Drying time concrete, cement, plaster, mortar...

[xl15]

I haven't really wrapped my head around drying time for concrete, etc. You only hear "2-3 months." But it must depend on the thickness.
I found this on http://www.quick-step.com/europe/se/sv/faq/0016.aspx

"The concrete floor must dry sufficiently long. You should count on one week per cm of concrete, up to 4 cm. Count on twice as long drying time for the remaining part of the floor if the floor is thicker than 4 cm. In other words, for a floor that is 6 cm thick, you should count on at least (4 x 1) + (2 x 2) = 8 weeks of drying time. For concrete thicker than 6 cm, you should count on 4 weeks of drying time per remaining cm."

What does the mixed expertise say about that statement?

 

[Mikael_L]

Have not really figured out this drying time for concrete etc. You only hear "2-3 months". But it must depend on the thickness.

Yep.
And also on:
The dryness required (/desired)
The surrounding drying temperature.
The surrounding humidity.
Single or double-sided drying.
The quality of the concrete and its original moisture content.
and perhaps some more factors I don't know or forget.

There is a program that you can play around with, torka-s
http://www.fuktcentrum.lth.se/index.php?id=20446
As far as I know, it is still free, you just have to register.

The concrete station can normally calculate this for the customer. They should possess this competence.
They can also mix concrete for you that meets the requirements for extra quick drying if needed.

In the first step after pouring, the concrete sets (or cures), using a lot of the water mixed with cement and aggregates during concrete manufacturing, as the water binds with molecules in the cement to form set concrete.
The water that wasn't used in the process forms the moisture that then needs to dry.

The concrete station can work some magic if you are in a hurry; I remember that by using more cement, more water is simply consumed in the chemical processes. This concrete is, of course, a bit more expensive, as cement is the costly raw material in concrete. But if you're in a hurry with drying, it might be worth it.

If you're building an open carport, you don't need to worry about drying. After 2-3 days, the concrete has reached 60-80% of its final strength (take this piece of data with a large grain of salt, I just guessed with numbers that may be roughly correct) and you can start building.
Then the concrete doesn't need to dry any further, as it is outdoors.

But if you, for example, are laying flooring, you should always let the rH drop to a maximum of 85% rH.
If you build in moisture more than 85% in the concrete in a house, you have almost guaranteed yourself a sick house.
If you have time to let the concrete dry down to 75%, it's great, because below 75%, all organic growth is stopped, i.e., completely mold-free and good.
Even if you wait out for a really dry slab, I think you should never skip some kind of sill insulation and such under the walls' sills, etc. Always consider concrete as a building element that dampens what is applied against the concrete.

Absolutely no expert advice here now. But I don't think I'm completely off in most of what I wrote now.

 

[xl15]

Very grateful for this detailed response, as well as the link to the program. I was indeed able to download it for free after registration and have been experimenting with it now. I could even choose betweenbjälklag (which is relevant in my case).
Unfortunately, you couldn't choose thinner than 7 cm. I will not be laying more than 2 cm to level a floor. Sure, you can use self-leveling compound, but I was thinking of using finbetong because it costs around 1/4 as much.

 

[prototypen]

But as thin as 2 cm is difficult to get to stay in place. Self-leveling compound is the way to go.

Protte

 

[xl15]

Aha, in that way. Thanks for the info

 

[Robert-san01]

Can you start laying the sill (with insulation) and erect the studs after a week?

If you have it open with cross ventilation, shouldn't you also be able to build the walls and ceiling while the slab dries out? (I am converting a carport into a garage)

I imagine you can build the rinse edge in Leca after 2-3 days, or?

 

[Matti_75]

Can you start placing base plates (with insulation) and erect the studs after a week?

If there's cross ventilation, you should be able to build the walls and ceiling while the slab is drying, right? (I'm converting a carport into a garage)

I imagine you can build the splash edge in Leca after 2-3 days, or?

You can start erecting walls just 2 days after pouring in this heat. You already have half the strength value then. It's only if you need to have flooring on the concrete that you need to wait for the concrete to dry out.

 

[Robert-san01]

Thank you for the answer!!

This will speed up the construction significantly. That I can't lay tiles until later this fall doesn't matter.

 

[Mikael_L]

You don't lay tiles until the concrete is 3 months old (it's almost done shrinking by then) - rule of thumb. Otherwise, joints and possibly tiles will crack.

If a moisture barrier is to be applied, the concrete should have reached down to 85% rH or lower.

Tiles directly on concrete do not completely stop drying, so if the concrete hasn't quite reached 85% rH, you might still be able to lay the tiles. Wide joints should therefore be an advantage then.
This last part is just wild speculation. If you want to be completely sure of the correct execution, you wait for the concrete to reach 85% rH even for tiles directly on the concrete.

 

[Robert-san01]

3 months I had read somewhere else too, so that was my thought. Lucky it's a garage, it wouldn't have been so fun to have to wait 3 months if it had been in the kitchen or living room.