Watertight Diaphragm Wall Joint

[Zambo]

I am researching the detailing of a joint between a diaphragm wall and the base slab. The base slab is at -15m, 1,200mm thick and will be cast against the diaphragm walls. My main concern is forming a watertight joint.

The first thought I have is that if we place bend out starter bars in the diaphragm wall when bending the bars out local crushing of the concrete and micro cracks may be formed causing a water path.So maybe couplers are required.

Next is the possible leakage at the joint between diaphragm wall panels where there may be a waterpath from under the base slab and around the panel joint on the inside face of the wall.

Can anyone point me towards any details on the internet. I have already ordered a book which promises me details, but the more info the better....

 

[JAE]

Are you OK with using waterstops?

Try here: Hydrotite

 

[hokie66]

I doubt if the type joint you describe has ever been completely waterproofed. The normal course of action is to try your best with a hydrophilic waterstop (see JAE's suggestion), but at the same time provide a drainage system adjacent to the wall. This drain will cater for water coming through the slab to wall joint and also the joints in the diaphragm wall.

 

[Zambo]

JAE, hokie66

thanks for your input. I agree that 100% watertight may be a high expectation - but a good starting point.

We are considering grouting the diaphragm panel joints on the inside face above and below the base slab.

The main leak path (assuming that the diaphragm walls themselves don't leak - but we will treat that as a separate problem) would then be from the underside of the slab, through the wall/slab construction joint. I have sent a message to the supplier suggested by JAE, but yet to see if they have a prescence in S.E. Asis.

What about casting in grout tubes so that in case of a leak grout can be pumped in. I have used such tubes for shaft grouting bored piles, but I don't know how the system would work in a construction joint.

 

[dik]

I've used blueskin clamped against the concrete surface with an angle and wrapped the blueskin around the angle and cast the concrete against this and it provides a fairly decent seal... I've also used Volclay RX bentonite strips...

Dik

 

[Zambo]

Dik,

Volclay RX bentonite strips sounds like a bentonite based product similar to Hydrotite hydrophilic waterstop as suggested by JAE.

But what is blueskin? I don't like the idea of an "angle" as steel is increasing in price every day. But if the cost is required.....!

 

[dik]

http://www.bakor.com/residential_weatherbarrier.asp

It's not intended for this application, but it works well... The blueskin I normally use is for commercial/industrial applications...

Dik

 

[bkjd]

there is a product call FUKO that is a square pvc sectiont that has injection ports extending from it that rise above the slab. The idea being that if you do have a leak post construction you can come back and inject a special flowable grout that will expand upon contact with water.

about two years ago in the NW of the US this system was runnng about $2/lf, not bad for a fail safe.

Basically you do the best you can with all other measures and then you have this system installed to get problem areas fixed later if you do, belts and suspenders.

 

[Zambo]

bkjd,

thanks. I also followed JAE's link which took me to a company called Greenstreak. Greenstreak don't distribute outside USA so have recommended me to a FUKO contact for grout tube (in Germany) and Itochu Specialty Chemicals, Shamburg, IL 60173 for the hydrophilic waterstop - but expect I can easily get a local distributor for this kind of product.

I'm still looking for standard construction details for a typical joint (e.g location of waterstop top or bottom of base slab)

 

[civilperson]

Place waterstops at base of wall if using bentonite strips, place at 4-6" above slab if using plastic waterstops. Concrete is NOT watertight, has low permeability under pressure. Some patented additives claim for water tightness. FRP liners or FRP by itself is watertight.

 

[SlideRuleEra]

For utility cooling tower basins and underground structures permanently immersed in groundwater we have had good performance from Bentonite waterstop, as Dik recommended. I'm not familiar with the product that JAE suggested, but it looks good, too.

I have some out-of-print recommendations from the Portland Cement Association on constructing "watertight" concrete on this page of my website

http://www.slideruleera.net/PCA-Page.html

http://www.SlideRuleEra.net