Concrete counter top defoaming alternative

Old 05-15-18, 04:30 AM
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Concrete counter top defoaming alternative

Hi folks,

I'm embarking on a concrete counter top project and am struggling to find a defoaming agent where I live (south of France).

I understand this is recommended to counter the tendency of the plasticizer to induce foaming, resulting in air bubbles.

Is there a simple alternative that I can use? Are there measures I can take to reduce the impact? I propose using an orbital sander sans paper and my hammer drill with an improvised attachment to vibrate the forms to try and remove air bubbles once the pour is complete.

Thanks in advance all.

One final question, is there any reason I can't use an angle grinder to create a rough bull nose and then finish by sanding?
Old 05-15-18, 05:08 AM
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I have never used a defoaming agent. I use a palm sander with the sanding pad removed. After the concrete is in the mold hold the pad of the sander against the side of the mold and the bottom side of the form. The high frequency vibration breaks the bubbles free and allows them to float to the surface quite well.

Depending on the size of your bull nose you may want to form some of it in place. I use triangular shaped strips of wood. Then after the concrete has cured a grinder and sander can make a bigger bullnose without having to remove so much material. For a small bullnose I would do as you mentioned and just grind and sand it. It is dusty but it works. Try using the grinder for most of it as sanding belts/disks don't last long against concrete.

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