Underwater Grouting Works - Offshore 1

[Meesamali512]

Hi everybody,
We're bidding for a project where we have to do some grouting works onshore as well as offshore. Offshore grouting will be done underneath an outfall structure consisting of diffusor structure (diagram attached). The structure got dislocated from it's original position and got tilted due to excessive outfall pressure. Now we can reinstate the diffusor along with side slabs and protection using heavy aggregates (scour protection). To fix the slab to sea-floor as well as to grout the cavities between aggregates, we need to do the grouting works. I've attached the diagrams of the areas that need grouting. Now my question is that what should be done to ensure that there is no segregation of our grout for under-sea application as well as what can be the optimum design of grout to achieve the same. The grout will be ideally normal CS grout along with some admixture. I know about specialized underwater grouts but using those alone will be extremely costly. Note that overall grouting quantities is about 10 - 12 m3 of grout.
Would really appreciate if someone can guide me regarding the grout mix design as well as other precautions and things to be considered for the same.

Here is the overall grouting requirement image:

http://tinypic.com/view.php?pic=10qxm3c&s=5

Here is the image of diffusor box:

http://tinypic.com/view.php?pic=29cus0p&s=5

 

[Ingenuity]

The last underwater grouting project I undertook was back in the late 90's and whilst it was tidal (seawater) we also encountered underwater springs causing significant grout segregation. We added BASF "Rheomac UW 450" anti-washout admixture - solved the majority of our issues. The project entailed anchoring a concrete seawall with 30 to 50 feet deep permanent rock anchors - also hit underwater caverns too.

We trialed a lot of w/c ratios with a lot of different admixtures, and if I recall, and finally adopted w/c=0.4 with the UW 450.

 

[Meesamali512]

Dear Ingenuity,
Thank you very much for sharing your experience. I have one last question before I prepare my final estimation and quotation for client. I'm bit confused regarding exact mix-design. Should I use some proportion of coarse or fine aggregates for my final mix design or is it OK that I just go for cement-sand (1:3) mortar and use the admixture "RHEOMAC UW404" (got latest quotation from BASF) for my project. Kindly help me selecting the suitable mix-design for underwater grouting. I have also attached technical datasheet of "RHEOMAC UW404" for your reference.

 

[Meesamali512]

Hello Ingenuity,
Welcome back. I got results from the supplier i.e. BASF and following are the results. Just sharing as a reference for other people who may come across such jobs in future.

Please see the mixing ratio of Masterflow 190 with Rheomac UW404
Masterfow 190 : 25 kg
Rheomac UW 404 : 500ml per bag
Water : 6.2 ltr to 6.5 ltr

Regards