Carbonation Test is a durability assessment method used to determine the depth of carbonation in concrete and to evaluate the potential risk of corrosion of embedded steel reinforcement. It is an important test for assessing the long-term durability and service life of reinforced concrete structures.

Principle: Carbonation occurs when carbon dioxide from the atmosphere reacts with calcium hydroxide in concrete, reducing its alkalinity. As the pH level decreases, the protective layer around steel reinforcement is weakened, increasing the risk of corrosion.

Equipment: Phenolphthalein solution, hammer or core cutting tools, spray bottle, and measuring scale are used to conduct this test.

Procedure:

Sample Preparation: A fresh surface of concrete is exposed by breaking or cutting the concrete member.

Application of Indicator: Phenolphthalein solution is sprayed on the exposed concrete surface.

Observation: Non-carbonated concrete turns pink or purple, while carbonated areas remain colorless.

Measurement: The depth of the colorless zone is measured to determine the carbonation depth.

Applications:

• Assessing the durability of existing reinforced concrete structures
• Evaluating corrosion risk of steel reinforcement in buildings and bridges
• Supporting maintenance, repair, and retrofitting decisions
• Assessing long-term environmental exposure effects on concrete structures

Advantages:

• Simple, quick, and cost-effective test
• Provides direct indication of loss of concrete alkalinity
• Helps estimate potential risk of reinforcement corrosion

Limitations:

• Requires partial surface exposure, making it semi-destructive
• Only measures surface carbonation depth, not internal conditions
• Results may vary depending on environmental exposure and concrete quality