×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

cracks in corner of building slab

cracks in corner of building slab

cracks in corner of building slab

(OP)
Recently poured slab for a 2 story metal building has developed diagonal cracks in each corners. The cracks are in the slab only, the grade beam had poured several weeks ago. Each corner had embedded anchor bolts (in grade beam/foundation). Not a crack pattern that I have seen that I remember. Possibly due to restraint from embedded anchor bolts. There is 4x4 4 gauge mesh in slab and cracks are tight but owner is worried. I have to pull out my form letter that says concrete cracks but am I missing something?

RE: cracks in corner of building slab

What is the orientation of the cracks relative to the corner? Can you post a photo or sketch?

RE: cracks in corner of building slab

Is it a slab on grade that is cracking?

RE: cracks in corner of building slab

Probably due to slab curling as the corner is restrained from uplift by the anchor bolts.
May also be due to shrinkage from the same restraint.

RE: cracks in corner of building slab

The image of the crack I have in my head is shrinkage due to restraint by the gradebeams. Like Ron said, a picture or sketch would help.

RE: cracks in corner of building slab

Shrinkage crack.

RE: cracks in corner of building slab

Agree with dcarr, and points to Excel for guessing without a picture it was foundation restraint.

RE: cracks in corner of building slab

What was the concrete mix design? aggregate, strength, water:cement ratio, and slump?

Dik

RE: cracks in corner of building slab

Do you have hairpins at the corners in addition to the WWF?

Mike McCann
MMC Engineering

RE: cracks in corner of building slab

(OP)
No hairpins. Anchor bolts are embedded in grade beam/pedestal (with rebar).

Slab is roughly 80x90 and so far no other cracks in slab, though I expect there to be some. These showed up quickly.

The metal building has a second floor and there is not a lot of lateral force at column bases.

RE: cracks in corner of building slab

It is shrinkage crack. Something at the corner restrained the concrete shrinkage and caused the crack.

RE: cracks in corner of building slab

I concur about the comment on the mix design. That really looks like a pasty mix. I don't like the color or the texture at the top.

They added water to the mix, while it was in the truck would be my guess.. It started to kick some, and the added water for workability.

Concrete contractor will never admit to it though :p

Anyway, just my assumptions based on the photo... And yes, stress reversal at the corners of a square pad due to shrinkage.

If we made our slabs on grade oval, this would be so bad.. :p


RE: cracks in corner of building slab

shrinkage

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources