The Road Research Laboratory of the Technical University of Catalonia hasconducted a study to determine the effect of adding crumb rubber on the functional characteristics of gap-graded mixtures, particularly texture andnoise on the basis of full-scale measurements of several test sections. All sections were constructed with a gap-graded mixture, where three types of binders were used, i.e. bitumen with crumb rubber added by the wet process, same bitumen with addition of crumb rubber by the dry process (1% and2% crumb rubber content) and polymer-modified bitumen acting as the reference. The test sections are located on road B-140 near Barcelona. Texture and skid resistance were measured by SCRIM, noise levels were quantified in a semi-anechoic chamber (Close Proximity Method CPX) and the use of different tires was analyzed (by the Laboratory of Acoustics Applied to Civil Engineering of the University of Castilla-La Mancha). The results revealedthe impact of construction and service conditions on the surface characteristics of pavements and the fact that, in general, addition of crumb rubber by the dry process may positively influence skid resistance and tire/pavement noise despite decreasing texture levels.
Abstract