Laboratory Investigation of Warm Porous Asphalt Mixtures Containing Crumb Rubber for Motorway Wearing Course

In recent decades, the growth of road transport systems has contributed significantly to global warming and environmental pollution. In addition, the constant increase in transport vehicles also implies the generation of a significant amount of end-of-life tires (ELTs) to be landfill disposed. In this framework, the combination of warm-mix asphalt (WMA) technology with crumb rubber (CR) from ELTs, seems to be a valid and sustainable technical solution. Furthermore, the use of CR in asphalt mixtures has proven to improve pavements' acoustical performance. In this context, the present research shows the results of a laboratory characterization of a dry rubberized semi-porous asphalt mixture produced with WMA technology aimed at optimizing an eco-friendly and low-noise solution for motorway pavements. To this end, several WMAs (with different bitumen and CR content and a reference WMA without CR) were tested and qualified by means of testing for mechanical analysis (Compaction Energy Index, Indirect Tensile Test, Cantabro Test, and Indirect Tensile Stiffness Modulus) and for surface properties detection (by Darmstadt Scuffing Device and Wehner-Schulze machine). Traditional test results show that the workability and mechanical performance of optimized warm mixtures with CR are comparable to those of the reference one. Also, surface test results show adequate values of raveling resistance and friction after polishing, demonstrating that warm mixtures with CR can be considered as a green feasible technical solution for motorway pavements.