During this research, the theoretical analysis of dependence concrete's frost resistance of sample and energy, which is emitted by a sample at destruction, was carried out. The offered method includes measurement of residual deformation of a sample after the one cycle of freezing defrosting, measurement of long strength and measurement of short-term strength. Frost resistance of a sample is as the mathematical relation of these energies, and the frost resistance of concrete is calculated as arithmetic mean on samples. The offered method doesn't demand long tests, it's high efficiency and wide scope, but special laboratory equipment is necessary.
The main purpose of this research is to create the new reference method to determine the freeze-thaw resistance of concrete that is characterized by small labor inputs, high efficiency and a wide scope application. The offered method is based on the measurement of long strength by a nondestructive method.During this research, the theoretical analysis of concrete specimen dependence on freeze-thaw resistance and energy, which is emitted by a specimen during destruction, has been carried out. Freezethaw resistance of a specimen is calculated as the mathematical relation of these energies, and the freeze-thaw resistance of concrete is calculated as an arithmetic mean across specimens.Correctness of the offered method is proved by experiments. The offered method doesn't demand long tests. It is highly efficient and has a wide scope, but special further laboratory test duration is needed.
Main purpose of research is establishing correlation of decreasing strength limit at the time of concretes thermo cycling. Research is based on invented in 2008 Method for definition of concretes frost resistance. This method is concerning to estimation of concrete's deformation after saturating of concrete sample by water, its freezing to standard temperature and defrosting. It has small labor input and high operability. During research, the theoretical analysis of results of experiment by the offered Method was carried out. Correlation between decreasing strength limit and unit strain of concrete samples was establish.
Stress-strain model is an appliance for research of the strength and deformations. It can be used to solve technological problems in the production of materials. Rheological element is a part of stress-strain model. There are some disadvantages of existing rheological elements. They can’t be applied for research of the material strength and some experimental facts which are observed for many materials. The aim of the new element is to eliminate these disadvantages. The new rheological element includes the matrix and the puncheon. It differs from its analogues by configuration and characteristics of its parts. If the value of the friction coefficient between the matrix and the puncheon is not zero and greater than the tangent of the angle between the axis and the matrix on the section with the variable cross-section, the puncheon is jammed by frictional force under loading. When unloading and subsequent loading the puncheon retains a permanent deformation until the load exceeds the maximum value during the previous cycle. If the above-mentioned angle matrix is equal to zero, displacement of the puncheon does not require increasing of the load within this section. The plastic flow is observed. Deformation can be accompanied by strengthening on the section where the value of the friction coefficient is greater than the above-mentioned tangent. Fragmentation of the element is possible on this section. Thereby the new rheological element permits to relate different types of deformations of simulated solid. In other words, it allows researching the strength of material.
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