**7. Metallic waste additives**

The amount of industrial metallic waste is huge and can be challenging to recycle. These metals, however, can be added to concrete and mortar to improve their properties. In this context, Małek et al. utilized metal chip waste generated by lathes and CNC machines as an additive to concrete. Results show that adding metal waste can improve the physical and mechanical properties of concrete [36].

Norambuena-Contreras et al. utilized two kinds of steel industrial wastes, steel shavings and steel wool fibers, to manufacture mortar. They concluded that there were small variations in flexural and compressive strength, but an overall improvement of the mortar due to adding the steel [37].
