Expert: Dan Griffin - 11/27/2007

Question
I am building a 16 x 24 cottage on granite in a Northern climate (Canada). There is between one foot and three feet of earth, small crushstone and backfill until bedrock is reached. I plan on pouring a 18"x18"x 6" thick footing below each of the 12 10" sonotubes in my customer's plans. I have bored into the granite 6" and installed rebar, as required by my local codes. The problem is, my holes are filling with water, both from rain and melting of a recent light snowfall, and the temperatures are rapidly nearing below freezing at night. The water can be removed, but I worry about the holes refilling and turning my cement to mush. I can't protect the cement from water by inserting a poly 'condom' in the hole, because it would have to be perforated by the rebar.
Is my only option to pump the hole dry and use a quick set cement?
Thanks

Answer
Concrete made with regular Portland cement will set under water just fine.  You are making a mountain out of a molehill.  Most engineers don't want concrete poured into standing water, though the water will continue to rise to the top as you pour.  Pump the holes down when you're ready to pour and get em filled up.  It is bad practice to pour in frozen ground.  You can blow a weed burner to melt ice and snow and get the ground above freezing.  Once poured, snow makes a great thermal blanket.  If you don't have snow and you're headed for a deep freeze, throw concrete blankets/ hay bales/ or even a tarp over the piers.  The concrete makes heat and the ground is above freezing until deep cold gets deep in the ground.  Once they are poured, don't worry about ground water, don't worry about rain.  The concrete will NOT be mushy.