Hydraulic Lime or Water Lime contains clay and some amount of ferrous oxide. It sets under water and hence also known as water lime. Depending upon the percentage of clay, I.S.I has divided hydraulic lime in three classes namely,

Class A- Eminently hydraulic,
Class B – Semi- hydraulic, and
Class C- Non- hydraulic (or Fat Lime)

Class A (Eminently Hydraulic Lime) :
This lime contains about 25% clay content sets readily under water within a day or so. This lime slakes with difficulty. The mortar and lime concrete prepared from this lime is very useful for construction under water or in damp places.

Class B (Semi – Hydraulic or Moderately Hydraulic Lime):
Semi- hydraulic lime contains about 15% clay content and sets under water at a slower rate within a week or so. The mortar and concrete prepared from this lime is strong and used for superior type of masonry work.

Class C (Non- Hydraulic or Fat Lime):
This lime contains about 7.5% of clay content and is prepared from pure lime stone. This slakes vigorously within few minutes but does not set under water. This is used for whitewashing and color washing.


other types of lime are,

Quick Lime or Caustic Lime
Slaked Lime or Hydrate of Lime
Fat Lime