Hello all Im pouring my second level this friday and want to coordinate my truss delivery Here in eastern Canada were a few deg on either side of freezing at this time of year and Im wondering how long I should wait before attaching my top plates and subsequent trusses? cheers P

Cover the top of the walls and I would wait about 36 hours. But even then I would wait a week or so before tightening your anchor bolts.

Take a flat blade screw driver stick it thru the foam about mid wall.  Give a twist if it penetrates, the concrete has not set enough.  In cold weather you should pump a 2 or 3 slump and add mid range water reducer to increase flow.  This takes 25% to 30% of the water out of the mix and gives you stronger concrete and faster drying.

Posted By smartwall on 24 Nov 2010 02:58 PM
Take a flat blade screw driver stick it thru the foam about mid wall.  Give a twist if it penetrates, the concrete has not set enough.  In cold weather you should pump a 2 or 3 slump and add mid range water reducer to increase flow.  This takes 25% to 30% of the water out of the mix and gives you stronger concrete and faster drying.

HI,
That was great if your installed strong concrete will fast drying...what brand is that?
Can you shared with us here...?

In general, concrete reaches it's maximum strength in 28 days. Concrete "never" stops curing.

However, in cold weather, if the top of the wall was not protected on the second or third night you could have suffered mild freezing.

I would wait as long as possible before I really cranked down on the anchor bolts. You should have no trouble working the top plate if you don't hammer on the anchor bolts.

If you pour with less water the concrete will be stronger and will dry faster. I've seen concrete poured in the winter that didn't dry for 3 months.

The pour went very well, The mixing plant used hot/warm water so the set up seemed to progress well
It was about 0 deg C that day here and I covered the wall with plastic, All seems good now

You footings may be pockmarked or if they are still in a form then they could be diluted, which will require longer for it to cure. So if you just poured the truss then you should be okay. I am more concerned about the temperature. It is going to be drop near to freezing in my area tonight and that will be detrimental to the concrete, which is why it is normally only poured in the spring and summer (concrete can only be poured at temperatures between 50 to 70 degrees Fahrenheit, as near as 73°F as possible). The goal is to keep concrete cool and moist so it gains strength slowly, but efficiently