Civil Engineering Reference
In-Depth Information
deck (Grantham et al., 2005). Tests were performed by coating areas of
the concrete with inhibitor and then using a combination of rest potential
and galvanostatic pulse monitoring to evaluate their effectiveness. Neither
product proved effective and subsequent tests by Sika showed penetration of
their product to only about 25 mm, which was the approximate depth of the
top of the shallowest steel reinforcement.
A report prepared by Sprinkel (2003) for the Virginia Dept of Transport in
the USA concluded, 'In summary, this project does not show any benefit from
the use of the corrosion inhibiting admixtures and the topical applications
made to the chloride-contaminated concrete surfaces prior to placement of
the patches and overlays.' Although it did go on to state that, 'Additional
years of monitoring of the exposure slabs and bridges may provide useful
results.'
The UK Highways Agency, in its Design Manual for Roads and Bridges,
Part 8, BA57/01 (Highways Agency, 2001) refers to research carried out by
the Transport Research Laboratory and concludes:
The TRL research, which was conducted with reasonably good quality
concrete, indicates positive results for the effectiveness of inhibitors in
the form of cast-in concrete admixtures based on calcium nitrite and
amino alcohols, used in new construction. The results for the migrating
surface applied and the pelleted delivery system corrosion inhibitors
tested is less encouraging. However other researchers have found in tests
conducted in lower quality concrete that there may be some beneficial
effects with these migrating inhibitors. They may be considered for use
when applied to concrete of poor quality, where the chloride levels are
low. However for the present their use is not advocated on high quality
relatively impermeable structural concrete.
Sika Ltd, manufacturers of Sika Ferroguard 901 and 903 were asked for
any data and reports that they had regarding the efficacy of their products
for corrosion inhibition. Reviewing the data provided confirmed the view
that admixed Ferroguard inhibitor was successful in inhibiting corrosion
behaviour, as has been confirmed by other workers. However, the data
regarding the behaviour of the 903 penetrating inhibitor product, while
confirming that penetration could be achieved, was not sufficiently robust
in proving a sufficient effect on corrosion current or potential when used in
penetrating mode. However, see also later comments on the possibility of
using a pumping method to introduce the inhibitor, as suggested by Cailleux
et al. (2008). Sawada and co-workers (Sawada et al., 2005) also attempted to
improve the efficiency of injection of ethanolamine and guanidine inhibitors
by electrochemical methods, and found that in carbonated concrete,
significant improvement in penetration was achieved. In uncarbonated
concrete, some improvement was found with guanidine, but little effect was
observed with the ethanolamine inhibitor.
