Energy, environmental and technical assessment for the incorporation of EAF stainless steel slag in ceramic building materials

Abstract

The paper studies the addition of electric arc furnace stainless steel (EAF-SS) slag to clay raw materials for ceramic brick manufacturing in order to get more sustainable materials without compromising their final properties. Different amounts (10 wt%, 20 wt% and 30 wt%) of EAF-SS slag were added to a reference clay material. The samples were processed by extrusion and the main technological properties were determined to characterize the behavior of the materials during the shaping and drying processes (working moisture, drying linear shrinkage and modulus of rupture) and the final properties of sintered materials (bulk density, linear shrinkage, water absorption and modulus of rupture) at five maximum temperatures (850, 900, 950, 1000 and 1050 °C). The environmental impact was evaluated by qualitatively analyzing gaseous emissions during firing and by leaching tests on laboratory specimens. Furthermore, energy demand and fuel (natural gas) required to produce the formulated compositions, according to a standard industrial scale, was calculated in both the dryer and the kiln. Calculation of CO2 emissions during such theoretical industrial processing was also performed. Results show that the incorporation of EAF-SS leads in general to adequate technological properties and causes a potential saving of up to 17% of natural gas consumption and a reduction in CO2 emissions of up to 24% during manufacturing materials with 30 wt% of EAF-SS slag at 950 °C. However, in these materials the higher metals leaching potential would restrain the EAF-SS slag incorporation to a content of about 10 wt% or less and to sintering temperatures >950 °C. Therefore, clay ceramics incorporating EAF-SS slag in their composition can be technologically feasible and environment-friendly depending on both sintering temperature and amount of waste addition.