Curing Concrete

[stament]

I understand that the normal suggested waiting time to cure concrete is 28 days. I wonder do they follow this in Thailand?

 

We are having concrete kitchen units built and my wife wants the insides painted white not tiled white as most people do. I think if sealed properly it should be easier to clean.

 

Do we need to wait 28 days or is there some solvent that can be applied to speed up the process? I am pretty sure the builder won't wait 28 days...

[MJCM]

There are paints for NEW concrete and for OLD concrete.

 

AFAIK the Paint for NEW concrete can be used after approx 1 week.

 

Ask your local DIY Shop. (HomePro etc etc)

[sometimewoodworker]

25 minutes ago, stament said:

Do we need to wait 28 days or is there some solvent that can be applied to speed up the process? I am pretty sure the builder won't wait 28 days.

You need to get the correct paint. With the correct paint used in the correct dilution (hint; mostly do not dilute) you can start as soon as the surfaces are dry, though waiting 72 hours after the render is on, is good practice.

[Encid]

Curing time of concrete is typically 24-48 hours, after the initial set forms can be removed and people can walk on the surface.

 

After one week, concrete is typically cured enough to handle continued construction and traffic from vehicles and equipment is OK.

 

Concrete is recognized to be fully cured and has reached full strength 28 days after placement.

 

For painting purposes, I'd agree with 72 hours (3 days) as already recommended.

 

[sometimewoodworker]

15 minutes ago, Encid said:

Concrete is recognized to be fully cured and has reached full strength 28 days after placement.

That is incorrect.

 

Concrete is mostly cured and has the major part of its strength, yes. Will more time make a significant difference? No.
 

However there are examples of Roman concrete that are centuries old and are still curing, so that idea is wrong and modern formulations are similar

[moose7117]

Next time they mix it, throw a couple of Kilo's of sugar in the mix.

It aids curing time.

[Encid]

On 2/14/2023 at 4:43 PM, sometimewoodworker said:

That is incorrect.

 

Concrete is mostly cured and has the major part of its strength, yes. Will more time make a significant difference? No.

I don't wish to argue with you but that is what is taught  in civil engineering classes at university.

 

I was taught it when I went to uni in the West many years ago, and my niece was taught it last year at Khon Kaen university.

[sometimewoodworker]

29 minutes ago, Encid said:

I don't wish to argue with you but that is what is taught  in civil engineering classes at university.

 

I was taught it when I went to uni in the West many years ago, and my niece was taught it last year at Khon Kaen university.

As a rule of thumb it is good enough. As an actual definition it is not accurate. 

But then you have to go far deeper into the differences in concrete composition than is required in undergraduate level physics or architecture 

 

you probably need to go up to a post doc and specialise in material science for that.

[AndyAndyAndy]

You are mixing two things together - strength and being able to paint.

 

Yes, concrete is hard enough to be worked on after 48 hours. But it is no dry. That is why you wait about 4 weeks before painting it, otherwise you are traping water inside, which will be trapped right under the paint, cause bubbles under paint and peeling and damage and less durability. There are some fresh concrete paints, that are special in a way, that they will let moisture out.

[sometimewoodworker]

18 minutes ago, AndyAndyAndy said:

Yes, concrete is hard enough to be worked on after 48 hours. But it is no dry. That is why you wait about 4 weeks before painting it, otherwise you are traping water inside, which will be trapped right under the paint, cause bubbles under paint and peeling and damage and less durability. There are some fresh concrete paints, that are special in a way, that they will let moisture out.

There is so much misinformation in your post it is ridiculous.

 

The majority of the water that is not required for the curing process is gone in about 36 hours.

 

For maximum strength keep the fresh concrete wet, even with ponded water on it, for the first 7 days.

 

The cure process transforms the material including the entrained water over the next years, however the vast majority of the transition is completed within 28 days.

 

Water within the concrete is required for the cure process.

 

High alkaline levels also can stop paint from sticking to the concrete. It can take anywhere from 30 to 90 days for alkaline levels to drop enough for painting. Unless you use alkali resistant paint that is moisture permeable

[stament]

On 2/14/2023 at 7:30 AM, sometimewoodworker said:

You need to get the correct paint. With the correct paint used in the correct dilution (hint; mostly do not dilute) you can start as soon as the surfaces are dry, though waiting 72 hours after the render is on, is good practice.

so 3 days after the concrete is dry we can paint with the special paint right @sometimewoodworker?

[sometimewoodworker]

2 hours ago, stament said:

so 3 days after the concrete is dry we can paint with the special paint right @sometimewoodworker?

Yes, though it isn’t that special, virtually every paint supply shop has it, you just need to read the label of ask.