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Function and history of polycarboxylate ether (PCE) in dry mortar and concrete

eye 4 Minute Read eye By Dr Markus Arnold
Concrete being poured

 

Concrete is the second most used substance in the world after water. It is used to provide support, stability or fire resistance to the majority of man-made structures across the world. The mix of ingredients used has been updated, improved and tweaked over time to create the best building materials that provide us with the qualities we desire. Polycarboxylate ether (PCE) is one such ingredient that has been realised over time to give substantial benefits to the quality and workability of concrete. Here, we look at the history of PCEs and the benefits they provide.

 

In this technical article:

 

What is PCE?

Polycarboxylate ether (PCE) is a type of superplasticizer used in the production of high-performance concrete and dry mortar. This synthetic polymer is added to concrete and dry mortar mixes to improve their workability, reduce water content, and increase their strength and durability. Its increasing popularity in the construction industry is due to its versatility as an additive and its ability to improve the quality and performance of concrete and mortar.

 

Concrete being poured

Figure 1: Concrete is used widely in modern buildings due to its strength and resistance to fire but it is still evolving and improving with new technologies.

 

When were superplasticizers first used in concrete?

The history of superplasticizers can be traced back to the 1930s when lignosulfonate-based additives were used to improve the workability of concrete. However, these early additives had limitations and were not effective at reducing water content or increasing the strength of concrete. In the 1960s, the first generation of synthetic superplasticizers was introduced. These were based on sulfonated melamine-formaldehyde resins and sulfonated naphthalene-formaldehyde condensate and allowed improved workability and could reduce water content. This being said, their performance was still limited at high temperatures, and they had low compatibility with other additives.

 A third generation of superplasticizers was introduced in the 1980s, and these were based on polycarboxylate ethers. These additives had superior performance compared to the earlier generation of superplasticizers, and they could significantly reduce water content while improving workability and strength.

 

Why are PCEs better than other superplasticizers?

PCEs are highly efficient and have excellent compatibility with other additives, making them ideal for use in a wide range of concrete and dry mortar applications. They work by adsorbing onto the surface of cement particles, creating a steric hindrance effect that prevents the particles from aggregating. This improves the dispersion of cement particles in the mix, reducing the amount of water required to achieve the desired workability. The result is a more compact and dense concrete or dry mortar mix, which has improved strength, durability, and reduced permeability.

 

Concrete particles with PCE adsorbed onto the surface causing steric hindrenceFigure 2: PCE particles adsorb to the surface of the concrete particles and create steric hindrance which prevents aggregation.

 

What are PCEs used for?

PCEs are commonly used in the production of ready-mix concrete, self-compacting concrete, and precast concrete, as well as in the production of dry mortars like self-leveller, flowing screeds and grouts. They are also used in the production of decorative concrete, which requires a high degree of workability and flowability.

 

What are the benefits of PCEs?

ViscoCrete® from Sika is one such polycarboxylate ether that is a highly used additive in the production of high-performance concrete and dry mortar. Compared to traditional superplasticizers, ViscoCrete® requires up to ten times lower dosage as well as short mixing times. In contrast to other superplasticizers, such as ones based on melamine or naphthalene, PCEs do not contaminate the building with formaldehyde or ammonia.

The low water and resulting higher strength concrete means that not only can water be saved during the production process, but thinner construction components are possible allowing for material savings too. This allows for a more sustainable concrete as well as cost savings.

 

How to achieve the correct slump flow profile?

Achieving the correct slump flow within concrete is a balancing act. It must flow when poured and level out easily, but conversely, the viscosity must be high enough to prevent segregation that may otherwise occur. Depending on the application, different slump flow profiles are optimal and Graph 1 shows 3 different options that can be achieved using ViscoCrete.

For a material that needs to flow well before structuring up to reduce cracking and shrinkage problems caused by segregation, a water-reducing ViscoCrete grade gives the perfect consistency curve. However, for a concrete that needs to flow consistently for a longer period of time, a slump-keeping ViscoCrete is more ideal. For an option that allows for a longer flow but with high viscosity once poured, the slump-controlling ViscoCrete would achieve this. For an idea of which ViscoCrete from Sika would be best for your purpose, utilise the guides in the Appendix.

 

A graph showing 3 different types of ideal slump flow profiles that can be achieved using Viscocrete

Graph 1: Consistency curves that show some wanted slump flow profiles that can be achieved by various ViscoCrete® Polymers.

 

Summary

In conclusion, Sika® ViscoCrete® polycarboxylate ethers have become an essential additive in the production of high-performance concrete and dry mortar. Their ability to reduce water content, improve workability, and increase strength and durability has revolutionized the construction industry. With ongoing research and development, it is likely that PCEs will continue to play a critical role in the production of innovative and sustainable building materials in the future.

 

Appendix

The below tables can be used to start determining which grade of ViscoCrete will be best suited to your needs. All Sika® ViscoCrete® powders are pure polycarboxylate ether (PCE) that is not deformed and are free of formaldehyde and ammonia. If you would like to discuss this in further detail or get recommendations from our expert technical team, contact us to find out more.

 

A table showing the different applications of ViscoCrete and which grade would be best for each application

Table 1: Depending on the application of the concrete, different grades of ViscoCrete will provide the required properties.

 

Different performance requirements for concrete and which grade of ViscoCrete would be best to achieve each one.

Table 2: Similarly to above, this table can be used to determine the best grade of ViscoCrete for the required performance features of the concrete.

 

Headshot of Dr Markus Arnold
Dr Markus Arnold, GUEST - Sika

Having studied at both Heidelberg University and the University of Siegen, Markus specialised in construction chemistry. He then held technical roles in the construction material industry before joining our partners, Sika, where he is now an Area Sales Manager.

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