6.3 : 生コンクリートの分離

Excessive horizontal movement of concrete within forms, or dropping it from a considerable height or through narrow spaces with directional changes, can lead to the segregation of its components.

Segregation is a phenomenon wherein the heavier coarse aggregate particles tend to settle at the bottom of the form. At the same time, the lighter, finer components migrate upwards, leading to an uneven distribution within the concrete mix.

Another type of segregation occurs when the grout, consisting of cement and water, tends to separate from the rest of the concrete mix.

Concrete should be prepared as close to its final location as possible, reducing transportation distance to prevent segregation.

If too much work is performed on the concrete, like using a vibrator for a long time to distribute a heap of concrete over a vast area, it may segregate the concrete ingredients.

To observe probable segregation due to excessive vibration, concrete in a cube can be vibrated for approximately 10 minutes. Removing the mold will allow for the inspection of the coarse aggregate distribution.