Permanent deformation behaviour of unbound recycled mixtures

Nowadays, the use of recycled waste materials in road construction and rehabilitation processes aimed to preserve non-renewable resources and to solve management problems related to the expansion of landfills become a promising engineering solution. The current paper deals with the feasibility of using material from construction and demolition wastes (C&D) as aggregate for unbound layers (base and/or subbase) of road pavements. In particular, the permanent deformation behaviour of a recycled C&D mixture under repeated triaxial loading was investigated and compared with that of two natural granular mixtures selected as reference materials. An analytical model, proposed by the authors, was used to describe the long-term permanent strain accumulation of materials. The results, in addition to showing the ability of the model to predict change in mechanical behaviour depending on the different nature of materials, highlight how the C&D mixture performs better under specific stress and moisture conditions compared with traditional materials. Finally, the results obtained in this study not only provide a practical approach for ranking granular materials for pavement with regard to their rutting potential but also promote the use of C&D materials as a sustainable and effective alternative to traditional aggregates.