The article shows the relevance of the assessment of physical deterioration (PD) of elements and structures of buildings and structures. The drawbacks of existing time-based PD prediction techniques are shown. The need to develop PD models for various types of structures and operational conditions is justified. The logistic dependence of the ultimate service life of civil structures on PD indicators is considered. A study of the forecast dependence of PD for concrete and reinforced concrete structures based on the logistic trend was carried out. Coefficients are proposed that increase objectivity of using logistic dependence of prediction of concrete elements, reinforced concrete elements and structures. Values of constant wear (λ) for different time intervals, as well as weighted average values (λsr) for different types of iron-concrete elements and operating conditions were obtained. The obtained values of constant wear were analyzed with existing ones.

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The article substantiates the need to study the carbonation of concrete and evaluate the maximum carbonization of it. The basic equation of prediction of change in time by concrete cross section of carbonate component of cement-sand fraction of concrete is given. An expression is proposed for estimating the limit value of concrete carbonation (PVC). PVC from concrete composition (amount of used cement) for concrete without additives, compressive strength classes С8/10–С50/60, mixture compositions, grades for ease of laying P1...P5 and G1...G4 for each class of concrete in terms of compressive strength and different tempering strength of concrete was investigated. The obtained PVC values were analyzed. Dependencies of PVC change on the amount of used cement for any class of concrete in terms of compressive strength and different grades of mixtures in terms of ease of laying, as well as dependence of change of limit value of carbonization of non-addition concrete on the amount of used cement for different tempering strength of concrete and grades of mixtures in terms of ease of laying are obtained.

Based on the results of many research years on concrete carbonisation: both immediately after manufacture (using heat-moisture treatment) and in reinforced concrete elements operated for the periods of various length (in an open atmosphere); the effect of carbonisation on the change in the protective properties of concrete in relation to steel reinforcement; for determination of the dependence of the corrosion state of steel reinforcement on the degree of concrete carbonisation in the area of steel reinforcement; the obtained regression dependences of the change (by time in the cross section) of the degree of concrete carbonisation of various classes in strength, – the analysis of the time of the onset of the boundary values of the degrees of concrete carbonisation (strength classes C12/15–C30/37) for the operating conditions of the open atmosphere was performed. Based on it, the regression dependences of the time variation of the depth of corrosion damage of steel reinforcement were construed (for fixed thicknesses of the concrete protective layer). The obtained nature of dependences made it possible to offer, in a general form, the regression dependences of the depth of corrosion damage and corrosion rate of steel reinforcement for concretes (strength classes C12/15–C30/37) for operating conditions in open atmosphere.