I just replaced my radiator today and decided to refill it with coolant concentrate and mix in water myself. Instead of mixing the stuff properly before hand, I poured in 1/2 gal. of water directly into the radiator, and then proceeded to pour in 1/2 gal of coolant in and it filled up only after pouring in 1/4 gal.

Q. Do I have to mix the coolant beforehand or can I count on it mixing in the radiator? Also, will my pipes freeze/crack overnight (it's 29° f tonight) if there is like 60% water and 40% coolant?