Concrete Slab and Radiant Heat

[UNCLEBUCK]

I asked my old dad about concrete curing and he said 3 days minimum at above 40 degrees outside air temp and the same 80% strength at 7 days but 3 days minimum for 1/2 strength . I am poruing a slab tomorrow and I got rebar in it and I asked my dad if I should have the concrete plant put in "kicker" so it will dry fast at below freezing temps and he said "kicker" is calcium chloride and it would rust the rebar out but I am definately having them put in 3%air when they mix it "liquid oxygen" which will prevent it from cracking after I have removed all the tarps and straw off of it around 2 weeks from now.yuck !  Glad you got your slab poured Steve

[OneWithWood]

Maple, yup that is a Taco.  I do remember reading something about the position of the pump.  It would not be the first time I read one thing and did just the opposite.  Dislexia?  Dead brain cells?  I will be sure to pull out the instruction sheet and read it again.  I was very carefull to bleed all the air from the system and let the primary pump circulate water through this one before I switched it on.  :
Thanks for the heads-up.

[Vermonter]

Unclebuck:
3 days should get you 50-60% of rated strength.  I think the "liquid oxygen" they are talking about is air entraining cement powder.  This should increase the air content, and, as you said, help with freeze/thaw cycles.
As for CaCl (Chloride),  the rebar rusting is the least of your problems.  CaCl weakens the mix, the more you add, the weaker it gets.  Around here, you can have them mix it with hot water, which shouldn't decrease your strength, but gives you a quicker set time.  I try not to use the chloride if possible.  For slabs, if at all possible, I like to pour inside, so I usually schedule any pour I can for after the building is closed in.  On rougher finish concrete, I can finish outside, so in cold weather I can usually get a bit of a finish on it before it cools off, and cover it with insulating blankets.  The hydration process gives off heat, so that helps it keep warm.  I have only been using the insulated concrete forms for walls, so I can pour any time of year because there is so much insulation it takes close to a week to cool down.  Don't forget your expansion/contraction joints in your slabs.