Settlement cracking is most likely to occur when which condition is present?

Settlement cracking is most likely to occur when concrete sets slowly. When concrete has a slow setting time, it remains in a plastic state for an extended period. During this time, if the ground underneath the concrete continues to settle or if other external factors lead to uneven support, the concrete can be subjected to stresses that cause cracks.

As the concrete hardens, the lack of sufficient structural integrity combined with continuing ground movement can result in cracks that manifest as the concrete begins to cure. In contrast, quicker setting times would reduce the window in which the concrete is vulnerable to settling effects, thereby minimizing the likelihood of these cracks developing. In addition, extreme temperatures or overworking concrete during finishing can lead to other issues, but they do not specifically contribute to settlement cracking in the same manner as a slow-setting process.