Expansion joint

Joints in the refractory masonry used to absorb thermal expansion; the joints are ideally offset.

Nowadays, appropriate cords or other combustible materials such as cardboard or pieces of wood are inserted in the joint; they burn after heating up or preheating and leave a joint. The required width of the expansion joint depends on the refractory material used.

Stone qualityThermal expansion up to 1000 °C in %Width of the expansion joint in mm
Silica1.2 to 1.410 to 15
Magnesia1.3 to 1.420
Chromium ore0.8 to 0.913
Fireclay0.5 to 0.75 to 8

Additional references:
Basic lining