Geopolymerization: A novel method for manufacturing tiles from copper mine tailings

This study investigated the technical feasibility of valorizing copper mine tailings as the sole aluminosilicate precursor to produce novel geopolymer tiles (geo-tiles) using a low-energy process. The alkali activator used to make geo-tiles was aqueous NaOH (15 M). Two input factors were optimized: First, the particle size distribution (PSD) classification, defined as the sieve size tailings were passed through prior to use (150, 212, 300, 425 and 600 µm), and second, the forming pressure applied to shape geo-tiles (0.1, 0.2, 0.3 and 0.4 MPa) prior to curing at 105 °C for 48 h. Geo-tiles were also evaluated against key International (ISO 13,006) and South African (SANS 1449) standards, compliance with mechanical performance benchmarks therein (breaking strength and modulus of rupture (MOR)) determined mechanical feasibility. Response surface methodology analysis indicated that PSD had a larger influence on MOR than forming pressure. Optimal geo-tiles (PSD = 150 µm; forming pressure = 0.1 MPa) achieved breaking strength of 986±151 N, MOR of 18.5 ± 0.7 MPa and water absorption of 8.5 ± 1.5%. Since results exceeded the targets of 800 N and an individual minimum of 16 MPa for water absorption between 6 – 10%, geo-tile production proved mechanically feasible. Embodied energy for geo-tiles (10.9 kWh/m 2 ) was 60% and 35% lower than conventional porcelain and cement tiles, respectively. Whilst geo-tile abrasion resistance to American standards (ASTM C418 , C936 ) indicated suitability for sidewalks and driveways, additives are recommended for metal leaching results per XRF and ICP-MS analyses to environmentally comply with residential versus exclusively industrial construction applications.