Crumb Rubber Modified Asphalt Concrete for Low Noise Surfaces

The principal advantage of introducing some percentages of crumb rubber in production of asphalt mixtures is related to pavement environmental sustainability, since this process allows to recycle a significant amount of an industrial waste and, in some specific cases, to reduce tire/road noise emissions; there are some other not unanimously recognized advantages related to this process that are the improvement of asphalt mixture mechanical properties and durability as well as friction on pavement surface. This paper reports on a research project carried out to evaluate the advantages of using crumb rubber in construction of low noise gap graded asphalt concrete surfaces, specifically designed to reduce rolling noise by optimizing surface texture. The study also aimed to define the mechanical and functional performances of the mix obtained by using the wet process in order to assess its potential for use as viable alternative to other low noise asphalt surfaces aimed to improve pavement sustainability by reducing environmental, social and economic impacts. Results of laboratory and on site tests, carried out on one specifically built field trial, clearly show this mix can have optimal mechanical and functional performance as well as it can reduce tire/road noise and warrant greater durability of wearing layers; this considering, crumb rubber modified asphalt concrete can be classified as a construction material that can enhance the three dimensions of sustainability.