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.



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