Civil Engineering Reference
In-Depth Information
In
Figure 8.8
a typical effect of a two-stage treatment of deeply chloride
contaminated concrete can be seen; the initial chloride content is reduced in
the outer 8 cm, but increases later, when more chloride is moved from deeper
zones with capillary suction from drying processes. A second application is
made for the final treatment and reduces the chloride content down to an
uncritical level.
Five months after finishing the second treatment, a repeated potential
survey showed a very even potential distribution with low deviation from the
average value (-100 mV vs. CSE) and no signs of possible macro elements
(and related corrosion activity) any more. The highest potential shift of
about +400 mV has been observed in the areas of initially most negative
potentials (
Figure 8.9).
Centre column of a bridge across a highway
A very different target was set for this project - a column of a bridge over a
highway close to Kassel in Germany had some chloride accumulated in the
splash zone and needed to be rehabilitated preventatively by a combined ECE
and hydrophobic gel treatment, so that an expensive and traffic disrupting
conventional repair of this column could be avoided, and the long-term
effect of a new hydrophobic gel application could be surveyed (
Figure 8.10).
In this case, the effect of chloride reduction in the concrete was not that
great, but was also not necessary yet. Another intention was to alkalise the
reinforcement vicinity with respect to the following hydrophobic application.
4.00
3.50
3.00
2.50
2.00
1.50
1.00
0.50
28.09.2003
03.012.2003
20.04.2004
14.010.2004
0.00
0-2
2-4
4-6
6-8
0-2
2-4
4-6
6-8
0-2
2-4
4-6
6-8
0-2
2-4
4-6
6-8
0
-2
2-4
4-6
6-8
R9C4
R11C4
R3C11
R8C9
R8C14
locations; dark bars show chloride content in the vicinity of the upper reinforcement.
