Admixture Types Used In Concrete

Admixtures improve concrete’s performance. Any element added to concrete that isn’t aggregate, water, or cement is an admixture.

Concrete Admixture Types

Concrete admixtures are classified into the following types:

1. Water-Reducing Substances
2. Retarding Substances
3. Admixtures that Accelerate
4. Admixture of air-entraining concrete
5. Pozzolanic Compounds
6. Damp-proofing Substances
7. Admixtures that produce gas
8. Admixtures for air detraining
9. Anti-washout additives

1. Water-Reducing Substances

Water reduction admixtures, as the name suggests, are used to reduce the amount of water used in a concrete mix. Workability is an essential quality of concrete that improves with the addition of water, but if too much water is added, the strength and durability of the concrete suffer. It enhances the strength of concrete, the link between concrete and steel, and it avoids cracking, segregation, honeycombing, bleeding, and other problems. Plasticizers are water-reducing admixtures that are categorized into three types: plasticizers, mid-range plasticizers, and superplasticizers.

2. Retarding Substances

Retarding admixtures reduces the early hydration of cement and increases the first setting time of concrete. These are also known as retarders and are often employed in high-temperature areas where concrete sets fast. In certain cases, the rapid setting may cause structural discontinuities, poor bonding between surfaces, and needless voids in concrete.

3. Admixtures that Speed Up

Accelerating admixtures are used in concrete to decrease the initial setting time. They accelerate the first stage of concrete hardening, which is why they are also known as accelerators. These accelerators help increase the early strength of concrete by increasing the rate of hydration.

4. Concrete Admixture with Air Entrainment

One of the most significant innovations in concrete technology is air-entraining admixtures. Their major role is to strengthen the durability of concrete when it is frozen and thawed. When these admixtures are applied to a concrete mix, they generate millions of non-coalescing air bubbles throughout the mix, improving the characteristics of the concrete.

5. Pozzolanic Compounds

Pozzolanic admixtures are used to create a thick concrete mix that is ideal for water-retaining structures such as dams and reservoirs. They also minimize hydration heat and thermal shrinkage.

6. Damp-proofing Substances

Dampproofing or waterproofing admixtures are used to make the concrete building watertight and to avoid dampness on the concrete surface. They operate as accelerators in the early stages of concrete hardening, in addition to being water resistant. Dampproofing admixtures are available in liquid, powder, paste, and other forms.

7. Admixtures That Produce Gas

Aluminium powder-activated carbon and hydrogen peroxide are common chemical admixtures utilized in gas formation. When gas-forming admixtures are introduced, they react with the hydroxide produced by cement hydration to generate minute bubbles of hydrogen gas in the concrete. Many elements influence the range of bubble formation in concrete, including the quantity of admixture, the chemical makeup of the cement, temperature, fineness, and so on.

8. Admixtures for Air Detraining

Air-detraining to remove extra air from concrete voids, admixtures are utilized. When aggregates release gas into concrete, and the amount of air entrained is greater than what is required, admixtures of this type are useful. Tributyl phosphate, silicones, water-insoluble alcohols, and other commonly used air-detraining admixtures

9. Washout Prevention Admixtures

Anti-washout admixtures are used in concrete, particularly in underwater structures. It keeps the concrete mix from being washed away by high water pressure. It increases the cohesion of concrete. Admixtures of this type are made from natural or synthetic rubbers, cellulose-based thickeners, and other materials.