When the word concrete comes into our mind we start imagining an unyielding or a hard, solid material which would be perfect for construction.
But do we ever think how this concrete is made flexible and compatible. Here is where the superplasticizer admixtures come into picture.
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Superplastisizing admixtures are the unacknowledged heroes which play a very important role in enhancing the durability and workability of concrete.
Concrete Admixture
Concrete Admixture are the material which is added in the concrete mixture either before or during the mixing process so that it optimizes the use of the concrete.
Concrete admixtures plays a vital role in improving the overall performance of the concrete, reduces the setting time, enhances the strength.
Depending on the needs of different types of projects various types of admixtures are applied for best performance under various environmental conditions.
Related Post: Select How to Choose the Right Concrete Admixture for your Project?
There are Various Types of Concrete Admixtures
Amongst them are plasticizers and superplasticizers which are used to increase the overall performance, allowing the concrete to flow easily without adding extra amount of water.
Accelerators help in speeding up the curing procedure thus allowing the concrete to set faster, which is a must demand in winter seasons or when early setting is required. On the contrary, retarders slow down setting period which is helpful in hot weather or long-distance transportation.
Some of the other admixtures includes air-entraining agents, which helps in producing tiny air bubbles to stop freeze –thaw cycles .
Water reducing agents helps in reducing water needed without impacting the mix strength.
There are corrosion inhibitors which are added to provide protection to the steel reinforcement from rusting thereby increasing the lifespan of concrete structures.
So up till now we can clearly understand that use of admixtures helps in providing better control over the concrete performance making it the ultimate solution for meeting up the diverse construction related challenges.
What is Concrete Superplasticizing Admixtures?
Concrete superplasticizing admixtures are additives which when added in the concrete help in improving the consistency and flow of the concrete mix.
Thus, allowing easy flow & spreading of concrete with addition of extra water.
One of the key benefits is that while use of this admixture makes the mix more fluid it does not compromise the strength of the concrete.
In fact, it makes it more elastic, long –lasting structure due to this they are widely being used in modern constructions.
Superplasticizers Can be Broadly Classified into 4 Types:
1. Sulfonated napthalene formaldehyde condensate (SNF)
2. Sulfonated melamine formaldehyde condensate (SMF)
3. Modifies lignosulphonate (MLS)
4. Others including sulphonic acid ester, polystyrene sulfonates etc.
How Does it Works?
Superplasticizers help in spreading the particles in the mixture of concrete and minimize the friction between them. Concrete basically consist of sand, cement, water, and aggregates.
These ingredients tends to stick together, making the concrete mix thick and hard to handle.
Use of superplasticizers brings a dynamic change in the mixture by reducing the surface pressure between the particles , making them freely flowable.
Making the mix more workable, smooth and easily pourable to moulds.
The most interesting part is inspite of the above benefit the strength of the concrete is not impacted but is enhances and the water-cement ratio is balanced.
This is most important for structural integrity.
Benefits of Superplasticizer Admixtures:
Superplasticizers are most widely used due to the following reasons.
Enhance Working Ability
Superplasticizing admixtures like polycarboxylate ether admixture (PCE), Sulfonated napthalene formaldehyde, Sulfonated melamine formaldehyde & Modifies lignosulphonate , are best in terms of water retention capacity and increasing efficiency of the mix.
Enhances Strength
Superplasticizers work best with less amount of water, creating balance in the water-cement ration and improving the overall strength.
Provides Longetivity
Treating concrete with superplasticizers stops the development of cracks, shrinkages and other wear and tear thus making the structure long lasting and bearing the test of time.
Prevents Segregation
These admixtures make the mix flow with ease preventing separation of heavier particles from the rest of the mix.
This makes the concrete paste more uniform and consistent.
Maximum Benefit
The use of super plasticizing chemicals helps in providing best results in terms of strength of the concrete by reducing water content from 5-10 % from the required quantity.
Reduction in Labour Cost
Mixing these chemicals helps is easy working for the workers due to ease of pouring of concrete quickly, Saving time and labour cost in the construction process.
Related Post: How to Choose the Right Superplasticizer for Your Concrete?
Application of Superplasticizer Admixtures
In modern construction practices superplasticizers are widely used in a wide range of construction applications, specifically where high performance of concrete is demanded. Some of the examples are as below.
1. Precast Concrete: In case of precaste structures such as beams, slabs, walls use of superplasticizers helps in smooth and easy flow of concrete to moulds allowing them to have a perfect finishing.
2. High Strength Concrete: In the case of projects like bridges, flyovers, highways, high rise buildings superplasticizers help in giving the benefit of higher strength and heavy load bearing capacity.
3. Ready Mix Concrete: In case of ready-mix concrete where high performance and stability are key elements. Superplasticizers help in achieving both parameters, retain fluidity in transit and ease in pouring.
4. Mass concrete: In large concrete pours, use of superplasticizers helps is reduction of heat generation inside the concrete which could otherwise result in crack formations.
5. Self Compacting Concrete (SCC): Superplasticizers are very important for SCC creation which helps in filling gaps without requirement of vibrations
Dosages
In the case of Sulfonated napthalene formaldehyde condensate (SNF) & Sulfonated melamine formaldehyde condensate (SMF), the recommended dosage is 0.5% to 2.0% of the weight of cementitious material
In case of Modifies lignosulphonate (MLS) the recommended dosage is 0.2% to 0.6 % of weight of cementitious material
In case of polycarboxylate ether admixture (PCE) the recommended dosage is 0.1% to 0.6 % of weight of cementitious material
However, the dosages may vary according to the requirement of projects, environmental conditions, cement type and other factors also.
Conclusion
To conclude, superplasticizer admixtures have made it easy to meet up the complex modern day challenges in the construction industry.
It helps in optimizing the construction material use, providing efficiency, reduction in cost of future wear and tear making it the best option.
FAQS
What is superplasticizer?
It is an additive which when mixed in the concrete and gives the benefit of early setting and very good final strength.
What are concrete admixtures applied for?
To Increase the workability of the concrete without increasing or reducing the amount of water.
Which Superplasticizer concrete is considered to be the best?
Polycarboxylate ether admixture (PCE) is considered to be the best as it helps in reducing the amount of water requirement and enhances strength and workability of concrete.
How much admixture is recommended to be used in concrete mix?
Standard dosage should be less than 5 % of the weight of cement, however is dependent on other factors also.
