Table 4-5. Recommended duration of protection for concrete placed
in cold weather (air-entrained concrete)*.
Effects on Low Concrete Temperatures
Figure 4-16 demonstrates that temperature affects the hydration rate of cement; low temperatures retard hardening
and compressive strength gain. The graph shows that the strength of concrete mixed, placed, and cured at
temperatures below 73...F is lower than concrete cured at 73F during the first 28 days but becomes higher with
age and eventually overtakes the strength of the concrete cured at 73...F. Therefore, you must cure concrete placed
at temperatures below 73F longer. Remember that strength gain practically stops when the moisture required for
hydration is removed.
Figure 4-16. Effects of low temperature on concrete
compressive strength at various ages.