A study on sampling methods for chloride profiles: simulations using data from EPMA

Investigating marine concrete by determining the chloride profile is a common way for making a prediction of the remaining service life of a structure. The most common methods of sampling concrete for this purpose is dust sampling by dry drilling or sampling cores which are analyzed by profile grinding in a laboratory. Now, a similar study has been performed, by simulating different sampling techniques in data from EPMA. The results from the simulations of the concrete specimen analyzed with the EPMA, confirm the results from earlier performed dry drilling tests in laboratory and shows the same extensive variations when chloride content is presented as % by weight of concrete instead of as % by weight of calcium oxide. Comparing the results from the earlier performed sampling by dry drilling with the results from the EPMA simulations, it is seen that the dry drilling probably is afflicted with a systematic error by “movement” of dust into the sampling holes when drilling. This study also shows effects of large aggregates in small bores even though the cement content is referred to. However, no signs of “shadowing” by the aggregates was detected when the simulations where performed. Even “horizontal” drilling was simulated in order to be able to detect this possible effect of the aggregates on the chloride ingress into the concrete.