WINNING
All photos by Kal Tire
Most quarry fines are produced during the crushing, milling, and size classification of quarried rock to produce single-size aggregate.
material, such as quartzite or dolerite, will produce fewer fines compared to a fine-grained material such as limestone or dolomite. To produce less blasting-related fines, the blasting method can be adapted to produce larger fragmentation, but this would require a trade-off study between the costs of blasting and crushing. A reduction in blasting costs may be offset by increased crushing-related cost or vice versa.
Rocks that contain a high percentage of flaky material, such as mica, have the effect of gradually blinding the screen, reducing the overall efficiency of the screen and product quality. In both crushing and screening, it is advisable to keep the moisture content less than five per cent.
The type of impact applied in a vertical shaft impact crusher can also influence the production of fines. Rock-on-rock
Oversize pieces of rock will slow the loading process and may exceed the maximum screen size set for the primary crusher, leading to reduced efficiency.
26 _ QUARRY SA | JULY / AUGUST 2018