UKC

/ Hot concrete?

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mkean - on 16 Apr 2018

Quick question for the builders and engineers of the forum...

I know concrete doesn't really like getting hot and the surface can break up, but is there anything you can do to stop it? My wife wants a fire pit in the garden and as the surround will be concrete it makes sense to cast the bowl at the same time. Is there anything I can mix in to improve the thermal stability; I'd avoid any aggregate in the top layer as I know some rocks can shatter impressively when heated. I want to avoid going down the route of using refractory cement as it isn't normally very weather proof and works out pretty pricey! 

 

Thanks!

IPPurewater on 16 Apr 2018
In reply to mkean:

Make it oversize and line it with clay or firebricks perhaps.

mkean - on 16 Apr 2018
In reply to IPPurewater:

Clay is a good idea, also cheap

If I had a load of fire bricks lying about I could find a few more interesting things to make:

https://hackaday.com/2016/12/05/insanely-hot-oven-makes-pizza-in-45-seconds-avidan-ross-on-food-hacking/

 

yorkshireman - on 16 Apr 2018
In reply to mkean:

> My wife wants a fire pit in the garden 

Be careful 

https://www.youtube.com/watch?v=OeUqjYwhEik

Philip on 16 Apr 2018
In reply to mkean:

Fire clay is one option but even better you can use a castable cement for furnaces. Build the oven from refractory bricks. Make sure you take the time to bed it in, the cracking is the change of temperature and particularly the contraction from loss of water during first use.

Your firepit won't get near my 1600C furnace I'm planning to build my wood fired oven from same material.

Timmd on 17 Apr 2018
In reply to mkean:

Is the surround made from concrete because there is already concrete on the ground around where the fire pit will be?

summo on 17 Apr 2018
In reply to mkean:

When you use the cement in stoves and furnaces mentioned above, it is often mixed with iron filings and swarf (spelling). It makes the cement expand and contract at the same rate as the stove and doesn't crack etc.. 


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