Building Materials, Third Edition

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X Limestone is heated for four hours on open fire; CO 2 escapes and it loses weight.
From this the carbonate percentage in the limestone can be worked out. Lumpy form indicates
quick lime or unburnt limestone. A porous structure may indicate quick lime.

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X2The test is carried to know the classification and the carbonate content of
lime.
When a teaspoon full of lime is put in a test tube containing 10 ml of 50 per cent hydrochloric
acid, effervesence takes place. Too much of effervesence indicates high percentage of calcium
carbonate in limestone. The residue at the bottom of the tube indicates percentage of inert
materials present in the limestone. Abundant of liberation of CO 2 indicates unburnt lime.
In case of class-A lime, a good gel is formed above the layer of inert material. A thick gel
indicates class-B lime and absence of gel means class-C lime.
For eminently hydraulic lime, the gel formed is thick and does not flow. Absence of gel
indicates non-hydraulic or fat lime. If gel flows, it indicates feebly hydraulic lime.

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X Balls of stiff lime paste are made and left for six hours. They are placed in a basin of
water. If expansion and disintegration of balls is observed, the lime is of type C. Little expansion
and numerous cracks indicate it to be class B lime.

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The analysis determines the cementation and hydraulic properties of lime.

Cementation value of Lime =





2.8A 1.1B 0.7C

D14E

where A = Silica oxide content (SiO 2 )
B = Aluminium oxide content (Al 2 O 3 )
C = Ferric oxide content (Fe 2 O 3 )
D = Calcium oxide content (CaO)
E = Magnesium oxide content (MgO)

€™—2„XSampling for testing lime should be done as quickly as possible so that the
material does not deteriorate. From each lot, three test samples are takes for quick lime as well
as for hydrated lime. The sample size for quick lime is given in Table 8.3 are that for hydrated
lime should not be less than 5 kg.

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