Building Materials, Third Edition

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Some of the tests to check the durability of stone are as follows. Of these tests, the crystallization
test is prescribed by Bureau of Indian Standards. The durability (soundness) test is performed
to find out the capacity of stone to resist disintegration and decomposition.

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X Break off the freshly quarried stone chippings to about the size of a rupee coin and
put them in a glass of clean water, one-third full. If the water becomes slightly cloudy, the stone
is good and durable. If water becomes dirty, it indicates that the stone contains too much of
earthy and mineral matter.

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— for frost resistance — Few small pieces of freshly quarried stone are immersed
in boiling solution of sulphate of soda (Glauber’s salt) and are weighed. These are then removed
and kept suspended for few days and weighed again. The loss in weight indicates the probable
effect of frost.

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— to check weather resistance — confirms the power of stones to withstand the
atmospheric conditions. 100 g of stone chips are kept in a 5 per cent solution of H 2 SO 4 or HCI
for 3 days. Then the chips are taken out and dried. The sharp and firm corners and edges are
indication of sound stone. This test is used to test the cementing material of sand stone.

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2@sƒ2IIPTAX Three test pieces of 50 mm diameter and 50 mm height are
dried for 24 hours and are weighed (W 1 ). The specimens are suspended in 14 per cent sodium
sulphate solution (density 1.055 kg/m^3 ) for 16 to 18 hours at room temperature (20° to 30°C).
The specimens are then taken out of the solution and kept in air for 4 hours. They are then oven
dried at a temperature of 105° ± 5°C for 24 hours and then cooled at room temperature. This
process is repeated for 30 cycles. The specimens are weighed (W 2 ) and the difference in weight
is found. This test is repeated thirty times and the loss in weight after every five cycles is
obtained. The change in weight indicates the degree of decay of stone. Durability should be
expressed in percentage as change in the weight. The average of three test results should be
reported as durability value.

Change in weight =^12

1

WW

W



where W 1 is the original weight of the specimen and W 2 is the weight of the specimen after 30
cycles of the test.

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2sAA Samples of stone weighing at least 25 kg each
of the unweathered spcimen should be obtained from quarry. To test stone for compressive
strength, specimen pieces in the form of cubes or cylinders are made from samples of rock. The
lateral dimension or diameter of test piece should not be less than 50 mm and the ratio of height
to diameter or lateral dimension should be 1:1. A minimum of three specimen pieces are tested
in each saturated and dry conditions. Separate tests should be made for the specimen when the
load to parallel to the rift and perpendicular to the rift. In all twelve test pieces should be used.
The specimen pieces of diameter or lateral dimension 50 mm are immersed in water at 20 to
30°C for 72 hours and are tested in saturated condition. The specimen pieces are also tested in