I noticed on the pictures a tremie concrete pour in South Africa.

Here is a tip- attach a 5 foot length of flat rubber discharge hose to the end of the tremie pipe or hose.

This will act as a check valve and keep the water out of the tremie pipe/hose and this way your concrete will not have rock or sand pockets. as long as the concrete is flowing through the hose you must keep it in the concrete pour, never let it free fall through water as the portland cement will wash out of the concrete and all you have is sand and gravel.

when the concrete pour is done the hose will close and keep water out of the tremie pipe/hose.

Use heavy duty rubber flat discharge hose for the check valve.

Flat rubber discharge hose can be used as a check valve for other requirements.

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Hello Fred, you are quite right in your comments, the flat rubber hose was attached, but it was below water level. Only the 6 inch steel pipe is visible in this photo . Additionally this was not a tremie pour, but was done with a Putzmeister concrete pump. In our terms, and correct me here, a tremie is a piece of pipe with a hopper opening on top of it, the concrete then gets dumped into the hopper by means of a banana bucket or pump, whereby it then flows in by gravity feed, not pressure. In both instances, Tremie or pressure pump, the pipe must stay in the ever expanding "Blob" of concrete, otherwise if it comes out, your concrete will mix with water and the cement will wash out, leaving you with inferior sub sea concrete with low or zero integrity!

Thanks for the nice tip and your fine comments, its nice to hear the comments of someone who knows what he's talking about.

Regards

Xagene Lotz, Breakwater Diving, South Africa
Hello Dale,

Good thoughts man! We also found that using vibrators seem to seperate the stone from the mix, I think using it sparingly is the trick. Hammers work well, especially in the tight corners of the formwork, but also not to much. Most of the time we work with self levelling concrete and it pretty much does it's own thing. Then on the heavy duty lay flat hose on the end of the steel pipe, ours is only about 4 feet long, it works well, but then it must be heavy duty, not too soft. Then on all of the civils I have done, all concrete pour's is done on rock bed. So the formwork will be placed in position, dredged down to hard bottom, levelled, plugged with sand bagging on the outsides, then only we cast the concrete.

Thanks for your advice on restarting to pump a mix on a fresh pour if more concrete is needed, It makes perfect sense, I will keep this in mind, we have always worked out the amount of concrete before hand and then cast all in one go.

Regards

Xagene
On a safety note always keep a jet hose handy in case you need it to wash away concrete if a form fails or you get stuck as you tremie.
And print these tips for your info, later on any one of you divers out there may be called upon to do an underwater concrete pour.

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