The Investigation of the Relationship between Drying and Restrained Shrinkage In View of the Development of Micro Cracks

Abstract Especially, the shrinkage has an essential role for the cement based materials. The shrinkage which is defined as volume change affects the strength and the characteristic properties of the materials and form the degradation mechanisms. Nowadays, according to some researches, the cracks of the restrained shrinkage has an important effect on the deformations of the materials. In laboratory researches, the crack width of the restrained shrinkage is measured by the electron microscope. On the other side, the amount of the shrinkage is measured for the drying shrinkage. The crack width of the drying shrinkage is not measured because it is no possible to measure the crack width accurately and the destructive methods are used to measure the development of the cracks of the drying shrinkage. In this study, the crack widths of the drying shrinkage are measured by the electron microscope used for the measurement of the crack widths of the restrained shrinkage. Therefore, the relationship between the amount of the drying shrinkage and the crack widths is determined. Also, the difference between the crack widths of the drying and restrained shrinkage is evaluated. Besides, there is a relationship between the drying shrinkage and restrained shrinkage. As a result of the microscopic observations of the crack widths of the drying and restrained shrinkage, if the dimensions of the ring samples and drying shrinkage samples are close each other and there are no different stresses, the drying shrinkage is just enough to determine the shrinkage behavior of the plain concrete. Especially, when the maximum aggregate grain size increases, the aggregate holds the cracks as the micro-cracks and supply the self-healing of the cement based materials because when the crack width is constant or develops less, the smaller widths become to close and forms self-healing of the cement based materials.