Segregation of Concrete

Segregation of Concrete

Definition:

• Segregation of concrete refers to the separation of the components of fresh concrete, which negatively impacts its uniformity and quality.

Types of Segregation:

1. Coarse Aggregate Segregation:
   • Larger particles separate from the rest of the mix and settle at the bottom.
2. Paste and Aggregate Segregation:
   • Cement paste separates from the aggregates and rises to the top (bleeding).

Causes:

• Improper mixing techniques.
• Over-vibration of concrete.
• Excessively high concrete pouring from heights.
• High water-cement ratio leading to a very fluid mix.
• Use of poorly graded or excessively large aggregates.

Effects:

• Weakening of concrete structure.
• Uneven strength distribution.
• Compromise in aesthetic appeal.
• Increased permeability leading to durability concerns.
• Formation of voids and honeycombing.

Prevention Methods:

• Ensure proper grading and proportioning of aggregates.
• Maintain an appropriate water-cement ratio.
• Use controlled and appropriate mixing techniques.
• Careful handling and placing of concrete to avoid excessive vibration and dropping from heights.
• Employ admixtures that can help maintain mix consistency.

Test Methods:

• Sieve Analysis: To check the grading of aggregates.
• Slump Test: To assess the consistency and workability of the concrete mix.
• Visual Inspection: Observing the concrete mix for signs of segregation.

Importance of Preventing Segregation:

• Achieving the desired concrete properties.
• Ensuring structural integrity and longevity.
• Maintaining required aesthetic standards for concrete surfaces.