New cracks this spring

[Rich D]

I am very concerned about these new cracks I found after the ice was gone from the pool. The Pool company is coming out today to open the pool and check them out. I was hoping to get some input from the experts here if they look like structural cracks and the best way to tell if they are something to concerned with. The rust in the pics is from the poor (uneducated ) Boulder choice of my doing. I am hoping the rust will stop at some point after a few seasons.

Thanks, Rich..

 

[ajw22]

That rust from the iron in the rocks is going to continue for many years.

I don't know the buildup of materials above the crack. My concern is the pool shell is a separate structure from the deck. They should be able to move independently as the ground moves with temperature and freeze and thaw cycles. There should be expansion joints between the structures.

The rocks and decking should not be putting pressure on the bond beam and pool shell. If those heavy rocks are putting pressure on the pool shell something will crack.

You say “new” cracks. What is the prior history of cracks?

 

[Rich D]

That rust from the iron in the rocks is going to continue for many years.

Yea. I was afraid of that. Do you think some type of sealer would help?

I don't know the buildup of materials above the crack. My concern is the pool shell is a separate structure from the deck. They should be able to move independently as the ground moves with temperature and freeze and thaw cycles. There should be expansion joints between the structures.

It was a monolithic shoot. the Boulder shelfs did go deep. I am not convinced they were below the frost line (4' in this area). The site material is a course gravel with excellent drainage . I honestly do not think the frost got under the shelf as I would not think we had any more than 2' of frost around the pool.

The rocks and decking should not be putting pressure on the bond beam and pool shell. If those heavy rocks are putting pressure on the pool shell something will crack.

Would it have been possible to achieve the sunken Boulder shelf and have it a separate structure?

You say “new” cracks. What is the prior history of cracks?

I have not seen any cracks until now.

 

[ajw22]

I don’t think any sealer with withstand the weather over time. And once the iron begins rusting it will not stop. It is a chemical process. There are chemical treatments like this - How to Remove Rust Stains From Landscaping Rocks But I don’t know how well it will work with large boulders like you have.

Show me the expansion joint between the sunken boulder shelf and the pool structure and confirm the expansion joint was not compromised during the build.

Do you have any engineering drawings of that area? Any construction pics?

 

[Rich D]

There was no expansion joint for the Boulder shelf or the sunken Boulder shelf.

Here is the plan

Unfortunately the very few pics I have of dig and rebar do not show the shelf at all. View attachment 96457

 

[ajw22]

It looks like the boulder shelf is part of the pool structure.

Did you select the boulders? Who placed them? Are any boulders overlapping the boulder shelf and ground? Anyone discuss what the maximum weight that the boulder shelf can support is?

Lets see if anyone has experience with boulder shelfs - @bdavis466 @PoolguyinCT @jimmythegreek @kadavis

 

[Rich D]

It looks like the boulder shelf is part of the pool structure.

correct

Did you select the boulders?

yes, they were all on site boulders

Who placed them?

I did. I have been in the excavation trade for 30yrs. They were placed extremely gently.

Are any boulders overlapping the boulder shelf and ground?

only one. looking at water fall on left side. It was placed on crushed stone the depth of Boulder shelf. It was just a over hang. all bearing weight was placed on shelf.

Anyone discuss what the maximum weight that the boulder shelf can support is?

no.

Lets see if anyone has experience with boulder shelfs

- @bdavis466 @PoolguyinCT @jimmythegreek @kadavis

 

[JamesW]

It looks like you're getting a lot of efflorescence, which is water from the ground bleeding through the wall and carrying minerals, like calcium.

That usually indicates that the ground is saturated. Does the area behind the boulders stay wet?

You're probably getting some structural cracks.

What was the wall thickness and the concrete psi?

 

[Rich D]

Sorry the plan Pic disappeared for a while. I went to edit out my address and the site went down for maintenance for a while. the plan is now posted above.

It looks like you're getting a lot of efflorescence, which is water from the ground bleeding through the wall and carrying minerals, like calcium.

That usually indicates that the ground is saturated. Does the area behind the boulders stay wet?

I think you might be mistaking my white spotting issue with the Grey plaster as efflorescence. The only place I get the efflorescence is under the coping dripping down onto the tile. the small bit in the crack is really the only place it is on the shelves. The white directly beneath the tiles is just the mortar from the tile install.

I backfilled all boulders with crushed stone and a poly barrier in between the crushed stone and soil, with a drain at base of stone. Site material is a very well draining gravel. I do not believe there is any water behind the walls.

You're probably getting some structural cracks.

I was afraid of that looking at the efflorescence coming out of the crack. The pool tech they sent out to look at the cracks and open the pool said he did not think it was a structural crack and he did not see any dye going into the crack, But he did admit his test was inconclusive and he could not say for sure if the dye was getting sucked in. the pool company is sending me a dye kit so I can monitor it myself.

What was the wall thickness and the concrete psi?

The plan called for a 8" wall. I could not find a detail on the PSI.

 

[Rich D]

This looks bad. When I set the boulders I had put a layer of morter on top of the tiles to protect them from getting bumped by any bars when adjusting the boulders. So I chipped some of that layer off and it looks like the crack goes all the way through the boulder shelf. Would this pic confirm a structural crack? If so what would my next step be?

Thanks for all the great info... Rich

 

[Rich D]

Here are some pics from behind the boulders, before crushed stone and poly.

 

[Rich D]

The pool company said they simply want to V out the crack and patch it... Is possible to do that kind of repair on a crack like this and not have it simply crack again? I was thinking more of hammer out plaster back to rebar and reinforce with rebar with specs from a structural engineer...

 

[ajw22]

The concrete is very thick there. I don't know how you do it but I would want to lift the boulders off the crack and see how far back it goes.

Concrete staples is the way to fix structural cracks - Home | The Concrete Staple

 

[Rich D]

The concrete is very thick there. I don't know how you do it but I would want to lift the boulders off the crack and see how far back it goes.

Concrete stapes is the way to fix structural cracks - Home | The Concrete Staple

Thanks for the reply and link. Lifting Boulder would be major project. Digging behind could confirm the same and allow for at least 2 staples (top and side) on the back. I have seen a lot of cracked concrete in my time (not on pools) and my guess would be this crack goes all the way to the back of the shelf.

This crack is at the break point for the deep end.

 

[Rich D]

The pool builder is still wanting to just V out -> patch -> replaster the crack. I Only found I thread where these staples were used. Has any one had personal experience with these?

Thanks, Rich..

 

[ajw22]

@PoolguyinCT may be close enough for you to talk with him

 

[Rich D]

The wife was holding out on me. Turns out she did get some pics of rebar before and during gunite. The crack area is the close to the last visible rebar on the right of the pics.

Not sure why some of the vertical rebar just stops short and does not tie into the top.

How does the spacing look?

Thanks for any input on this.