Concrete Testing

Purpose:
To assess the workability and consistency of freshly mixed concrete.

Procedure:

1. Clean and moisten the slump cone (height: 300 mm, bottom diameter: 200 mm, top diameter: 100 mm).
2. Fill the cone with concrete in three layers, tamping each layer 25 times with a tamping rod.
3. Remove the cone vertically.
4. Measure the vertical difference (slump) between the top of the cone and the highest point of the concrete.

Interpretation of Results:

• True slump: Concrete maintains a uniform shape.
• Shear slump: Concrete slides, indicating low cohesion.
• Collapse slump: Indicates excessive water content.

Acceptable Values:

• Reinforced concrete: 25–75 mm.
• Pavement concrete: 20–30 mm.

Compression Test on Concrete

• Purpose:
  To measure the compressive strength of concrete cubes or cylinders.
• Procedure:
  1. Prepare concrete cube molds (150 mm × 150 mm × 150 mm).
  2. Cure the cubes for 28 days in water.
  3. Place the cubes in a compression testing machine.
  4. Gradually apply load until failure.
• Calculation Formula:

Example Calculation:

Standard Reference: IS 516