Civil Engineering Reference
In-Depth Information
and thus might inhibit the incipient anode effect in chloride contaminated
concrete. In the author's view, sacrificial galvanic anodes or a full CP system
would be a better choice if any significant chloride content were present.
Cailleux, Pollet, Dubois and Michaux (Cailleux et al., 2008) also trialled
the use of an ultrasonic pump to introduce a nitrite inhibitor into grout in
tendon ducts, with some success.
Figure 10.2
shows a photograph of the
condition of rebars in grout with various levels of chloride after introduction
of a nitrite inhibitor using an ultrasonic pump, after 12 months.
Sample autopsy after 2 mon
ths
Two months after treatment, the first autopsies were performed and half of the samples were fractured.
The concrete covering and the ducts were removed in order to inspect the tendons. The Fig. 11 compares
the corrosion state of the steel between the reference samples and the treated ones. The following
observations can then be noticed:
-
In the case of the chloride concentrations of 1% and 2%, a very clear reduction of the corroded
areas was observed on the rebars after treatment. With 1% of chlorides, nearly no corrosion can be
detected after injection.
-
For the chloride concentration of 3%, corrosion layers can be observed both on the treated and the
non-treated tendons. However, the treated samples might present a low corrosion state.
The presence of the inhibitor was evaluated by analytical test strips (Merckoquant 1.10020.000) which
were applied directly at the surface of the tendons. The nitrite concentration was evaluated semi
quantitatively by visual comparison of the reaction zone of the test strip with the field of a colour scale.
The results showed a significant colour change forthe strip applied on the surface of the treated samples
indicating that the rebars were recovered by the nitrites after the treatment.
Chloride
content
(%)
0%
1%
2%
3%
Figure 10.2
Comparison of the corrosion state of the treated and the non-treated
Cailleux et al., 2008).
