Exposure conditions that represent the greatest threat to concrete in cold climates are those that combine a number of parameters. These include the frequency of freeze-thaw cycles, the absolute lowest temperature reached, the period of freezing, and the rate of cooling. The lower the temperature and the longer the freezing period the more extensive the effect on the volume of pores exposed to potentially damaging conditions. Concrete has a low rate of heat transfer and therefore significant penetration of the ice front requires very low temperatures, long periods of freezing, or a combination of both. The rate of cooling can be a factor. The slower the rate of cooling, the greater is the opportunity for dissipation of the pressures from expansion and expulsion of water from the capillaries. This may prevent the cumulative build up of tensile stresses beyond the capacity of the concrete.
The cumulative effect of freeze-thaw cycling makes the frequency of cycle more significant than the period spent at low temperature.
