Application of tailing from small-scale gold mining in the production of soil-cement brick

ABSTRACT

The use of mining tailings meets the needs of circular economy as it increases the useful service life of this material. The present work evaluated the use of gold mining tailings (main raw material) in the production of soil-cement bricks formed by cement, tailings and soil. Mixtures were prepared with traces of cement CPII-Z-32 (1): tailings (5-10): soil (0-5) and subjected to physical characterization (particle size distribution - NBR 7181, specific mass by picnometry - helium gas, and specific surface area - BET), chemical (X-ray fluorescence), mineralogical (X-ray diffraction), geotechnical (consistency limits) and compaction tests (NBR 12023), the latter being used to determine the optimum moisture content used in the production of the bricks for each mixture. The mechanical parameters of the bricks were characterized according to NBR 8491 and the environmental assessment was carried out using NBR 10004. The soil-cement brick with the addition of 50% of soil reached values of ft = 3.1 MPa and A = 17.0%. However, even if it meets the specifications of NBR 8491, each mining tailing has unique characteristics of hazardousness. Therefore, the brick with 50% of soil was evaluated according to NBR 10004 in which it was classified as non-dangerous, but not inert due to the high content of aluminum. The higher the soil content, the closer these parameters are to the maximum allowed by the standard. The chemical evaluation showed phases of cement hydration that are related to the stabilization of contaminants such as cyanide. Finally, the tailing studied demonstrated their potential use as a raw material in the manufacture of soil-cement bricks by meeting the Brazilian’s specifications. It is suggested that new bricks with higher proportions of soil be evaluated.

Keywords
Sustainable mining; Mining circular economy; Tailing characterization; Ecological brick