples analyzed at a temperature of 25ºC showed a sl ight increase in the values of storage modulus (G'), except the sample with 20% of the polymer in the composition, and the loss modulus (G") also showed increase in its values in relation to the samples before aging. Those samples that were analyzed at 125ºC did not present the sarne tendency to increase the values of G' and G" of the samples that were aged in relation to the unaged samples. The action of aging may have caused the samples to stiffen, causing them to increase in their modulus values, but at the sarne time this enrichment is no longer observed by the softening of the sample. Stiffness at low temperatures can decrease the resistance that would cause successive deformations, causing a decrease in its useful life