What is Admixtures in Concrete
Admixtures of concrete: In this Civil Experience article, we briefly explain about Admixtures of concrete, Type of Admixtures in concrete, Use/functions of admixtures in concrete, advantages of admixtures in concrete & Limitation of different admixtures used in concrete, Classification, adverse effect, everything in detail so read the whole article carefully and bookmarks civil experience for future.
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What is Admixtures in Concrete?
Admixtures in concrete is material which is defined as used to modified some property of cement concrete in a fresh or hardened position to improve the quality and workability of Concrete etc to achieve specific results in construction site work by adding different admixtures used in concrete.
Admixture is not a basic ingredient, The basic ingredients of concrete are cement, sand, aggregate, and water. They should not affect any kind of property of concrete. Admixtures are no substitute for good concrete practices.
Admixtures are primarily used to reduce the cost of concrete construction projects.
Now you are clear about what is admixtures in concrete now lest go to admixtures to concrete use
Why Admixtures Used in Concrete?
Admixture in concrete use for the modification of setting time of concrete, Workability of concrete, air-entrainment dispersion, etc.
In recent times the development increased on an extremely large scale, so we started using high strength concrete for bridge construction projects and high-rise buildings like skyscrapers. So creating concrete mix design manually on-site by labor is not possible so the use of ready mix concrete has really promoted and the use of RMC has really promoted the use of concrete admixtures.
In the market, various types of admixtures used in concrete are available like accelerators, retarders, air-entraining agents, pozzolanic materials, waterproofing admixture, etc which are used in practice by civil engineers constructors in the construction industry.
The admixture dosage in concrete is normally used in small quantities like 0.005 to 2% by the weight of cement.
But plasticizers and superplasticizers (water reduces) are widely used in recent times. Types of admixtures to concrete are specially invented in japan and Germany around 1970.
Most of the admixtures used in concrete are provided in ready-to-use liquid form and are added into the concrete at the construction site.
Types of Admixtures Used in Concrete
Types of chemical admixtures in concrete are as follows.
- Chemical admixtures
- Mineral admixtures
Classification of Admixtures Based on Functions
IS CODE: 9103-1999 has covered main five types of admixtures for concrete which as given below which also provide answers for what are admixtures used in concrete.
Air Entraining Admixtures in Concrete
Air-entraining admixtures in concrete: Small bubbles of air formed uniformly throughout the concrete mixture to increase cohesion and resistance to freeze-thaw durability of concrete.
Create more workable concrete
- Workability is high
- The high degree of durability
- Reduce the cycles of wetting and drying
Increased the cohesiveness of cement concrete
Accelerating Admixtures in Concrete (Accelerators)
Accelerating admixtures in concrete: Admixtures are used in concrete to reduce the time of early strength development of concrete also decrease the time of concrete curing.
Increase the rate of early strength development in concrete.
Retarding Admixtures in Concrete (Retarders)
Retarding Admixtures in Concrete: Admixtures for concrete are used in concrete to increase the setting time of fresh concrete to make sure it is workable.
Slow down the setting rate of concrete in hot weather condition.
Water Reducing Admixtures in Concrete (Workability Admixtures)
Water reducing admixtures in concrete help to decrease the quantity of water content required to reach a required concrete slump.
Low cement contains results in a low rate of CO2 emission.
Reduce the water contain demand by 5 to 10%.
Super-plasticizing Admixtures
Super-plasticizing Admixtures benefits of admixtures in concrete has the ability to decrease the water content to 12-25% to create highly fluid.
Reduce the water demand by 12 to 30%.
The other types of admixtures are:
Corrosion Inhibiting Admixtures
For reducing the rate of corrosion of reinforcement in concrete.
Frequently used in marine structures, bridges, and others that will be exposed to high levels of chloride.
Slow down the corrosion of reinforcement
Other types of admixtures are:
Pozzolana Admixtures
Grouting Admixtures
Waterproofing Admixtures
Air-detraining Admixtures
Bonding Admixtures in Concrete
Gas forming Admixtures
Coloring Admixtures (Admixtures concrete colors)
Alkali-aggregate expansion inhibiting admixtures
Fungicidal, Germicidal, Insecticidal admixtures
Classification of Mineral Admixtures Based on Functions
Functions of admixtures in concrete: IS code 456:2000 give the guidelines for construction for the use of mineral admixtures.
The various mineral admixture of concrete used with cement is:
What are the Advantages of Admixtures in Concrete?
Why we use admixtures in concrete – benefits of admixtures in concrete is the most common question in now day in civil engineer mind as well as contractor, owner of the house.
The list of advantages of admixtures in concrete in concrete is written below which also represents the importance of admixtures in concrete.
Proposed/Uses of admixtures in concrete listed here in Civil Experience – Best Civil Engineering blog. Role of chemical admixtures in concrete:
- Admixtures are used in concrete to increase the strength of concrete/mortar.
- To accelerate the initial setting time of cement concrete.
- To retard the initial setting time of concrete.
- To improve the Workability of concrete.
- To increase the durability of concrete.
- To reduce heat during hydration.
- Admixtures are used in concrete to produce lightweight concrete.
- To reduce the permeability of fina concrete.
- To control the alkali-aggregate expansion.
- To improve the resistance to sulfate attack.
- To increase the bond capacity between old and new concrete.
- To increase the bond between concrete and reinforcements steel bar.
- To reduce the segregation of concrete.
- To decrease the bleeding of concrete.
- Admixtures concrete colors are used in concrete to give color to concrete (mortar).
- To control the corrosion of concrete.
- Admixture makes the concrete acid proof.
Adverse Effect of Admixtures in Concrete
Disadvantages of Admixture in Construction: Extreme use of admixture in concrete creates Harmful effects for the property of concrete.
Following are the adverse effects of excessive use of admixtures in concrete.
- One of the common plasticizers generally used is lignosulphonate acid in the form of calcium or sodium salt. At higher dosages, it may cause retardation in setting time.
- A higher dosage of Super-plasticizer affects the shrinkage and creep properties of concrete.
- A higher dosage of plasticizer may cause segregation and premature stiffening under certain conditions.
- A higher dosage of Super-plasticizer may increase the rate of loss of workability in concrete.
- Perhaps the most commonly known retarder is calcium sulfate (gypsum). The addition of an excess amount of gypsum may cause undesirable expansion and indefinite delay in the setting of concrete.
- Excess use of accelerators causes more heat evolution and there are chances of cracks in the concrete.
- In the case of air-entrained concrete strength decreases in proportion to the amount of air. It is observed that 1% of entrained air reduces strength by about 5.5%.
- The optimum air content is ranging from 3 to 6 percent.
FAQ 1: What is Admixtures of Concrete?
Admixtures in concrete is material which is defined as used to modified some property of cement concrete in a fresh or hardened position to improve the quality and workability of Concrete etc to achieve specific results in construction site work by adding different admixtures used in concrete.
FAQ 2: Why Admixtures Used in Concrete?
Admixture in concrete use for the modification of setting time of concrete, Workability of concrete, air-entrainment dispersion, etc.
FAQ 3: What are Types of Admixtures Used in Concrete?
Types of chemical admixtures in concrete are as follows.1. Chemical admixtures, 2. Mineral admixtures.
FAQ 4: Classification of Admixtures Based on Functions
1. Air Entraining Admixtures in Concrete, 2. Accelerating Admixtures in Concrete (Accelerators), 3. Retarding Admixtures in Concrete (Retarders), 4. Water Reducing Admixtures in Concrete (Workability Admixtures), 5. Super-plasticizing Admixtures, 6. Corrosion Inhibiting Admixtures, 7. Pozzolana Admixtures,8. Grouting Admixtures,9. Waterproofing Admixtures,10. Air-detraining Admixtures,11. Bonding Admixtures in Concrete,12. Gas forming Admixtures,13. Coloring Admixtures (Admixtures concrete colors),14. Alkali-aggregate expansion inhibiting admixtures,15. Fungicidal, Germicidal, Insecticidal admixtures.
FAQ 5: What are the Advantages of Admixtures in Concrete?
1. Admixtures are used in concrete to increase the strength of concrete/mortar,2. To accelerate the initial setting time of cement concrete,3. To retard the initial setting time of concrete,4. To improve the Workability of concrete,5. To increase the durability of concrete,6. To reduce heat during hydration… read more
