Tests on Limestones

Practical tests are made on lime stones to decide their suitability is following:

    i.       Physical tests

   ii.        Heat test

   iii.       Chemical test

   iv.       Ball test.

(i) Physical Test: Pure limestone is white color stone. Hydraulic lime stones are brown, bluish grey or it has dark colors. The hydraulic lime gives out earthy smell. They are having clayey taste. Presence of lumps gives indication of quick lime and unburnt lime stones.

(ii) Heat Test: A piece of dry stone which weigh is W1 is heated in an open fire for few hours. If weight of sample stone after cooling is W2, the loss of weight is W2 - W1. The loss of weight shows the amount of carbon dioxide. From this the amount of calcium carbonate in limestone may be worked out.

(iii) Chemical Test: A teaspoon with full of lime is placed in a test tube and dilute hydrochloric acid is poured in it. Content is stirred and test tube is kept in the stand for 24 hours. Vigorous effervescence and less residue show pure limestone. If effervescence is less and its residue is more it shows impure limestone.

If thick gel is formed and after test tube is held upside down it is possible to recognize class of lime as shown below:

• Class A lime, if gel do not flow.
• Class B lime, if gel tends to flow down.
• Class C lime, if there is no gel formation.

(iv) Ball Test: This test is conducted to recognize whether the lime belongs to class C or to class B. By adding adequate water approximate 40 mm size lime balls are building and they are left undisturbed for 6 hours. Then the balls are placed in a basin of water. If within minute's slow expansion and slow disintegration begin it indicates class C lime. If there is little or no expansion, but just cracks appear it belongs to class B lime.