Innovative Use of Recycled Rubber and Mining By-Products for Sustainable Rail and Road InfrastructureKeynote

Encouraging more real-life applications of circular economy perspectives in transportation infrastructure design and construction, this paper focuses on utilising granular wastes (i.e. coal wash and steel slag) from coal and steel mining for port reclamation, and recycled rubber elements including granulated rubber particles, rubber mats, tyre cells and truck tyre segments for stabilising track formations and reducing ballast degradation. The mixtures of coal wash and steel slag were optimised through a proposed novel customer-made selection criteria and verified through field trial. Moreover, the promising damping property of rubber (with respect to strain energy capacity) was fully exploited to design substructure energy retention layers to minimise deformation and degradation of track elements including impact damage caused by track irregularities such as rail corrugations. The large-scale laboratory testing results obtained using the large-scale triaxial, Process Simulation Prismoidal Triaxial Apparatus, and the prototype National Facility for Cyclic Testing of High-speed Rail and the field trial verify that rail tracks altered with the above-mentioned rubber elements easily satisfy the specified standards and are even superior to conventional ballast tracks in terms of degradation, deformation, stress distribution, and track vibration. In addition, these environmentally friendly approaches promote the reuse of mining by- products and discarded tyres and conveyor belts in transportation infrastructure while providing long-term cost benefits that can save millions of dollars annually in track maintenance and quarrying natural rock aggregates.