Concrete crack 1

[BatMan]

I'm trying to find out general location and shapes of cracks in the foundation due to freeze/thaw, corrosion or even carbonation.
The cracks that I'm seeing is a shallow footing with cracking all around at around 3~4" above grade. It seems like cracks/separation is happening at concrete covers.
I don't see heavy leeching of rebar corrosion. Any ideas? I've attached a sketch in an attempt to illustrate this.

http://files.engineering.com/getfil...a088-47f5-a8a1-85ec791ec28c&file=Untitled.jpg

 

[dik]

That's really ugly concrete... could it be a weak mix with little air entrainment?

Dik

 

[Ingenuity]

I don't see heavy leeching of rebar corrosion.

Significant concrete cracking often proceeds surface staining ('rust marks') due to rebar corrosion. Break off a piece of concrete and 'see' what's under.

 

[Ron]

Where is this concrete located? Have you considered alkali-silica reactivity? Crack pattern is from internal expansion, not freeze-thaw. If ASR, that's why you don't see rust stains.

Get petrographic examination of the concrete done.

Also...why is foundation exposed above grade? Is this an equipment pad?

 

[RahulAtkins]

As Ron mentioned above why is the foundation above the grade? By the look of it, it is susceptible to further seepage of water into the concrete. The horizontal cracks are most probably due to splitting of concrete above the rebar. Check for the bond strength of the concrete which will be compromised if water penetrates inside.

 

[dik]

Petrographic examination is good... it's too extensive to be rebar related or ASR, unless, the ASR aggregate is the sand component of the mix... never seen concrete that bad, all over. Tear it out and reconstruct.

Dik

 

[charliealphabravo]

What is the slab for? Is there a chloride or marine exposure? Also is the slab doweled to anything that could be inducing stresses?