Concrete slab with low psi

[jimtheengineer10]

One of my clients called me and said the contractor really screwed up his basement concrete slab. He had some cores tested for psi and it was found to be 1,500 psi. Is there a way to fix this other than removing the entire slab and re pouring? The contractor also failed to install a vapor barrier.

 

[JAE]

1,500 pai is pretty low. And I'd want a VB in my basement. Remove and replace seems to be the only option in my view.

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[Guastavino]

Sounds like there is something wrong with the concrete. Maybe too much water added, maybe a bad mix, but 1500 to me says "something went really wrong". I'd also vote to tear it out or have the contractor do petrographic work, but it will still likely be best to tear out.

I mean unless the client is OK with it. Then maybe a warranty or compensation?

 

[rapt]

I doubt that 1500psi would be deemed to actually be concrete!

 

[dik]

JAE's correct... Should be removed and good stuff with PEVB installed. Concrete exposed to moisture will 'wick' it up and the floor will be damp.

if going the petrographic route be careful on the terms of failure. My experience with petrographic testing has been spotty at best.

rapt: Better than CLSM...

 

[JLNJ]

ACI 318 says something like, "If it's not 2500 psi it's not concrete."

 

[Ron]

Remove and replace. If you have enough vertical clearance you could consider the existing slab as a mud slab and waterproof above it then place new, proper strength concrete.

 

[racookpe1978]

Residential?

If a residential or commercial standard basement (non-loaded) floor is on a solid "compacted fill dirt" that then is covered by a very poor grade (but "solid" concrete, then why not apply a full-thickness slab of good concrete right over the bad stuff?

Sure, it is not forklift compliant, not truck and trailer rated, but the extra height will make no difference in any of the basements that I have seen.

 

[oldestguy]

Removing, probably by hand, will be costly. If the site will benefit, I'd allow the contractor to dig a ramp down to basement, saw cut a door in the wall, use a bob-cat to move the broken concrete to that ramp for removal. I'd also want a new wall (area-way) at that door and a set of stairs, plus a Bilco door on top. Chances are it will be less costly than hand labor for the floor inside. If not cheaper, I'd pay only a small part of the new exterior entry way to the basement.