How do you make refractory concrete?

Answer 1

Ingredients: River gravel or crushed fire bricks

Sand

Calcium Aluminate cement. (if available in different grades choose the better one)

Lime (lime is usually cheaper, about 80% of the cement price)

Water

You can add into this mix a little standard Fireclay if you like. Mixture: (parts ratio is 3 x 2 x 2 x 0.5, plus water)

3 shovels of the gravel or crushed firebricks

2 shovels of sand

2 shovels of the (portland) cement

half shovel of lime

This amount will require approximately 6-7 liters of water to mix the concrete. Put dry gravel and sand on a thin metal or plastic sheet, or on a clean concrete surface in an area you can make a bit dirty. (Be sure to clean the area and tools with water after working with cement.)

Add the cement and lime on top of the gravel and sand.

Calcium Aluminate cement and Lime will work the best as the cement in hot cooking conditions- This applies to refractory concrete as well as to heat resistant mortars.

(Lime is sometimes mixed into fire clays. This is mixed like a normal cement based mortar, but with half the cement replaced with the lime. The cement holds it together when it is drying but when the heat gets into the cement and burns it out, the lime holds it all together. Lime used in building - calcium hydroxide Ca(OH)2 [oxide of calcium CaO of limestone] is used for making mortar and cement.)

Ingredients in the now days Portland cement are:

60% to 67% CaO

17% to 25% SiO2

3% to 8% Al2O3

up to 6% Fe2O3

plus can contain also mini amount of MgO, MgSO4, Na2O, and K2O

Answer 2

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