Concrete Mixtures 18

Subbase Preparation - Concrete Placement

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Vapour barriers should be placed under all concrete ground level floors to prevent the transfer of moisture and soil gases such as radon gas. Sloping the landscape away from the building, placing a 100 mm granular subbase between the soil and the slab, adding a subbase drainage system, and using drain tiles and vapour barriers will reduce moisture problems.

After new concrete is poured and hardened it is roughened to make a better bond with the next placement. Wood forms should be oiled or treated with form release agent to prevent damage to the concrete when they are removed. Reinforcing bars should be clean and without loose rust and scale. Concrete should be placed as close as possible to its final destination. The placed concrete layer, usually 300 mm in depth, should be consolidated, and made uniform and horizontal, before the next layer is added. Concrete should not be poured into piles and placed by moving it horizontally because it will segregate as the cement and water mixture moves ahead of the aggregate. 

  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.
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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