## 4 Discussion Based on Practical Examples
### Technical Condition of the Structures--Correlation with Chemical Examination Results  
The technical condition of all analyzed structures was defined independently for underground and above-ground elements. Three situations were identified--only after external inspections--determining the intensity of observed damage. The technical condition was found as: satisfactory, bad, and very bad, which is summarized in Table 4.  
The total assessment of the technical condition, given in Table 4, was based on a number of factors. In terms of this article, the main determinant of technical condition should be the chemical condition of concrete associated with the risk of corrosion. However, the general condition of structure was also influenced by: Area of significant corrosion damage, the actual amount of reinforcement, conditions of use (both in the past and during the expected further operation), and the expected period of further use. Therefore, it is difficult to determine the unambiguous quantitative criteria for the classification of a structure to a given technical condition, because each time it was a combination of the factor described. The author's experience, which is difficult to quantify and based on many years of research and observations of similar structures played an important role in this identification of the technical condition. This, an attempt to quantify the condition of the structure, for example in the form of intervals of the number of points given in individual aspects and added up for the whole structure, can \begin{table}
\begin{tabular}{c c c} \hline \hline
**Structure** & **Underground Parts** & **Ground Parts** \\ \hline A & - & very bad \\ B1–B3 & satisfactory & satisfactory \\ B4 & - & satisfactory \\ C1–C2 & satisfactory & bad/very bad \\ D & - & very bad \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Results of identified technical condition. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Structure**} & \multicolumn{4}{c}{**Chloride Ion Content * [\%]**} \\ \cline{2-5}  & **Foundation** & **Columns** & **Beams** & **Slabs** \\ \hline A & - & 3.4 & 1.1–4.3 & 3.4 \\ B1–B3 & 0.2–0.7 & 0.1–0.4 & 0.1–0.5 & 0.1–0.4 \\ B4 & - & 0.3 & 0.2–0.5 & 0.2 \\ C1–C2 & 0.1–0.4 & 0.2–1.2 & 0.2–2.1 & 0.6–1.9 \\ D & - & 2.9 & 3.3–7.5 & 6.5 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Results of chemical tests. be very misleading because determining such a score and adopting appropriate weights will always be subjective. During the inspections, corrosion intensity, damage of concrete (including mechanical ones), and different surface deposits were assessed and classified. In particular, the condition of structures observed was caused by corrosive damage to concrete (20 - 80% of the surface of structural elements) as well as corrosion of reinforcing steel (from surface concrete to through practically the entire rebar) of varying intensity. In general, a good correlation between the chemical test results and the structure technical condition was observed. The best condition was demonstrated by all the elements from group B both in underground and above-ground parts. The corrosive damage to rebars was present only in the areas of original defects of the concrete cover which decreased its thickness (Figure 2a,b). The corrosion was visible mostly on the surface, with only small, isolated pitting spots. As shown in Table 3, the pH of all elements of those structures was at least 10.6 which indicates only a partial loss of the protective ability of concrete. Also, the content of chlorine and sulfate ions exceeded the permissible values only in certain areas. Interestingly, those foundations were made of concrete of the lowest class (C12/15), so it could be expected that their corrosion would be the highest. One of the reasons for the high ion concentration is the low density of concrete, which can be identified with its low class. However, the pH value was relatively high and pointed to only a small carbonation of the concrete.