PELCON offers analysis of the chloride migration coefficient according to NT Build 492 (Nordtest Method). The chloride migration coefficient determined by this test is a measure of the tested materials resistance to penetration of chloride.
The test is usually conducted on samples with a maturity of at least 28 days. Depending on the case and the concrete mix it can be relevant to analyze samples with a higher maturity – e.g. 56 days or 90 days.
The principle of the test is to analyze the penetration depth of chloride ions in a 50 mm thick slice of a drilled concrete core or a cast cylinder. Dissolved chloride ions are forced through the section of the slice due to an applied voltage in approximately 24 hours.
Sketched principal setup for measuring the non-steady-state chloride migration coefficient according to NT Build 492.
After the exposure of the specimen it is split in two halves and the section is sprayed with a solution of silver nitrate. This leads to a precipitation of grey-white silver chloride in the part of the section that was penetrated by chlorides during the test. The penetration depth is easily measured and based on the test parameters the non-steady-state migration coefficient (Dnssm) is calculated. Dnssm is stated in 10-12 m2/s in the final test report.
A split sample with clear precipitation of silver chloride in the part of the section that was penetrated by chlorides during the test.