How Long Should Concrete Stay In a Mold?

When making concrete or cement mortar castings, knowing when to demold them could mean the difference between success and failure. If you try to remove a concrete casting from a mold too soon, it could break if the concrete has not hardened (cured) enough, especially if there is small or fine details.
Knowing when to demold your concrete casting will be unique to each project and things like the mix design, the shape and thickness of the concrete poured and the ambient temperature are just a few of the variables that play a part in knowing when to remove the concrete casting from the mold.
Letting the curing concrete for at least 24 hours will let the concrete get to about 35% of the finished strength. This is often enough to demold the concrete, but if there is are small or fine details, 35% may not be strong enough to keep those little its from breaking during demolding. At 72 hours (3 days), the concrete is just a little over 60% of the way to its full finished strength.
So, there is no perfect time or set time to when exactly concrete should be demolded but this video should be able to give you an idea of how to judge your project and when your concrete is ready to be removed from the mold.
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[@WilliamoCurrano]

Hi Steve. happy to subscribe. i’ve been enjoying and learning tips over the holidays and look forward to new ideas. good luck.

[@nunyabitnezz2802]

Great information. Thanks again.

[@harviecz]

BTW. I am using 3d printed mold made from PLA plastic. I've feeling that either cement or moisture in it is corrosive for PLA and is making the mold milky matt, brittle and deteriorating rather quickly after few uses. I guess it kinda makes sense, since PLA is acid and cement is strong base. But it's just something that i've found. Probably might be alleviated by using thicker mold release or completely fixed by using PETG plastic instead.

[@karenblaeholder469]

Firstly I want to thank you for your videos they are so helpful, secondly After spray misting a small project the first 2 or 3 days , can I then wet cure it in a pan of water? I just learned about wet curing today from watching your videos.

[@chimerahitman]

Hello Steve, I've been searching on the internet and can not seem to find the answer to my question. Fisrt, my goal is to reduce shrinkage of mortar and concrete to as much as possible. Heres the question. If using a bonding admixture or acrylic admixture can be used a 50% of the water, can I not add water reducing admixture to further reduce the content of water in the mix so to reduce double fold or eliminate the shrinkage that happens when water leaves the mix over time? And bonus question. Access to acrylic fortifiers is cost prohibitive or outright impossible for the small player, but acrylic paint primer for concrete is plentiful. Can it not be used as a substitute? The acrylic paint primer is a milky liquid that is used for roofing impermiabilization, it's almost like water. I've heard of people having used it to form a "crystaline coat over roofs" when it leaks, usage is instead of water use that with Portland cement.

[@spherevsgravity]

I approve the answer by experience

[@Helen-cw1qs]

When we cast in West Africa we always wet cured. I would walk along the line of moulds with a hosepipe twice a day. It’s standard practise in Africa to cure like this. We were casting blocks for building

[@louienoble4179]

If it's in mould for 3 days how do I keep it wer

[@1deecee12]

Submerge it water for 28 days!!! WOW!

[@Standbackforscience]

Unicorn farts, eh?