Chloride Migration

UKAS Accredited

Standard(s): NT BUILD 492.1999-11
Site Test
Lab Test
The Chloride Migration test measures the rate at which chloride ions penetrate hardened concrete. Conducted in accordance with NT BUILD 492 (1999-11), the test determines the chloride migration coefficient using a non-steady-state method. This provides an indication of how resistant concrete is to chloride ingress, which is a key factor in the long-term durability of reinforced concrete structures.

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The Process

A cylindrical concrete specimen is cut to produce a disc sample and sealed into a test cell. One side of the specimen is exposed to a chloride solution while an electrical potential is applied across the sample to accelerate chloride movement. After a set testing period, the specimen is split and sprayed with a silver nitrate solution to reveal the depth of chloride penetration. The penetration depth is then used to calculate the chloride migration coefficient.

The Reason

Chlorides can penetrate concrete and reach embedded steel reinforcement, causing corrosion that leads to cracking and structural deterioration. The chloride migration test helps assess the resistance of concrete to chloride ingress, allowing engineers to evaluate durability and service life in aggressive environments.

The Application

Chloride migration testing is commonly carried out for concrete used in marine structures, bridges, tunnels, car parks, and structures exposed to de-icing salts. The results help engineers assess durability performance and select appropriate concrete mixes for environments where chloride exposure is a concern.

Frequently Asked Questions

Can Amtest carry out chloride migration testing for concrete durability?

Yes. Amtest provides chloride migration testing in accordance with NT BUILD 492 to assess the resistance of concrete to chloride penetration.

Why is chloride migration testing important for reinforced concrete?

Chloride ingress can lead to corrosion of steel reinforcement. Amtest testing helps evaluate the durability of concrete and its suitability for aggressive environments.

What types of projects typically require chloride migration testing?

The test is commonly used for marine structures, bridges, car parks, tunnels, and infrastructure exposed to salt or coastal conditions.

What information will the chloride migration test report provide?

Amtest provides a laboratory report detailing the calculated chloride migration coefficient, helping engineers assess the durability performance of the concrete mix.

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Chloride Migration

Chloride migration testing determines the chloride migration coefficient in concrete, mortar, or cement-based repair materials, evaluating their resistance to chloride ion penetration. This test is vital for assessing the risk of chloride-induced corrosion, which can weaken reinforced concrete structures over time.

Testing Procedure

  1. Specimen Preparation: Concrete or repair material samples are prepared and cured according to standards, typically in cylindrical or prismatic shapes.
  2. Experimental Setup: A chloride solution is applied to one side of the specimen, while an electric field is used to drive chloride ions through the material.
  3. Measurement: After migration, the chloride concentration at various depths is measured using ion chromatography.
  4. Calculation: The chloride migration coefficient is determined, indicating how resistant the material is to chloride penetration.

Applications

  • Reinforced Concrete: Assesses durability in saltwater or deicing salt environments.
  • Repair Materials: Evaluates the chloride resistance of cement-based repair products.
  • Quality Control: Ensures materials meet durability standards.

Conclusion

Chloride migration testing is essential for evaluating the long-term durability of concrete and repair materials exposed to chloride, ensuring structural safety and performance in aggressive environments.

NT BUILD 492.1999-11