I have a few spots in my foundation where the concrete/topcoat has flaked off exposing ends of rebar. The builder said this top coat was only for looks but it seems that isn't the case. Did the builder screw up or is there an easy fix?

https://imgur.com/a/OuoHmEX

Post stressed slabs are the suck, but be thankful that your builder even put the skimcoat at all. A lot of builders won't even do it for you.

I'd think you'd see other signs if you had a cracked and/or settling slab. Sorry to not be of much help.

Not a big deal. Would just patch it up again like the builder did. Just want to get it knocked out while it's on your radar so it doesn't go unresolved and then the inspector finds it when you sell the house.

I have the same thing all around the house. What do I patch it with?

Use a high strength non shrink grout.

Spray with OSPHO to neutralize and stop rust
Cover with a dab of the appropriate type of quickcrete.
Thats what I did.

Howdy Dammit said:

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Use a high strength non shrink grout.

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Don't use grout. Go to a Whitecap or CMC Construction services and get a product called Patch Crete by Lyons Manufacturing. It is a I gallon polymer and a powder. Mix to peanut butter consistency and apply. You can use the polymer as a bonding agent for the patch.

I was in that industry for 13 years. The purpose of NS grout is to be placed under equipment legs as a bearing surface.

Yes the purpose of the grout skim coat layer is to improve the aesthetics of the exposed slab edge.
In general, Agree with the post above regarding repair.

You can
A) chip it off, apply a bonding agent/primer, reapply an Ardex product and it will look nice again for a year or until something starts beating it up again.

Or B) you could pick up a product similar to this Sika sealant for vertical Concrete applications and apply some to the exposed PT/rebar to prevent further corrosion/staining.

https://usa.sika.com/en/construction/adhesives-sealants/joint-sealants/architectural-sealants/polyurethane/sikaflex-1a.html

Either way you can get anything you need at CMC or Whitecap. An inside sales rep can probably recommend the best Ardex product or epoxy/sealant if you show them the pic and tell them what you're goal is.

Assuming those are indeed PT cables, then I would not worry about the rust other than it may cause spalling in whatever repair you do. But the integrity of the PT cable will be fine. They are sheathed and then the cables are greased with heavy duty grease so the rust is not going to travel along the cable - just rust at the exposed end.

Curious as to the poster who mentioned that PT slabs are "the suck". Why?