What are Plasticizers in Concrete?
What are Plasticizers in Concrete?
Plasticizers are substances that are added to concrete to reduce the amount of water needed for proper mixing and workability. This allows for the production of concrete with higher strength, as the water-cement ratio (w/c) is inversely proportional to the strength of the concrete.
Plasticizers, also known as high range water reducers, are additives used in the production of concrete to reduce the amount of water needed while maintaining or improving workability. This can lead to an increase in concrete strength, as the strength of concrete is inversely proportional to the water-cement ratio.
These additives can reduce the water content of concrete by as much as 12-30% and are typically used to create high-slump, flowing concrete that can be easily placed without the need for vibration or compaction.
However, the effects of superplasticizers only last for a limited time, usually 30-60 minutes, after which the concrete may lose some of its workability. For this reason, superplasticizers are often added to concrete at the construction site just before it is used.
How Does Plasticizers in Concrete Work?
Plasticizers are substances that can be organic or a combination of organic and inorganic compounds that are used to reduce the water content in concrete while maintaining a certain level of workability.
They are typically added to the concrete mix in small amounts, between 0.1% and 0.4% by weight of cement, and can reduce the amount of water needed by 5% to 15% while also increasing the workability of the concrete, measured by the slump, by 3 to 8 cm.
When mixed into the concrete, the plasticizers interact with the cement particles, causing a change in the surface charge that results in repulsive forces and improved dispersion, resulting in increased plasticity and workability.
Types Of Plasticizers
Plasticizers used in concrete can be classified based on their mode of action.
- Hydrophilic plasticizers work by increasing the wettability of the concrete mixture, improving its plasticity and flow characteristics.
- Hydrophobizing plasticizers, on the other hand, work by introducing a large amount of air into the concrete mixture, which reduces the moisture tension and increases its plasticity.
Both types of plasticizers are used to improve the workability of concrete, but they do so in different ways. Hydrophilic plasticizers work by increasing the wetting of the concrete mixture, while hydrophobizing plasticizers work by introducing air into the mixture.
Uses Of Plasticizers In Concrete
Plasticizers are useful in a variety of situations, including when maintaining workability for a long period of time is difficult, when high strength concrete is needed, when the cement content needs to be reduced, when mass concreting is required, when pumping concrete is necessary, when pozzolan concrete is being made, when shrinkage reduction in concrete is desired, when pre-stressed concrete is being used, when corrosion resistance is desired, when permeability reduction is needed, when durability needs to be enhanced, when pile foundation construction is being done, and when underwater concreting is necessary.
Advantages Of Plasticizers In Concrete
Using plasticizers in concrete can offer a number of benefits, including:
- Improved workability of the concrete mix without the need to add extra water
- Increased strength of the concrete without increasing the cement content
- A 25% increase in the strength characteristics of the finished concrete foundation
- Easier compaction without the use of vibrators
- Improved flowability and adhesion to surfaces
- Concrete with higher density
- Reduced moisture content in the concrete, making it more resistant to frost and less prone to cracking
- The ability to adjust the setting time of the concrete mix by using accelerators in conjunction with plasticizers.