What characteristic do workability agents enhance in concrete mixtures?

Workability agents are specifically designed to improve the workability and ease of placement of concrete mixtures. This enhancement allows for better flowability and reduces the effort required for mixing, handling, and placing the concrete. By increasing workability, these agents help ensure that concrete can easily fill forms, encapsulate reinforcement, and be compacted without leaving voids or air pockets.

While other options may reflect beneficial properties of concrete, such as cost-effectiveness, durability, or heat resistance, they do not directly relate to the primary function of workability agents. Each of these characteristics is important in its own right, but they are not the specific purpose of workability agents. The use of these agents directly targets the practical aspects of working with concrete, making the mixing and application processes much more efficient and effective.