Making firebrick tiles, no furnace/kiln

[Ohmans]

I’m planning a project and will have some extra materials on hand and wanted to know if I used Portland cement, fire clay, vermiculite mixture and let dry naturally if this would produce a useable brick/tile? Only use would be to line warm area out of the way of physical damage.

[david s]

Portland cement begins to degrade north of 300C, so anything below that should be ok. The addition of vermicrete to any mix severely compromises its strength (see attached table), so unless there is another reason for adding it, then I think it should be omitted.

[Ohmans]

So if I want something to stand up to some heat what formula would you suggest? I really like the idea of making some custom tiles as it would be a good project for my kids

[david s]

Ok, so if no access to a kiln you could try the homebrew (3 parts sand, 1 part each of hydrated lime, powdered clay and Portland cement by volume) you could add some oxide for colouring. Made up to a stiff mix and pressed into some frames (coated in diesel for release) about an inch high. Keep covered for a week to cure. There are some excellent thinners based concrete and stone sealers that you could coat them with when they’re finally dry.

[Ohmans]

that formula i have ran across on a few websites. I might try some fly ash and refractory cement due to the 300C degradation of portland cement. the more i dig into this, the more interesting this puzzle becomes.

[david s]

I offered the formula I gave you because you said you wanted to use materials you had at hand. It can be used to make an entire oven that is serviceable for the temperatures we use, so if it’s in an area that sees less heat you shouldn’t have problems, The lime takes over as the cementious material where the Portland fails.
Making your own clay tiles from a suitable potters clay and taking them to a local potter to be fired to at least 1100C would be a better but more involved and costly solution.

[Ohmans]

I appreciate your help! I think I have a good idea now how this all fits together