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 quality||Thermal expansion up to 1000 °C in %||Width of the expansion joint in mm|
|Silica||1.2 to 1.4||10 to 15|
|Magnesia||1.3 to 1.4||20|
|Chromium ore||0.8 to 0.9||13|
|Fireclay||0.5 to 0.7||5 to 8|