Manufacturing sand

Dredging watercourses for sand is becoming increasingly unpopular in today's world of environmental sensitivity, pushing aggregates producers towards substitutes for natural products. In March 2005, Ecuador's fi rst Merlin-vertical shaft impact (VSI) crusher was installed to produce a -2.4mm manufactured mortar sand. The Merlin-VSI crusher was part of a complete new plant supplied by Sandvik Spain for INTACO ECUADOR at Guayaquil.

An RP108 Dual Drive crusher, with 2 x 132 kW motors, was chosen to operate in closed circuit at 55M/sec. to produce 55 tonnes per hour of -2.4mm mortar sand. The raw feed size was -50mm +20mm and the crusher was operated in closed circuit with a fi ve-deck screen.

The feed material was a clean blasted Limestone and was transported to the site for processing by truck. Due to severe restrictions and availability on the use of water, the whole process is dry in operation.

The -75µ content is not screened out of the product. Tests have revealed that as clean rock is fed into the system, the output from the Merlin-VSI is also clean with no contamination. The usual requirement to wash out the -75µ content to remove deleterious material (as would be the case for natural sand), is therefore not required. Tests have shown that less cement is required in the fi nal product and that compressive and fl exible strengths have also increased.

The contractual requirements of the customer was for the Merlin-VSI to produce 55 tonnes per hour of -2.4mm sand. The typical grading required was:

• 0 - 0.09mm = 17%

• 0.09 - 0.6mm = 36%

• 0.6 - 1.2mm = 24%

• 1.2 - 2.4mm = 23%

After initial commissioning, and the crusher running in Bi-Flow mode, all of the above gradation requirements were achieved, and the rate of production was measured at 55 tonnes per hour.