Mechanical Characteristics of Axially Restrained Concrete Specimens at Early Ages

This study was performed to investigate the development of restraint stress and strain in axially restrained concrete specimens at early ages. Axially restrained specimens, generally, well represent field conditions of actual structures. In this study, uniaxial restraint tests were performed with two levels of concrete strength, high- and normal-strength concrete, and three levels of restraint were applied, namely, high-restraint (H), low-restraint (L), and nonrestraint (N). It was revealed from the test results that a high tensile restraint stress was developed at an early age in high-strength concrete and that the inherent high tensile strength may not be utilized for the structural performance of high-strength concrete members. The tensile restraint stress was gradually reduced due to the creep effect with time. An analytical calculation considering creep under varying stresses and the time-dependent properties of concrete at early ages was compatible with the test results.