type of waterstop

[Structures33]

Hey all - I am working on a large waste water treatment plant. We will have a lot of waterstops specified. I know that personal preference is a factor here but can you please tell me what type of waterstop you prefer to use/specify and why? Practicality of construction is definitely a concern, as is working the reinforcing around the waterstop. I am debating between hydrophilic and pvc but am open to any economically feasible alternative. I have not used hydrophilic but feel it may be necessary because of the waterstop interfering with reinforcing.
Thanks!

 

[jike]

Use pvc and detail the rebar so that it does not interfere with the waterstop.

 

[JedClampett]

Unless this is the first WWTP your company has done, you should have (typical) details for construction joints with waterstop. Use them.
I agree with jike, use 3/8 inch thick PVC waterstops. Construction joints should be 6 inches long. Moving joints should be 9 inches long and have a centerbulb.
Make sure your specifications direct the contractor to build watertight structures and give them procedures to correct leakage.
I'd stay away from hydrophilic until it's a last resort.

 

[Structures33]

We have differing opinions within the company - typical details on each side... so that's why I've thrown this out to the forum. JedC - why are you so opposed to the hydrophilic?

 

[civilperson]

Bentonite in square wrapped coils.

 

[cvg]

if the joint moves or spreads, hydrophilic can fail. If it rains before the structure is completed, some bentonite strips can be ruined by premature wetting. pvc is designed to handle a lot of movement. With pvc, support is required with hog rings or other methods to attach to the rebar. special requirements for splicing and fabricating the bends and angles requires an experienced, qualified installer and inspector to make sure it is done correctly. bentonite strips are definitely the cheapest to install, but generally considered to be inferior to conventional waterstops

 

[jike]

Make sure the contractor hydro test the tanks before backfilling. Have them repair any leaks!

 

[miecz]

We have always used 6"x3/8" PVC. However, I have had good experience with Krystol crack repair products and am intrigued by the Krystol Waterstop System, by Kryton. Has anyone here used this product?

 

[sforesman]

The president of our company used the bentonite type waterstop at his house and it leaks, so we only spec pvc waterstops here. It seems like the hydrophilic stuff is difficult to install: you need to paint the area with the goop, then tack the waterstop in place, hope it stays during placement of concrete, etc. PVC waterstops are ususally integrated with key formwork and therefore stay in place much better during the chaos of placing concrete.

 

[civilperson]

Bentonite works good with correct installation. Twist wires can hold the bentonite strips securely to the rebar in cold joints or the bentonite can be pressed into the plastic concrete in the first pour while finishing. The continuity of PVC ribbed water stop at corners and cold joints is problematic.

 

[jike]

As cvg said, bentonite must be kept dry, otherwise it will expand before you want it to. I have been to too many jobsites where the contractor doesn't take precautions such as covering up formwork to keep the bentonite dry before the pour.

PVC waterstops can be done well if drawn, spec'd and constructed properly. It is alot more foolproof than bentonite!

 

[JedClampett]

Besides all the objections to hydrophilic waterstop mentioned above, I've got a couple more:
It takes time for the hydrophilic waterstop to activate. So if you have a gap, it will leak for a couple of days before the hydrophilic stops it. I don't like explaining this to a nervous client.
While the new hydrophilic waterstops are supposed to be better, I worry that that they'll only work for a limited number of cycles. We build concrete vessels to last more than 40 years, but I don't have data to show that hydrophilic waterstop will continue to work that long.
I'm an old fashioned type engineer. I don't like changing what works until there's a real good reason. So it's barrier waterstops for me.