Tests on Limestones
The following practical tests are made on limestones to determine their suitability:
(i) Physical tests.
(ii) Heat test.
(iii) Chemical test.
(iv) Ball test.
(i) Physical Test: Pure limestone is white in colour. Hydraulic limestone is bluish gray, brown or dark in colour. Hydraulic lime gives off the smell of clay. They have an earthy taste. The presence of lumps indicates sharp lime and unburnt limestone.
(ii) Heat Test: A piece of dry stone weighing W1 is heated in an open fire for a few hours. If the weight of the sample after cooling is W2, then the weight loss is W2 – W1. Weight loss indicates the amount of carbon dioxide. From this the amount of calcium carbonate in limestone can be detected.
(iii) Chemical Test: A spoon full of lime is put in a test tube and dilute hydrochloric acid is added to it. The material is stirred and the test tube is placed in a stand for 24 h. Vigorous effervescence and low residue indicate pure limestone. If the effervescence is low and the residue is high it indicates impure limestone. If a thick gel is formed and after holding the test tube upside down it is possible to identify the class of lime as shown below:
- Class A Lyme, if the gel does not drain.
- Class B lime, if the gel flows downhill.
- Class C lime, if no gel is formed.
(iv) Ball Test: This test is done to find out whether the lime is of class C or class B. Lime balls of about 40 mm in size are made by adding enough water and left undisturbed for six hours. The balls are then placed in a basin of water. If slow expansion and slow dissolution begins within minutes, it indicates class C lime. If there is little or no expansion but only cracks are visible then it belongs to class B lime.
Uses of Lime
Following are the uses of lime in civil works:
(i) For whitening.
(ii) For making mortar for masonry and plastering.
(iv) For soil stabilization.
(v) As a refractory material for lining open hearth furnaces.
(vi) For making cement.