Do only certain types of concrete set underwater? 2

[syvmn]

Hi everyone. I have a question about concrete setting underwater.

I am setting a few posts in 8" x 8" x 8" half cinder blocks. The plan is to fill the center of the cinder blocks with 5000psi bag concrete from Menards. I'll set the posts in this concrete and let it sit overnight to start hardening.

I am wondering if giving them 12 hours to start setting and then putting them in the water will be a problem or not. Will the concrete continue to set underwater?

Sorry for such a basic question. Concrete is not my forte.

Thanks for any help!

 

[SlideRuleEra]

Portland cement based concrete, like the one you have specified, will set (cure) better underwater than in air.

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[TehMightyEngineer]

I wouldn't even wait 12 hours. As soon as the finished concrete surface begins to dry it wants more water to continue curing. At that point it would be very hard to give it too much water.

Professional and Structural Engineer (ME, NH, MA)
American Concrete Industries

http://www.americanconcrete.com

 

[Ron]

Don't move them too quickly as that will affect the bond between the post and the concrete; however, 12 hours is sufficient to gain enough bond strength to move. Submersion is good at that point...