Cold pour slab porch - discolored and cracking

Any ideas what might make a slab crack and discolor like this??

Worse on one side than the other?? :shock:

My first impression is too watery or something on it when floated, but I’m not a concrete guy…

I only know sooner or later it cracks… :mrgreen::mrgreen:

I’m unable to tell you why this porch slab is surface cracked like it is. It may have been too much water not floated off or some other liquid that got on it while drying. No large structural cracking was noted. You may wish to have a contractor who deals with a lot of concrete and slab pours evaluate it further and make recommendations for repair. It may be as simple as sealing it and putting a porch paint over it.

You guys can stop proffering ides now… :mrgreen::mrgreen:

ok, i’ll stop proffering, but will keep on searching :wink:

discoloration and more

I did find this…

Fine Cracks in the Surface of the Concrete: In some cases the surface layer of concrete may begin to form a network of fine cracks. This problem is often caused when a rapid drying procedure was used, or there was inadequate curing of the concrete. Other contributing factors may include water on the surface during finishing, or the sprinkling of cement on the surface in order to dry the water bleed. "

Mayhap it was the ‘sprinking’ of a different and darker concrete to absorb the bleed after the float…

No matter, it’s all behind me now.

Thanks though Barry…:mrgreen:

Hi. Mike and hope you are fairing well.

That pattern to me looks more like crazing which is the development of a network of fine random cracks or fissures on the surface of the concrete or mortar caused by shrinkage of the surface layer.
Crazing cracks are sometimes referred to as shallow map or pattern cracking. They do not affect the structural integrity of concrete and rarely do they affect durability or wear resistance. However, crazed surfaces can be unsightly.

Concrete surface crazing usually occurs because one or more of the rules of “good concrete practices” were not followed.
The most frequent violations are:

Poor or inadequate curing.

Too wet a mix, excessive floating.

Finishing while there is bleed water on the surface or the use of a steel trowel at a time when the smoooth surface of the trowel brings up too much water and cement fines.

Sprinkling cement on the surface to dry up the bleed water.

Hope this helps a little.

Marcel :):smiley:

I think Marcel has it…

Thanks Larry, I had the book but not the link. ;):p:)

Saved the link .pdf for Future Reference - Thanks Larry…:smiley:

Now I know exactly what to call it, even if I can’t say exactly what caused it - Thanks Marcel…:smiley:

This was an informative thread for me, Thanx to all who participated.

Good link Larry!

I’m not sure about the discolouration but salt can cause corrosion and cracking. You would know better then I would if that was the problem. If by any chance that is it this article talks about how to protect concrete from salt damage.

Marcel got it right. It is called crazing and it happens when the slab is sealed closed with a steel trowel while there is bleed water at the surface. As for the discoloration, it looks to me, the slab may have been poured in the winter and covered with a blanket or plastic, which will cause it to cure inconsistently. Unfortunately, the discoloration does NOT go away.