Friday, July 27, 2007

Pouring concrete in the rain.
I wouldn't have thought that would be practicable,
but there they are doing it.


SippicanCottage said...

Hi Dave- I enjoy seeing your pictures of Madison and environs. It is a most useful thing, that the internet is perfect for, and few people do.

Let me help you with the concrete question. I've done it a lot.

That concrete is being "placed," not poured. Concrete does not dry, concrete has a chemical reaction and sets. A light rain or overcast is actually perfect for this. Hot sun is bad, as the water in the concrete evaporates out before the hydration of the mixture is complete, weakening it. Ideally, you actually mist the concrete with water for 28 days after it is placed to maximize its compressive strength. This is rarely done in practice. It's only if the rain is heavy enough to make puddles and dilute the admixture that it's a problem.

The concrete finishers like it because it's daunting working in the hot sun, and the mist makes it easy to work the concrete. The finish on the surface is made by machine and hand tools, and a little water helps bring the "fines" to the surface easily to be struck with the tools.

DaveO said...

They must have been loving it this morning when they were pouring the rest of the corner in the rain. Then, too bad for them, the sun came out and the humidity climbed into the 95% range. That's gotta suck.