PSI - Issue 26

Petr Konečný et al. / Procedia Structural Integrity 26 (2020) 430 –438 Author name / Structural Integrity Procedia 00 (2019) 000–000

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Attention was focused on the three studied parameters: carbonation effect determined via pH value, chloride concentration given as a percentage by mass of concrete, and the corrosion risk quantified as the ratio of chloride and hydroxide ions. For all parameters, the results were provided in the form of mean values and variation coefficients. 2.4. Example of the evaluation (bridge 55I-030) The process of evaluation of the data has been done identically for every single bridge. The complete process has been described in detail in Konečný et al. (2020) on road bridge no. 55I-030, which is a single-pole bridge across the Dřevnice river in the center of Otrokovice. The bridge was built in 1953 and sampling was done in 2015; the service life in the time of the diagnostic is 62 years. 15 sampled cores were analyzed in total, 11 of them in three depths from the concrete surface, and 4 of them were injection grouts, so the values were analyzed only in one depth. 3. Results and discussion The evaluation of the other bridges was processed based on the aforementioned methodology of the analysis by Konečný et al. (2020). The exposure time was considered as the difference between the year of inspection and the year of finalizing the construction. Although for the oldest bridge built in 1937 the service life is not the same as the length of exposure to chlorides since the regular de-icing in Central Europe started after World War II. The summary of the basic information about the bridges is given in Table 1. Six of the bridges are across a river or brook, and eight are across a road. The location of the bridges is important because the bridges across the water are influenced by the source of moisture, which increases the rate of carbonation. The bridges across the road are affected by two sources of the chlorides, from the road and the actual de-icing of the bridge itself. The mean values of the studied parameters and the variation coefficients for the bridges on the main roads and motorways are given in Table 2. Table 2. Summary of the statistics of carbonation effect (pH), chloride concentration (Cl - ), and corrosion risk c(Cl - )/c(OH - ) of studied bridges. ID. Bridge Samples pH [-] Cl - [wt.-%/concrete] c(Cl - )/c(OH - ) [-] Mean Co.Var. Mean Co.Var. Mean Co.Var. R Main road 169 10.85 0.08 0.06 1.03 84.38 1.85 M Motorway 129 10.13 0.11 0.15 1.17 187.09 3.65 A All bridges 298 10.49 0.09 0.11 1.10 135.73 2.75

Table 3. Detailed Statistics of carbonation effect (pH), chloride concentration (Cl - ), and corrosion risk c(Cl - )/c(OH - ) of studied bridges and respective construction components.

Girders, Cross Bars & Longitudinal Joints

Support Columns& Intermediate support

Abutments & Bearing Seats

Concrete Patches

Injecting Grouts

All Samples

Evaluated Parameter

ID .

Mean

Co.Var. Mean

Co.Var.

Mean Co.Var. Mean Co.Var. Mean

Co.Var.

Mean Co.Var. 10.85 0.08 10.13 0.11 10.49 0.09 0.06 1.03 0.15 1.17 0.11 1.10 84.38 1.85 187.09 3.65 135.73 2.75

pH [-]

R 10.60 M 9.73 A 10.17 R 0.09

0.06 0.09 0.07 0.95 0.97 0.96

10.98 11.39 11.18 0.05 0.07 0.06 11.62 2.55 7.09

0.04 0.04 0.04 0.78 0.88 0.83 1.55 2.44 2.00

11.74 0.02 11.42 0.02 11.58 0.02 0.08 0.46 0.61 0.18 0.34 0.32 0.21 0.54 3.66 0.60 1.93 0.57

11.49 0.03

11.60 10.01 10.81 0.03 0.08 0.05 0.22 46.04 23.13

0.03 0.08 0.05 0.84 0.81 0.82 2.13 1.53 1.83

9.89

0.10

10.69 0.06

Cl -

0.08 0.24 0.16 1.31

0.41 0.91 0.66 0.85

[wt.%/concr.] M 0.20

A 0.15

c(Cl - )/c(OH - ) R 144.28 1.27

[-]

M 280.95 2.51 A 212.62 1.89

379.58 2.29 190.45 1.57

Based on Table 2, one should note that the average pH values are lower than 11.8 for all the bridges, with the uniform dispersion throughout the sampled cores. This value was stated in Neville (2012) as the depassivation threshold. The variation coefficient (Co.Var) is in the range of 0.08 to 0.11. The average value of chloride concentration for the motorway bridges is higher than 0.1 [wt.-%/concrete], which is considered to be the corrosion initiation threshold within the range given in Locke and Siman (2009). The average values of corrosion risk expressed