The raw materials mined from the quarry cannot be directly mixed into concrete. Raw material should be processed through crushing, screening and washing steps and made into the aggregate which can meet the grading requirement finally.
In order to break the mined materials into the prescribed particle size, we should carry on several crushing steps. Generally, we can divide the crushing processes into coarse crushing (breaking the original material to 70~300 mm), secondary crushing (crushing the raw material to 20~70 mm) and fine crushing (grinding the materials to 1~ 20 mm).
The materials need to be crushed by stone crusher machinery. The types of frequently-used stone crusher machinery are jaw crusher, cone crusher, roller crusher, impact crusher and hammer crusher.
Screening refers to the grading of natural or artificial mixed sand and gravel according to the particle size. There are two methods of aggregate screening operations including mechanical screening and artificial screening. Large and medium-sized projects generally adopt vibrating screen machine to finish the screening operation.
Washing is to remove the dirt from the sand and gravel aggregate. Common sand washing machines are the wheel bucket sand washer machine and spiral sand washer machine.
The mixture of gravel and water enters the grit chamber after the coarse aggregate is screened and washed. The mud and impurities spill over through the overflow of the grit chamber and the heavier gravel particles sink to the bottom. Next, we can use the sand maker to process the large-sized gravel.( related equipment: VSI sand maker or vertical shaft impact crusher.)
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