Chloride conductivity testing of concrete - Past and recent developments

The chloride conductivity index (CCI) is a quality control parameter used to assess the resistance of concrete to chloride ingress. It is determined from the chloride conductivity (CC) test which has been in use in South Africa for close to two decades. During this time, it has undergone a number of changes to improve on its robustness, reproducibility, and repeatability. Plans are now under way to incorporate the test and other durability index tests (oxygen permeability and water sorptivity) into the SANS standards, and it is important that the end user is aware of the changes and why they were made. Specifically, aspects concerning a new design of the CC testing rig which is already in use, and a modified old design which is still being used in some laboratories, are highlighted, such as the significant but variable differences in CCI results that could occur between the old and new CC test rigs. Experimental investigations were carried out to establish the cause of these differences, which was identified as largely due to possible incomplete filling of the original device. Modifications were therefore made to the old CC test rig to ensure that both the new and the modified CC test rigs give similar results.