GRK 2802: Four-Point Bending Tests at High Temperatures on Commercial MgO-C Refractory Bricks with and Without Recyclate Considering Different Carbon Contents

Abstract

Given the growing emphasis on refractory recycling, the performance characteristics of commercial MgO-C bricks incorporating MgO-C recyclates are of considerable economic and environmental relevance. In the present study, four-point bending tests are conducted in an argon atmosphere on three commercial MgO-C brick grades over a temperature range from room temperature to 1300 °C. One MgO-C brick grade is produced exclusively from virgin raw materials, whereas the other two grades incorporate MgO-C recyclate at a high mass fraction of 47.5 wt.%. Due to the different sources of the recyclates, their carbon contents vary, resulting in different total carbon contents in the two MgO-C brick grades containing recyclate. Post-mortem SEM investigations show predominantly transgranular fracture through the MgO-C recyclates. The evaluation of the four-point bending tests reveals no detrimental effect of the MgO-C recyclates on bending strength. Instead, a decisive influence of the total carbon content is observed, with lower total carbon contents correlating with higher bending strength values. Furthermore, the heterogeneous structure of the MgO-C recyclates contributes to enhanced stress dissipation caused by anelastic deformation processes in the respective MgO-C brick grades, despite the accompanying decrease in virgin flake graphite content.