"SteveB" wrote in message
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"Robert Neville" wrote in message
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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


I think your right and wrong. The concrete is still curing but the water
lines to take the heat away have since been filled with concrete to avoid
them being chocked down and when the heat level reached a certain point they
forced concrete in them before they were compromised.

Rich