Replies

1. 
   calvin | Jun 22, 2020 07:49am | #2

   I removed the spam post and Link from that goofball Houston home builder that asked if it was marble.......

   The only time I’ve seen dark lines like that in concrete was when moisture wicks up through hairline cracks. Do these disappear in dry weather?

1. 
   davis237 | Jun 22, 2020 09:04am | #3

   No, they are always there. They are cracks however. It looks like they might have put down some kind of sealer on all the cracks?

1. 
   calvin | Jun 22, 2020 03:55pm | #4

   I can tell you that while the guarantee on slabs are that they will/can crack, that job is not right. Since 1974 I’ve poured or worked around a lot of concrete and I can’t say that I’ve ever seen anything like you have and explain.

   What the heck does the contractor say?

1. 
   davis237 | Jun 22, 2020 04:08pm | #5

   I haven’t broached it with them yet because we don’t have the best relationship. I really appreciate your opinion and would love to get other experts to weigh in also. I would feel more comfortable with more opinions before I go to the contractor that I don’t trust

2. 
   davis237 | Jul 09, 2020 07:35am | #7

   Contractor's response: "What you are seeing there are micro surface cracks that can occur during the concrete curing process. Not the same as a structural crack, those cracks happen within the top layer of the concrete when drying and curing. There are a number of different variables that could cause that type of thing and happens pretty often given that concrete cures through a chemical reaction. There is a common practice for when these types of cracks appear and that is to fill them in concrete dust. Within the first 24 hours or shortly after you cut into the concrete to create what's called control joints, those are the square cut lines in the slab. They are called control joints in that because concrete will crack structurally the control joints give us the option of where we want it to crack. The dust that is created by the cutting of the control joints will then be scraped up and wiped into the surface cracks and then once a sealer is added onto the slab it seals up the cracks. By looking at the picture I assume it had just rained and that is why the color of the cracks seems to be accentuated and should return to normal once the sun dries the slab out again." I told them the marks are there rain or not.

2. 
   davis237 | Jul 02, 2020 09:18pm | #6

   is there anyone else who knows concrete that can weigh in?

3. 
   davis237 | Jun 21, 2020 03:20pm | #1

   No marble, just plain concrete.