A bigger issue than the concrete freezing overnight is the fact that you are pouring over frozen ground. There’s no way to compact properly, and any heat generated by the concrete curing will be lost to the frozen material beneath. Most jurisdictions won’t let you pour concrete when the ground is near or below freezing. If you do move forward, build your visqueen tent and heat with propane or kerosene prior to prep and pour. I’ve done this-it’s a pain to keep heaters going constanty, and takes forever to thaw the ground. Also-visqueen wants to melt/burn when too close to that much heat.