Improving asphalt mixtures behaviour using scrap tires

Abstract

Used tires represent one of the major solid waste problems in the world. Recycling or disposing of tires in a manner which is economically feasible and environmentally acceptable has been a challenge that requires further research and development. The use of scrap tires in asphalt pavements, known as asphalt rubber, can minimize environmental impact and maximize conservation of natural resources. One of the most promising techniques for pavement rehabilitation to improve the pavement performance is the use of asphalt rubber mixtures, which make use of crumb rubber from scrap tires for the modification of bitumen. Crumb rubber used in this work was produced by ambient grinding. Asphalt rubber has been used to produce asphalt rubber mixtures to be used in pavement overlays subjected to heavy loads and high temperature. In severe conditions, these mixtures are capable of resisting permanent deformations to have an extended fatigue life and to resist crack propagation in comparison to conventional ones. The main objective of this work is comparing the mechanical performance between four asphalt rubber mixtures in relation to conventional asphalt mixture as reference. A laboratory research was conducted to determine the performance properties of overlay layers with asphalt rubber mixtures produced in wet processes using a gap and a dense graded gradation. The asphalt rubber was prepared by the both process, continuous and terminal blend, and its properties were measured through mechanical tests, such as fatigue and permanent deformation. An identical study was carried out for a dense graded conventional mixture used as reference. An extensive study in which the mechanical properties of the studied mixtures were determined and compared was carried out. The permanent deformation and the fatigue life of two different mixture designs manufactured with modified and unmodified binders, with the same aggregates and different binder contents, were evaluated. Results showed that asphalt mixtures using terminal blend asphalt rubber presented better performance than the conventional asphalt mixture.