CMH Ltd Distributors of Testing Equipment and Labware Rapid Chloride Test Systems
 
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 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.

 Precision and accuracy

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.

In a recent comparison, the Swedish National Testing Institute produced concrete powders containing known amount of chlorides induced in the concrete by diffusion. The powders were made from concretes with different binders as illustrated in the table below. Testing, according to AASHTO T 260 standard laboratory potentiometric titration was done by five certified Scandinavian laboratories, and by RCT in parallel.

The RCT readings were taken after the extraction samples with dissolved concrete powder had been left over-night for full extraction. Alternatively, if the result is needed after 5 minutes of shaking the vial, a correction factor has to be applied.

The precision of the RCT compared to the known amount of chlorides is as good as with the AASHTO T 260 potentiometric titration. The average deviation of the RCT from the known amount of chlorides is within 4%.

For repeated testing with the RCT on the same concrete powder the normal variation on the test results is in average 5%.

With the RCTW for water soluble chlorides a similar close agreement as with the RCT, in terms of precision and accuracy, has been found to standard titration tests in the laboratory.

 Testing examples

Chloride profiles measured with the RCT are illustrated in the Profile Grinder section.



Adjacent is shown two other profiles, obtained after profile grinding in-situ on a highway bridge column subjected four years to deicing salts. The concrete powders produced at depth increments of 1-2 mm were analyzed for acid soluble chlorides by the RCT and for water soluble chlorides with the RCTW. The depth of carbonation was measured with the Rainbow Indicator to be 2 mm, corresponding to the initial peaks of the chloride profiles produced.

 

 Ordering numbers


RCT-500

The manual included in the RCT-500 kit covers testing for acid and water-soluble chlorides of hardened as well as of fresh concrete. Separately delivered is a binder (RCT-1100) with 15 years of testing experience, included advanced theory for chloride diffusion modeling.

 Extra Parts

RCT-1030 set of calibration liquids

RCT-1000-1 EWA

RCT-1032 Mixing Container and Cup

It is recommended always to have one extra set of clean RCT-1030 set of calibration liquids at hand to make sure the chloride electrode is working properly should deviations from the usual obtained calibration values occur. The RCT-1000-1 EWA (Electrode Wetting Agent) contains 300 ml for refill of the RCT-1000 EWA bottle with spout fitting the electrode hole.

The RCT-1032 mixing container and cup is for testing of fresh concrete.

 Consumables

The extraction liquids for RCT (acid soluble chlorides) are the following for testing of hardened concrete and for testing of fresh concrete

RCT-1023 vials, set of 25,
for testing of hardened concrete

RCT-1031 vials, set of 25,
for testing of fresh concrete

Similarly, for RCTW (water soluble chlorides) the extraction liquids are

RCTW-1023-1 vials, set of 25
RCTW-1023-2 buffer vials, set of 25,
for testing of hardened concrete

RCTW-1031-1 vials, set of 4
RCTW-1031-2 buffer vials, set of 4,
for testing of fresh concrete

 Optional items

RCT-1032 balance for 1.5 gram, for checking the
powder weighing ampoules supplied in the RCT-500 kit



 

Detailed information information on all of our product ranges can be found in our catalogue, available for download in the Products area.

CMH Ltd, Unit 3, Winston Business Centre, Chartwell Road, Lancing, West Sussex, UK|  FAX +44 (0) 1903 751188  |  PHONE +44 (0) 1903 751133