As cast in the mould along two lines spaced 200 or

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Unformatted text preview: as cast in the mould, along two lines spaced 20.0 or 13.3 cm apart. The axis of the specimen shall be carefully aligned with the axis of the loading device. No packing shall be used between the bearing surfaces of the specimen and the rollers. The load shall be applied without shock and increasing continuously at a rate such that the extreme fibre stress increases at approximately 7 kg/sq *Specification for moulds for use in tests of cement and concrete. 15 IS : 516 - 1959 cm/min, that is, at a rate of loading of 400 kg/min for the 15.0 cm specimens and at a rate of 180 kg/min for the 10.0 cm specimens. The load shall be increased until the specimen fails, and the maximum load applied to the specimen during the test shall be recorded. The appearance of the fractured faces of concrete and any unusual features in the type of failure shall be noted. 8.4 Calculation — The flexural strength of the specimen shall be expressed as the modulus of rupture fb, which, if ‘a’ equals the distance between the line of fracture and the nearer support, measured on the centre line of the tensile side of the specimen, in cm, shall be calculated to the nearest 0.5 kg/sq cm as follows: p × lf = --------------b b×d 2 when ‘a’ is greater than 20.0 cm for 15.0 cm specimen, or greater than 13.3 cm for a 10.0 cm specimen, or 3p × a f b = ---------------2 b×d when ‘a’ is less than 20.0 cm but greater than 17.0 cm for 15.0 cm specimen, or less than 13.3 cm but greater than 11.0 cm for a 10.0 cm specimen where b = measured width in cm of the specimen, d = measured depth in cm of the specimen at the point of failure, l = length in cm of the span on which the specimen was supported, and p = maximum load in kg applied to the specimen. If ‘a’ is less than 17.0 cm for a 15.0 cm specimen, or less than 11.0 cm for a 10.0 cm specimen, the results of the test shall be discarded. 8.5 Report — The following information shall be included in the report on each specimen: a) identification mark, b) date of test, c) age of specimen, d) curing conditions, e) size of specimen, f) span length, g) maximum load, h) position of fracture (value ‘a’), j) modulus of rupture (kg per sq cm), and k) appearance of concrete and type of fracture if these are unusual. 16 17 IS : 516 - 1956 FIG. 3 ARRANGEMENT FOR LOADING OF FLEXURE TEST SPECIMEN IS : 516 - 1959 9. DETERMINATION OF THE MODULUS OF ELASTICITY BY MEANS OF AN EXTENSOMETER 9.1 This clause specifies the procedure for making and curing test specimens, determining the modulus of elasticity of concrete in compression by means of an extensometer where the maximum nominal size of aggregate does not exceed 38 mm. 9.2 Size of Specimens — The test specimens shall consist of concrete cylinders 15.0 cm in diameter and 30.0 cm long. Alternately, other sizes of cylinders or square prisms may be used provided that the height/diameter or height/width ratio is at least 2. 9.3 Sampling, apparatus and procedure shall be as described i...
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