n Journal of the South African Institution of Civil Engineering = Joernaal van die Suid-Afrikaanse Instituut van Siviele Ingenieurswese - Assessing the repeatability and reproducibility values of South African durability index tests : technical paper

Volume 48, Issue 2
  • ISSN : 1021-2019



An inter-laboratory test programme was conducted to estimate the repeatability and reproducibility of the durability index tests developed and used in South Africa: the oxygen permeability index (OPI) test, the water sorptivity test and the chloride conductivity test. Between the University of Cape Town and the University of the Witwatersrand, ten different concrete mixtures were cast with a range of properties. From each of these mixtures, test samples were prepared and then randomly distributed among the participating laboratories. Sufficient laboratories participated to enable nine laboratories to perform each test. The estimated repeatability was 1, 4 % for the OPI test, 9, 9 % for the water sorptivity test, and 9, 1 % for the chloride conductivity test. The estimated reproducibility was 1, 8 % for OPI, 12, 8 % for sorptivity and 21, 1 % for chloride conductivity. The variability in the oxygen permeability test is attributed mainly to material variability, while significant variability in the chloride conductivity test is attributed to the tolerances of the test apparatus, although there were indications that the procedures were not being followed correctly, either due to a lack of clarity in the procedures or the inexperience of the participating laboratories.

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