There are many reasons to love our precast concrete bowls, and the surface detail is one of them! You may have noticed air pockets or surface irregularities on our bowls in some of the pictures here on Fireplace Doors Online. This is 100% normal and effects of air voids in concrete are in no way detrimental to the product. In fact, they are a tell tale sign that we have gone to great lengths to ensure your concrete bowl has been crafted from an eco-friendly, sustainable material as opposed to a structural cement variety. Let us explain!
Concrete is a mixture of sand, stone, gravel, and fine mineral powders that are mixed with water to form a thick cement material. When you add synthetic polymers or composites to this mixture (with or without steel or rebar for reinforcement), you get what's called modern reinforced (or “structural”) concrete. Our precast concrete is made from natural raw materials and is produced under strict quality control regulations, ensuring that the end result is a durable, environmentally friendly product that can be enjoyed for years to come.
The manufacturing process that goes in to our concrete bowls takes place right here in the USA. We can produce a wide array of colors, and special shapes and sizes with this extremely moldable material. During the mixing process, a color additive is released into the vat so that it can incorporate with the concrete. This ensures that the shade you choose is consistent throughout the bowl.
Next, the cement is poured into the mold and goes through a process called “vibration”. An external air or electric driven machine is mounted to the impermeable formwork and vigorously shakes the concrete mixture. This process helps to guide any trapped air and excess water toward the edges of the mold, and then vertically up the sides. Does every single air bubble dissipate during this procedure? No. Do the remaining voids cause harm to the structural integrity of the bowl? No. Does this give your product a unique appearance that cannot be duplicated? Absolutely!
As you can see by the pictures shown on the infographic shown to the left (click on it to view a larger size, then click on it again for an easy-to-read view!), air pockets can appear in any area of the bowl and occur in many different sizes, from small pinholes to slightly larger voids. (Just a quick note, the larger hole at the bottom of the square charcoal concrete bowl has been pre-drilled for gas lines or water drainage. That is not the result of vibration.)
Because each concrete bowl is hand-crafted to order, the concrete is mixed and poured on the spot. Therefore, the size, shape, and frequency of the air pockets will vary per product.
Precast concrete is safe. It will not get hot under the duress of the flames from your burner if you choose to create a fire feature. In addition to this, it's thermal inertia properties allow it to maintain a constant temperature in both cold and hot climate regions. Air pockets actually improve the durability of the concrete so that they can survive Mother Nature's elements. This means that you can leave your bowl outside year round without worrying about structural damage from freeze-thaw conditions. The air pockets essentially help to relieve internal pressure by allowing any moisture (such as dew) on the bowl to safely expand when subjected to freezing temperatures. You can help to reduce the accumulation of moisture by placing a vinyl cover with a drawstring over the bowl for a snug fit during the colder seasons.
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