What happens to the strength of concrete at very low temperatures?
The general pattern is for it to increase abruptly in the range from 40 º to minus 150 º F and then to fall off slightly as the temperature drops to minus 250 º F. For example, for a 5.5-bag mix the following approximate values can be read from a chart published in a report by G.E. Monfore and A.E. Lentz, "Physical Properties of Concrete at Very Low Temperatures," Portland Cement Association Research Department Bulletin 145:
75 5000
40 5000
0 8000
-75 12,000
-150 17,000
-250 16,000