Technical feasibility for the replacement of high rates of natural aggregates in asphalt mixtures

This research demonstrates the technical feasibility of replacing new raw materials by recycled and renewable alternative ones to make different sustainable asphalt mixes. In order to verify performance, a comparative analysis of different alternative materials was carried out. Electric arc furnace (EAF) slag, basic oxygen furnace (BOF) slag, waste foundry sand and reclaimed asphalt pavement (RAP) were used to replace natural aggregates in different proportions to enable the impact on asphalt concrete to be studied. Moreover, with the aim of restoring the properties of old binder from RAP and maximising the reduction in the amount of virgin binder needed, the effect of two rejuvenators was evaluated. The technical feasibility of using asphalt mixtures with a natural aggregate replacement rate of 80–98% was demonstrated at laboratory level. In this sense, the use of EAF and BOF slag to replace high-quality natural aggregate in the coarse fraction and the use of waste foundry sand to replace natural aggregate in the fine fraction proved to be a promising option. Furthermore, a significant virgin binder reduction was achieved with the combined use of RAP and rejuvenator, without compromising the mechanical performance of the mixtures.