Purpose
On-site, accurately and quickly to test the chloride content of concrete for
- Establishing the chloride profile for service life estimation
- Establishing the depth of removal of a chloride contaminated surface layer
- Diagnosing a structure for corrosion activity, e.g. in combination with the Mini Great Dane, the GalvaPulse and the Rainbow Indicator
- Monitoring the chloride content during electrochemical removal of chlorides
- Measuring the chloride content of fresh concrete and/or its constituents
Principle
A sample of concrete is obtained by drilling/grinding from the structure, or from the fresh concrete, mixed into a distinct amount of extraction liquid and shaken for five minutes. The extraction liquid removes disturbing ions, e.g. sulfide ions, and extracts the chloride ions in the sample.
A calibrated electrode is submerged into the solution to determine the amount of chlorides expressed as percentage of concrete mass.
The test is either the RCT (Rapid Chloride Test) for acid soluble chlorides, or the RCTW (Rapid Chloride Test Water) for water-soluble chlorides, using different kinds of extraction liquids. Both hardened and fresh concrete can be tested with the system for chlorides.
Numerous correlations have during the past 15 years been made between RCT and standard laboratory potentiometric titration as the AASHTO T-260, ASTM C 144-81, DS 423.28 or NS 3671. Below are illustrated such correlations made by various laboratories in the Scandinavian countries and the USA.