USE OF QUARRY FINES TO MAKE A CONSTRUCTION AGGREGATE

More than 390 aggregate and crushed stone mining operations in North Carolina produce tailings, usually composed of fine particles that cause environmental issues for storage and disposal. Disposal of tailings is a growing concern as more tailings are produced from the increasing demand for mined material. The purpose of this project was to produce a usable product from tailings, which in this case was a synthetic aggregate. The tailings used came from a granite quarry that produces crushed stone in North Carolina. The synthetic aggregate was produced by mixing colloidal silica with the tailings, pelletization, and then firing at 1,100°C in a laboratory kiln. The resulting aggregate was tested according to methods for coarse natural aggregate per the North Carolina Department of Transportation, which included sieve analysis, Los Angeles Abrasion, absorption, specific gravity and soundness tests. The synthetic aggregate produced passed all tests for NCDOT and in some instances rated better than a natural aggregate.