Were pouring a small 15 x40 slab here in alabama, its unusually cold here in the mornings (15 deg). I want to have the concrete truck here at 8 am so I know i will have plenty of time for it to set. How do you figure how much calcium to add, I dont want to leave it to the cement guys there idiots. You say a 4 in slump with these guys and its running out the shoot like white water rapids:no: Does the calcium effect finishing quality? Any help will be appreciated, I'm a concrete newbie.