At a rate of approximately 140 kgsq cmmin until the

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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 noted. 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 field, 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.

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