Environmental risks and mechanical evaluation of recycling red mud in bricks

Area of Science:

• Materials Science
• Environmental Science
• Construction Engineering

Background:

• Construction materials increasingly incorporate industrial by-products.
• Natural materials and by-products can contain heavy metals and radionuclides.
• Incorporating by-products may elevate contaminant concentrations, impacting public health.

Purpose of the Study:

• To evaluate red mud as a clay substitute in fired bricks.
• To assess the physical, mechanical, radiological, and leaching properties of these bricks.
• To determine safe red mud incorporation limits for environmental protection.

Main Methods:

• Fired bricks manufactured with red mud replacing clay up to 80 wt%.
• Sintering at 1173K and 1373K analyzed.
• Leaching tests (batch and monolithic) and radionuclide analysis performed.

Main Results:

• Higher sintering temperatures increased mechanical strength.
• Red mud alone showed chromium leaching above European Landfill Directive limits.
• Bricks with high red mud content at 1173K showed no Cr issue, but vanadium levels were high.

Conclusions:

• The study identifies maximum red mud percentages for brick manufacturing without environmental risk.
• Careful control of sintering temperature and red mud proportion is crucial.
• Potential environmental risks from heavy metal leaching must be managed.