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rebar, cold weather and chloride

Q. I'm concerned about re-bar corrosion and slab integrity with my contractors concrete cold weather precautions. My contractor mixed 1% CaChloride,hot water & entrained air for a rebar re-inforced garage floor & footing. In Montana, we have had the coldest seasonal temps in 20 years over the last 7-10 days which is starting to warm up now. The bed had been covered for a week with thermal tarps without heaters. The night temps had just been in the single digits for the last week.
He decided to pour against my requests to wait 2-3 days until the predicted temps returned to 50's, warming up the bed & hopefully avoid adding Chloride. He poured in 24 degree F weather with frost. The following morning,the crew returned, uncovered the slab in 25 degrees to cut stress lines around the footing/floor junction & recovered it after. What do you think? A 44x32 garage/shop floor. Should I be concerned about re-bar corrosion, staining through, strength and surface.

A. CaCl is a salt and does cause corrosion, but rebar corrosion is not really an issue with residential applications. That would be a concern for bridge construction and big time commercial work. So don't lose any sleep over that. Your concern is whether the concrete froze or not and whether the subgrade was frozen when it was poured. Insulation blankets can keep the freeze out if there are enough. Hopefully the ground didn't freeze, but the consequences of pouring on frozen ground don't show up until it thaws.
Whether or not they kept the surface of the concrete from freezing is another issue. The first few days, the concrete is generating its own heat and the blankets will hold much of the heat in. So whether or not the concrete froze depends on how well it was covered, especially the first night.
You do have some legimate concerns, but unforunately, a problem caused by freezing temperatures usually doesn't rear its ugly head for weeks or even months. The best thing you can do is seal the floor and cross your fingers. Hopefully your contractor stands behind his work.