Experimental studies on creep of sealed concrete under multiaxial stresses

The majority of research studies and prediction models on the creep of concrete have been concerned with the uniaxial stress state. Research on creep under multiaxial stresses, however, has been relatively scarce even though concrete is subjected to multiaxial stresses in many structural members and structures. Although some experiments on the multiaxial creep of concrete have been performed, the results of these experiments, which mainly considered low-strength concrete, are controversial. Consequently, for today's standards and practice—and for a better understanding of the properties of concrete—more experimental data are needed on the multiaxial creep of concrete with various strengths. In this study, multiaxial creep tests with 27 cubic specimens (200 mm × 200 mm × 200 mm) were carried out for three different strengths of concrete, namely 26, 44 and 54 MPa, and creep strains were measured in three principal directions. From the measured strains, Poisson's ratio at initial loading was obtained, as was Poisson's ratio resulting from creep strain and Poisson's ratio resulting from the combined creep strain and elastic strain. These Poisson's ratios were approximately equal for each concrete mix. The Poisson's ratio at initial loading and the Poisson's ratio for the combined strain increased slightly as the strength of the concrete increased. The volumetric creep strain and deviatoric creep strain were linearly proportional to volumetric stress and deviatoric stress, respectively.