Several sources state that if hydration is stopped during cement curing, is not possible to resume it, and final strength will be compromised. But so far, I haven't found a reliable explanation.
I wonder whether:
Is it plainly wrong: cement hydration will continue as before, as soon as there is water or enough humidity available again.
It is right, but it just applies to large chunks of cement/concrete (e.g 1m wide) , because water take too much time getting back to the interior, But this does not make much sense, because it got dry in a relatively short period of time, so water actually moved through.
There is some other reason (chemical or related to microscopic structure) why water cannot resume hydrating the grains if the curing cement gets dry. I'm suspicious of this as well, as water does in fact penetrate cured cement/concrete so much that sealing compounds (silicone oils, TEOS) are needed in some environments.
Edit: the best source I got is this paragraph in a book by Kosmatka et al., that barely touches the subject and fails to provide an explanation :
When moist curing is interrupted, the development of strength continues for a short period and then stops after the concrete’s internal relative humidity drops to about 80%. However, if moist curing is resumed, strength development will be reactivated, but the original potential strength may not be achieved. (emphasis mine)
So, I guess, the answer is not 1) and it seems that hydration can be resumed but at an sluggish pace, or that something else prevents the full gain of strength. Any clue?