Crushing test of Aggregate
The crushing value test of aggregate provides the resistance of an aggregate sample to crushing under a gradually applied compressive load. Generally, the test is conducted on aggregate passing 12.5 mm and retained on a 10 mm sieve. The aggregate sample is filled in a cylindrical mold and a load of 40 tons is applied through a plunger in a compression testing machine.
The crushed aggregate sample which is finer than 2.36 mm is separated and expressed as a percentage of the original weight taken in the Mould. The percentage of weight passed through the 2.36m IS sieve is known as the Aggregate crushing value.
In situations, when the aggregate value is 30 or higher the result may be a mistake and in such cases, the “ten percent fines value” should be determined and used instead
Procedures for Conduction of test:
1. Put the sample in 3 layers, each layer being subjected to 25 strokes using the tamping rod (W1) of the measuring cylinder
2. Put the material in the test cylinder and now put the aggregate in three layers and temped by temping rod in 25 number of blows
3. Level the surface of aggregate carefully and insert the plunger so that it rests horizontally on the surface. Care being taken to ensure that the plunger does not jam in the cylinder.
4. Place the cylinder with plunger on the loading platform of the compression testing machine.
Apply load at a uniform rate so that a total load of 40T is applied in 10 minutes.
Release the load and remove the material from the cylinder.
Sieve the material with 2.36mm IS sieve, care being taken to avoid loss of fines.
Weigh the fraction passing through the IS sieve (W2).
Credit: @SagarmathaEngineeringCollege
Timecodes:
0:00 Introduction
0:22 Apparatus
0:40 Temping in test cylinder
2:00 Load application in Compression testing Machine
3:20 Sieve through 2.36 mm IS sieve
The links for the previous videos on Test of Highway Materials are :
• Practical Field Works Civil Engineering
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