Certain concrete structures during their service life are exposed to variable repeated loads with significant magnitude and duration. Typical examples are bridges, parking garages and storage buildings where besides permanent, variable loads can also affect the long-term concrete behavior. Currently, this concrete phenomenon to creep under variable loads is well-recognized in the codes and considered through the so-called quasipermanent load. However, the creep and the recovery property under these load types are still far from clear.

This paper is concerned with a study of the effects of variable repeated stresses on the creep and creep recovery of concrete. For that purpose, two separate experiments were performed in which concrete specimens were exposed to time-variable uniaxial compressive stresses. The first experiment aims at assessing the influence of different service stress levels at loading (30% and 45% of fc) as well as different level of unloading (full and partial unloading). The second one focusses on the influence of different drying conditions of the specimens (sealed and unsealed condition).

The results indicate that regardless of the stress level, the creep becomes fully recoverable after a sufficient number of loading and unloading cycles. On the other hand, the drying conditions show remarkable influence on the irreversible proportion of the creep in each loading cycle. Moreover, the absolute value of the creep recovery seems unaffected by the hygral exchange conditions of the specimens.

The obtained results demonstrate that the creep behavior under repeating stresses in a large scale differs from the ones under just sustained stresses.