Clause 2.8 Size of Test Specimens -. Test specimens cubical in shape shall be 15 X 15 X 15 Cm. If the largest nominal size of the aggregate does not exceed 2 ecm, 10 cm cubes may be used as an alternative. Cylindrical test specimens shall have a length equal to twice the diameter. They shall be 15 cm in diameter and 30 cm long. Smaller test specimens shall have a ratio of diameter of specimen to maximum size of aggregate of not less than 3 to 1, except that the diameter of the specimen shall be not less than 7·5 cm for mixtures containing aggregate more than 5 percent of which is retained on IS Sieve 480.