Spalling Under In-Pool Countertop

[CA_Tallguy]

Hey folks -- we have an in-pool countertop, with the underside maybe 4 to 6 inches over the water line, and we had some spalling from rust on a thin piece of reinforcing wire. It looks fairly thin so I don't think it is rebar. A good chunk of concrete has come off from 1/2 to 1 inch thick. I have no idea if the moisture is coming from above or below. Thin rock surfacing on the top and sides. We can hear hollow sound underneath on the top side when tapping on it.

What would be the recommended repair on this? The counter is not very thick so of course it concerns us from a structural standpoint that this large of chunk has come out, however it feels generally solid.

I assume we have to address the rust by either removing the rusted wire or neutralizing and perhaps encasing it -- maybe POR15. In my brief research, I have read about rebar and kevlar staples for reinforcement of cracks in pool walls. Should we attempt to embed something like this into a repair, even drilling some anchor holes? Running a hammer drill for some holes seems a bit scary. Or perhaps we at least should embed some kind of mesh in whatever grout/concrete/plaster we use? I still need to try to figure out what finish we have down there and if it is straight concrete, and/or if there is (or should be) any plaster or other coating over it. The rest of the pool has pebble-tec but this area does not have that coating.

 

[CA_Tallguy]

A few more photos — looks like there are developing problems on 10-12 inch spacing nearby. Also a chunk missing and other signs of rust/small cracks down to the other end.

 

[ajw22]

Gunite/concrete/cement is not water proof. It is the plaster that makes the shell water proof. All the concrete should have got a layer of plaster.

The concrete is absorbing water and rusting the steel reinforcement put in it.

They need to be rebuilt with proper water proofing.

 

[CA_Tallguy]

Thanks. That's kind of what we feared..... at least that it seemed like an "out of sight, out of mind" (at best) type of situation during construction.

So is standard plaster the recommended coating for the under the bar? The pool is actually my father's and he said that the pebble-tec may be due for refinishing in a few years, so his inclination is to try to patch this up for now to try to get through until getting into a deeper renovation at that time.

Should we have plaster or other waterproofing underneath our tile and pebble-tec, or are those surfaces deemed to be "waterproof" enough without? I'm a bit concerned about other areas of the pool that we might not see, as I assume there is high likelihood that some of this salt water is soaking into other places.

 

[ajw22]

Properly applied plaster should be waterproof. Waterproofing like Basecrete is best applied behind tile. Water gets behind tile through cracks in the grout lines.

Are Concrete Pools Waterproof?

Is concrete waterproof? No. But concrete swimming pools can have dense enough shotcrete (4000+ PSI) and waterproofing membranes to make them watertight.

blog.orendatech.com

 

[CA_Tallguy]

Will an anode protect rebar, if the anode is wired to the rebar? I do have some rusting rebar so am trying to determine if an anode may have been connected when the pool was built. If so, it has not been replaced and is long overdue.

 

[ajw22]

Will an anode protect rebar, if the anode is wired to the rebar? I do have some rusting rebar so am trying to determine if an anode may have been connected when the pool was built. If so, it has not been replaced and is long overdue.

Rusting is a chemical process that a sacrificial anode does not address.

 

[CA_Tallguy]

@ajw22 Sika and others make anodes that can be embedded into concrete repairs, directly tied to the rebar. Maybe these only help when there is new metal being placed near or in contact to old metal rebar? The Sika XPT/XP2/XP4 series are "anodes for chloride contaminated concrete" which I am guessing could apply to a concrete SWG pool, in particular in areas lacking waterproofing or damage where water may seep through and make contact. https://ca.brockwhite.com/userfiles/documents/info/sika-galvashield-xp.pdf

I'm not putting new rebar into the repair. Would this type of anode, embedded and attached to the exposed rebar, have any benefit?

 

[ajw22]

Sacrificial anodes protect metals from galvanic corrosion, not rusting. Rusting is a chemical process.

Connecting it cannot hurt. I say your rebar will still rust.

 

[JoyfulNoise]

The shortest answer I can give is - no, they do not help even though they are sold as magic miracles. The science and engineering of sacrificial anode design is so poorly understood by the pool industry that it has created its own little world of pseudoscience about what they are and what they can do. Please don’t get caught up in the nonsense searching for a quick and cheap miracle cure, they don’t exist.

Your rusting rebar issues are quite possibly the result of just poor pool construction. There may be very little you can do about. But if you post pictures of your concerns and give more details, folks may be able to help.

 

[Jimrahbe]

Guy,

I have three saltwater pools and none of them have a "Sacrificial Anode." In total the pools have been saltwater pools for over 25 years without any sign of corrosion or saltwater damage. I don't know anyone is Texas that has a magic anode.

Thanks,

Jim R.

 

[CA_Tallguy]

My question arises after coming across anodes that are placed directly within repairs in reinforced concrete structures. Apparently, dissimilar conditions between damaged and undamaged areas, or later on, patched areas surrounded by original/untouched areas, can create anode/cathode situations.

Excerpt from an article in the "Concrete Repair Bulletin" of the Institute for Concrete Repair:

More commonly, the concrete is repaired leaving significant portions of the original concrete in place. If a corrosion-damaged structure is repaired, but the underlying corrosion issue is not addressed, there can be a recurring corrosion issue in the concrete adjacent to repaired areas, known as patchaccelerated corrosion, or the halo effect. This subsequent corrosion damage takes place due to the reinforcing steel being exposed to the variation in chemistry between the new repair mortar or concrete and the remaining chloride-contaminated concrete. The environment left by the repair process may lead to a new or accelerated electrochemical reaction resulting in the corrosion of the steel that is encased in the original concrete outside of the repair, as well as the eventual breakdown of the original concrete surrounding the repair.

Example of anode sold for embedding in a repair....

 

[Jimrahbe]

Guy,

Well I have to admit I have no proof that what you show is total bull feathers.. But I'd be willing to bet lunch on it.

Let's see if we can get some better educated comments from @JoyfulNoise.

Thanks,

Jim R.

 

[CA_Tallguy]

Here's a presentation/workshop where Sika reps are explaining/demonstrating their system....

This presentation from the American Concrete Institute discusses the "ring effect" at 2:35 in this video:

 

[JoyfulNoise]

I don’t disagree with any of that. But my question(s) is this - what are you trying to repair?

What makes you think you have chloride attack?

Bolting an anode on to the rebar and burying it may stop corrosion in one area but it would likely not protect the entire structure. The corrosion would simply shift to a different area. When anodes are placed on a large submerged structure, they are placed equally around the structure to ensure uniform coverage. Do you plan to pen up your entire pool shell to make repeated placements?

 

[CA_Tallguy]

This is spalling on the underside of an in-pool countertop. You can see the typical waterline from the calcium build up. More photos in this thread here.

I don't know much about types of corrosion but as I said, I came across those anodes when looking for material for repairs. The anodes seem to be used on roads, parking structures, sidewalks, bridges etc that have damage from de-icing salts. I figure that might be similar to this corrosion in a SWG pool but I am just guessing. On the other side of this wall/counter, we do have a very small amount of seepage which we notice more because of white stains than any water. There are solid white stains under the counter on the other side. In this photo, you can see that the rebar is very close to the surface with no waterproofing or plaster over the concrete. All that being said, we do see white stains come up out of other cracks in our concrete, such as in the driveway on the other side of the house. And of course, the driveway is unlikely due to pool salt.

I am thinking about using SikaTop 123 Plus to fix this up. The two part product includes "FerroGard" corrosion inhibitor which also leeches into the nearby concrete for additional protection.

Sika also sells the embedded anodes under the FerroGard product line which prompted me to consider them.

Please let me know if you guys have other suggestions. I'm not sure if we should put a layer of plaster or some other waterproofing on top of The SikaTop. Are we wanting an impermeable waterproof layer or should there be some permeability there? My thinking right now is to build up the thickness on the underside of this counter with SikaTop so that the reinforcing metal is at least deeper into the concrete from that side. After we fix the bottom, we are going to fix some missing grout on the top and reseal the countertop to try to keep penetration minimized from the other direction.

 

[JoyfulNoise]

Ahhhh … yes, I thought I remembered your thread. Just a side note - please keep all of your questions and posts on the same thread. It’s highly confusing for those of us on the helping end to help you when your information is all over the place.

That rust and failure was caused by the underside of that counter not being properly sealed. It should have either been plastered or tiled like the rest of the pool. Gunite (cement) is NOT waterproof and thus the constant exposure to pool water, condensation moisture, etc, has caused the rebar to rust and fail and likely is the cause of the deterioration you are seeing in other areas. I don’t what these PBs are thinking when they design these pool (many other examples like yours) but ALL gunite surfaces, except those buried in the soil, should be sealed against the detrimental effects of the outside environment.

I think you can simply clean up the rusting rebar as much as you can and then add an anode if you like or some other kind of rust inhibitor and then seal everything up using hydraulic cement. Once the cement is set and cured then you need to finish those surfaces with a moisture barrier like Hydroban ( Latticrete product) and then either plaster, tile or stone. Paint is not a good idea as it doesn’t last.

If you have cracked wall structures then I suggest you get contractor to look at it. If the cracks are structural then they need to be filled with epoxy and stapled. It’s a fair bit of remediation work but a good contractor will be able to fix it.

 

[CA_Tallguy]

Thanks so much @JoyfulNoise -- I wasn't sure what cement/grout/waterproofing to use there. Those suggestions are massively helpful as we were about to go down the wrong path. Now I just have to find a local supplier.