A fire pit is kind of an essential installation to have when you think of enjoying the backyard during the winter or throwing a party there at night. It provides the surrounding area with heat, an aesthetic appearance, and calmness in the user’s mind. Among the materials that can be used for making a fire pit, concrete surely comes to mind as one of the first. But while they have some superb benefits, there remains serious speculation among users about whether a concrete fire pit can explode, or if concrete left in a fire pit can explode.
Yes, concrete can explode in a fire pit. It happens mainly because the moisture and water trapped inside the concrete get heated in use, and the resulting steam wants to get out. There is some other probable reason for this happening. But this is not a regular case, and in general, the explosion will not likely cause you any harm. So before panicking, read the content till the end to understand why concrete can explode in a fire pit, how you can prevent it, and some recommendations on how to safely use it.
7 Reasons For Concrete Exploding In A Fire Pit
Concrete fire pits have a robust and permanent structure to hold the fire. But on numerous occasions, they have cracked and even exploded. There could be several reasons why concrete could explode in a fire pit. Some of them are mentioned below:
1. Moisty Concrete
The most scientifically logical reason for concrete exploding in a fire pit is due to moisture in the concrete. Concrete may seem like a very solid substance once it is cured. But not more than a stone or rock. This means that technically, they are still porous in structure. Normally, water droplets house these porous spaces. When a fire pit is made of concrete or concrete is being put on the fire pit, this gets heated by fire.
It leads to heating the water within it too. It causes the water to be vaporized. Once this vapor becomes intense in amount, they start looking for spaces to get out. That’s when water vapor’s intense pressure creates cracks or even explodes to get out.
2. Concrete Mixture Type
Another primary reason for concrete exploding in a fire pit is the very nature of the concrete. There are different types of concrete, specially developed for different purposes. Neither all of them are developed equally, nor does the quality remain the same. If that particular concrete is made light, then its chance of exploding becomes higher. Because light concrete can’t sustain heat as much as heavy-duty concrete.
For example, limestone-based concretes can hold a higher temperature than quartz-aggregate-based concretes.
3. Lacks Ventilation
As mentioned earlier, water and moisture within concrete can convert into vapor at high temperatures. At the same time, using wood or a similar flammable substance in the fire pit to create fire can also cause a gaseous byproduct to emerge. All of these combined can pressurize the fire pit and explode like a gas chamber.
Using concrete blocks to build the fire pit’s surface wall leaves cement joints to attach them. These joints have relatively weaker integration than a poured concrete wall. This means that these portions are fragile against holding such pressure and often fail to do so.
4. Over Fueling Causes High Temperature
Even over-fueling can cause the concrete to explode in a fire pit. High fuel flow results in higher fire intensity. This way, fire can cross its intended area limit and heat places where it wasn’t supposed to. Also, using the wrong fuel, such as softwood, can create excessive gas while burning. Injecting high-performance fuel, such as gasoline, can suddenly raise the fire’s intensity.
Many of us think that concrete is the toughest material to build a fire pit, and such gas pressure and sudden temperature rises won’t damage it. But in reality, such over- or wrong-fueling and excess heat can make concrete explode in a fire pit.
5. Poorly Made Fire Pit
A fire pit should be well-built using the right techniques and materials. At the same time, ensuring skilled workmanship is also important. A DIY fire pit made by a fire pit enthusiast will not match the quality of a professionally built fire pit. For example, the concrete mixture is a major factor in determining how well the fire pit is built. The concrete mix should be fire-resistant. This means that while they will house fire, this won’t damage much to the concrete fire pit. For that, the types of cement, aggregate, and sand and their usage ratios should be well balanced.
6. Size Of The Fire Pit
Fire pit size can also influence concrete to explode in a fire pit. When you have a big concrete fire pit, it will likely take longer to get heated and cooled. Technically this can raise the chances of damaging the concrete in a fire pit. Uneven fueling within the large fire pit can cause some of its concrete portions to get heated more than the other parts. Such uneven temperature can damage or in worse scenarios, can explode it.
Concrete exploding in a fire pit is possible due to its location. Fire pit areas with high wind can alter the flame’s direction to a certain angle frequently. This can damage that particular area more than the other parts, leading to exploding the concrete.
Preventive Methods To Stop Concrete Exploding
Concrete exploding in a fire pit doesn’t happen every day. At the same time, the explosion intensity isn’t too high to worry about. But you should be cautious and take preventive steps to avoid such mishaps.
- High-Quality Material: Using high-quality material helps to reduce the risk of concrete exploding in a fire pit. The sand should be as per grade, high-class Portland cement and limestone aggregate should be used to make a concrete fire pit.
- Use Fireproof Concrete: In addition to prioritizing high-quality material, the concrete should be made fire-resistant. To do so, you can either buy purpose-made class A1 ready-mix concrete or add slag, oyster shells, and coal-fired power plant ash alongside other chemicals and minerals to make the concrete fire-resistant.
- Add Inner Linings: Inner linings are very important to keep the concrete away from direct fire contact. You can add metal barriers, ceramic tile, brick, and different protective coating over or between the burner and concrete wall as inner lining.
- Keep Proper Ventilation: You should keep a proper ventilation system throughout not only the concrete build but also every type of fire pit. Keeping the fire pit top portion open isn’t enough to release the excess gas and smoke generated. This will ease the pressure within the fire pit and make the concrete safer.
- Ensuring Correct Moist Level: The concrete moisture should be well within the standard moisture level. According to the American Society for Testing and Materials standard, the acceptable moisture levels in concrete, when testing should be at or below 75%. Less moisture means less steam generation within the concrete.
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How hot can concrete get before it explodes?
There is no fixed scale for how much heat can explode concrete. It depends on the building material and how well it was built. However various experiments have found anything above 1600°F to 1800°F is dangerous to the concrete and can cause it to explode.
Concrete Fire Pit Safe Temperature Level
Not all types of concrete have the strength to withstand the same amount of heat. Usually, when you ignite a fire pit, the average temperature starts at 500°–600°F. As the fire gets denser, the temperature rises too. An average-sized concrete fire pit can get heated up to 1000°F to 1200°F when it is burning at a moderate level.
To give you an idea of the maximum heat a concrete fire pit can withstand, it is 1500°F for limestone-based Portland cement concrete. For quartz aggregate-based concrete, the safe margin is 1200°F. Higher above that, your concrete fire pit is getting degraded structurally and can explode.
Can a portable fire pit cause damage to a concrete surface?
Yes, a portable fire pit can cause more or less damage to a concrete surface. A fire pit can have a temperature of almost 2000°F, based on fuel intensity. Depending on the height at which the fire pit is set, this temperature can circulate to the underneath concrete surface, leading to damage.
Recommendation For Using A Concrete Fire Pit
To ensure the safe and sound use of your concrete fire pit year after year, you can follow these recommendations:
- Hire a Professional: Don’t build a heavy fire pit, like a concrete one, by yourself if you don’t have proper expertise in this. Rather, hire a professional unless you want to see your fire pit get damaged after you DIY-built it.
- Abide Instruction: You should be aware of the concrete fire pit’s default perimeters. There should be some instructor guideline manual, or you can ask a professional or a similar user to give you a better idea about running a concrete fire pit.
- Right Fuel in the Right Amount: You might want to add an excess amount of fuel to your fire pit to raise the temperature. But this can add to the maximum heat handling capacity of your concrete fire pit. So use natural gas or propane-based fuel at a moderate level.
- Regular Maintenance: To enjoy a safe and comfortable fire pit season, you should maintain the fire pit regularly. Movable parts should be cleaned to ensure proper fuel supply and burning.
In the end, let’s summarize from the beginning: yes, concrete can explode in a fire pit. Although this explosion will not be strong enough to make you jump for protection, it can still be scary. It all starts with heating the moisture and water trapped in the concrete. They can get vaporized due to the immense heat of the fire and start looking for a way out. They start putting pressure on the concrete wall, leading to cracks and even a small explosion of the concrete. This event can also happen due to the type of concrete mixture, material used, fire-fit construction method, method, etc. To avoid such a mishap, you should be careful about how you build and use the fire pit.
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I am Donald M. Beyer and I am backyard enthusiasts. I am a homeowner who has been doing DIY projects in and out of my house for many years. From simple backyard lunches to making an old-school pizza oven in my own backyard, I have a lot of experience in turning my backyard into my and my family’s personal playground.