What adverse effects can occur from improper joint placement in concrete?

Improper joint placement in concrete can lead to visible cracking in undesirable areas, which is a significant concern in flatwork finishing. Joints are critical in controlling where cracks will occur; they are designed to allow for natural movement and shrinkage of the concrete as it cures. When joints are spaced incorrectly or not placed according to the guidelines, stresses can build up beyond the concrete's capacity, resulting in cracks forming in locations that are not intended. This can compromise both the appearance and integrity of the finished slab. Proper joint design and placement help manage tension and pressure within the concrete, thereby minimizing the risk of unwelcome cracking that could detract from the functionality and aesthetics of the flatwork.

The adverse effects highlighted by the other options, such as increased aesthetic appeal or better stress distribution, are not outcomes of improper joint placement but rather represent features associated with correct practices. Enhanced water drainage, while an important aspect of concrete design, is also not directly related to the placement of joints.