How to Make Fireproof Mortar

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Things You'll Need

  • Silica sand

  • Lime

  • Fireclay

  • Calcium aluminate cement powder

  • Large bucket

  • Measuring cup

  • Drill with stirring attachment

Fireproof mortar adds additional fire and heat protection to a wall or building.
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Most mortar is fireproof to some extent. The materials of clay, cement, lime and sand are naturally resistant to fire and heat. However, there is a formula for mixing mortar that will not only resist fire, but it will also resist heat damage as well. This mixture of mortar is easy to mix up and is ideal for use around fireplaces and other areas where there is a risk of fire or extreme heat. Follow the intended uses and thickness instructions for the mortar for best results. You can also use fireproof mortar in any area where you would use traditional mortar.


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Step 1

Mix the sand, lime, cement and fireclay together in a large bucket. Use 10 parts sand, three parts cement and fireclay, and one and a half parts lime. Wear a dust mask while you measure the powders as they are very dusty, which can be damaging to the lungs.

Step 2

Mix the ingredients together until they are dispersed evenly. You should no longer be able to identify the separate substances once the mixing is complete.


Step 3

Stir the mixture with the stirring attachment on the drill. Slowly add water to the mixture, continuing to stir the entire time. Add enough water to change the mixture from a powder to a thick mud or peanut butter consistency.

Step 4

Spread the mixture around areas that get consistently warm, such as around fireplaces and outdoor barbecue pits or cooking spaces. Do not spread the mixture thicker than one-quarter of an inch or the mixture can crack, flake or break off in clumps, necessitating replacement.