Sustainability in Concrete Production: Reclaimed Asphalt Pavement as Recycled Aggregate

In recent years, scientific research on concrete has focused on the development of sustainable mixes containing recycled materials to avoid the exploitation of non-renewable resources and to reduce the amounts of landfilled materials. In this regard, considering that aggregates are the most used material for concrete production, a virtuous solution may involve the use of recycled ones, such as reclaimed asphalt pavement (RAP). Few studies on RAP as concrete recycled aggregates and their use in concrete production have been already published. Aiming to fill this gap, a systematic study on the use of RAP to produce more sustainable concrete is proposed. Firstly, RAP sourced from two Italian collection sites was characterized as concrete aggregate. Then, microstructure of concrete containing RAP was studied by mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM). Finally, the environmental assessment of concrete containing RAP and natural aggregate was carried out using a life cycle assessment (LCA) tool in terms of the global warming potential (GWP) impact category reduction. Results showed that the well adherent bituminous layer on the aggregate surface in RAP induces hydrophobic behavior, not evident in natural concrete aggregates. In hardened concrete containing RAP, an increase in total open porosity and discontinuity in the interface between RAP and cement paste were observed. Finally, the use of RAP as natural aggregate replacement is a promising route in terms of sustainability issues, as demonstrated by LCA analysis.