Help bad cracks in post tension slab PICS

[Joshp18]

A bunch of cracks in post tension slab. Slab was poured about 9 days ago and they have not tightened the tension cables yet. Should I get a foundation engineer to come out to look at it? The DSLD engineer said the cracks are normal in post tension slabs but I don?t trust his word because I have friends with new homes where there tile had cracked over the years from I guess cracks in the slab. The cracks are 8 to 10 inches deep on the side of the slab in 4 different locations. Any info would be great!!






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[Jerry Peck]

A bunch of cracks in post tension slab. Slab was poured about 9 days ago and they have not tightened the tension cables yet.

Should not be anything to be concerned with because you said the key words:
"they have not tightened the tension cables yet".

[Lon Henderson]

Concrete always cracks as it cures. The cables hold the slab together, and your slab should be at the point where they apply the tension.

https://www.concretenetwork.com/post...on/basics.html

[Jerry Peck]

odd stratification
almost looks like three distinct layers were poured
i'd be more concerned that the right concrete was used versus some cracks that may close upon tendon tensioning

If they took concrete cylinders as they should have, and the breaks are coming in with the right strength at failure, the concrete should be okay, but ... after 9 days and not having already been tensioned?

Yeah, they could be having a problem with the cylinder break tests and they keep waiting for the strength to come up, but if it not ready after 7 days? I wonder how many cylinders they took and if they have enough to keep testing?

Rule of thumb for regular mix concrete is approximately 50% design strength in 3 days, 75% in 7 days, 100% design strength in 28 days, and then it typically just keeps getting stronger as it ages and finishes it hydration process (some conditions affect it not doing that, that's just "generally speaking").

[Jerry Peck]

ok
so we know tendon stressing is generally performed after 3~10 days post pour unless test cylinders don't pass muster & require more cure time
still doesn't explain the stratification pour
Jerry can you explain why?
i'd request the engineer of record furnish a letter explaining why if it were my slab

Looks like three distinctly different mixes and pours, but done one after the other with no defined cold joint, and evidence that no vibrator was used to consolidate the concrete.

I agree with having the engineer of record assess/explain the three distinct mixes ... and why it hasn't had the tendons tensioned yet (low strength results from the cylinder breaking testing?).

[Ken Amelin]

Looks like three distinctly different mixes and pours, but done one after the other with no defined cold joint, and evidence that no vibrator was used to consolidate the concrete.

I agree with having the engineer of record assess/explain the three distinct mixes ... and why it hasn't had the tendons tensioned yet (low strength results from the cylinder breaking testing?).

I don't see three layers, I see the cream on the top from finishing. I am also unaware of any requirement for vibrator use in a pour of only a few inches. I don't see any air entrainment?