INTERDEPENDENCE OF CREEP AND SHRINKAGE FOR CONCRETE UNDER TENSION

The various approaches to the problem of drying creep of concrete and their limitations are analyzed. The simple phenomenological approach describing extra deformation of concrete under drying creep as a sum of shrinkage-induced creep and creep-induced shrinkage is suggested. It is shown that the first component is linearly proportional to free shrinkage strain, but behaves as an ordinary creep component, i.e., it varies linearly with stress. The second one is linearly proportional to basic creep, but should depend on the intensity of the shrinkage process in the material. The test results of concrete on drying creep under tension are presented. It is shown that in the initial period when creep-induced shrinkage is dominating, the total time-dependent strain is less than a sum of basic creep and free shrinkage, as opposed to the compression case; but later on, shrinkage-induced creep becomes dominant, and the total strain becomes larger than the previous sum, similar to the compression case. The microcracking in concrete skin, as one of the known explanations of extra drying creep deformation, is called into question.