Superplasticizers are polymers that are added to concrete to reduce the water content of the mixture. They also help in improving workability and strength. They are commonly used to produce high performance concrete.
Some of the properties of these admixtures include lower water-cement ratio, self-leveling, and high early strengths. They can be incorporated into concrete in a dose of 0.5 to 3% by weight. Compared to standard plasticizers, these admixtures provide better control over the setting time, and they are a great choice for small corrections on the job site. They are also used to prevent slump.
These admixtures may contain a range of retarders to help maintain temperature. They can also contain accelerators, which can enhance the setting time.
The effectiveness of superplasticizers depends on the type and quantity of the admixture. There are two main types: lignosulfonates and polycarboxylate. Lignosulfonates are a low cost admixture that can be incorporated into the concrete to reduce the set time.
Polycarboxylate (PC) has a strong affinity to cement particles, and it can be mixed into the concrete in a range of 0.15% to 0.30% by weight. It helps improve the initial strength of the concrete, and it can also help reduce the water by 40%. PC is also a more economical base.
Besides the benefits of reducing the water content, superplasticizers can be used to overcome the slump problem. This is mainly done in high strength concrete, and it can give the concrete a higher workability.