Minimum temperature for concreting

[Neddy flanders]

mondays forecast says max 5 deg falling to 0 or -1 overnight. Would you lay concrete at 9.30 am and hope surface has sort of dried by dusk?
Cover it with some sort of tarpaulin tent?

 

[RWG Contracts]

Ideally wants to be above freezing and an average temperature of over 6 degrees for 48 hours after pouring

 

[Neddy flanders]

Ideally wants to be above freezing and an average temperature of over 6 degrees for 48 hours after pouring

thanks. would you pour on Monday morning?

 

[RWG Contracts]

thanks. would you pour on Monday morning?

Depends on a few things.

What mix?

Where is it?

How desperate are you?

 

[Neddy flanders]

C32/40 mix outside. will get dappled sunshine. desperate.

 

[RWG Contracts]

C32/40 mix outside. will get dappled sunshine. desperate.

I'd ask for a straight OP mix with no additives so it goes off faster.

Sheet it up at night of it freezes and cross your fingers

 

[Nearly]

C32/40 mix outside. will get dappled sunshine. desperate.

Couple of layers of sheet with air gap will make a big difference.

 

[Greenasgrass]

-1 will not have a big effect on your Conc especially if you can get some polythene over it. Below +5 Conc takes a long time to cure/ gain strength and below +2 it basically ceases curing until the temp rises. It will have no long term detrimental effect on your Conc as long as you let it cure before trafficking.
I have laid Conc with much colder over night temps without problems and it hasn't been covered.

 

[sheepwise]

So if temp is above 5C how long does it need before trafficking with tractor and feed wagon.

 

[RWG Contracts]

So if temp is above 5C how long does it need before trafficking with tractor and feed wagon.

2 weeks ideally

 

[Courier]

If you are able to lay a thin sprinkling of bedding straw under a polythene sheet it would stand 5 deg below for overnight with no problem.
The straw will brush away next day[emoji6]

 

[Greenasgrass]

Below is an extract from a method statement that i did recently which may be of use to you!


The following points will be strictly adhered to in relation to the placing and curing of concrete in cold weather conditions:


Slab:


Concrete Type – PAV 2 Designed Mix

• Ambient site temperatures will be >0°C at the time of pouring – the current Met Office forecast for the area is that the temp. will be >0°C from approx 8am tomorrow morning through to approx 3am Wednesday morning
• Concrete to be not more than 70 slump to minimise water content – PAV 2 concrete also has air entrainment to protect the finished surface from freeze thaw cycles.
• Top surface of concrete will be treated with Easycure R90 (90% efficient) curing agent as per manufacturers instructions to aid curing
• Exposed surfaces (ie. top surface) will be protected using frost blankets where there is likelihood of frost within 48 hrs of casting. Side formwork will be left in place for 48 hrs before striking

The only way to be sure when it is ready for traffic is to take a number of concrete cubes - cure them in the same conditions as the slab itself and start crushing one per day from day ten say.
I have also attached some info from Hanson regarding pouring conc in cold weather.