Laboratory see 2 73 size of specimens the standard

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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 Apparatus 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 TEST SPECIMENS 8.1 This clause deals with the procedure for determining the flexural strength of moulded concrete flexure test specimens. 8.2 Apparatus 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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This document was uploaded on 10/01/2013.

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