underwater concrete casting 4

[csclsaba]

we are doing a project, where most of the concrete casting is below the sea level (including the formwork). we intend to use sikament antiwashout admixture with the concrete mix. Is there anything we should pay particular attention to when pouring the concrete (using pump)?

 

[SlideRuleEra]

I have not placed underwater concrete with a pump or using and ad mixture, but have placed underwater concrete using cement rich mixes with a tremie pipe and hopper.

With the tremie system: When concrete flow has been established, maintain the flow and keep the end of the tremie pipe below the surface of the concete. This forces fresh concrete (from the pipe) to the bottom and insures that it does not come in direct contact with water.

With a pump you are doing the same thing, just using the pump's pressure instead of gravity. The same logic should apply.

Best Wishes

 

[SirAl]

I have very little experience with the use of anti-washout admixtures but I would suggest that you check the compatibility of this product with other admixtures if applicable. Our firm performed some lab testing on such a mix. In that case, the mix was a proprietary product of the concrete supplier so I am not aware the mix details (proportioning, etc.). The mix included air entrainment. The air did not disperse well. At the request of the supplier, we performed linear traverse tests on samples and found that the spacing factor was way out of whack. Otherwise, the slump was as specified and compressive strength exceeded the project requirements.

 

[KCCE]

You should check out ACI 304. It has a great section on mix design for underwater concrete placement as well as what to look for during placement. We have used Rheomac anti-washout admixture by Masterbuilders with great success. You should look at using a superplasticizer to get the slump you need to pump the mix without upping your water content. Like stated above, be sure to check all of the admixtures against each other for compatibility.