Civil Engineering Reference
In-Depth Information
•
A chloride measuring unit (Schneck et al., 2006) signals saturation of the
ion exchanger and switches off the related electrodes.
•
The control of the ECE is based on a uniformly provided voltage of
40 V and a pulse width modulation (PWR) (Schneck et al., 2001) that
switches the electrodes or groups of electrodes in intervals - normally
12 hours. The on-time is reduced when defined parameters such as
current or potential readings are exceeded.
•
Chloride saturated electrodes are regenerated in a solution at pH = 14.
So the bound chloride is replaced by OH-, can be analysed to measure
how much chloride has been removed and the electrodes get a fresh
alkaline buffer capacity. Waste from the ECE application is thus avoided.
8.3 Influencing factors and side effects
As already mentioned, the effect of the ECE is influenced by many factors,
which are not easy to determine in practical cases, and these factors can vary
strongly within a few square metres. The ECE itself influences the treated
structural part not only by the removal of chloride and increase of alkalinity,
but also perhaps in unwanted ways if the structure is not assessed and the
ECE is not designed and applied appropriately.
The reinforcement is the internal electrode for the ECE; concrete cover
and rebar spacing have a great influence on the desalination effect. The main
part of the process takes place between the concrete surface and the upper
reinforcement layer; if the concrete cover is low - less than 20 mm - the
area directly above the bars will be desalinated almost totally, but only a
negligible chloride removal can be achieved in concrete areas behind the
RAS connection
Remote control and
monitoring
Power supply
Data acquisition
Host central control,
surveillance and data
recording
Actor and sensor
control for
- switch
- voltage
- current
- reference signal
Grid layout on a bridge abutment
Combination electrode
active / passive
