Conducted in general as a reliable indication of

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Unformatted text preview: ncrete shall be operated on the work site. The laboratory shall be fully equipped with apparatus for conductipg all the usual physical tests for concrete. The compression-testing machme shall have a capacity of not less than 100 metric tonnes ( or 100 tons ) and shall be capable of applying the test load at a uniform rate of application. 7.3 Test Records - A complete An accurate daily record shall be strength, water-cement ratio and concrete placed in each part of the record shall be kept of all operations. made of the location, mix, compressive other physical data pertaining to the structure. 7.3.1 The density, durability, imperviousness, generation and loss of heat, expansion and other physical characteristics of the concrete shall be tested as often as may be requi;ed to maintain the required properties. 7.4 Test Pieces-In general, not less than one sample shall be taken from approximately each 380 cu m ( or 500 cu yd ) of mass concrete and from 190 cu m ( or 250 cu yd) of reinforced concrete placed and for each class of concrete deposited in any one day’s run. Three cylinders or test beams shall be made from each sample. The normal number of coutrol specimens, however, may be changed at the discretion of the engineer-incharge. Samples for compression test shall be taken in the field in accordance with Appendix E of *IS : 456-1957. All specimens shall be moulded immediately after the taken. They shall be stored in a protected place under a moist condition at 27 f 2°C ( or 81 f 4°F ) without being disturbed or moved for at least 24 hours after being zast. 7.4.1 For standard 15 x 30 cm ( or 6 x 12 in ) cylinders, all aggregate having a maximum dimension of more than 4 cm ( or 14 in ) shall be removed by wet-screening the sample just before moulding the test pieces. For large cylinders, the maximum size of aggregate left in the sample shall not be more than one-fourth the diameter of the cylinder. Occasional specimens as large as can be tested in the field laboratory shall be cast without removing any aggregate. Such specimens shall be tested to establish the relation between unscreened and normally screened samples. The corrective factor thus determined shall be applied to the tested strength of screened specimens in recording the average daily unit strength of the concrete placed in the structure. 7.4.2 For dams and other large structures, all field specimens .shall be finally cured under m&t conditions at a constant temperature of 27 f 2°C ( or 81 f 4°F ) and at 85 percent relative humidity. For small jobs where a moist room is not available, the specimens shall be cured in accordance with the standard methodg of making znd storing compression test specimens in the field. l eared revisionin 196% S 33 IS : 457 - 1957 ‘i.4.3 Age of Specimeras - kegular tests shall be run at the age of 7 and 28 days, with occasional tests of representative specimens at 14 days and at 3. 6 and 12 months. Compression 7.5 Tests 7.5.1 For compre...
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This document was uploaded on 10/01/2013.

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