When and How Should Chloride Profiles be Calibrated for Paste Fraction?

Due to stochastic and systematic variations in the paste fraction, data for total chloride content are occasionally calibrated using parallelly measured calcium content as a measure of the actual paste fraction - assuming non-calcareous aggregates and no calcium leaching. Data from concrete exposed at the marine Fehmarn Belt Exposure Site questions the latter assumption. In the outer zone experiencing calcium leaching (ten mm after ten years), errors will be introduced by calcium calibration. To account for the wall effect, calcium profiles from cores taken before exposure might be used to correct for the systematically higher paste fraction at cast surfaces.