What is meant by 'bleeding' in freshly poured concrete?

Bleeding in freshly poured concrete refers to the phenomenon where water rises to the surface of the concrete during the settling and hardening process. This occurs as the heavier solid components, like aggregates and cement, settle down under the influence of gravity, allowing the lighter water component to move upwards. When the mixture initially loses its workability and sets, the water that appears on the surface can create a layer of water, often referred to as "bleed water."

The presence of bleed water is important to monitor because it can affect the surface finishing and overall quality of the concrete. For example, if the finishing is performed too early while bleed water is still present, it can lead to a weak, improperly bonded surface. Thus, understanding bleeding is crucial for ensuring high-quality concrete work.

The other options refer to different issues related to concrete but do not accurately describe the term "bleeding." Cracks during curing, uneven aggregate distribution, and separation of materials may all occur in concrete work but are not related to the rise of water on the surface.