A waste fraction produced in the ore processing contains a large amount of black mineral, arfvedsonite. The fine, Si-containing, grains have a wide range of sizes making them suitable as a substitute for sand in brick production. The relative dark colour make the bricks darker than usual. They have a normal brick colour at the very low temperature of 850 deg C and a dark colour at 1025 deg C. The bricks consisted of 30% mine waste fraction and 70% red burning clay from Denmark.

The strength of the bricks was extremely high. The brick burned at 850 deg C had a strength 4 times stronger than normal bricks burned at 1025 deg C. When burned at the same temperature, 1025 deg C, the strength was 5 times higher.

Figure: Sample brick burned at temperatures from 850 to 1025 deg C (from right to left).

Contact: Andreas Peter Vestbø, aspv@teknologisk.dk, +45 7220 2827