PSI - Issue 33

Francesco Freddi et al. / Procedia Structural Integrity 33 (2021) 371–384 Author name / Structural Integrity Procedia 00 (2019) 000–000

378 8

of 30°C diffuses into the specimen starting from its left side. The carbonation front is calculated numerically and compared with the experimental evidences and numerical results available in literature.

Fig. 3 Domain used for the validation of the carbonation model

The results for the carbonation depth reported in Table 1 show a good agreement with the experimental and numerical results reported in the literature.

Table 1. Carbonation depth results comparison

Days

Experimental results [mm] (Papadakis et al., 1991)

Numerical results [mm] (Papadakis et al., 1991)

Numerical results [mm]

1 3 5

3 5 8

3.5 5.5

3.3 4.5 6.6 9.3

7

10 15 20

10 12 15

8.9

11.5

11.4 14.4

14

Eventually, the corrosion process results are investigated and compared against the average results for the corrosion current density for the reinforcement bar with a passive layer (I corr < 0.1 μA/cm 2 ), and without passive layer (I corr ≈ 1 μA/cm 2 ) (Medagoda Arachchige, 2008; Stefanoni et al., 2018). A square domain with side L = 76 mm of ordinary Portland concrete with a 16 mm diameter bar is considered. The w/c ratio has been assumed equal to 50% at 65% RH. An external concentration of 0.036% carbon dioxide is set on the left and bottom side of the specimen at a temperature of 25 °C. The electrochemical parameters used in the corrosion equations are reported in Table 2. Table 2. Electrochemical parameters .

Parameters

Values

Anodic Tafel slope (b a ) Cathodic Tafel slope (b c ) Anodic potential (E 0,a ) Cathodic potential (E0, c )

0.090 V/dec -0.180 V/dec

-0.440 V 0.401 V

Anodic exchange current density (i Fe ) Cathodic exchange current density (i O2 )

3∙10 1∙10

-6 A -7 A