ABSTRACT:

This study presents an analysis of maximum concrete strength retrogression under the effect of variable-polarity thermal fields (VPTF). Absence of reasonable freeze-thaw resistance criterion causes necessity to specify maximum strength retrogression, which is understood invariable for structure of every investigated material. It is proved that though concrete freeze-thaw process is a thermodynamic one, it is impossible to apply the first law of thermodynamics in explicit form for material freeze-thaw resistance. This study explains why it is impossible to use specific potential energy at volume expansion/compression of the material when such energy transforms to deformation energy according to the Hooke's law. By application of thermodynamic physical-mathematical justifications there is given a method, which considers specificity of every created material structure. It is shown that freeze-thaw coefficient (kmrz) describes qualitative variations in concrete system by way of quantity. Thus we may measure constructive/destructive processes at kinetic destruction of investigated material. It is suggested to implement method of Maximum Permissible Strains (MPS) by designed computerized multifunctional information system for assessment of material quality and durability (CMISQD).

INTRODUCTION

Analysis of stressed concrete condition under the effect of variablepolarity thermal fields (VPTF) and variation of some calculated concrete properties show that freeze-thaw resistance criterion is insufficiently reasonable from the physical point of view. Stressed concrete condition at freeze-thaw cycle may be compared with long-term loading. Available experimental data show that the concrete strength under long-term effect of statistic loading is lower than the concrete strength under short-term loading. Such a difference ranges 0~30%, and it increases with the time of loading the sample. Further improvement of test methods, study of the destruction process and solution of the problem of the construction material durability under VPTF effect are mainly defined by application of various factors (technologic, structural, thermodynamic, etc) to concrete resistance.

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