Introduction to Concrete Admixtures
Concrete admixtures are mineral or chemical elements that are added to the concrete mix to enhance the desired properties, such as strength, workability, corrosion resistance, water requirement, etc. Based on your requirement, you can select the right admixture for your project.
5 Commonly Used Concrete Admixtures in India
Concrete admixtures come in different types that enhance the properties of the concrete.
1. Waterproofing Admixtures
Waterproofing admixtures are added to concrete mixes to improve their waterproofing qualities. These admixtures are particularly useful for projects located in those regions of India that experience heavy rainfall and where water damage can be a significant problem.
Waterproofing admixtures work by reducing the size and number of pores in the concrete, which makes it less permeable to water. They can also improve the overall strength and durability of concrete, which helps to prevent cracking and other forms of damage that can compromise its waterproofing capabilities.
There are several types of waterproofing admixtures available on the market, such as Crystalline admixtures, Hydrophobic admixtures, Integral waterproofing admixtures, and Polymer-based admixtures.
2. Water Reducing Admixtures
Water-reducing admixtures are used to reduce the amount of water needed in a concrete mix without compromising its workability. They are also known as plasticizers or dispersants and are primarily used for projects located in dry regions of India. Water-reducing admixtures work by dispersing the cement particles in the concrete mix, which allows the water to be distributed evenly. This reduces the amount of water needed in the mix, which improves its strength and durability by increasing the ratio of cement to water.
The use of water-reducing admixtures can also help to reduce the risk of cracking and shrinkage in the concrete. Some of the commonly used plasticizers include polycarboxylates, carboxylate ether, and acrylic-based admixtures.
3. Retarding Admixtures
Adding retarding admixtures to the mix slows down the setting time of the concrete. They are often used in hot weather conditions or in large construction projects where concrete needs to be transported over long distances.
These admixtures can also help to reduce the risk of cracking and improve the overall quality of the concrete. Polycarboxylate Ether and Hydroxycarboxylic acids are the most commonly used retarding admixtures in India.
4. Air-entraining Admixtures
Air-entraining admixtures are advanced admixtures that introduce microscopic air bubbles into the concrete mix. These bubbles act as a lubricant between the concrete particles, which improves the workability of the mix and makes it more resistant to freeze-thaw damage.
Air-entraining admixtures reduce the surface tension of the water in the concrete mix, allowing air to be entrained into the mix as it is mixed and agitated. These admixtures are generally found in two types: Synthetic surfactants and Natural surfactants.
5. Corrosion Inhabiting Admixtures
Corrosion-inhibiting admixtures protect steel reinforcement in concrete from corrosion. They work by forming a protective layer around the steel, which prevents water, oxygen, and other corrosive substances from reaching the steel surface.
These types of admixtures are commonly used in construction projects along the coastal regions of India. Nitrite-based admixtures are the most commonly used corrosion-inhabiting admixtures in India.
How to Use Concrete Admixtures
Admixtures are added to the concrete during the mixing process. Generally, a small amount of admixtures is added to a large quantity of concrete mix.
The table below provides an estimated average dosage of different admixtures.
| Type of Admixture | Average Dosage |
| Waterproofing Admixture | 0.1% to 2% by weight of the cement in the concrete mix |
| Water-reducing Admixtures | 0.1% to 0.5% by weight of cement in the concrete mix |
| Retarding Admixtures | 0.1% to 2% by weight of cement in the concrete mix |
| Air-entering Admixtures | 0.05% to 0.3% by weight of cement in the concrete mix |
| Corrosion-inhabiting Admixtures | 1% to 5% by weight of cement in the concrete mix |
However, the manufacturer’s instructions should always be followed when adding waterproofing admixtures to concrete, as the dosage may vary depending on the specific product and the intended use.
Final Thoughts
Selecting the right admixture depends on the structural and regional demands of the project. While water-reducing and retarding admixtures are best suitable for hotter regions of India, water-proofing and air-entering admixtures are ideal for colder regions prone to rain and snow. You can also use multiple admixtures to combine their results and further enhance the quality of the project. L&T-SuFin is the leading marketplace in India where you can find a variety of admixtures, suitable for hot and cold regions of India.