To investigate the underlying mechanisms of delamination cracking behavior in cylindrical post-tensioned concrete structures, three quarter-circle post-tensioned concrete wall assemblies were constructed and tested to delamination failure under monotonically increasing prestressing loads. The two main testing variables comprising the experimental program were specimen size (wall height, wall thickness, and cylinder radius) and the maximum nominal aggregate size. To compare the test results obtained, a size parameter, which represents the relative size of the wall specimen with respect to the maximum concrete aggregate size, was employed and found that characteristics of wall delamination responses were highly correlated with the specimen size parameter. The idealized through thickness and vertical responses proposed in this paper could be used as a guideline for the design, evaluation, repair, and strengthening of cylindrical post-tensioned concrete structures.