Compaction factor:

In this test, the hopper 'A' is filled up with the concrete mix up to the top. By opening the trap door of hopper 'A', the concrete is allowed to fall in hopper 'B'. By doing so, some standard amount of work has been done on concrete. Now, by opening the trap door of hopper 'B', the concrete is allowed to fall in the cylinder 'C'. Again some fix amount of work is done on the same concrete.  The concrete thus received in the cylinder had been compacted by standard amount of work by falling through hopper-to-hopper and hopper to cylinder. The concrete in the cylinder is then flushed with the top of cylinder. Let the weight of this concrete in the cylinder is W'. Now, the same concrete mix is poured in layers in the cylinder in specified manner and is compacted in standard manner to achieve the full compaction. Let the weight of the fully compacted concrete in the cylinder is W. The compaction factor (c. f.) is then given by the following formula:

c. f . = W '/W

This test relates the workability requirements more closely as compared to other tests. However, the compaction effort provided in this method does not match with the any compaction methods used at site. Moreover, the compacted concrete sample being blind (as it is closed in metallic cylinder), one cannot observe whether compacted concrete is free of segregation or not. Also, the compacting effort used in this method is such that for harsh mix the degree of compaction achieved in the test is always less than the actual degree of compaction, which could be achieved at sites by using conventional compaction methods.