Hair line cracks in fresh concrete

[samsung]

Just on concreting our yard.
Full works visqueen, mesh, fibres, C45 .
As it dries we're getting hairline cracks appearing .
Its been tampered with mechanical and then float and brush finish.
I'm assured it won't affect finished strength , but its really annoying. !
Any suggestions.
Thanks S

 

[Chuckie]

It's drying out too fast on top. Spray water on to keep it damp.

 

[Fendt516profi]

@RWG Contracts

 

[bobk]

It's fairly normal , won't do any harm

 

[HolzKopf]

'plastic shrinkage' if conditions too sunny, warm or breezy. Fine spray, better still cover as well. Not easy if its a large area of course but plastic sheeting or tarps would be ok. Sacking that retains moisture is better. Some cracking in a slab is inevitable but surface crazing if it does dry out to fast is ok really as long as not deep

 

[samsung]

Yes all watered as soon as we can without marking it.Until I go to bed about 11. Still cracking.

 

[jackp]

If the cracks are quite big brush some cement powder into them the next day , also if you are doing more try putting plastic under it if the ground underneath is very dry and sucking the moisture out

 

[Forever Fendt]

'plastic shrinkage' if conditions too sunny, warm or breezy. Fine spray, better still cover as well. Not easy if its a large area of course but plastic sheeting or tarps would be ok. Sacking that retains moisture is better. Some cracking in a slab is inevitable but surface crazing if it does dry out to fast is ok really as long as not deep

All above good advice, you can get a spray that puts a film on top to stop the shrinkage cracking although your fibres should do this perhaps you are having it to wet and you could try a blended cement if the spec will allow it

 

[samsung]

It's drying out too fast on top. Spray water on to keep it damp.

 

[samsung]

Yep visqueen under all
Contractors said there is 2 tutypes of concrete, some cracks as you're laying it, the other cracks eventually !
True enough I suppose.
Thanks.

 

[Gordy1]

As others said, its most probably drying out too fast.

 

[Vincent]

My dad always put a polythene sheet over fresh concrete and will keep some water under it for a few days after. This prevents the cracks from it drying out to fast. A few shovels of sand and timbers to keep the sheet in place.

 

[David.]

^this
Wouldnt think of laying a slab without keeping it covered with silage sheet for at least a week, condensation under it is enough to keep it damp.