"Material segregation", often referred to simply as segregation, is a phenomenon that occurs when the various components of a bulk material separate under certain conditions. This can cause the material to become unevenly mixed, which can affect the quality and accuracy of sampling.
Segregation can occur for several reasons:
- Particle size: Larger particles tend to move to the lower layers of a bulk material due to gravity, while smaller particles rise to the surface. This is called the sieve or classification effect.
- Particle shape: Irregularly shaped particles may tend to separate. Spherical particles, for example, can flow through the rest of the material and collect at the bottom.
- Density: Higher density particles tend to settle to the bottom, while lighter particles rise to the surface.
- Vibration and movement: Vibrations or movements, such as those that can occur during transport or handling of bulk materials, can also lead to segregation.
To ensure representative sampling, it is important to minimize the risk of segregation. This can be achieved through careful planning and execution of sampling, including the selection of appropriate sampling techniques and equipment. In some cases, it may also be helpful to homogenize the material before sampling to ensure an even distribution of the particles.