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IBRACON Structures and Materials Journal • 2012 • vol. 5 • nº 4
C. G. NOGUEIRA | E. D. LEONEL | H. B. CODA
values adopted for all random variables considered in this appli-
cation, as well its statistical information are presented in table 2,
which are based on the work of [12,16].
The evolution of probability of corrosion initiation in function of co-
ver depth and w/c ratio, considering C.A. II, is presented in figures
7, 8 and 9. As presented in three figures above, the probability of
corrosion initiation reduces faster when the cover thickness incre-
ases from 10 to 40mm. However, this reduction tends to stabili-
ze when the cover depth is larger. Then, these results show that
by increasing the cover thickness, an effective improvement on
the structural safety is not observed from a certain value of depth.
From this value, the structural cost grows faster than the structural
safety against the corrosion initiation failure. However, this type of
behaviour is different for each value of w/c ratio adopted and the
time considered. For concretes with low value of w/c 0.40 to 0.50
for instance, the stabilization process is faster observed than in
permeable concretes, with w/c 0.60 or 0.70. Considering permea-
ble concretes, it is required thicker covers in order to achieve the
stabilization on the reliability index value.
The analyses aiming the determination of the evolution of proba-
bility of corrosion initiation in function of cover depth and w/c ratio,
involving C.A. III, are presented in figures 10, 11 and 12.
The behaviour of the curves observed in these three last figures
is similar to those presented for C.A. II. However, due the high
environment aggressiveness, the probability of corrosion initiation
tends to be higher than in C.A.II for the same structural life time
and cover depth. The stabilization of the probability of corrosion
initiation values, observed in previous analyses, also occurs for
C.A.III. However, this process, for C.A. III, is observed for cover
depth values thicker than in C.A.II case.
Another important aspect that should be mentioned is the time de-
pendency considered on time corrosion initiation analyses. As long
is the time desired to avoid the corrosion initiation or even thou-
gh to reduce the probability of corrosion initiation process, thicker
Figure 7 – Evolution for probability of corrosion
initiation – C.A.II structural life-time = 5 years
0,0
0,2
0,4
0,6
0,8
1,0
10,0
20,0
30,0
40,0
50,0
60,0
Concrete cover (mm)
Probability of corrosion
initiation
w/c=0,4
w/c=0,5
w/c=0,6
w/c=0,7
Figure 8 – Evolution for probability of corrosion
initiation – C.A.II structural life-time = 15 years
0,0
0,2
0,4
0,6
0,8
1,0
10,0
20,0
30,0
40,0
50,0
60,0
Concrete cover (mm)
Probability of corrosion
initiation
w/c=0,4
w/c=0,5
w/c=0,6
w/c=0,7
Figure 10 – Evolution for probability of corrosion
initiation – C.A.III structural life-time = 5 years
0,0
0,2
0,4
0,6
0,8
1,0
10,0
20,0
30,0
40,0
50,0
60,0
Concrete cover (mm)
Probability of corrosion
initiation
w/c=0,4
w/c=0,5
w/c=0,6
w/c=0,7
Figure 11 – Evolution for probability of corrosion
initiation – C.A.III structural life-time = 15 years
0,0
0,2
0,4
0,6
0,8
1,0
10,0
20,0
30,0
40,0
50,0
60,0
Concrete cover (mm)
Probability of corrosion
initiation
w/c=0,4
w/c=0,5
w/c=0,6
w/c=0,7
Figure 9 – Evolution for probability of corrosion
initiation – C.A.II structural life-time = 25 years
0,0
0,2
0,4
0,6
0,8
1,0
10,0
20,0
30,0
40,0
50,0
60,0
Concrete cover (mm)
Probability of corrosion
initiation
w/c=0,4
w/c=0,5
w/c=0,6
w/c=0,7