Level an uneven concrete countertop

[combato]

Hi Pro's,

For the first time, I've attempted to cast a concrete countertop that I plan to use for a kitchen island.
I have now cast it by building a frame with batten on a plywood board and filled it with 4 bags of fine concrete and reinforcement in the middle layer. I mixed it with maximum water (3L water/25kg bag) and whisked well (about 15 minutes and let it stand and then whisked for another 5 minutes).
Immediately after casting, I smoothed over the top surface, which becomes the underside of the countertop, and tapped the underside with a rubber mallet for about 30 minutes.

Now that I removed the slab, there are a lot of holes in the surface, and I was so damn disappointed that it turned out so poorly.
What is the best way to patch this before I wet sand and seal it?

 

[doubleH]

Tapping with a hammer is not enough - I learned that the "hard way." A hammer drill with a steel rod that can be used as a concrete vibrator is probably better. Our slab is used for a garden table so a slightly rough surface with small "air bubble holes" doesn't matter much. However, I evened out the surface using a diamond grinding disc on an angle grinder. It might be possible to use floor leveling compound to fill the holes, but it probably won't be as durable as the surrounding concrete...

 

[sixten88]

At work, we fixed the pores in the concrete with colored epoxy. The result was quite okay, however, you will need to sand and polish the surface.

 

[combato]

At work, we fixed pores in concrete with colored epoxy. The result was quite okay, but you will need to sand and polish the surface.

Okay… do you know where you can buy that?
I googled "colored epoxy" but mostly found a bunch of boat sites.

 

[combato]

I'm considering mixing up some more fine concrete of various types that I used when casting the slab and trying to "plaster" it more evenly, but it might be a worse idea than epoxy...

 

[sixten88]

This should definitely work https://www.biltema.se/bat/batvard/...MI0M6jrI7p9QIV6UeRBR1-ugfzEAQYASABEgKPJ_D_BwE

or some other colored epoxy filler

 

[Violina]

Nonono..

Not gelcoat

 

[sixten88]

No no no..

Not gelcoat

Why? It adheres to concrete, can be likened to ballast, can be sanded, and is durable.

 

[Violina]

Why? It adheres to the concrete, can be compared to ballast, can be sanded, and is durable.

Because you can't "touch it up" without having to remove it completely if you need to redo it.

 

[nybyggarn3]

The solution is spelled expanderbetong. So not the solution for your already cast slab but for the next one.

 

[doubleH]

This should definitely work [link]

or some other colored epoxy putty

The product you linked to is not an epoxy putty but a polyester product.
Polyester probably adheres quite poorly to concrete, epoxy is a better alternative.