Iron leaching from coping

[KCD]

Iron stains are showing up on several areas on the coping (see pics). The PB did not warn us that this would happen. This coping stone was one of the choices made available by the PB. On one area, the stain is even dripping down into the plaster area of the pool. I would hate to be swimming in a pool with ugly rust stains coming down the side from the coping that is leaching iron. The pool is under construction with decking and plaster still not installed. Because the PB took on too many jobs, this pool build has been going on for almost a year. What recourse do I have?

 

[Texas Splash]

I'm sure this thread will get some discussion, but before we do, I had a few questions:
- What kind of stone was used?
- Where did the water come from used by the contractors who applied the mortar?
- Are you on a well?
- Because your project has taken so long, if there any chance that tools, equipment, or other product(s) might have contributed to the rust residue?

We'll put our heads together and see what we can give you.

 

[JamesW]

I don't think that it is from the stone.

I suspect that it is from rebar under the stone.

I would pull up the stones with the most rust to see if rebar is near the surface of the gunite/shotcrete wall/bond beam.

 

[ajw22]

How long has those stones been installed?

Your recourse is to tell the PB to remove the stones , examine the area under it, and select replacement stones that don't show any veins.

Let the replacement stones sit outside and weather before installation for a few weeks to confirm they don't show any rust signs,

I don't think rebar rusting stains would flow up.

 

[JamesW]

This rust seems to be coming from the crack in the grout.

Maybe rain water is sitting in a depression in the stone and bleeding into the crack and the rust is bubbling back up through the water.

It's essentially a type of effloresence.

In any case, the stones should be removed and the base should be examined for steel wire or rebar including using a strong magnet to detect any steel.

If steel is found, the steel should be removed to prevent further rust.

If the stones can be cleaned and reused, then that would be acceptable if the stones are definitely not the source of the rust.

If no steel is found and the stones are the source of the rust, then the stones should be replaced with stones with no iron.

 

[KCD]

We use city water. There are rebar rust stains coming from a couple of areas on the wall of the gunite; and looking closely, this coping stain appears to be coming from the joints, not the stone. Further, we kept all of the unused stone, and none of them shows any iron leaching out. So, I’m thinking it is likely coming from under the stone, maybe rebar rust, just like the ones on the gunite wall. The PB said it’s the stone causing the stain so I believed the PB but now it looks questionable.

 

[JamesW]

Crush up some vitamin C tablets and make a solution with some water.

Use a plastic bristle scrub brush and the vitamin C solution to see if the stain can be scrubbed off.

Then watch to see if the stains reappear from the cracks.

In any case, you probably need to deal with the rebar to prevent further rust stains.

 

[KCD]

I just found an unused stone with same rust stain, so it’s the stone. I’m trying to find out what kind of stone it is.

 

[JamesW]

It might be both rebar and the stone.

 

[KCD]

I don’t understand why a PB would sell a problem stone like this when the PB is aware of the problem???

 

[KCD]

It might be both rebar and the stone.

You are right. I should also check rebar as a cause.

 

[KCD]

I did the vitamin c rub test and it is rust in the brown areas of the stone, since it turned white.

 

[KCD]

Coping was done a couple of months ago.

 

[KCD]

What kind of stone was used?

Tumbled blue stone.

 

[JamesW]

Rust on Bluestone FAQ's

Frequent Questions - Rust on Bluestone patio and paving. We get numerous requests for help on removing Rust on Bluestone. Here are some facts: "Bluestone" is somewhat of a misnomer, as there are few installations using true Northeastern Bluestone consisting of Sandstone. Some "bluestone" is...

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[KCD]

PB used muriatic acid to clean the rust off.

 

[JamesW]

PB used muriatic acid to clean the rust off.

What's going to keep it from coming back?