Slags and rubber from end-of-life tires represent a liability to the steel and tire industry, causing economic and environmental problems that are difficult to manage. Transport infrastructures can use these industrial by-products instead of extracting natural raw materials, but the adequate mechanical performance of the materials needs to be assured. This paper addresses the mechanical behaviour of slag–rubber mixtures in the laboratory with CBR, monotonic and cyclic triaxial tests. In addition, light falling weight deflectometer tests were also performed in a physical model. The results were analysed to meet technical specifications from Brazil, Portugal and Australia using railway sub-ballast layers, capping layers or road pavement layers as the base and sub-base to identify the applicability range of slag–rubber mixtures for transport infrastructures. Concerning the analysed parameters, it was demonstrated that slag–rubber mixtures can show resilient behaviour and strength adequate for the support layers of transport infrastructures provided that the rubber content is below 5% in weight and that the slag is milled to comply with the grain size distribution ranges available in the technical specifications of the cited countries.

Railway lines require a significant amount of natural raw materials. Industrial by-products can be used instead, reducing the costs of natural aggregate exploration. This work analyzes a ballasted track’s short- and long-term performances when replacing conventional sub-ballast aggregate with steel slag. After an extensive laboratory characterization of the steel slag, the material performance was analyzed in a 3D numerical model of a ballasted track when included in a railway track. An empirical model was implemented and calibrated to predict the long-term permanent deformation induced in the track after many train passages. The results are compared with the allowable deformation limits required for conventional high-speed ballasted track railway lines. An additional analysis was conducted to assess the influence of steel slags on the critical speed of conventional railway tracks when used. The results show a residual impact on the critical speed value compared to the conventional sub-ballast made with natural aggregates.

A construção de infraestruturas de transporte mais sustentáveis requer a utilização de materiais que combinem eficiência técnica e viabilidade económica e ambiental. Este estudo, desenvolvido no âmbito do projeto de investigação ECO_RORAIL, avalia misturas de escória de aciaria com borracha triturada de pneus em fim de vida para camadas não ligadas de apoio de infraestruturas de transporte. O programa experimental compreende ensaios triaxiais monotónicos e cíclicos para avaliar resistência ao corte e módulo resiliente. Em paralelo, recorre-se à modelação numérica 3D pelo método dos elementos finitos para avaliar a resposta estrutural da ferrovia com camada de sub-balastro constituída por estas misturas, variando o teor de borracha. Os resultados laboratoriais indicam comportamento adequado quando o teor de borracha é inferior a 5% em massa e a escória cumpre a granulometria especificada. A análise numérica sugere uma redução das tensões deviatóricas, melhoria da dispersão das cargas em profundidade, contribuindo para mitigar a degradação do balastro e a concentração de tensões no solo de fundação, aumentando a resiliência estrutural.