Rheological behavior and scanning electron microscopy for the analysis of long digestion time asphalt rubber

Abstract

The asphalt modification by the addition of crumb rubber is a technique used in the last years to improve the properties of the asphalt mixtures mainly the fatigue and permanent resistance deformation. The analysis of the asphalt rubber properties to predict its performance can be done through different tests being rheology a widely used technique since asphalt is a viscoelastic material and highly dependent on temperature. With the rheology test, parameters such as complex shear modulus (G*) and phase angle (?) are obtained, being possible to understand the evolution of the fatigue and permanent deformation resistance as well as the viscous and elastic characteristics of the asphalt. Also, the properties of the asphalt rubber are dependent of the asphalt type and crumb rubber used in the modification of the asphalt. In this work four asphalt rubbers were studied produced with 35/50 and 50/70 pen asphalt modified with cryogenic and ambient grinding crumb rubber. Since the digestion has an important influence in the asphalt rubber, in this work the mixing time of each asphalt was studied, testing asphalt rubbers produced up to 48 hours of digestion time. For each digestion time studied (30 minutes, 1 hour, 2, 3, 4, 5, 6, 7, 8, 24, 30 and 48 hours) rheology and scanning electron microscopy (SEM) tests were conducted. The results of rheology tests show that G* and ? are dependent on digestion time as well as the type of conventional asphalt and crumb rubber modifier. These results were compared with the scanning electron microscopy characterization.