LIME
Lime has been used as cementing material from ancient times. It contains clay (8 to 10%),
magnesium carbonate (not more than 30%) and very small quantities of soluble silica, alkalies,
sulphate and iron apart from the main constituent calcium carbonate.
Lime is classified as fat lime, hydraulic lime and poor lime. Fat lime contains 95% of calcium
oxide. When water is added, it slakes vigorously and its volume increases 2 to 2.5 times.
Hydraulic lime sets by chemically combining with water. It is classi fied as feeble hydraulic lime
(5 to 10% clay), moderately hydraulic lime (10 to 20% clay), eminently hydraulic lime (20 to 30%
clay). It is used for making mortar to be used for plastering and in damp-proof constructions. Lime
containing more than 30% clay is poor lime.
Manufacture of lime involves preparation, burning and hydration (slaking). For burning clamps or
kilns are used. The kiln may be intermittent or continuous.
IS: 1624-1974 specifies various tests to assess the quality of lime. The tests prescribed are:
(1) Physical properties tests; (2) Acid tests; (3) Heat test; (4) Ball test; (5) Impurity test; (6)
Plasticity test; (7) Workability test.
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