A finely ground refractory blended with clay or chemical binders and mixed with water to bed and join bricks. Heat-setting mortars only develop strength when fired, air-setting mortars use binders such as sodium silicate to harden at room temperature, and phosphate-bonded types give strong joints in between. Refractory joints are kept thin, often 1 to 2 mm, because the mortar is weaker than the brick and joints are where slag gets in; many basic linings are simply laid dry.
Dip-and-rub joints with the air-setting refractory mortar, thin enough you can't get a fingernail in.
Match the mortar to the brick chemistry. A fireclay mortar in a high-alumina or basic lining becomes the joint slag finds first.
Also heard as
- mortar
- refractory cement
- mud
Related terms
Butter
To spread mortar onto the faces of a brick before setting it in place.
Mud
Shop word for the clay used to plug a blast furnace taphole, and bricklayers' word for mortar.
Expansion joint
Gap deliberately left in a lining so bricks or castable can grow with heat without crushing or lifting.
Brickie
Shop name for a refractory bricklayer, especially in Britain, Australia and steel plant crews.