Civil Engineering Reference
In-Depth Information
for patch repairing to restore alkalinity will determine whether realkalisation
is preferred either because it is more economic, or in other cases to avoid the
noise, dust and vibration required for extensive patch repairing. In practice,
the technique comes into its own when the area to be treated is very large,
when it is more economic to use a treatment that will deal with all the latent
damage (areas which are carbonated but have not yet spalled) rather than
individually identifying, breaking out and dealing with such areas. It is
interesting to note that a very large number of contracts are using migratory
corrosion inhibitors to deal with such latent damage, although the case for
using such products is rather weak according to much of the research that
has been carried out (see
Chapter 10).
The technique has been used in Europe and the Middle East (in North
America very little attention is paid to carbonation). The choice between
realkalisation and patching and coating is a question of convenience and cost,
together with a realistic appraisal of the effectiveness of anti-carbonation
coatings.
The patentees and the licensees of the system claim that:
•
It is financially competitive with the alternatives.
•
There is greatly reduced vibration and noise.
•
The entire surface is treated.
•
Guarantees are offered.
9.3 Conclusions
Surprisingly, both realkalisation and chloride removal have struggled to
gain a foothold, certainly in the UK, where cathodic protection seems to be
the preferred option. In Germany, numerous contracts are using chloride
removal, but research suggests that realkalisation is not often used. This is a
pity for both methods as they are technically very sound and work very well.
Clients and Engineers should look again at this technology when dealing
with large carbonated areas and UK contractors should take a further look
at employing the technology in appropriate circumstances.
Acknowledgements
The author would like to acknowledge the help of Dr John Broomfield in
preparing this chapter.
References
Al Khadimi, T. K. H., Banfill, P. F. G. et al., 'An experimental investigation into
the effects of electrochemical re-alkalisation on concrete'
Proceedings of an
International Symposium on the Corrosion of Reinforcement in Concrete
Construction
, Cambridge. Royal Society of Chemistry. 1996.
