Round-Robin test on chloride analysis in concrete - Part 1: Analysis of total chloride content

The present paper gives part of the results of a Round Robin Test on chloride analysis in concrete, carried out by the Technical Committee TC 178-TMC. In this RRT, the analysis of total chloride, free chloride and the colourimetric determination of the front of chlorides in concrete have been tested. This paper reports the results corresponding to total chloride content. Water soluble chloride and colourimetric front are reported respectively in Parts II and III of the paper. A total of 30 laboratories around the world have participated in this RRT, and a total determination of 64 different analyses on triplicate specimens have been carried out. The procedure for the analysis of total chloride has been divided into two steps: extraction and analysis, discriminating the reliability of the procedure followed in each of them. Two different methods of extraction of total chloride from the solid sample (A1 and A2) as well as six different forms of analysing the resulting liquids (C1 to C6) have been tested. It was also decided that other methods could also be used to the choice of each laboratory, as "other methods" (A3 and C7 for extraction and analysis respectively). (The complete recipes of these methods can be found in Annex 1 of the paper.) The statistical treatment of the data has been carried out according to the International Standard ISO 5725-1981 (F) for the determination of the reliability of testing methods: "Determination of the repeatability and reproducibility by Round Robin tests". As a final result the methods of extraction and analysis recommended for total chlorides have been the following: C1-C1, A2-C4*, A2-C7, A3-C4* and A3-C7.