What’s going on here?

[Lawless]

Hi
Had a slab poured recently (Monday) and this has started to happen on the surface.
Should I be concerned? RC40 mix mesh no fibres.

 

[milkloss]

I'm no concrete man but it's that dry at the minute I'm not surprised. Did you do anything to keep it covered etc?

 

[RWG Contracts]

Hi
Had a slab poured recently (Monday) and this has started to happen on the surface.
Should I be concerned? RC40 mix mesh no fibres.

looks like plastic shrinkage. Top has dried very fast and the water has evaporated

 

[Lawless]

Will it be ok.
what can I do to avoid it happening Again?

 

[Lawless]

Has it been over trowelled?

 

[Highland Mule]

Will it be ok.
what can I do to avoid it happening Again?

An expert will no doubt be along soon, but I think you can/ should cover the top during hot weather (with a polyethylene sheet or something) and maybe even get the garden spinkler out and occassionally dampen it for the first few hours. Remember that concrete curing is a chemical reaction, not a drying out process - it needs water to be able to go off properly.

 

[Paul E]

An expert will no doubt be along soon

You called??
I'm an expert in many things......
Just not concrete.
But it does look like it has dried too fast.

 

[suffolksmallholder]

Get some straw or hessian and soak it or both. Soak it for a week now. If you've had the hot weather this week like we've had it in sunny Suffolk speed is of the essence.
WhyTF don't the concrete co's just put a note on the ticket on 'How-to-cure-concrete-properly-with-care!' It really isn't rocket science, just keeping it moist is so simple but such a big issue. A 150mm cube cured properly will rate another ten tons in the press against a poorly cured cube. I know we all did this at college and the results were interesting to put it mildly.

SS

 

[David.]

Get a clean roll of silage sheet and waft it gently down onto the slab as soon as the wetness has gone off the top (try not to drag it over the surface), perhaps couple of hours from tamping and edging. Weight the edges down the outside of the shuttering with timbers or similar to stop wind getting under it, and leave it covered for a week minimum. The next morning the sheet will be sucked down tight to the surface, and the condensation underneath will keep the slab wet for the duration.

 

[br jones]

Should of kept it wet

 

[Cjm]

Definitely dried out too quick. I’ve used this in the past which works well:

Adawall Concrete Curing Aid - 20 Litre | Drainage Superstore®

This is a non-staining solution that when applied to fresh concrete/renders/screeds, reacts with the free lime and creates minute crystals which seal the po...

www.drainagesuperstore.co.uk

Plastic sheeting works but always leaves marks.

 

[RWG Contracts]

Will it be ok.
what can I do to avoid it happening Again?

sorry for late reply. Cover it in plastic or hessian and keep it wet, slows the drying proccess