Low-noise friction courses containing treated and un-treated crumb rubber to mitigate tire/road noise in urban contexts

Tire/road interaction is one of the main causes of traffic noise. This generates health, social, and environmental issues. Bituminous mixtures containing crumb rubber, CR, and with low-nominal maximum aggregate size, NMAS, can be used to mitigate the aforementioned issues in both the short and long period. The main objective of the study presented in this paper is to investigate the variation of volumetric, surface, mechanical, and acoustical properties of friction courses due to the presence of treated and un-treated CR. Low-noise mixtures were designed during the ongoing project “E-VIA” (LIFE18 ENV/IT/000201) and were used to pave a street in Florence. In the laboratory, samples were created using the Superpave Gyratory Compactor (AASHTO T-312, UNI EN 12697-31). Specimens with NMAS=6 mm and bitumen in the range 6-7% were used as a reference. Other two sets of specimens were created adding treated and un-treated CR (dry method). Results show how the different composition affects the properties and performance of the mixtures under investigation. Future studies will include the comparison between the in-lab produced specimens (herein analyzed) and the cores extracted from the aforementioned street.