What would be considered overworking concrete?

Overworking concrete refers to the process of excessively manipulating the surface of fresh concrete, which can lead to a variety of issues, including compromised strength and surface quality. When too much water and fine material is brought to the surface, it creates a weak layer known as "bleed water," which can reduce the overall durability of the concrete. This phenomenon can also lead to problems such as scaling, cracking, and difficulty in finishing tasks like troweling.

The context behind this understanding is that maintaining the proper consistency and composition of concrete is critical for achieving optimal results. When the surface is overworked, it disturbs the proper bonding between aggregates and the cement paste, leading to a poor overall structure. Therefore, option C accurately identifies the conditions under which concrete becomes overworked and highlights why it's essential to minimize excessive handling of the surface.

The other options, while relevant to the concrete mixing and curing processes, do not directly address the specific action of overworking concrete. Removing excess water, adding more aggregate, and inadequate curing time relate to other aspects of concrete preparation and finishing rather than the mechanical action that leads to overworking.