Producing manufactured sand is a construction material produced by crushing or grinding, screening, and classifying rock or gravel to meet specifications set forth by the ASTM, Federal and State Highway Departments, and the U.S. Army Corp of Engineers.
The demand of economical and efficient sand producing crusher has grown as natural sand deposits diminish. Prior to the development of the Gyradisc Crusher, manufactured sand was produced by rod mills, impact crushers , and roll crushers. The rod mill is capable of producing fines, but the power and metal cost and the tendency to produce an excess of extreme fines are the principal factors that contribute to the relatively high final cost of rod mill sand.
Impact crushers develop high wear rates when crushing abrasive materials and also normally create an excess of extreme fines. Most specifications permit only 2 to 10 percent passing a No. 100 sieve, any excess produced in this range must be removed. Roll Crushers, on the other hand, have difficulty in producing a sufficient quantity of fines in the 30, 50 and 100 sieve sizes. Roll shell wear contributes to seize control problems and develops high circulating loads.
Experience has shown that material which is excessively wet, sticky or muddy is generally unsuitable for producing manufactured sand in the Gyradisc Crusher. There is no exact moisture content at which the Crusher will become ineffective. An examination of the potential feed by Rexnord representative will confirm the suitability of the material.
Moisture problems can usually be overcome through the use of dewatering screens before the crusher.
Most materials that qualify as sound construction aggregate can be used as raw material for the sand circuit.