Use of tire rubber to improve fatigue performance of asphalt mixtures

Abstract

The accelerated failure of pavements is one of the main problems in Brazilian roads resulting from fatigue cracking due to the repeated application of traffic induced stresses. The incorporation of crumb rubber from waste tires in asphalt, named asphalt rubber, is a method which has been used in several countries to improve the properties of asphalt pavement mixtures and, at the same time, has been a ecologically alternative to deal with the proper disposal of waste tires. This paper describes the results obtained from a laboratory investigation that was undertaken to evaluate the fatigue performance of asphalt rubber mixtures produced by using the wet process with asphalt rubber binder from the continuous and terminal blend. The results were compared to the ones obtained from a reference mixture produced with conventional asphalt typically used in pavement rehabilitation. The laboratory performance of these mixtures was evaluated in terms of fatigue through four-point bending fatigue test. The dynamic mechanical properties, namely the stiffness modulus and fatigue resistance of rectangular beam specimens were evaluated for both types of mixture. The results showed that the asphalt rubber mixtures produced with Brazilian materials and asphalt rubber from the terminal blend system presented the largest fatigue in comparison with the typical mixtures used for pavement rehabilitation. This research allowed defining alternative mixtures which may improve the performance of Brazilian pavements. Correlations between fatigue performance and asphalt rubber characterization in terms of penetration, softening point, resilience and apparent viscosity, were established indicating that the fatigue performance can be predicted through the softening point of the binder.