Influence of phosphate binders on the physical and mechanical properties of magnesia carbon monolithics composed of recycled refractory aggregates

Abstract

In this study, the effect of using phosphate bonding materials such as sodium hexametaphosphate (SHMP) and sodium tripolyphosphate was investigated in the presence of water and recycled magnesia carbon (MgO–C) refractory aggregates as raw materials. For this purpose, different compounds are prepared, and some parameters such as bulk density, volume per cent of apparent porosity and cold crushing strength were measured at different temperatures (200, 500 and 1100°C), and phase and microstructure studies were performed by X-ray diffraction, SEM and energy dispersive spectroscopy. Statistically, effects of the factors were also determined using the analysis of variance method. Results indicated that MgO–C monolithic refractory samples were successfully produced from recycling the spent MgO–C bricks, and use of these phosphate binders especially that of 5 wt-%SHMP produce some phosphate bonds like Mg₂P₂O₇, Mg₃(PO₄)₂ and AlPO₄ and improve the physical and mechanical properties.

Keywords:

• Magnesia carbon
• Sodium hexametaphosphate
• Sodium tripolyphosphate
• Spent brick
• Monolithic refractories
• Recycling

Acknowledgements

The authors are thankful to Mr Chami in Advanced Materials Research Center in IslamicAzad University of Najafabad branch for their helpful cooperation.