I have a question. I have cast a concrete countertop that is 1.8x1.5 meters in size. Now there are quite a few small holes when we flipped it, and that was actually how we wanted it to get a more industrial look, but when I talked to the paint store, they mentioned that Osmo has a "top-oil" that lays transparently in the hole and then hardens so we get the surface but seal the holes. We tried this, but the oil just gets absorbed into the holes and doesn't dry but instead penetrates into the slab.
What alternatives are there to seal the holes?
I would like to apply a surface over the entire slab that seals the holes, sand down to the holes, and then treat with something like a concrete glaze.
A friend suggested resin plastic? What do you think?
What alternatives are there to seal the holes?
I would like to apply a surface over the entire slab that seals the holes, sand down to the holes, and then treat with something like a concrete glaze.
A friend suggested resin plastic? What do you think?
Not tested myself but seen tips about mixing a cement slurry, i.e. quite a loose mixture. And apply to fill smaller cavities. It's something to search for in any case.
edit: https://betong.se/2017/04/05/fraga-experten-tappa-till-luftblasor/
"Another option is to mix a slurry of cement and water, and if the cavities are a bit larger, it's good to mix in some fine sand into the slurry. Mix to the right consistency and fill the holes, wipe off excess with a damp cloth or sponge, in the same way as grouting tiles. If the concrete is dry, it might be a good idea to moisten the surface a bit before (damp, but not wet). If you have surface treated the concrete, certain preparations may make it difficult for the repair to adhere properly."
edit: https://betong.se/2017/04/05/fraga-experten-tappa-till-luftblasor/
"Another option is to mix a slurry of cement and water, and if the cavities are a bit larger, it's good to mix in some fine sand into the slurry. Mix to the right consistency and fill the holes, wipe off excess with a damp cloth or sponge, in the same way as grouting tiles. If the concrete is dry, it might be a good idea to moisten the surface a bit before (damp, but not wet). If you have surface treated the concrete, certain preparations may make it difficult for the repair to adhere properly."
The problem with making a slurry is that I seal the holes and don't get the effect I want.engs said:
Aha, sorry. "Reading comprehension zero"
Without any direct knowledge, it feels wrong to mix plastic that does not breathe with stone that does.
A few years ago, I made a dining table with a concrete top. The result was just like yours, lots of small holes.
I started trying to sand it, it turned out poorly and was extremely time-consuming, so I gave up on that. Then I tried something similar to what you did, some Osmo oil, and it absorbed just like for you.
Then we thought, never mind, and left it as it was. You quickly get used to it and it's clear that you created it yourselves.
But a protective oil is a must to prevent moisture from seeping in.
I started trying to sand it, it turned out poorly and was extremely time-consuming, so I gave up on that. Then I tried something similar to what you did, some Osmo oil, and it absorbed just like for you.
Then we thought, never mind, and left it as it was. You quickly get used to it and it's clear that you created it yourselves.
But a protective oil is a must to prevent moisture from seeping in.
We have concrete countertops - when the professionals cast them, they use a concrete vibrator to remove the air bubbles.
For our lounge furniture, however, we cast it ourselves, and even though we "tapped" the mold to remove the air in the concrete, it looks like yours.
I sanded the surface with a diamond disc on the angle grinder, but quite a few smaller holes remain.
But since it's outdoor furniture, it's not a problem.
I just treat the slab with brown soap to get a slightly more dirt-repellent surface.
For our lounge furniture, however, we cast it ourselves, and even though we "tapped" the mold to remove the air in the concrete, it looks like yours.
I sanded the surface with a diamond disc on the angle grinder, but quite a few smaller holes remain.
But since it's outdoor furniture, it's not a problem.
I just treat the slab with brown soap to get a slightly more dirt-repellent surface.
Thanks for the response. I'm considering adding a layer of epoxy to seal all air pockets and then possibly sanding it down to a matte finish and treating it again with a matte varnish if needed.
Any comments on this?
Regarding not "sealing in" concrete that breathes, I don't really understand since it's often done the same way when treating, for example, floors in warehouses, etc., but I might be mistaken. Rensin is also an option but I don't really understand the difference between this and epoxy.
Any comments on this?
Regarding not "sealing in" concrete that breathes, I don't really understand since it's often done the same way when treating, for example, floors in warehouses, etc., but I might be mistaken. Rensin is also an option but I don't really understand the difference between this and epoxy.