Characterisation of an unbound granular mixture with waste tyre rubber for subballast layers

Abstract

Scrap tyres are a solid waste material produced in large quantities. One potential way of disposal is to use rubber particles from shredded tyres as a construction material. Within this context, this paper presents a comprehensive set of laboratory and field tests carried out to evaluate the characteristics of coarse aggregates mixed with rubber particles. The main objective is to assess whether these mixes could be used to form the subballast layer in new railway lines. All the technical features usually required for subballast were tested, including degradation, bearing capacity, density, resilient modulus, etc. The results show that adding between 1 and 10 % of rubber (in weight) improves resistance to degradation. On the other hand, bearing capacity is reduced, but still well over the usual range for common subballast if the rubber content is limited to <5 %. Moreover, the extension and compaction of these mixes can be done using conventional construction equipment.