Chloride threshold values
The so-called chloride threshold
value, which may be defined as the minimum concentration of
chloride at the depth of the reinforcement that is able to initiate
corrosion of the steel, is a crucial input parameter for
modelling of the service lifetime of reinforced concrete
structures. Without an experimentally determined chloride threshold
value, engineers are generally forced to make rather conservative
estimates of this value, thus potentially underestimating the
service lifetime dramatically.
RILEM TC 235
CTC
Part of the research carried
out at the Infrastructure Expert Centre is focused on the
experimental determination of chloride threshold values for
reinforcement corrosion in concrete, and the centre is
participating in the Round Robin test of the newly suggested method
from the RILEM
TC 235 CTC group.
Reported chloride threshold values
in the literature display a wide scatter, which is partly due to
the fact that numerous different experimental approaches have been
used to obtain the chloride threshold values. In order to make
reasonable and scientifically sound comparison of experimentally
determined chloride threshold values, a generally accepted test
method for the determination of this parameter is greatly needed.
Presently, such a method is still lacking. In 2009 a RILEM group
(TC 235 CTC) was formed with the purpose of addressing this
problem, and after thorough discussions the group agreed on an
accelerated test method based on open circuit measurements on
rebars in concrete specimens exposed to a chloride solution.
Recently, a Round Robin test
involving 12 laboratories has been carried out to test the method
proposed by the RILEM group. The report below presents the results
from the Expert Centre's participation in the Round Robin Test:
Test report on participation in Round Robin
Test_RILEM 235-CTC
Presentation of results at
3rd International Conference on Repair, Rehabilitation
and retrofitting
Results from the research carried
out at the Infrastructure Expert Centre on chloride threshold
values have been presented at the 3rd International Conference on
Concrete Repari, Rehabilitation and Retrofitting, ICCRRR-3, 3-5
September 2012 Cape Town, South Africa:
H.E. Sørensen, S.L. Poulsen & E.P.
Nielsen: Testing of the chloride threshold values for
reinforced concrete structures