Fireplaces can be built from many materials. You should always use stones, at least for the border, to prevent the fire from spreading - for example by igniting the surrounding grass and causing a wildfire. However, not all stones are suitable for this project, because many types are not sufficiently refractory.
Not every concrete is suitable for the fireplace
Problematic concrete
The types of brick that are not sufficiently refractory include, for example, conventional concrete. The stone itself handles heat well, but its ability to soak up water is problematic. Concrete outdoor fireplaces are exposed to wind and weather and, of course, to rain. The moisture seeps into the concrete - only to evaporate or even deflagrate as soon as the fireplace is lit again at the next opportunity. The result is that the concrete bursts and, in the worst case, concrete blocks (as well as Ytong blocks, but these because of the air they contain) can even explode. For the same reason, the foundation of a fireplace should not be concreted.
Concrete fire pit ideas
If you still want to use concrete for your fireplace, the stone must be protected from rain and moisture. This can be done, for example, by a roof, but also by covering with a waterproof material. If these conditions are met, you cannot necessarily lay out the fireplace yourself with concrete blocks, but you can use them for the border. Disused manhole rings of various sizes, for example, are very suitable for this. It is absolutely safe to use fireclay bricks for your fireplace, because they are absolutely fireproof. Fireclay bricks are specially made to line chimneys and blast furnaces and must therefore be able to withstand high levels of direct heat.
Refractory Concrete
There is also the option of using refractory concrete instead of conventional concrete. So-called refractory concrete can withstand temperatures from 1,100 °C to 2,000 °C and is therefore perfect for concreting a fireplace. Incidentally, if you are planning a brick fireplace, we recommend using refractory mortar - otherwise the wall could not withstand the great stress caused by the heat.
tips
Instead of concrete, fired stones, such as clinker or bricks, are ideal for building a fireplace. These bricks are also inexpensive to purchase and are inherently fire resistant.