An experimental investigation on innovative pavements for city logistics

Crumb rubber modified asphalt mixtures (CRM, dry process) involve the blending of crumb rubber (usually 1%–3 % by weight of the total mixture, sizes 2.0 mm/6.3 mm) with hot aggregates prior to mixing with asphalt binder. It may cost more than conventional asphalt concretes. On the contrary, the wet process implies incorporating crumb rubber into asphalt binder prior to mixing with aggregates (usually about 1 % by weight of the total mixture, 18–25 % by weight of bitumen, rubber sizes below about 0.18– 0.42mm) and has a wide and quite sound theory and procedure system behind it. Crumb rubber modified asphalt pavements may cost 1.5 to 2 times as much as conventional asphalt concrete. Importantly, although the dry process has a number of technical issues (including lack of standards, and uncertain performance), it has the potential to recycle more crumb rubber compared with the wet process and its mechanical properties (modulus and mechanical impedance) appear to have the potential for constructing innovative urban and rural infrastructures and for greening European city terminals. In light of the above, the goals of this study were the following: a) designing and testing innovative bituminous mixtures containing high percentages of crumb rubber (dry process); b) designing and testing innovative pavements in which the pressures caused by vehicles and/or motorcycles and/or pedestrians are converted into energy. Several mixes were designed and produced. Based on the results obtained, several options emerged as a possible solution for urban and rural roads, aiming at a better management of flow of goods and transport activities in urban areas while considering lower environmental impacts