Concrete in the Cold — Basic Concepts

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Average daily air temperature from +5 ºCand minimum air temperatureless than 0 ºCwhen it wascold weather conditions for concrete worksevaluated as.  

 

In this case the concrete

 

manufacture,

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transport,

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placement

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dry

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made by taking special precautions.

When fresh concrete freezes;

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There is no change in the properties of the cement and aggregate in it, but

The water that will react with the cement freezes.

 

With the water freezingCement stops hydrationand thus the setting of concrete stops.

 

Moreoverfrozen water expandsand cause the concrete to crumble.

 

Freezing water forms a thin film of ice on the walls of the coarse aggregate Prevents adhesion between aggregate and cement mortar.

 

When the concrete, which freezes at a younger age and then hardens under normal conditions, is loaded to fracture load;

 

the coarse aggregates are separated from the concrete mass,

 

that the concrete is broken not from coarse aggregates but from cement mortar,

 

there are small gaps in the fracture region and ice crystals leave traces in these gaps.

 

observed.

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Freezing water does not cover all surfaces of coarse aggregates evenly. It concentrates mostly on the underside of the aggregates. The water collected at the bottom of the aggregates increases the water-cement ratio of the cement mortar in these areas. This reduces the strength of concrete.

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Critical Strength

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It is not economical to cure concrete at optimum temperature in cold weather conditions. For this reason, in practice, the concrete is cured   until it gains a strength that can withstand the internal stresses that will occur due to the freezing of the water inside.

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This strength value of concrete "critical strengthIt's called '.

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After reaching this strength, the frozen concrete gains its calculation strength under normal curing conditions when it is thawed later.

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Time for concrete to reach critical strength

 

speed (duration) of construction,

 

mold use,

 

labor and energy needs

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it is a factor that directly affects it. 

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In order to shorten the time of concrete reaching critical strength;

 

using heated concrete,

 

increasing the curing temperature of concrete,

 

Using cement with high activity,

 

prolonging the mixing time of concrete,

 

vibrating the concrete after it is placed,

 

use of low-consistency concrete,

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adding accelerator to concrete

 

measures can be taken.

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Surface Module

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One of the factors to be considered in determining the curing method to be applied to the concrete poured in cold weather conditions is the ratio of the cooling surface of the building element to which the concrete will be poured.

 

This ratio of the building elementsurface modulecalled. 

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