Segregation in concrete is the process by which different components of the mix, such as aggregates and cement, separate and become unevenly distributed throughout the mix. This can result in an inconsistent mixture that is weaker and less durable than it should be.
Reasons for Segregation of Concrete:
- Improper mix design: If the proportions of the ingredients in the concrete mix are not properly balanced, the mix can become too dry or too wet, leading to segregation.
- Inadequate mixing: If the mixing process is not thorough, the heavier components of the mix can settle to the bottom, causing the lighter components to rise to the top, resulting in segregation.
- Excessive vibration: Over-vibration can cause the heavier components to settle and the lighter components to rise to the surface, causing segregation.
- Long hauling distances: Transportation of the concrete over long distances can cause the mix to separate and settle during transit, leading to segregation.
Types of Segregation of Concrete:
- Coarse aggregate segregation: Coarse aggregates have a tendency to settle towards the bottom of the formwork, leaving the cement paste and fine aggregates at the top.
- Bleeding: Bleeding occurs when excess water rises to the surface of the concrete mix and evaporates, causing the cement and fine aggregates to settle at the bottom of the mix.
- Laitance: Laitance is a thin layer of weak and porous material that forms on the surface of the concrete when excess water is added to the mix. It can cause the mix to segregate and weaken the structure.
Remedial Actions to Prevent Segregation of Concrete:
- Proper mix design: The right mix design for the application should be chosen to ensure the proper balance of strength and workability.
- Adequate mixing: The concrete should be mixed thoroughly to ensure that all components are evenly distributed throughout the mix.
- Proper placement: The concrete should be placed carefully and evenly to prevent excessive vibration, which can cause segregation.
- Use of appropriate formwork: The formwork used for casting the concrete should be properly aligned, secured, and free of leaks, to prevent segregation.
- Use of admixtures: Admixtures, such as superplasticizers, can help reduce the water content of the mix, making it more workable and reducing the risk of segregation.
In summary, segregation of concrete can lead to an inconsistent mixture that is weaker and less durable than it should be. This can be prevented by ensuring a proper mix design, adequate mixing, proper placement, the use of appropriate formwork, and admixtures if necessary.
