How to Make Fireproof Concrete

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How to Make Fireproof Concrete
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Things You'll Need

  • Wheelbarrow or plywood for mixing concrete

  • Shovel

  • Trowel

  • Concrete forms

  • Gravel

  • Sand

  • Refractory cement

  • Hydrated lime

  • Spray bottle

  • Plastic sheet

  • Hose or other water supply

Fireproof concrete has several applications for homeowner's and industry. Many wood-fired ovens, kilns and fireplaces are built with fireproof concrete or other fireproof material known as refractory concrete. Commercially, fireproof concrete is made by mixing a product known as fly ash, a by-product of the production of Portland cement. You can make your own fireproof concrete with materials available at home improvement stores. If you are planning to build blocks, you will need to have you forms ready beforehand so you can pour the mix right into the forms when the concrete is at the proper consistency.


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Mixing the Concrete

Step 1

Place your sheet of plywood in the work area or the wheelbarrow. You should be near a hose so water can be easily added and so the area and tools can be rinsed when it's time to clean up.

Step 2

Portion the materials into a 3:2:2:0.5 ratio so you have 3 parts gravel, 2 parts sand, 2 parts refractory cement and 0.5 parts of the hydrated lime. Follow this ratio regardless of the volume of fireproof concrete you will be making.

Step 3

Place the gravel and sand into the wheelbarrow or onto the plywood.


Step 4

Add the refractory cement and hydrated lime over the top of the sand and gravel.

Step 5

Mix all dry ingredients together with a shovel. Mix until all components are evenly distributed. Create a depression in the middle of the pile with the shovel to receive the water.

Step 6

Add water to the mixture. Mix the dry materials and water together until the mixture doesn't have any dry pockets. Do not add so much water that the mixture becomes soupy. Water should be added to the mixture at a rate of about 1/2 to 1 gallon at a time and then mixed before adding more water.


Step 7

Continue to add water or more mix in the proper ratio until the concrete is workable. If you can pack a handful of concrete like a snowball and it doesn't fall apart, it is the proper consistency.

Step 8

Fill the forms with a shovel. Use the trowel to scrape off excess and to give the concrete a level surface.

Curing the Concrete

Step 1

Spray the edges and surface of the concrete with water in the spray bottle. This will prevent too rapid of a moisture loss while the concrete is curing.


Step 2

Cover the concrete once wet, with a plastic sheet for 48 hours.

Step 3

Remove the plastic after 48 hours. Allow to air-dry for a minimum of 48 hours before trying to remove the forms. If it isn't sunny or the air temperature is cool or cold, allow it to cure for up to three weeks before attempting to use.


Chris Bond

Chris Bond has been writing about gardening, sustainable agriculture and local history since 2005. He has been published in "The Plain Dealer," "The Repository" and online. Bond holds an A.A.S. from the State University of New York at the Finger Lakes campus in Canandaigua, N.Y.