Can you pour concrete slab on bedrock, and pour ICF ground floor walls in Muskoka Ontario in winter?
Its never idea to do winter pours & concrete needs prep for application so it doesn't crack, you can't just "pour it on a surface" , you will need to put rebar into the bedrock 1st, but yup its done all over Canada, all winter. Concrete suppliers have "winter concrete" and it costs a little more too. Make sure you hire a contractor who knows what they are doing and has the equip. to keep it covered, heated etc. during initial cure.
Following are the 'Cold Weather Requirements' described in the National Building Code 2019 Alberta Edition'.
1) When the air temperature is below 5 C, concrete shall be
a) kept at a temperature of not less than 10 C or more than 25 C while being mixed and placed, and
b) maintained at a temperature of not less than 10 C for 72 h after placing.
2) No frozen material or ice shall be used in concrete described in Sentence (1).
3) Concrete shall not be placed
a) Into mud, standing water or snow, or
b) on, against or above any frozen material.
During winter months there is a surcharge for 'winter heat' (not sure if they just heat the water or if it's all the ingredients). If you were to walk into your concrete supplier and ask for 'winter concrete' they might look at you kina funny.
It is common practice (at least in Alberta) to add 2% calcium chloride as an accelerant, however this practice isn't described in the Building Code however the Code does reference a concrete standard (CSA A.23.1:19 - Concrete Materials & Methods of Concrete Construction).
In your region the temperature is so marginally below freezing so as not likely to be a concern about placing concrete over the bedrock; however suggest you check with your municipal authority to verify local (Ontario) Code requirements and accepted practices.
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