Description
The modification of asphalt with crumb rubber from scrap tires has been a successful technique to improve the performance of asphalt mixtures with improved performance for the rehabilitation of road pavements. The incorporation of crumb rubber into the asphalt can be done by the wet process or by the dry process using crumb rubber obtained from grinding at cryogenic temperature or from ambient temperature. The characteristics of the resulted modified asphalt depends on the properties of its components and external factors such as digestion time and temperature. In the continuous blend process, where the asphalt rubber is produced in the asphalt mixture plant, the digestion time is relatively short and the produced asphalt rubber is added to the asphalt mixture. The objective of this work is to study the importance of the digestion time in the characteristics of the modified binder by evaluating the penetration grade, softening point, resilience and viscosity. Two different conventional binders (penetration grade of 35/50 and 50/70) were modified with cryogenic and ambient crumb rubber with a mixing time up to 48 hours. During that time, 12 samples of each the asphalt rubber were obtained on 30 minutes of mixing time and at 1, 2, 3, 4, 5, 6, 7, 8, 24, 30 and 48 hours. This paper concluded that the digestion time is an important factor to take in consideration during the mixing process, since it has an important influence on the properties of the modified asphalt.
