Atterberg Limits

Atterberg Limits

Atterberg limits – plastic limit, liquid limit, plasticity index, shrinkage limit – a clayey soil exists in one of four states; solid, semi solid, plastic and liquid, each dependant on the moisture content of the soil and which in turn define the soil’s engineering properties. To classify the consistency of a soil, the following terms are used:

  • Shrinkage limit – the moisture content at which a soil changes from the solid to semi-solid state.
  • Plastic limit – the moisture content at which a soil changes from the semi-solid to plastic state.
  • Liquid limit – the moisture content at which a soil changes from the plastic to the liquid state.
  • Plasticity index – the range of moisture contents at which a soil behaves plastically.

Results can include commentary on the shrinkage potential of the soil with regards National House Building Council guidelines.