Concrete Mixtures 23

Cold Weather Concreting


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Concrete can be protected from freezing in cold weather by hydration heat, and by using enclosures, windbreaks, portable heaters, insulated forms and blankets to maintain the temperature and moisture needed for curing. Forms, reinforcing steel and embedded fixtures also need to be clear of snow and ice before the concrete is placed. Thermometers and storage for test cylinders should be made available. These measures are important because concrete can lose up to 50 percent of its strength if it is frozen within a few hours of placement. Concrete that has been frozen once can be restored to nearly normal strength but it will not be as resistant to weathering or as watertight as unfrozen concrete. Type 30 High early strength Portland cement, reduces the time needed to harden concrete and remove the cold weather insulation and other devices. Accelerators such as Calcium Chloride can be used to reduce the setting time and entrained air can provide protection from freezing and thawing. Heating the mixing water and aggregates will help protect the concrete from freezing. Gradually cooling the concrete, after termination of the heating period, will help prevent thermal cracking.




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Concrete Mixtures Links

1.The Materials In Concrete.
2.Concrete Aggregates - Concrete Slump.
3.Concrete Placement - Vibration - Hydration.
4.Types of Portland Cement - Concrete Moisture & Cracking.
5.Watertight Concrete - Supplementary Cementing Materials.
6.Supplementary Cementing Materials.
7.Chemicals That Damage Concrete.
8.Concrete Aggregate Properties.
9.Angular & Smooth Aggregate Properties.
10.Admixtures.
11.Admixtures Continued.
12.Air Entraining Admixtures.
13.Air Entraining Admixtures Continued.
14.Conditions Affecting Concrete Air Volume.
15.Superplasticizers & Other Admixtures.
16.Ordering & Mixing Concrete.
17.Concrete Mixing - Subgrade Preparation.
18.Subbase Preparation - Concrete Placement.
19.Concrete Consolidation.
20.Concrete Finishing.
21.Concrete Curing.
22.Hot Weather Concreting.
23.Cold Weather Concreting.
24.Concrete Slump Test.

                                                     
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Ronald Hunter
           
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