Types of Concrete Admixtures and Their Uses

Concrete admixtures are added to a mix in order to improve various properties of the concrete, including strength, workability and longevity. Different admixtures serve different purposes; some are used to increase durability or reduce shrinkage while others impart workability, retard set or delay setting time. In this article, we’ll go over some of the most important and common types of concrete admixtures, so you can make sure your projects get off on the right foot.
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1. Water reducing admixtures Concrete admixtures, including water reducing admixtures, are materials added to concrete during the mixing process in order to alter its properties. Water reducing admixtures can be used to reduce the water demand by up to 30% while also improving strength and durability . There are three main types of water reducing admixtures: plasticizers, mid-range plasticizers, and super plasticizers. Common examples of these admixtures include calcium, sodium and ammonium lignosulphonates, acrylic polymer based products, poly carboxylate-based substances and multicarbovylaturated ethers. These water reducing admixtures can be a great help in constructing strong and durable concrete structures with minimum water requirement .
2. Retarding Admixtures Retarding admixtures, sometimes known as retarders, are concrete additives that are used to delay the setting time of freshly mixed concrete or mortar. By delaying the process of hardening, these admixtures provide more time to work with and shape the material to achieve desired results. Commonly used retarding admixtures include calcium sulphate or gypsum, starch, cellulose products, common sugar, and salts of acids. They are especially useful in high temperature zones where concrete will set quickly and can lead to discontinuities in a structure or poor bonding between surfaces. Additionally, most water reducing admixtures also act as retarding admixtures and are classified as "retarding plasticizers."
   
   
3. Accelerating Admixtures Accelerating admixtures, also known as accelerators, are added to concrete mixtures to reduce the initial setting time of the concrete. By hastening the initial hardening of concrete, accelerating admixtures allow for early formwork removal, shorter curing times and emergency repairs in colder climates. Commonly used accelerating admixtures include calcium chloride, triethanolamine, calcium formate, silica fume and finely divided silica gel. Among these substances, calcium chloride is the cheapest and most commonly utilized accelerator.
   
   
4. Air Entraining Admixtures in Concrete: A significant advance in concrete technology, air entrainment admixtures are used to make concrete more resilient in the face of freezing and thawing. When included in the mixture, these add-ins create numerous air bubbles that don't stick together, which boosts concrete's properties. Air entraining also tweaks workability, staves off segregation and bleeding, lowers unit weight and modulus of elasticity, improves cement or sand or water content, and bolsters its chemical resistance. Commonly seen types of air entrainers include vinsol resin, darex, teepol, cheecol and suchlike materials derived from natural wood resins, alkali salts plus animal or vegetable fats and oils.
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5. Pozzolanic Admixtures Pozzolanic admixtures are essential for creating a strong and durable concrete mix, which is key for the water - retaining structures like dams and reservoirs . They effectively reduce heat and shrinkage during hydration, reduce risks of alkali-aggregate reaction, leaching and sulfate attack . Both natural and artificial materials can be used as pozzolanic admixtures, such as clay, shale, volcanic tuffs , pumicite , fly ash, silica fume, blast furnace slag, rice husk ash, surkhi etc .
   
   
6. Damp-proofing Admixtures Admixtures can be added to concrete mixes to improve certain performance characteristics such as increased strength, improved workability, and/or enhanced damp-proofing properties. Damp-proofing admixtures are particularly important for construction methods that involve contact with underground or highly humid environments. These types of admixtures are typically composed of chemicals such as aluminum sulfate, zinc sulfate, aluminum chloride, calcium chloride, and silicate of soda which act as pore fillers. They can be found in forms including liquid, powder and paste .
   
   
7. Gas Forming Admixtures Gas forming admixtures are invaluable for creating concrete mixes of the highest quality . They work by releasing gas inside the mixture , allowing for enhanced workability . This is particularly useful for constructing lightweight concretes as it can reduce their densities without compromising strength . Furthermore, these admixtures create foamed concrete which is highly advantageous due to its excellent insulation properties and wide range of applications . Aluminum powder, zinc powder and hydrogen peroxide are usually used as gas forming admixtures in construction projects due to how they can improve the performance of concrete mixes .
   Gas forming admixtures are a vital part of modern concrete production. Offering enhanced workability and the ability to create lightweight, high-performance materials, these admixtures have become essential for contractors and builders around the world. One notable advantage of using gas forming admixtures is their ability to produce foamed concrete - an air-filled variant of traditional concrete favoured particularly for insulation applications. Three of the most popular gasforming admixtures are aluminum powder, zinc powder, and hydrogen peroxide - all utilised in the building industry to boost concrete performance.
   
   
8. Air Detraining Admixtures Air detraining admixtures are often added to concrete during mixing to minimize the number of air bubbles. Such bubbles can reduce the overall strength and durability of concrete, so removing them is essential. Tributyl phosphate, silicone, and glycol are all common air detraining admixture materials that work by lowering surface tension. This decreases the size and strength of air bubbles, causing them to break apart and spread throughout the mix.
   
   
9. Alkali Aggregate Expansion Inhibiting Admixtures The use of alkali aggregate expansion inhibiting admixtures is an effective way of preventing the formation of gel - like substances in concrete that are caused when the alkalis in the cement react with certain types of aggregates . These admixtures reduce the amount of alkalis available to react with the aggregates and commonly used types include lithium compounds and pozzolanic materials .
   
   
10. Anti-Washout Admixtures Concrete admixtures are additives used to improve the properties of concrete. Among them, anti-washout admixtures can be used in circumstances where concrete is poured underwater as they inhibit concrete segregation due to water erosion. Generally speaking, anti-washout admixtures consist of modified cellulose ethers and other natural polymers which increase the viscosity of the mix, thereby reducing cement and fines loss caused by washout.
    
    
11. Grouting Admixtures Concrete admixtures are added to the concrete mix to improve its properties. These include grouting admixtures, which are used to modify the properties of a grout solution - a fluid blend of cement and other materials used to fill spaces between precast units or poured masonry. Commonly used grouting admixtures include bentonite, silica fume, and superplasticizers, which help make the grout flow easily and reduce its water content for increased strength and durability.
    
    
12. Corrosion Inhibiting Admixtures Concrete admixtures are substances added to the concrete mixture during the mixing process to enhance certain properties and characteristics of the resulting concrete. Corrosion inhibiting admixtures, in particular, are designed to prevent or reduce corrosion of steel reinforcement contained within the concrete. The two most commonly used types of this type of admixture are calcium nitrite and organic corrosion inhibitors.
    
    
13. Bonding Admixtures Bonding Concrete admixtures are materials added during mixing to enhance the properties of concrete. One type of admixture, known as a bonding admixture, serves to improve the bond strength between old and new concrete layers. Bonding admixtures can include acrylics, epoxies, and polyurethanes, which create a chemical bond when applied to an existing layer of concrete before the addition of a new layer .
    
    
14. Fungicidal, Germicidal, Insecticidal Admixtures :  Concrete admixtures can be Fungicidal, germicidal, and insecticidal in nature. These are used in concrete structures that may be exposed to damp or humid environments which increase the risk of biological attack by fungi, bacteria, and insects. Some of the most commonly used admixtures are copper compounds, zinc compounds and organochlorines.
    
    
15. Coloring admixtures  : Coloring admixtures are specialized ingredients used to add a desirable color to concrete. These admixtures do not impact the strength or performance of concrete, and they come in a variety of shades. To produce colored cement, experts often mix them into a ball mill with cement powder. There are two main types of coloring admixtures: common ones like red oxide and yellow oxide that you can find at home improvement stores; and specialty pigments for unique hues. A handy chart of coloring admixtures, along with their respective colors, is provided below.

​Coloring Admixture	​Color Produced
​Iron oxide	​Red, brown, black, and yellow
​Chrome oxide	​Green
​Cobalt oxide	Blue
​Titanium oxide	​White
​Carbon black	​Black
​Organic dyes	​Various colors

When creating concrete, it is important to consider the use of admixtures. These are ingredients that are added to the mix before or during cement mixing . One type of admixture is a coloring agent, which can be used to change the color of the concrete. However, it is essential to conduct trial batches when using coloring admixtures as the amount added will affect the final color of the concrete .​