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Unformatted text preview: the laboratory ( see 2 ).
7.3 Size of Specimens — The standard size shall be 15 × 15 × 70 cm.
Alternatively, if the largest nominal size of the aggregate does not
exceed 19 mm, specimens 10 × 10 × 50 cm may be used.
7.4.1 Beam Moulds — The beam moulds shall conform to
IS : 10086-1982*.
In assembling the mould for use, the joints between the sections of the
mould shall be thinly coated with mould oil and a similar coating of
mould oil shall be applied between the contact surfaces of the bottom of
*Specification for moulds for use in tests of cement and concrete. 14 IS : 516 - 1959 the mould and the base plate in order to ensure that no water escapes
during the filling. The interior faces of the assembled mould shall be
thinly coated with mould oil to prevent adhesion of the concrete.
7.4.2 Tamping Bar — The tamping bar shall conform to 6.1(b) of
IS : 10086-1982*.
7.5 Procedure, curing, age at test, number of specimens shall be the
same as in 2 and 5.
8. TEST FOR FLEXURAL STRENGTH OF MOULDED FLEXURE
8.1 This clause deals with the procedure for determining the flexural
strength of moulded concrete flexure test specimens.
8.2.1 The testing machine may be of any reliable type of sufficient
capacity for the tests and capable of applying the load at the rate
specified in 8.3. The permissible errors shall be not greater than ± 0.5
percent of the applied load where a high degree of accuracy is required
and not greater than ± 1.5 percent of the applied load for commercial type
of use. The bed of the testing machine shall be provided with two steel
rollers, 38 mm in diameter, on which the specimen is to be supported,
and these rollers shall be so mounted that the distance from centre to
centre is 60 cm for 15.0 cm specimens or 40 cm for 10.0 cm specimens.
The load shall be applied through two similar rollers mounted at the
third points of the supporting span, that is, spaced at 20 or 13.3 cm
centre to centre. The load shall be divided equally between the two
loading rollers, and all rollers shall be mounted in such a manner that
the load is applied axially and without subjecting the specimen to any
torsional stresses or restraints. One suitable arrangement which
complies with these requirements is indicated in Fig. 3.
8.3 Procedure — Test specimens stored in water at a temperature
of 24° to 30°C for 48 hours before testing, shall be tested immediately on
removal from the water whilst they are still in a wet condition. The
dimensions of each specimen shall be noted before testing. No
preparation of the surfaces is required.
8.3.1 Placing the Specimen in the Testing Machine — The bearing
surfaces of the supporting and loading rollers shall be wiped clean, and
any loose sand or other material removed from the surfaces of the
specimen where they are to make contact with the rollers. The specimen
shall then be placed in the machine in such a manner that the load shall
be applied to the uppermost surface...
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- Fall '13