Concrete C uring Rates

[Tommy77]

Hello,
Can someone tell me how long it takes concrete to cure? Especially large volumes, like Hoover Dam. Is it still curing after all these years?

 

[pug]

Theoretically, yes, still gaining strength but practically, no. You picked the hoover dam and that is interesting because the saturated in fresh water portion may be fully cured (~99.99999%) at this stage but the outside air dried portion may still not have fully hydrated.

It is surprising how strong old concrete can be. We have cored old concrete where it was so deteriorated it was hard to find a core sample that would stay in one piece. Can't remember the compressive strength but it easily beat the 28 day strength requirements so we jacketed it.

The length of cure is not as important as having the design compressive strength when it is required. For example, you may need 3500 psi at 7 days (for construction purposes or for any other number of reasons) and design the mix accordingly even though the ultimate strength may be 6000 psi.

 

[ishvaaag]

The word curing is reserved usually for procedures practiced at the first stages of the life of concrete at which hydration is happening. In the more restricted and common sense, it is reserved for the means used to ensure an efficient initial hydration and prevent the problems related to not acting such way. Curing is this way understood as ensuring the proper ambiental quantities of water or water vapour are present in the inmediate period after concrete is poured.

Maybe a practical way of answering your question is that curing understood as a sustained process of hydration that prevails lasts for the whole period in which the strength of the concrete grows, in which we must surmise links between mollecules are still being built at a higher rate than distroyed.

Aging, a parallel process will bring aggressive agents that will attack the concrete in not much a dissimilar way to that what natural limestone suffers. This process is somewhat reverting to the inert materials used first to make the cement.