Pouring concrete in this weather

Builderfromhell

I am scheduled to start a new house extension next week. This weather is unusual I think you'll agree and I'm concerned about ;
1. How hard the ground will be to dig out.
2. Pouring concrete which might then freeze overnight.

I should know the guidelines on this but I am so used to mild winters that I have forgotten.

On a seperate matter; it has become common practice for foundations to be very shallow. Sometimes the top of a foundation may be at ground level. The reason this became common was because it's cheaper and hard frost was considered a thing of the past. I wonder how many foundations are suffering from frost heave now (where ground swells when frozen and pushes foundations up).

sinnerboy

http://www.askthebuilder.com/B104_Cold_Weather_Concrete_Checklist.shtml

Builderfromhell

Found this info. on a UK site;

Frost and snow

If ambient temperatures are low enough to delay the initial setting, concrete will not develop its full strength. Concrete should not be mixed or placed if the air temperature is not at least 3 degrees Celsius (C). The minimum temperature for placing concrete is 4 degrees C (steady) or 3 degrees C (and rising). These temperatures should be sustained or exceeded for the concrete to start to set properly.

Frost bound aggregates should not be used.

Local conditions may increase the risk of low temperatures. Temperatures decrease by about 0.6 degrees C for every 100 metres above sea level.

An unprotected concrete slab should not be laid during heavy rain or snow showers.

Bricks or blocks should not be laid, nor render applied, in temperatures of below 2 degrees C or if the temperature is expected to drop below 2 degrees C.

Green brickwork and render should be protected from rain, snow and possible overnight frost.

Do not handle or lay sheet membranes when the temperature is low enough to reduce their workability. Check the manufacturers instructions for the minimum working temperature.

Wet or frozen surfaces are nor suitable for bonding to.

Do not lay a greater area of hot applied adhesives than will stay fluid while the membrane is laid.

jwshooter

im a stonemason ,working on a house in the wicklow mountains. i have not worked now from a week before christmass.

the morning we gave up ,we went for breakfast at 10am we came back about 10.45 the mortor was frozen on the board.

cant see myself getting back this week.

No6

They pour concrete in Russia and places like that at - temperatures but I believe they do use admixtures or maybe antifreeze!! Personally I would wait for the weather to improve!!! Hows it going JW!!

40701085

Working it would be tough enough in itself, but whether it will go off properly or not would be a big risk. For me - I'd wait for the thaw. Especially when its a slab.
Happy new year

ddoc

no concreting or blockwork can be done in this weather at the moment it will not go off

gman2k

Watched an interesting documentary one night about a The Kingdom Cente in Saudi Arabia, and because of the very high ambient daytime temperature, they had to use ice in the concrete mix to prevent it going off whilst being pumped to the upper levels.

Now, back to Ireland - if it's very cold, no external wet work!

Poor Uncle Tom

Have stopped three jobs pouring, they are not happy campers, but with snow in the trenches before the pour what did they expect..:D

Wonky Knees

asking for trouble if you pour in this weather OP. Wait it out.

muffler

Poor Uncle Tom wrote: »

but with snow in the trenches before the pour what did they expect..:D

White concrete? :eek:

muffler

I remember someone saying to me a long time ago - "you dont put your washing out to dry when it's raining". I think the same analogy applies here.