Building Materials, Third Edition

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The test piece is carefully centred in the shear tool and the bolts drawn up tightly. The tool is
then centred in the testing machine with the centre of the spherical block in contact with the
centre of the top portion of the plunger of the shear tool. The speed of the moving head of the
testing machine during load application should not be more than 1 mm/min. During the test,
the beam of the testing machine should be kept constantly in floating position. The shear
strength of test piece is calculated by

S =

2

W
A
where
S = Shear strength (N/mm^2 )
W = total maximum load (N)
A = area of the centre cross-section of test piece (mm^2 )
The average of all the three results separately for each condition is calculated and taken as
the shear strength of the test piece.

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Centre lines are laid over one surface of the slab. Thickness of the slab is measured at three
points approximately equidistant around the circumference of a 50 mm circle centred on the
intersection of the two center lines. The test piece is centred in the punching device keeping it
under the plunger. The punching device is then centred in the testing machine with the centre
of the spherical bearing block in contact with the centre of the top portion of the plunger of the
shear device. The speed of the moving head of the testing machine during load application
should not be more than 1 mm/min. During the test, the beam of the testing machine should
be kept constantly in floating position. The shear strength of the test piece is calculated by

S =



ƒ

WWti
DT
where
S = Shear strength (N/mm^2 )
Wt = total maximum load (N)
Wi = initial load (N) required to bring the plunger in contact with the surface of specimen
D = diameter (mm) of the plunger
T = thickness (mm) of the specimen
The average of all the three results separately for each condition is calculated and taken as
shear strength of the test piece.

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The selected test pieces of stone are crushed or broken and the material passing 20 mm IS Sieve
and retained on 10 mm IS Sieve is used for the test. The test piece weighing about 1 kg is
washed to remove particles of dust and immersed in distilled water in a glass vessel at room
temperature 20 to 30° C for 24 hours. Soon after immersion and again at the end of soaking
period, entrapped air is removed by gentle agitation achieved by rapid clock-wise and anti-
clock-wise rotation of the vessel. The vessel is then emptied and the test piece allowed to drain.