Concrete at Swimming Pool

[bookowski]

I'm sure this must have been covered here before but I couldn't find much.

I'm working on a commercial swimming pool where I need to provide a concrete slab deck. The deck will be poured after the pool and cantilevers to the edge of the pool thus forming the pool deck. I need to have top bars because of the cantilever. I'm wondering if there are any long term issues with heavy wetting and drying of the pool water on the deck and corrosion of the top bars.

 

[msquared48]

You bet with a chlorinated pool!

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[bookowski]

Any suggestions to mitigate this?

 

[CANPRO]

Increase cover
Higher strength concrete
Use expoxy coated bars
Add protective coating to surface...

 

[dik]

CANEIT is pretty much on the mark...

Unless extreme care is used for the rebar, I would likely not use epoxy coated bars. You may consider HDG bars, though...

High cementitious material content, ie. high strength concrete is important. Proper curing as well...

Dik

 

[fegenbush]

I would like to add to CANEIT's recommendation. You could also use ACI 350 for leak tight service.

 

[bookowski]

Thanks. I am currently showing 2" clear cover and 5ksi concrete, should I go more?

Dik - With epoxy coated you are worried about them protecting the coating? I've never used galvanized bars, any idea of the uptick in cost? The owner is being extremely cheap.

 

[Brad805]

CRACK CONTROL and proper details are extremely important. There are some corrosion inhibitor admixtures on the market too that have been slowly gaining popularity. I have mixed thoughts on epoxy rebar.

Brad

 

[dik]

Galvanised bars work really well, but are costly. Epoxy coated bars appear to work well as long as the coating is intact. A breach in the coating will promote anodic corrosion.

In addition to the strength, you may want to specify a minimum cement content... all sorts of magic can be used to increase the strength and minimise the cement content.

You might strive for 2-1/2" conc cover and use regular bars (undamaged epoxy are OK, too).

If the owner want to go cheap, then have him look at a plastic wading pool... This is one type of project that you get what you paid for...

I was hoping that Ron would have a few kind words, too...

Dik

 

[EdStainless]

Pay extra attention to drainage. Preventing standing water will go a long way in minimizing chloride intrusion.
High cement (at least above rebar) is important.
I have done some rebar corrosion failure analysis.
If this is outdoors where it gets rained on that is good. Indoors or under roof is much more critical.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

 

[bookowski]

Thanks Dik & Ed.

This is indoors, it is being used for water exercise classes at a spa so there will be people climbing in and out every day from morning until night - a lot of wetting/drying and use in general. I am thinking that I'll increase the slab thickness to take a bit more cover and specify a min. cement content as well as you suggested. I'm still up in the air about epoxy coated bars.

Anyone have any experience with applying a sealer such as a sika product for this type of application?

 

[dik]

If you're looking at providing a coating, there are several urethane based coatings... sort of like a parking garage, but different <G>. Just watch out for traction issues...

Dik

 

[hokie66]

Agree with most of above. Plenty of portland cement in the mix. HDG reinforcement (where I am, it is cheaper than epoxy, but that apparently varies with location). Crack control bars about 0.6%Ag.

As the deck cantilevers to the edge of the pool, I assume it is not supported on the pool wall. That is good...keep it isolated so shrinkage of the deck is not resisted by the wall.

 

[bookowski]

Yes, the slab will have a 1/4" to 1/2" gap from the pool structure to prevent loading the pool wall.

I've been searching around more and found some people saying that pools have such low levels of chlorine that it's not really an issue. I'll keep researching.

 

[TXStructural]

I recommend looking at ACI 318 chapter 4 (Durability). WCM ratios below 0.40, minimum 5 ksi concrete are easily achieved economically and should keep things looking good for a long time (but are not required in this instance.) Pools are typically about 2 ppm chlorine, compared to seawater at 19,400 ppm, upon which the 318 provisions are based.

Avoid high cement fractions as it will encourage shrinkage cracking both initially and over time, and it adds unnecessary expense.

Epoxy-coated or galvanized bars are not needed if you attend to the proper cover depth (1-1/2 to 2 inches is good) and make sure the concrete quality is good.
--
Contrary to some information floating around, small holes in properly installed epoxy bars do not result in potentiation of corrosion UNLESS you connect epoxy bars to uncoated bars (something you should NEVER do.) The cases where this has been a problem result from macrocell corrosion.

 

[FishTheStructure]

You may also consider using an FRP reinforcing bar.
See the CSA Standard S806 "Design and Construction of Building Components with Fibre-Reinforced Polymers"

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