CONCRETO & Construções | Ed. 91 | Jul – Set • 2018 | 101
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Figure 6
Reliability index
β
for the minimum and maximum values of the carbonation rate
of the concretes ranked in figure 3 for nominal service life of 50 and 100 years
-3
-1
1
3
5
7
Beta value
XC1 XC2 XC3 XC4
Exposure class XC
Beta 50 y mim Beta, 50 y max
beta 100 y min beta 100 y max
meantime that this limiting value is
rationally selected, it can be taken
as an reference the deterministic
value (the mean one), which
corresponds to a failure probability
of 50% (
β
=0).
5. CONCLUSIONS
The main conclusions drawn up
from present paper are:
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The failure (steel depassivation)
probability of standard concretes
may vary with respect to
carbonation within those fulfilling
the prescriptive rules of the mix
proportioning for each exposure
class. This also happens with the
mechanical strength.
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In the case of the strength a
limiting value for exposure class
is established which is not still
agreed with statistical significance
for the carbonation rates or other
concrete properties.
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In the case of the carbonation
rate, the failure probability
depends on the cover depth
as indicated in the limit state
function (Eq. 1).
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Providing that this limiting value of
the carbonation rate should take
into account the importance of the
structure and the consequences
of failure, a fixed value seems
not logical. In the meantime a
more statistically based value
is decided for standards, the
deterministic, mean value (
β
=0)
can be a starting point.
6. ACKNOWLEDGEMENTS
The authors thank to CALIDUR
project for providing the experimental
data, in particular to Renata
D’Andrea. They are also grateful the
funding from the Technical Building
Code of Spain. Finally, they also
thank to the members of the fib
Commission 8 TG8.3 for the fruitful
discussions.
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