Benefits and drawbacks of air entrained concrete

Air entrained concrete is formed by providing little air bubbles into concrete is called air entrainment. Air entrainment is performed with the use of air entraining Portland cement or air entraining agents like admixture.

The amount of air in such concrete is normally kept among four to seven percent of the volume of concrete.

Various types of methods like galvanometric method, volumetric method and pressure method are used to work out the concrete volume. The air bubbles mitigate internal pressure on the concrete by arranging chambers for water to be extended at the time of getting freezed.

Method - Air in concrete in integrated in the following ways:

 By utilizing gas forming materials like aluminium powder, zinc powder and hydrogen peroxide.  With the application of surface active agents that minimizes surface tension. These may contain natural wood resins and their soaps, animal or vegetable fats or oils, alkali salts of sulfonated or sulphated organic compounds.  With the help of cement dispersing agents.

Benefits - Given below, some of the benefits of air entrained concrete:

1. Workability of concrete is raised significantly.
2. The impact of freezing and thawing is reduced with air entraining agent.
3. Bleeding, segregation and laitance in concrete are decreased.
4. Entrained air makes the sulphate repelling strength of concrete.
5. Minimizes the chance of shrinkage and crack development in the concrete surface.

Drawbacks - Given below, some of the drawbacks of air entrained concrete:

a. The strength of concrete is reduced.
b. Air entraining agent can raise the porosity of concrete and consequently the unit weight is decreased.
c. Air-entrainment in concrete should not be performed if the site control is not superior because the air entrained in a concrete differs with the alteration in sand grading, errors in proportioning and workability of the mix and temperatures.



Read more

~~~~~~~~~~~~~~~~~~~~~~~~
Published By
Rajib Dey
www.constructioncost.co
~~~~~~~~~~~~~~~~~~~~~~~~

Brief overview of workability of concrete

The strength & longevity as well as the cost of labor and look of the finished product is greatly impacted by the workability of concrete. The concrete can provide better functionality, if it is easily positioned and compacted consistently devoid of bleeding or Segregation.

The concrete that is not in good working condition should be supported with extra work and endeavor for being compacted in position, also honeycombs &/or pockets are also found in finished concrete.

Definition of Workability: Concrete workability defines how smoothly freshly mixed concrete is amalgamated, arranged, compacted and finished by keeping the conformity as it is. Workability refers to a property that directly affects strength, quality, appearance, as well as the cost of labor for placement and finishing operations.

The workability is impacted with the following factors :

1. Water content in the concrete mix
2. Amount of cement & its Properties
3. Aggregate Grading (Size Distribution)
4. Nature of Aggregate Particles (Shape, Surface Texture, Porosity etc.)
5. Temperature of the concrete mix
6. Humidity of the environment
7. Mode of compaction
8. Method of placement of concrete
9. Method of transmission of concrete

The workability of concrete can be improved in following ways :-

1. Raise the proportion of water/cement
2. Raise size of aggregate
3. Apply well-rounded and smooth aggregate rather than asymmetrical shape
4. Rise the mixing time
5. Enhance the mixing temperature
6. Employ non-porous and saturated aggregate
7. Include air-entraining mixtures

The most recognized method for measuring the workability of concrete is Slump Test.

Read more

~~~~~~~~~~~~~~~~~~~~

Published By

Rajib Dey

www.constructioncost.co

~~~~~~~~~~~~~~~~~~~~~