Characterization and recycling of the fine fraction of automotive shredder residue (ASR) for concrete paving blocks production

Shredder is the equipment used for ferrous scrap grinding that enables the recycling of steel in steel mills. The scrap is mostly originated from end-of-life vehicles (ELV).Therefore, this residue is known as automotive shredder residue (ASR). Throughout the world, is estimated that more than 25 million vehicles turn into an ELV every year, and most of their resources end up in landfill. Occasionally, hazardous substances may appear on the Shredder waste, which are very heterogeneous as a result of the variety of material fed into the equipment. Thus, Shredder waste has become a worldwide problem due to its environmental impact, heterogeneous composition and its recycling has been a challenge. Therefore, this manuscript addresses the characterization of the fine fraction of ASR generated in a plant located in Brazil. It is also proposed its recycling in concrete paving blocks to replace the natural fine aggregate through the Portland cement solidification/stabilization (S/S) technique. S/S prevents the release of hazardous chemicals from waste. As a result, with a 20% substitution content of the fine sand for the waste, 6 out 8 toxic elements presented in the residue were encapsulated by cement (total phenol, total iron, fluorettes, manganese, selenium, surfactants) and reached the required by the Brazilian standard. The two non-encapsulated elements were aluminum, whose concentration showed a 62.5% decrease, and cadmium, which is also found in conventional blocks. The concrete paving blocks showed good mechanical and physical performance. Therefore, the concrete paving block produced could be used as a potential solution for the mitigation of the environmental impact caused by the fine fraction of ASR waste.