Fusion of phosphate by-products and glass waste for preparation of alkali-activated binders

Landfilling of mine and industrial waste streams leads to environmental and economic issues. Sustainable management methods through valorization in manufacturing green construction materials are a current research interest. Here, a promising process for recycling mine tailings, such as phosphate sludge, is proposed. A mixture of phosphate sludge, kaolin clay (Al source), and glass waste (Si source) was prepared. Three fluxing agents were tested at 1000 degrees C (NaOH, Na2CO3, Na2SO4). Na2CO3 was selected as the most cost-effective. The precursors were alkaline activated with NaOH solution (2, 6, and 8 M). At 28 days of curing (20 h room temperature + 6 h 85 degrees C + room temperature), the best compressive strength (of more than 45 MPa) was obtained with 8 M NaOH. The reaction products, characterized by XRD, FTIR, SEM, and MAS NMR, show that the main reaction products is a gel N-A-S-H/(N,C)-A-S-H together with some unreacted crystalline phases formed during the fusion.

Automated summary

Landfilling of mine and industrial waste leads to environmental and economic issues. Current research focuses on sustainable management methods for recycling these waste streams into manufacturing green construction materials. This study presents a promising process for recycling mine tailings and identifies the optimal conditions through experimental investigations.