In concrete, what is the purpose of adding superplasticizers?

Adding superplasticizers to concrete primarily aims to improve workability without increasing the water-cement ratio. This is crucial because superplasticizers allow for a higher fluidity of the concrete mix, making it easier to place and work with, especially in complex forms or when working with congested rebar. By enhancing the flow characteristics of the concrete, superplasticizers help achieve better compaction and surface finish.

While some may believe that increasing strength or enhancing durability are main objectives, these outcomes are typically achieved indirectly as a result of improved workability. Better workability can lead to more uniform mixing and placement, which can contribute to a stronger and more durable final product. However, the direct function of superplasticizers is to enhance workability, making it the correct answer in this context.