As stated in many articles, fire pits are a great option in most backyards. One important consideration is what it should be made out of, stone, concrete or metal.
It seems natural to use metal or stone, however, is it really possible to use concrete?
Most people seem to have concerns about the use of concrete in the making of a fire pit because of its intolerance to high heat.
As a result, the question I am most commonly asked is, will a concrete fire pit explode?
Yes, a concrete fire pit can explode if the temperature while in operation gets too hot for the structure of the concrete blocks to withstand. High temperatures cause moisture in the voids of the concrete blocks to transform into steam which builds up pressure within the structure of the blocks causing them to explode.
How did moisture get into the concrete blocks?
Concrete is not as dense as stone or other natural products, therefore, it is possible for concrete blocks to absorb moisture while it is left outside in the elements – sun, rain and earth.
Moisture may be in the block even though you cannot see or feel it. Be careful when using concrete blocks because the explosions can be powerful enough to hurt someone close to the firepit.
In a previous article, is it OK to leave a fire pit burning overnight, I suggested that you can use water to put out a fire in a fire pit. However, when using a concrete fire pit, you want to be careful about using water.
Pouring water on hot stone or concrete can cause a violent explosion throwing off sharp chunks that could hurt you badly.
Don’t worry the explosion will not be so powerful that you have to dive to save a friend or family member.
It is just that if you are close sharp pieces of concrete blocks may hit you in the eyes or somewhere on your body that is delicate.
The Scientific Reason Why Concrete Blow Up When heated?
Concrete contains moisture.
When it is heated, the moisture turns to vapour and, under normal conditions, is hardly noticeable as to leaves the surface through small voids, capillaries and tiny pores.
However, sometimes when the concrete is quickly superheated, the internal vaporization overtakes the surface’s ability to allow the gasses to pass out through the surface and steam pressure builds up inside the concrete.
If the internal pressure of the vaporized moisture exceeds the tensile strength of the concrete, the concrete can fracture, allowing the pressurized vapour to escape.
When this action happens quickly under intense heat, the concrete can shatter, much like a small explosion.
How To Safely Prevent a Concrete fire pit from exploding?
Your fire pit may have exploded because the temperature was too high. At 250 degree Celsius the concrete start losing strength.
However, at above 450 degree Celsius the structural strength of the concrete get diminished immensely.
In order to maintain a lower temperature, try not to overstack the fire pit with wood. Only use a few pieces of logs at a time. Allow it to burn down before adding more logs.
Do not pour water on the firepit at the end of the evening when you are planning to leave.
Adding water may cause a sharp drop in temperature and thus causing the concrete blocks to explode.
Conclusion
The question of will a concrete fire pit explode has been answered. There are also suggestion of what can be done to prevent the fire pit from exploding.
