"Robert Neville" wrote in message
...
Smitty Two wrote:

Concrete fully cures in about a month

The time frame I've always heard is a hundred years. Seriously. Maybe a
moot point since it's a log curve, but hell it's Sunday.

No, it's not a moot point. Air cured concrete has about 30% of it's final
compressive strength in 7 days, about 50% after 28 days, and it gradually
increases from there over years. As you say, very close to a log function.

It's also important to get the correct mix and reinforcement. Cheap
concrete
might be 2500psi - better to get 4000psi and then use rebar or steel mesh.

I worked on a pan crew for high rise buildings. We put in all the forms for
the floors. When we did a pour, we had screw jacks underneath the forms,
about 8' apart. You could not touch any jack for five days after the pour.
After five days, you could remove every other jack. (50%) After one week,
you could remove every other jack. After one week, you could remove the
remaining jacks.

The concrete in Hoover Dam is still curing. They put water recirculating
lines in there that are still functioning and removing heat from the curing
concrete, poured in about 1932-1935. IIRC, they projected the concrete
would be fully cured in 100 years. By now, though, I would think that the
percentage per year would be a percent of a percent.

Steve