Determination of depth of carbonation

The highly alkaline environment in concrete provides protection of the steel reinforcements against corrosion in general. However, carbonation, a chemical reaction of the hydrates with carbon dioxides, can break down the protection by reducing the degree of alkali in concrete. Corrosion will weaken the reinforcement. Expansion of reinforcement bar will cause crack and even spalling in the concrete.

The examination provides information on the depth of carbonation in concrete using a chemical reaction between phenolphthalein solution and carbonated concrete. The results show degree of carbonation in a concrete structure. It is one of essential factors for engineer, architect and property managers to set up an appropriate maintenance plan.

General Test Procedures

1. Define a test area of a building.

2. Drill a hole or break the area.

3. Spray phenolphthalein solution onto the drilled hole or on the exposed area or extracted concrete sample.

4. Examine the broken surface for pink coloration where the surface without pink color is the carbonated concrete.

5. Measure the depth from the concrete surface.

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Last modified: December 15, 2004