I also read that curing can be up to 28 days. I only waited 21 days due to lots of rain on the way. Not sure if the right choice, but thought that 3 weeks was sufficient. How does one really know if curing is complete. Also, if cure wasn't totally complete, what can I expect to possibly happen to concrete? Or is there any recourse?

 

Hi,

Concrete is 100% cured with 28 days. The main problem is water evaporation: with 3 weeks concrete is still evaporating water.
Usually the sealer's manufacturers give instructions about this procedure.

My advice: contact the manufacturer and ask for advice for the product you used .

Good luck!

 

Actually concrete is at the 28-day design strength at 28-days. 90% of this strength was realized in seven days. At 28 days the concrete is 98% cured. The final 2% will happen over the life of the concrete. Applying the sealer at 21 days will not be a problem.

 

The best moment to apply sealer on new concrete is not related with strength, but with water evaporation.

If you apply sealer before the evaporation process is completed, manufacturers don't guarantee their products.

Regards,

 

Like Jeff said, if it's strength you looking for, most of it IS reached in 28 days, but it DOES continue to harden for years......if you don't belive this, drive a masonary nail in month old concrete and then come back and try it a year later...BIG difference.

As to applying sealer, I put it on the same day I pour, after the last troweling. Prevents suface evaporation that causes flaking of the surface later.

 

What Tn...Andy is referring to is when the concrete has essentially set (sometimes referred to as the plastic state). This is when the bulk moisture evaporation has ocurred. The concrete can be walked on. This is when a broom finish can be applied.

Like concrete strength gain, evaporation will never end in a well-cured slab exposed to the atmosphere. That is why modern sealers allow the concrete to "breath" so as not to trap moisture. Older waterproofing and sealer materials would fail (usually because of a different coefficient of thermal expansion than concrte) and trap moisture in concrete surfaces causing accellerated decay due to freeze-thaw.

 

Thank you ! Yeah, I've read about sealers that are 2-in-1 products...I saw one at HD in fact. Some sealers (label clearly states) are both cure and seal. It sounds from your statement, though, that ALL modern (everything sold today?) sealers allow the concrete to breath. If this is true, then all is okay.