I was amazed at how easy it is to create a concrete counter top. I've never done this before and I have little experience using concrete, but the result was amazing! If you need a durable countertop give this a go.
Start by cutting a mould out of melamine to the size of the slab you want. The 2 main things to think of here are thickness and over hang. I went with 45 millimetres thick and an over hang on the front of 30 millimetres. I’m sure you could go thinner if you wanted but the mix would need something like fibergalss added. I then measured the inside length of the mould, which would be the total length of the counter top and lined up the strips I cut earlier.
I clamped these down and screwed them to the base making sure to pre drill each hole because you don’t want the melamine to expand from the screw.
Once all the sides have been screwed into place it's time for caulking. The method I find works is to use soapy water and a lot of rags. This will be the round over on the top so find an object that reflects that edge. I used a rounded pen lid. You also want to make sure that where the silicone meets the melamine there is a feathered edge. After the silicone dries (24 hours is normally enough) wipe the inside surface of the form with olive oil. This will help release the concrete later.
Then it was finally time to mix the concrete. I used a high strength mix from my local hardware store. All the videos I've watched either used Quickrete, which I don’t think we have in Australia, or it’s not mentioned. I get the feeling that any concrete, besides quick set, would work fine. After the first layer I vibrated using a rubber mallet.
You really want to force the first layer on concrete into the corners of the form. Because you’ve mixed it dry it won’t run as much you think.
Here I'm adding strips of rebar to the concrete. These can be pressed into the concrete after all of it has been added, but make sure they don't come through the concrete. I should also point out that I wasn't wearing gloves while doing this which can be a bad idea. I recommend wearing gloves while handling cement products.
Once all the concrete is added it needs to be vibrated for about half an hour. I used a rubber mallet.
Screeding the top means that it will be parallel with the other side. Don't worry too much about this step though because this side will be the underneath so no one's going to see it.
Make sure to keep the concrete moist for about 4 days. You don’t need to cure it for any longer than that. Do a bit of reading up on curing if you’re unsure, it’s really interesting stuff.
After 4 days of curing remove the melamine strips and allow it to dry for another 2 days. After that you can flip the countertop over and you should have a consistent, smooth surface. A good way to test if concrete is dry is to take a piece of rubber and lay it on top. Leave it for an hour then remove it and if there is a damp patch then it needs to dry for longer.
Next seal the concrete. I used a water-based concrete sealer, starting with a 50:50 sealer/water mix for the first 2 coats, then used straight sealer for the next 3.
Then simply pick it up and move it into place where ever you need.
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