Cracking on industrial slab

[charliealphabravo]

Hi all. I have attached a photograph of some slab-on-grade cracks in a grid pattern. I have some ideas on cause but I wanted to poll the group. The slab is in an industrial shop and the photo was in the aisle for heavy axle loads. The documents are not very clear but seem to indicate a 5" slab with 10M? rebar at 16 inches on center, over vapor barrier, over 6" crushed granular base "Type 33 compacted to 100% Standard Proctor", over clay subgrade. The slab was poured in winter (-13F) with reportedly little or no heating of the ground prior or during the pour. Cores show 4" to 7" of concrete at 3000 to 4000 psi strength. Water table about 3ft below slab.

TIA

 

[dik]

What kind of heavy axle loads... 5" slab is too thin for this... Cracking is extensive, but, does not indicate heavy fatigue type of loading. Crack edges are sharp and would expect them to be more rounded. Maybe cut out and replace with quality 8" slab for heavy channelised loads.

Dik

 

[TehMightyEngineer]

Looks like it cracked at every bar. I'm going to go with plastic settlement cracks worsened by insufficient concrete thickness for the axle loads. Can you pour a thickened topping onto it?

Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries

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