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Unformatted text preview: sed continuously at a rate of approximately
140 kg/sq cm/min until the resistance of the specimen to the increasing
load breaks down and no greater load can be sustained. The maximum
load applied to the specimen shall then be recorded and the appearance
of the concrete and any unusual features in the type of failure shall be
5.6 Calculation — The measured compressive strength of the specimen
shall be calculated by dividing the maximum load applied to the
specimen during the test by the cross-sectional area, calculated from the
mean dimensions of the section ( see also 4.5.1 of IS : 1199-1959* ) and
shall be expressed to the nearest kg per sq cm. Average of three values
shall be taken as the representative of the batch provided the individual
variation is not more than ± 15 percent of the average. Otherwise repeat
tests shall be made.
5.6.1 A correction factor according to the height/diameter ratio of
specimen after capping shall be obtained from the curve shown in Fig. 1.
The product of this correction factor and the measured compressive
strength shall be known as the corrected compressive strength, this
being the equivalent strength of a cylinder having a height/diameter
ratio of two. The equivalent cube strength of the concrete shall be
determined by multiplying the corrected cylinder strength by 5/4.
5.6.2 Report — The following information shall be included in the report
on each test specimen:
a) identification mark,
b) date of test,
c) age of specimen,
*Since revised. 11 IS : 516 - 1959
d) curing conditions, including date of manufacture of specimen in the
e) weight of specimen,
f) dimensions of specimen,
g) cross-sectional area,
h) maximum load,
j) compressive strength, and
k) appearance of fractured faces of concrete and type of fracture, if
these are unusual. FIG. 1 CORRECTION FACTOR FOR HEIGHT-DIAMETER RATIO OF A CORE
6. DETERMINATION OF COMPRESSIVE STRENGTH OF
CONCRETE USING PORTIONS OF BEAMS BROKEN IN
FLEXURE (“EQUIVALENT CUBE” METHOD)
6.1 This clause specifies the procedure for determining the compressive
strength of concrete using portions of beams broken in flexure as the test
specimens. The results obtained from this test are approximately equal
to, and on the average may be up to 5 percent greater than those
obtained by the test specified in 5.
NOTE — For method of making and testing flexure test specimens, see 7. 6.2 Apparatus
6.2.1 Compression Testing Machine — The testing machine shall comply
in all respects with the requirements of 5.2.1. 12 IS : 516 - 1959
6.2.2 Bearing Plates — Two metal bearing plates not less than 6.5 mm
or more than 19 mm thick shall be provided. The plates shall be 10 cm
square for the beams 10 cm in depth and 15 cm square for the
beams 15 cm in depth with the surfaces machined to a permissible
variation not exceeding 0.02 mm. The distance between the opposite
edges shall be the specified size ± 0.02 mm and the angle between the
edges shall be 90° ± 0.5°.
6.3 Test Specimens...
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This document was uploaded on 10/01/2013.
- Fall '13