Test for determination of aggregate abrasion value
The aggregate abrasion value gives the resistance of an aggregate against wearing. The test involves taking specified quantity of standard size material along with specified number of abrasive charge in a standard cylinder and revolving it for certain specific revolutions. The particles smaller than 1.7mm sizes are separated out. Abrasion value should not be more than 30 percent for wearing surfaces and not more than 50 percent for concrete other than wearing surface.Generally for 5kg of sample 12 nos. of sphere approx.48 mm dia. and each weighing between 390 to 445 gm are used. Test sample and abrasive charge are placed in the Los Angeles Abrasion testing machine and the machine is rotated at a speed of 20 to 33 rev/min. The machine is rotated about 500 revolutions.
Test for determination of Flakiness Index
The flakiness index of aggregate is the percentage by weight of particles in it whose least dimension (thickness) is less than 3/5th.
Test for determination of Elongation Index of their mean dimension
This test is not applicable to sizes smaller than 6.3mm. This test is conducted by using a metal thickness gauge.
The elongation index of an aggregate is the percentage by weight of particles whose greatest dimension (length) is greater than 1.8 times their mean dimension. The elongation index is not applicable to sizes smaller than 6.3mm. This test in conducted by using metal length gauge.
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