Synthetic gravel for concrete obtained from sandy iron ore tailing and recycled polyethyltherephtalate

The exploration of banded iron formations (BIFs) as iron ore is an important economic activity in Brazil, especially in the State of Minas Gerais. The process to obtain iron ore concentrates from BIFs generates huge amounts of tailings. About half of the extracted volume is transformed into tailings, which are usually employed to fill exhausted open pits or stored in dams. Although these tailings are inert and non-hazardous, the huge volumes cause concerns related to safety of dams. With the shortage of space for dams and increasing costs of monitoring and licensing, the use of tailings as raw material for other manufacturing chains is becoming attractive. A synthetic gravel for concrete production was obtained with the sandy residue from BIFs exploitation and recycled polyehtyltherephatalate (PET). The process to obtain the synthetic gravel, its properties, as well as the properties of concrete is presented. The unitary mass of this gravel is 0,89 kg/dm3 (lightweight aggregate). The compressive resistance of the concrete after 7 days was around 9 MPa, the water absorption was 13.6-14.9%, and the density of the concrete was about 1.9 g/cm3. The concrete is suitable for making light bricks for masonry in the region of the mines.