Magnesia‐carbon refractories from recycled materials

Recycling of used refractories – in particular closed-loop recycling – gains in importance because of both ecological and economic benefits, such as the conservation of natural resources, reduced landfilling, and the reduction of greenhouse gases and energy consumption. In this work, the use of a magnesia-carbon (MgO-C) recyclate for the production of MgO-C refractories is investigated. Using fused magnesia, the mentioned MgO-C recyclate, graphite, novolak, and a modified coal tar pitch, test specimens with different recyclate contents (0, 40, 65, and 82 wt%) were prepared on a laboratory scale. The apparent porosity, which is usually higher in recyclate-based refractories than in recyclate-free ones, increased by 14% from the specimens made exclusively from virgin raw materials to those made from the mixture containing 82 wt% recyclate. The dynamic Young's modulus and cold modulus of rupture decreased, but the thermal shock resistance was improved by the use of the recyclate.