Ceramics-Silikáty 61, (3) 223 - 230 (2017)

The paper describes the post-mortem characterisation of spent class AC 70/5 refractory linings from steel ladles, focuses on the environmental impact of their dumping, and points to possibilities of reusing material that is less degraded by corrosion. The degradability of the spent refractories in water is an indicator of their degree of corrosion. Therefore the crushed refractory bricks were leached in water and a weakly acid medium (pH = 5.95 and 4.21, respectively). The pH value, conductivity, redox potential and concentration of ions were measured in the leachates. New AC 70/5 material generates a pH value of leachates of around 8.5, while the alkalinity of leachates from spent brick material increases with the increasing content of lime-corroding compounds (pH = 10-12). Alkaline environments inhibit the release of heavy metal ions. Under the thin strongly corroded surface the refractory material deteriorates only slightly. When bricks are crushed, a redistribution of components into grainy fractions occurs. C and MgO are concentrated in the fine fraction (under 1 mm) and Al₂O₃ in the coarse fractions (1-2.5 mm). In view of raw material prices it is desirable to proceed further with the recovery of grainy Al₂O₃.