Limestones are an important binding material used in building construction. Lime has been used as the material of
construction from ancient times. When it was mixed with the sand it provides a lime mortar and when mixed
with sand and coarse aggregate (40mm), it is forming lime concrete.
The following practice tests are made on limestones to determine their suitability:
- Physical tests
- Heat test
- Chemical test
- Ball test.
- Pure limestone is white in color. Hydraulic limestones are bluish grey, brown, or are having dark colors. The hydraulic lime gives out an earthy smell.
- They are having a clayey taste. The presence of lumps gives an indication of quick lime and unburnt limestones.
- 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, the loss of weight is W2 – W1. The loss of weight calculation indicates the amount of carbon dioxide (co2). From this test, the amount of calcium carbonate in the limestone can be worked out.
- A teaspoon full of limestone powder is placed in a test tube and dilute hydrochloric acid is poured into it the procedure. The limestone content is stirred, and the test tube is kept on the stand for 24 hours. Vigorous effervescence and less residue indicate pure limestone.
- If effervescence is less and the residue is more it indicates impure limestone. If the thick gel is formed and after the test tube is held upside down it is possible to identify the class of lime as indicated below
- Class A lime if the gel does not flow.
- Class B limestone if gel tends to flow down.
- Class C type lime is if there is no gel formation.
- This test was conducted to identifying whether the limestone belongs to class C and to class B. By this test adding sufficient water, about the 40 mm size lime balls are made and they are left undisturbed for after six hours. Then the balls are placed into the basin of water.
- If within minutes slow expansion and slow disintegration start it indicates class C lime. If there is little or no expansion activity, but only cracks appear it belongs to the class B type limestones.
usages of Limestones
The following are the uses of limestone in civil engineering works:
- For whitewashing.
- For making mortar for masonry works and plastering.
- To produce lime sand bricks.
- For soil stabilization.
- As a refractory material for lining open-hearth furnaces.
- For making cement.