What concrete deficiency is caused by corroded rebar or severe overstress and cannot be visually identified?

Delamination is a concrete deficiency that can be caused by corroded rebar or severe overstress, yet it typically cannot be visually identified without more invasive inspection methods. When rebar within the concrete becomes corroded, it expands and exerts pressure against the surrounding concrete. This pressure can lead to a layer of concrete separating from the underlying substrate, creating a delaminated area.

While other visible signs of deterioration such as cracking, spalling, and discoloration can be directly observed during a routine visual inspection, delamination often requires specialized methods like sounding or ultrasonic testing to detect, as it can exist beneath the surface without any external indicators. This makes it a particularly concerning issue, as it may compromise the integrity of the structure without being readily apparent during initial assessments. Understanding this distinction underlines the importance of thorough inspection methods beyond just visual observations.