Will Concrete Explode In a Fire Pit?

Fire pits are a beautiful addition to the home. They usually come in a variety of sizes and shapes. For most homeowners, fire pits need to have areas where people can enjoy the heat in the relaxing space. Most homeowners who want to install a fire pit normally wonder if the concrete will explode if the fire pit is placed on it.

Read on and get a clear picture of what would happen when you place your fire pit on the concrete.


How do explosions occur on concrete?

Concrete is actually as close to a wonder material as we will ever going to see. It is very strong, long-lasting, versatile, and cheap. However, when you heat concrete to extremely high temperatures, it can really explode.

Those explosions can have pretty significant consequences when a fire breaks out near a concrete structure, but scientists do not very well understand the actual process of how the blowups happen.
The researchers show that the explosion is caused by evaporating water vapor held inside the concrete.

The water normally expands when heated up, and eventually, the pressure reaches a dangerous point where the concrete shatters. But in this study, the scientists did not disclose the exact mechanism.

At the temperature of around 300°C, the concrete normally undergoes a normal thermal expansion. And above this temperature, the shrinkage occurs because of water loss; the aggregates continue to expand, which leads to internal stresses. To up to like 500 °C, the main structural change is coarsening and carbonatation of pores.

In another study, the researchers from Empa, Swiss Federal Laboratories for Materials Science and Technology, when concrete is heated up to 1,112 °F or 600°, it explodes. The researchers showed that the main reason it exploded was that tiny amounts of the moisture are locked inside the concrete, evaporate and move when heated.

When a concrete block is exposed to high heat, the damage starts to occur since temperature shocks the material. Essentially, like many other materials, concrete expands when heated. And when the extreme temperature is applied to it, the outer layer starts expanding faster than the inner layer.

This expansion isn’t absorbed easily by concrete materials; this can make layers disperse, leading to breaking away. In the same method, the effects can reverse once a fire is extinguished by a hose stream or an automatic sprinkler system.

Therefore, as the hot concrete suddenly cools down, the outer layer shrinks at a different rate, and it breaks away.

So the same result can arise in a reverse manner when sprinkler systems put off the fire. In this instance, when hot concretes are suddenly cooled, the outer section shrinks simultaneously, causing the breaking away.

What Cause Explosion?

Concrete comprises a mixture of cement, sand, and water. The chemical reaction occurs between water and cement, which physically and chemically holds water, and the mixture is hardened. If temperatures in the fire surpass 200 degrees Celsius, cement dehydrates, causing the bounded water to turn into vapor. As a result, very high-performance concretes usually have very low absorbency as well as very small pores.

These properties are beneficial because they provide high strength and excellent durability, making the concrete almost impervious to external contaminants.

So, the low absorbency of a high-performance concrete is not good in case of fire with a very high temperature is applied since water vapor will escape and very high vapor pressures build up. Thus, at a high temperature, high-performance concrete may explode.

Having known that, the researchers were able to develop different additives that could work to prevent these explosions from occurring. This makes the concretes safe when heated.


To What Extent Can a Fire Pit Damage The Concrete? Will Fire Pit Make Concrete To Explode?

Fire from a fire fit can slowly damage your concretes after a long period. And to this effect, cracking is experienced, and the surface weakens. In simple terms, it is true to say that fire fit will damage the concrete surface due to continuous heat transfer.

However, saying the concrete will be damaged does not mean that the concrete is going to explode. The heat from the fire fit cannot make the concrete explode but can cause other damages like cracking.

This does not mean the fire pit is not very hot, but remember that it is designed using proper materials like steel. This barrier automatically prevents the fire pit material from getting too hot, causing a lot of heat to stop radiating to the concrete.

Therefore, a significant amount of heat is retained in the fire pit. So, it would be best if you did not worry about explosions while using a fire pit. As we mentioned earlier, an explosion of concrete is brought about by extreme temperature.

Fire does not damage the concrete immediately the way it would damage the wood. Therefore, when exposed for a short term to the fire, concrete can be fire-resistant and can persist undamaged.

However, long-term exposure to a high temperature such as those produced from a fire pit that uses firewood can make the concrete base spall and crack after long-term use.


What Are The Top Alternatives of Using A Fire Pit on Concrete?

The best option is to invest in a fire pit with legs. You can also find many fire pits that are pre-fabricated. However, fire pits can be placed on concrete but will small chance of your concrete exploding. So again, ensure you apply all proper mechanisms of protecting heat from reaching the concrete.


Conclusion

Building your fire pit on concrete is safe and does not cause an explosion. It would be easier to remove the ash left in the fires. But, the concrete begins to crack over time because of heat. Due to this, you want to mount your fire pit on concrete that you will not mind if it is damaged.

Building a fire pit in your home is a great way to add more character and ambiance to your home. There are quite a few things to consider first; however, questions include: Can you put a fire pit on concrete, or will concrete explode on a fire pit? The answer to this question is “No,” but the concrete will be slowly damaged.