What Is Air Entrained Concrete? How it is Produced ? Uses of Air Entraining Concrete

What Is Air Entrained Concrete?

Air entrained concrete is a type of concrete that contains billions of tiny air pockets, and these air pockets allow water to expand when it freezes and relieve internal pressure on the concrete.

In order to create air-entrained concrete, either air entraining Portland cement or an air entraining agent in the concrete mix are used.

Air entrained Concrete
Air entrained Concrete

Air entrainment is the process used to create a microscopic bubble in concrete. Air entrainment admixtures are used to create air bubbles in the concrete during the mixing process.

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The majority of the bubbles in concrete remain in the hardened stage, where they are generated when the concrete is in the plastic stage.

The major objective of air entrainment in concrete is to increase the hardened concrete’s endurance in environments where there is a risk of freezing and thawing.

The important secondary goal is to make concrete more workable when it is in the plastic stage. The production of air that is stickier leads in fewer segregation results and a more desirable concrete surface.

How to Produce Air Entrained Concrete

How to make air entrained concrete? Following materials are used to make concrete,

  1. Air entraining cement
  2. Air entraining agents

1. Air Entraining Cement

One of the unique varieties of cement that produces air bubbles in the cement or concrete is air-entrained portland cement.

The concrete is shielded from damage and fissures by the air bubbles, which also provide it room to expand during freezing and thawing.

2. Air Entraining Agents

The following are examples of materials or air entraining agents:

1. Using gas-forming material:-

  • Aluminum powder
  • Zinc powder
  • Hydrogen peroxide

2. Lowering Surface tension agents:-

  • Natural wood resins
  • Animal fats
  • Wetting agent
  • Water-soluble soaps of certain acids

All of the aforementioned ingredients are combined with different forms of concrete to create foam, among other things. The stable foam produces tiny microbubbles in the air entrained concrete as a result of the water’s surface tension being lowered.

  • Calcium ligno-sulfate and calcium salts of glues
  • Using cement dispersing agents
Air entrained Concrete
Air entrained Concrete

What are the Properties of Air Entrained Concrete?

  1. Workability
  2. Freeze-thaw durability
  3. De-icers resistance
  4. Sulfate resistance
  5. Strength
  6. Abrasion resistance
  7. Water tightness

Workability

Reduce water and sand needs, especially in lean concrete mixes, if the workability of air entrained concrete is enhanced. Disconnecting the air bubbles will lessen the segregation and bleeding of plastic concrete.

Freeze-thaw durability

Water expands during the freezing process, putting enough pressure on the concrete for it to crack. Concrete is protected from water expansion and damage by air bubbles that act as reservoirs within the concrete.

De-icers resistance

Because entrained air inhibits scaling brought on by the use of de-icing chemicals for snow and ice removal, air entrained concrete is typically utilised where concrete comes in contact with de-icing chemicals.

Sulfate resistance

Entrained air and cement with a low tri-calcium aluminate content can help concrete that has a low water to cement ratio withstand sulphate attack. In order to protect concrete from sulphate assault, entrained air is highly helpful.

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Strength

The ratio of voids to cement essentially determines the strength of air-entrained concrete. Void volume is defined in this ratio as the sum of the volumes of water and air.

The strength of concrete varies inversely with the w/c ratio when the air content is constant. By keeping the voids to cement ratio constant, we can often retain a certain strength as the air content rises.

Abrasion resistance

The compressive strength of air-entrained concrete is equivalent to that of non-air-entrained concrete in terms of abrasion resistance. The compressive strength also increases as abrasion resistance does.

Water tightness

Concrete with air entrained particles has greater water resistance than concrete without air entrained particles. The formation of capillary interconnections is impeded by entrained air. So, where water tightness is necessary, air-entrained concrete is highly helpful.

Effect of Air Entrainment on Strength of Concrete

Workability and compressive strength of concrete are the key factors that are impacted by air-entrained concrete.

Without changing the water-to-cement ratio, the air-entrained concrete has improved the workability of concrete.

Workability and compressive strength are always inversely proportional to one another, therefore if the workability of the concrete increases, compressive strength immediately drops.

  1. Effect of air entrainment on compressive strength of concrete
  2. Effects of air entrainment on flexural strength of concrete

Effect of Micro Air Bubbles on Concrete Compressive Strength of Air Entrained Concrete

Commonly used as an additive to improve the workability of concrete without barely impacting its strength.

According to the study’s findings, air-entrained concrete with a 7.5 cm slump performs better than non-air-entrained concrete with a 12.5 cm slump.

The compressive strength of concrete is decreased if air entrained admixture is used in big or enormous amounts.

The proportions of the mix, the kind of concrete, the grading of the concrete, the type of cement, and the entraining agent are the common aspects that have an impact on the lowering of the strength of concrete.

Between 3 and 7% of the strength of concrete is lost when air-entrained admixtures are used. In the design of the concrete mix, the variance of this 3 to 7% is taken into account.

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Therefore, the needed quantity of admixture and workability is used to obtain the desired compressive strength.

Prior to the design, trial mix designs are carried out to precisely determine how the admixtures alter strength. The mix design is then appropriately corrected.

It is generally accepted that each 1% volume of entrained air in the concrete mix results in a loss of 5% in the compressive strength of the concrete.

Air entrained Concrete
Air entrained Concrete

Assuming the high goal mean strength, the water-cement ratio needed for an air-entrained concrete that allows for strength loss is integrated into the mix design.

The high target mean strength for an air entrained concrete mix is given by:-

Target mean strength = fc + m/(1-0.055a)

where,

f = specified characteristic strength

m = margin

a = % by volume of the entrained air

2. Effect of Micro Air bubbles on Flexural Strength of Air Entrained Concrete

In contrast to compressive strength, the drop in concrete’s flexural strength caused by air entrainment is typically not quantified.

According to the report, concrete will reach its maximum flexural strength if the air concentration is 4%.

It can be inferred from both situations that, as long as maximum water reduction is taken into account and a tiny maximum aggregate size is used, the compressive and flexural strength of lean concrete mix designs rises.

FAQs related to Air Entrained Concrete

What is Air Entrained Concrete?

A special kind of concrete called air entrained concrete has countless small air pockets that, when water freezes, cause it to expand and release internal pressure.

Either air-entraining Portland cement or an air-entraining chemical included in the concrete mix are used to produce air-entrained concrete.

A tiny bubble in concrete is made by the process of air entrainment. During the mixing process, air bubbles are introduced to the concrete using air entrainment admixtures.

What is Air Concrete?

An air-entrained cement or other air-entraining ingredient is used to add millions of small air bubbles to concrete to create Air concrete. The ability of air concrete to resist freeze-thaw damage and scaling brought on by de-icing salts or chemicals is one of its main advantages. Air concrete is simply another word for Air entrained concrete.

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What is Air Entrainment?

Air entrainment is the process used to create a microscopic bubble in the concrete. Air entrainment admixtures are used to create air bubbles in the concrete during the mixing process. The majority of the bubbles in concrete survive in the hardened stage, where they are generated when the concrete is in the plastic stage.

What are the Uses of Air Entraining Cement?

The resistance to freezing, thawing, and scaling is the main advantage of air-entraining concrete. When a freeze event occurs, the air gaps in concrete act as pressure relief valves, allowing the water inside to freeze without causing significant internal tensions.

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