Recycling waste rubber particles for the maintenance of different states of railway tracks through a two-step stoneblowing process

Abstract

Injecting recycled rubber particles under the sleeper through a two-step stoneblowing technique (partially replacing the small stones with rubber) could improve the performance of ballasted railway tracks. In addition, this results in fewer environmental impacts associated with maintenance whilst recycling an abundant waste material (End-of-Life-Tyres, or ELTs). Nonetheless, to continue the development of this solution before its widespread application, this paper assesses the volumes and dosages of rubber to be used during the correction of various levels of irregularities and track states. The aim is to extend the service life of the track whilst optimizing performance by the inclusion of the elastic particles (particularly in transition sections where gradual variation of track behavior is required). For this purpose, innovative laboratory tests were used to study the effect of applying various quantities of rubber (recycled from ELTs) over small stones to correct three different levels of settlement. This paper presents the resulting guide values for the volumes of small stones and rubber particles to be added. These values depend on the level of track settlement to be corrected and the need for resilience according to the section and characteristics of traffic to be supported. Further, it appears that it is preferable to add the rubber after the compaction of the layer of small stones, which results in a lower tendency towards settlement and irregularities. Therefore, the current findings indicate that a two-step stoneblowing process (adding appropriate quantities of rubber) could be a cleaner technique for improving track behavior and reducing environmental impacts associated with maintenance.