New slab is already cracking- am I too picky?

[jeopardy98]

So my 24'x44' slab was poured a few days ago. They used compacted gravel, a vapor barrier, rebar in the foundation block, and keyway expansion joints in lieu of saw cuts. It looked pretty good but I'm very picky and kind of a perfectionist. I'm also not a concrete guy so I don't know when/if I should speak up but I've already noticed that where the keyways were placed, the concrete is cracking. Is this normal? I know that is the point of the joints but should it be cracking this early? Also it seems the that expansion joints are a 1/16" to 1/32" above the rest of the pour. They don't stick up over the concrete but I can rub my hand over them and feel where they are placed. I can also see the very center of the metal. Is this all normal?

I plan to rust bullet the floor before I move in. Will the cracks be an issue when I do that or will they fill in okay?

Thanks in advance for anyone that can help put my mind at ease. I think I'm just being way too picky but I wanted to double check.

 

[boobag]

concrete actually shrinks a little as it dries. so thats why you see the cracking, and it occurs controlled along the keyway expansion joints. you have to give concrete somewhere to crack. either by expansion joint, saw cutting, keyway, etc. the worst is to get a random crack in a slab.
it looks like they did a nice job from the pics.

 

[jeopardy98]

Thanks. I know that it has to crack somewhere I just didn't realize it wouldn't happen so soon. Also after I posted this I went looking for similar threads and found the guy who is in MUCH worse shape than I.

The keyway being visible down the middle like that is okay? Nothing I should worry about? Also can I just put the RB over the cracks when it is time?

 

[boobag]

you could maybe smooth out the cracks before epoxy. could even run a diamond saw blade down the crack to open it up and even it out, then fill with a sealant?
i'd wait a little and see how much those cracks grow. if any.

 

[WarDamnEagle]

Keeping the concrete wet for 2 weeks will help minimize shrinkage cracks. I always put a sprinkler on immediately after it's hard enough to walk on. Having said that, you will still get shrinkage cracks.

 

[jeopardy98]

Yea I'll keep an eye on them over the next couple weeks. I'll do the coating right before I move in.

 

[stikman56]

Keeping the concrete wet for 2 weeks will help minimize shrinkage cracks. I always put a sprinkler on immediately after it's hard enough to walk on. Having said that, you will still get shrinkage cracks.

Yeah, keep it wet is the key. I sprayed our foundation down between the time it was poured and the framers getting started which was a week and half or more. It helped I'm sure.

 

[jeopardy98]

Mine was only 2 days. Then 1 day of framing led me to my current status.

 

[Bates]

Mesh is important to keep a floor from cracking as well. But unfortunately it's too late for you. Styrofoam around the outside 2' would have been good to keep the frost from creeping in as well.

 

[jeopardy98]

They used that expansion board around the perimeter. I really only have that one crack right on the keyway and it's less than a quarter's width. I'm sure it just came from not being watered while it dried.

 

[boobag]

Mesh is important to keep a floor from cracking as well. But unfortunately it's too late for you. Styrofoam around the outside 2' would have been good to keep the frost from creeping in as well.

mesh doesnt prevent cracking. it just sorta holds it together if it does.
using a lot of rebar will help, but then thats a big add-on expense.

They used that expansion board around the perimeter. I really only have that one crack right on the keyway and it's less than a quarter's width. I'm sure it just came from not being watered while it dried.

your floor cracked on an expansion joint.
i think why it shows up a bit worse is that your concrete finishers floated a little concrete over the top of the expansion joint, instead of even to the top. not a big deal though.

 

[Ponchoguy]

They used that expansion board around the perimeter. I really only have that one crack right on the keyway and it's less than a quarter's width. I'm sure it just came from not being watered while it dried.

Propex makes something called Fibermesh which helps stop that. My coworkers father is a mason and when he knew I was doing a driveway, he told me to make sure I spec it in my mix, which I did.

I did get some sinking (65+ ft driveway, 8" thick concrete, truck had to make like three trips back and forth), but I will deal with this in an appropriate way.

 

[greran]

the slab has cracked exactly where it's suppose to with that system (i believe called zip-strip..) I've had my slab for close to 3 years now and haven't seen any new cracks form or have the cracks getting any bigger over the zip strips.

Come coating time, like others have said, a little epoxy filler and you should be fine,

 

[jeopardy98]

Thanks everyone. I'm feeling okay about this. It seems it shouldn't be an issue.