Metal crushed by Jaw crusher is flaky and have more corners. Out put of V.S.I. crusher is Cubical. Cubical material is having less surface area compared to flaky material. Flaky material have approximately 16% more area then the cubical material for the same volume/ weight of the particles. For Asphalting or Page3
In cement concrete, the overall surface of the metal must be coated with the asphalt or Cement slurry. It is obvious the more surface area will require more asphalt or Cement. More over the flaky material have more voids then cubical material. To fill this voids more fine aggregate are required. So again more surface area, so more consumption of Cement or Asphalt. Or in other words we can say the strength of the concrete increases for the same cement/ asphalt consumption.
This can be proved with the help of following example.
Flaky material means chip of the stone having more length and width compared to thickness.
Let us take a piece of stone having length 2 units X 1 unit X 0.5 unit So the Volume of this particle will be 2 X 1 X 0.5 = 1 cu unit.
At the same time the surface area of this particle will be 7 sq. unit.
( 2 X 2 X 1 + 2 X 2 X 0.5 + 2 X 1 X 0.5 = 7 sq unit.)
For the Same volume if we select a cubical particle it's length breath and height will be 1 Unit. So the Volume comes to 1 X 1 X 1 = 1 Cu unit. And surface area is 1 X 1 X 6 = 6 Sq. Units.
Thus for the same volume the surface area of the particle is increased by 16% approximately.
Crushed metal from Jaw crusher is generally flaky, and from V.S.I. Crusher is cubicle.
There fore there is 10 to 15% more strength for the same cement or asphalt Consumption. There is also a problem with flaky material while rolling it gets break and the broken surface do not have any coating of asphalt, makes the section weak. Hence more life of the road can be achieved by using the cubicle metal. Again less voids in the cubical metal so more dense concrete, so more strength.
For Crushing 6,000 cft (aprox. 250 tons) of 20 mm metal per day requires minimum for crushers of 20X12 or 24X10 size. The unwanted material produced is about 65% . Total H.P. required to run four crushers is about 120 H.P. ( Excluding Conveyors and Grading Screen etc)
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