Foundry wastes reuse and recycling in concrete production

The industrial process of a cast iron foundry plant located in the North of Italy was analyzed in order to determine the amount and kind of produced wastes. The main fractions are core and moulding sands, muds and powders from dust abatement plants, furnace and ladle slags, and exhaust lime, making about 750-800 t/d of residues for a production of about 800 t/d of globular and grey cast iron. All wastes were sampled and characterized by means of particle-size distribution and chemical analyses to evaluate the best reuse and recycling solutions. On the grounds of the gathered results, the residues may be divided in three categories according to the particle-size dimensions: below 0.1 mm, between 0.1 and 0.6 mm and above 0.6 mm. The fraction above 0.6 mm, mainly made of metallic iron, may be reused in the furnaces. The fraction between 0.1 mm and 0.6 mm may be reused in cores production, after a regeneration treatment. The fraction between 0.1 and 0.025 mm may be recycled as raw material for the concrete industry, and the below 0.025 mm fraction may be reused in green moulding operations. An economic evaluation of the proposed reuse and recycling solutions was performed.