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Thermal cracking occurs due to excessive temperature dif- ferences within a concrete structure or its surroundings. The temperature difference causes the cooler portion to con- tract more than the warmer portion, which restrains the con- traction.
If newly placed concrete freezes, immediate and permanent damage can occur; subsequent curing will not restore the concrete’s properties. Damage occurs because water expands 9 percent in volume when it freezes.
There is no such thing as concrete antifreeze. … The concrete doesn’t know how cold it is outside. Accelerators can also be used to help it set. The best news is once concrete is set, it cannot freeze.
Q.: Some concrete specifications contain a maximum temperature for the freshly mixed concrete as delivered. Typical values are between 80° and 95° F as measured by ASTM C 1064-86.
A: The behavior of concrete at high temperatures is influenced by several factors, including the rate of temperature rise and the aggregate type and stability. Abrupt temperature changes can cause cracking and spalling due to thermal shock, and aggregate expansion can also produce distress within the concrete.
In Phase II, the temperature of concrete can be measured as the concrete is poured. … The main reason behind this measurement is to ensure the concrete does not reach temperatures that are too high or too low to allow proper strength development and durability of the concrete.
The use of ice does effectively accomplish the purpose of cooling the mix in hot weather and is far more effective than cold water. One rule of thumb for determining how much ice to use is that the concrete temperature can be reduced one degree F for each two percent of total water replaced by ice.