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I was hoping to get more opinions on the spalling on my post tension concrete foundation. I was wondering if I can just patch this up with some quikrete myself or if I should have a professional clean out and reinforce this area. (Was quoted $3500). It’s a 2 story home in California. pictures

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  • Some photo would be helpfull
    – Martin
    Commented Oct 19, 2023 at 17:14
  • Why is that concrete pulverized like that? Was it cracking, followed by you digging out all of the loose material? It looks like the concrete might not have had the bearing strength to deal with the pressure from the PT cable.
    – popham
    Commented Oct 19, 2023 at 18:12
  • Is that cable's end just floating in the air? Or is there some concrete that is still somehow holding the cable's tension. If it's a 1/2" cable like is common in residential construction, then that cable had 43,000 pounds of tension in it when installed.
    – popham
    Commented Oct 19, 2023 at 18:53
  • Did you accidentally cut the cable? I've never seen the corresponding damage, but I imagine that the energy released from a snapped post tension cable could have caused this damage. Is there analogous damage at the other end? If the cut was near the other end (or the cable broke free of its wedge at the other end), then less of the strain energy would have gone to that end.
    – popham
    Commented Oct 19, 2023 at 19:23

1 Answer 1

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Every 10 feet of post tension cable has about 1 inch of stretch in it:

(0.80)(275ksi)(1in/in/29000ksi)(10ft)(12in/ft) = 0.9 in

As the end of that post tension cable moves, your post tension cable is losing its stretch, which will make your slab more prone to cracking.

Best you can do at this point is fill the gap with a material with good compressive strength that isn't going to shrink. Looking at a "water stop" branded Quikrete hydraulic cement, I see a 7 day compressive strength of 4500psi. That sounds excellent.

Now that the post tension cable is patched up, the hydraulic cement is also a good product for patching the spalled concrete. Some latex bonding agent couldn't hurt. Once the cement has dried, then paint it for protection from moisture.

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