The limestones are tested to determine the quality of lime which can be obtained from them. Most important test conducted on lime are as follows:
1. Physical Properties tests: Many tests are carried out on lime for examining their physical properties. Some of them are
a. Soundness Test: It is performed to find the disintegration or unsoundness of the lime sample. Soundness testis performed by using Le-chatelier apparatus. Whether the lime is properly slaked or not is determined by soundness test.
b. Visual Test: This test is carried out to check the physical appearance of lime. If colour of lime is pure white, it indicates fat lime or pure lime. If colour lime is dirty white, it indicates the presence of impurities. If lime contains lumps, it indicates quick lime or unburnt lime stone.
c. Chemical Test: This test is performed to find the cementation value and hydraulic properties of lime sample.
d. Transverse Strength:
2. Heat Test: A piece of dry limestone is weighed and it is heated in an open fire for few hours. The sample is weighed again and loss of weight indicates the amount of carbon dioxide. From this data, the amount of calcium carbonate in limestone is worked out.
3. Acid Test: Acid test is carried out to find the class of lime and its carbonate content.
a. A teaspoon of powdered lime is taken in a test tube and dilute hydrochloric acid is poured in it. The contents are now stirred and the test tube with its contents is then kept standing in its stand for 24hrs.
b. It content of calcium carbonate is high, there will be vigorous effervescence and less formation of residue. Such an action will indicate pure limestone. On the other hand, if content of calcium carbonate is less, there will be less effervescence and more formation of residue. Such an action indicates impure or hydraulic limestone.
c. If a thick jel or semi solid material is formed which does not flow even when the test tube with its content turned upside down, it indicates lime of class A. If the jel is not quite thick and tends to flow when the test tube is tilted, it indicate lime of class B. If however there is no jel formation, it indicates lime of class C.
4. Ball Test: In this test, the balls of about 40mm size of stiff lime formed by adding enough water are made and they are left undisturbed for six hours. The balls are then place in a basin of water. If there are signs of slow expansion and slow disintegration within minutes after placing in water, it indicates class C lime. If on the other hand, there are very little or no expansion and numerous cracks, it indicates class B lime.