Angularity Number of Coarse Aggregate
Procedure
Calibration of the metal cylinder-
Calibration of the cylinder to the nearest gram of the weight of water at 27°C that is required to fill it, shall be done, to avoid the presence of a meniscus above the rim of water.
Preparation of the test sample-
a) Take a sufficient quantity of aggregate, at least 10 kg, to be retained between pairs of IS Sieves from the following sets: 20 mm & 16 mm, 16 mm & 12.5 mm, 12.5 mm & 10 mm, 10 mm & 6.3 mm, 6.3 mm & 4.75 mm.
b) The aggregate shall be oven dried at a temperature of 100-110°C for 24 hours in shallow trays and then cooled in an airtight container.
Fill the metal scoop with the aggregate overflowing which has to be placed in the metal cylinder.
Fill one-third of the cylinder with aggregate and then subject it to 100 blows uniformly at the rate of 2 blows per second using a tamping rod. The rod shall be held vertically, having its rounded end 5 cm above the surface of the aggregate such that it falls freely.
Now, perform the same procedure as mentioned above for filling the second and third layers. The third layer should have just enough aggregate to fill the cylinder at level.
After tamping the third layer, the excess aggregate shall be struck off using the tamping rod as a straight edge.
Add individual pieces of aggregate which shall be rolled into the surface by rolling the tamping rod until no aggregate lifts the rod off the cylinder’s edge. After that, no downward force shall be exerted on the tamping rod and no aggregate piece shall be introduced into the cylinder.
Weigh the aggregate in the cylinder to the nearest 5 grams.
Make three separate determinations and calculate the mean weight of the aggregate. In case the result of anyone determination differs by more than 25 grams from the mean, three more deductions shall be made on the same sample and then the mean of all six deductions shall be estimated.