Classification of admixtures ppt
What are the classification of admixtures?
Admixtures are classed according to function. There are five distinct classes of chemical admixtures: air-entraining, water-reducing, retarding, accelerating, and plasticizers (superplasticizers).
What are admixtures Slideshare?
AdmixturesAdmixtures • The term admixture as “a material other thanThe term admixture as “a material other than water, aggregates, hydraulic cement, and fiberwater, aggregates, hydraulic cement, and fiber reinforcement, used as an ingredient of a cementitiousreinforcement, used as an ingredient of a cementitious …
What are the types of chemical admixtures?
Chemical admixtures can be divided into five types: accelerating, retarding, water reducing/plasticizing, air entraining, and waterproofers. Chemical admixtures should be used judiciously because the addition of wrong quantities can affect the long-term performance of concrete in many ways.
What are the classification of superplasticizer?
Superplasticizers are broadly classified in four groups, viz, sulphonated melamine-formaldehyde condensates (SMF), sulphonated naphthalene-formaldehyde condensates (SNF), modified lignosulphonates (MLS), and others including sulphonic acid esters, carbohydrate esters, etc.
What is meant by admixture?
An admixture is defined as “a material other than water, aggregates, cementitious materials, and fiber reinforcement, used as an ingredient of a cementitious mixture to modify its freshly mixed, setting, or hardened properties and that is added to the batch before or during its mixing” (ACI Committee 212, 2010).
What are natural admixtures?
Admixtures can be of two types – natural and chemical admixtures. Natural admixtures include rice husk, egg mix, flour, ghee, etc. while chemical admixtures include GGBS, fly ash, pozzolana and so on.
What are the 4 types of concrete?
Let’s take a quick look at the most common types of concrete and what they are used for:
- Reinforced Concrete.
- Lightweight Concrete.
- High-Strength Concrete.
- High-Performance Concrete.
- Precast Concrete.
What are the properties of admixtures?
Air entraining concrete admixture: Water Reducing concrete admixture: Superplasticizers.
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Special concrete admixtures:
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Special concrete admixtures:
| Quality Measure | Effect |
|---|---|
| Drying shrinkage and creep | Low concentrations usually have single effect. High concentrations of ground slag or fly ash may increase shrinkage. Silica fume may reduce shrinkage. |
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5 abr 2013
What are admixtures and what are its uses?
Admixtures are used in concrete to alter its properties in various ways. Some common uses include improving workability, increasing or decreasing cure time, and increasing concrete strength. Admixtures can also be used for aesthetic reasons, such as to change the color of the cement.
What is Retarder admixture?
Retarding admixtures are used to slow the rate of setting of concrete. By slowing the initial setting time, the concrete mixture can stay in its fresh mix state longer before it gets to its hardened form. Use of retarders is beneficial for: Complex concrete placement or grouting.
What are air entraining admixtures?
Air-Entraining Admixtures and What They Do: Air-entraining admixtures facilitate the development of a system of microscopic air bubbles within concrete during mixing. They increase the freeze-thaw durability of concrete, increase resistance to scaling caused by deicing chemicals, and improve workability.
Why superplasticizers are used in concrete?
Superplasticisers are commonly used in dry-pressed concrete to improve the workability and to enhance the compaction of concrete for increasing density and to improve the surface finish of the concrete product.
What is the admixture in concrete?
Concrete admixtures are natural or manufactured chemicals or additives added during concrete mixing to enhance specific properties of the fresh or hardened concrete, such as workability, durability, or early and final strength.
What is the difference between additive and admixture?
The main difference between admixtures and additives is the stages at which the substances are added to concrete or cement. Additives are added in the cement manufacturing process, while the addition of admixtures is done when making concrete mixtures.
What are air entraining admixtures?
Air-Entraining Admixtures and What They Do: Air-entraining admixtures facilitate the development of a system of microscopic air bubbles within concrete during mixing. They increase the freeze-thaw durability of concrete, increase resistance to scaling caused by deicing chemicals, and improve workability.
What is water repellent admixture?
Waterproofing admixtures are porous materials that have the ability to absorb water and water-borne contaminants. Hydrophobic and pore blocking ingredients react with products of the cement hydration process to produce a hydrophobic material which resists external water, decreasing absorption into the concrete.
What are the properties of admixtures?
Air entraining concrete admixture: Water Reducing concrete admixture: Superplasticizers.
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Special concrete admixtures:
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Special concrete admixtures:
| Quality Measure | Effect |
|---|---|
| Drying shrinkage and creep | Low concentrations usually have single effect. High concentrations of ground slag or fly ash may increase shrinkage. Silica fume may reduce shrinkage. |
•
5 abr 2013
What is the use of admixtures?
Summary. Admixtures are used in concrete to enhance the performance of the mix in various ways. Generally added before or during the mixing process, admixtures can increase the strength the mix, accelerate or slow down the curing process among other benefits.