Characterisation of a crumb rubber mixture for road restraint systems

The need for studying new materials for the construction of road restraint systems arises from past design experiences and from road construction and maintenance demands. This is particularly true for the development of crash cushions. New materials shall comply with requirements of mechanical strength and energy absorption capability with regard to the shape and the class of the system itself (gating or not gating, redirective or not redirective). In particular, the behaviour of materials in the conformation assumed in the system when impacted shall guarantee: - the respect of crash cushions performance parameters; - the redirection-ability, if required; - the avoiding of the detachment of any part or portion that could be hazardous during and after the impact; - an easy repairing and/or substitution of damaged parts; - the durability of parts before and after the impact. This paper investigates the possibility that a crumb rubber mixture has to fulfil those requirements with the not negligible environmental advantage related with the use of recycled materials obtained from minced truck and car tyres. The experimental phase consisted both in the static and dynamic characterization of the material also by means of a drop-dart equipment, as well as the numerical modelling of tests with the aim of assessing the values to be given to the mechanical parameters of the materials in the future simulations of impacts on road restraint systems’ models.