Наука и техника (Jul 2018)
On Longevity of Solid Construction Materials
Abstract
Reliable forecasting of longevity for solid construction materials, especially for concrete and reinforced concrete is considered as a rather complicated scientific and technical problem which is often described in a great number of research papers. However this problem does not have a reliable analytical solution with the required statistical realization level. The paper contains a brief analysis of modern views pertaining to breakage processes in solid construction materials including concrete and reinforced concrete due to action of force (in particular, on the basis of temporary strength dependence with a static load) and non-force factors comprising as well carbonization and decrease of hydrogen index. Peculiar features concerning strength decrease of construction materials in time due to action of creep processes (plasticity) have been described in the paper. The paper presents two variants for assessment of possible longevity: without initial damage and with available initial defects. According to the first variant distribution of the test specimens of material for longevity corresponds to a lognormal law and in the second variant the distribution follows more complicated law. The paper provides levels of carbonization indices and a hydrogen index when corrosion of steel reinforcement does not occur. The following necessity has been established that is recommended to take into account not only characteristics and specific features in structure of solid construction materials in their strength theory but also statistical regularities because the breakage process represents in itself an integral phenomenon and due to this the final result can change according to random values of available structural defects, test errors and other factors. In this connection probability of their possible combinations has been described with the help of statistical laws. It has been shown that it is desirable to pay due consideration to maximum number of similar factors in order to increase a reliability of probabilistic-statistical methods for calculation of longevity.
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