Concrete pour in rainy weather

[Kelvin]

Well again that is their choice. I have been to pours in driving rain, snow, hot, dry, humid, etc. In the end, it all comes down to how the concrete is cured (treated in the days following placement). Admixtures and curing regeime can do alot to affect the final quality of the material.

For those who want the conversion, 300 kg/cm2 is ~30 MPa (normal) concrete or 4,300 psi. However is is not necessarily immediatly comparable to North American cylinder tests (6x12 or 4x8) if it was a cube test.

[bsereny]

If water was an issue, nothing would get built in Florida where it rains all the time!

[Xelebes]

Originally Posted by bsereny

If water was an issue, nothing would get built in Florida where it rains all the time!

He's talking about Vancouver. I know with a certainty that Vancouver has more rain than Miami, unless Miami gets hit with more than its fair share of hurricanes.

Anyways, I work at a cement factory. Water makes not the difference if it is already mixed within ratio (25:4 (kg)). Once it is in, it has a harder time being broken and the sort. If there is too much water in the mixing - then yes, it does become a problem, not when it is pouring.

[texcolo]

Concrete does not dry it cures. It is a chemical reaction of the lime in the portland cement and does not loose any water content.

If you are pouring a large slab in the rain you have to worry about the raindrops potmarking the slab and about pooling. Water can and does have a negative effect on the PSI of a slab. But, the concrete ordered is always stronger than necessary, and the rebar and/or post-tension cables are always over-engineered for reasons such as rain effecting the PSI.

Cylinders are cast to break on different days as the slab cures. The cylinders give an indication of how strong the concrete is at the time they are broken. Approximatly 99% these cylinders pass there break requirements - NO MATTER WHAT HAPPENS!!! Concrete is pretty amazing stuff.