Strength development and self-desiccation of saline cemented paste backfill

Area of Science:

• Geotechnical Engineering
• Materials Science
• Sustainable Mining

Background:

• Mines often face freshwater scarcity, driving interest in saline water for cemented paste backfill (CPB).
• Stringent sustainability standards necessitate evaluating environmental impacts and engineering properties of CPB using saline water.

Purpose of the Study:

• To investigate the effect of mixing water salinity on the strength and self-desiccation of CPB.
• To explore the influence of binder type (Portland cement and slag) on saline CPB properties.

Main Methods:

• CPB samples were prepared using silica tailings and Portland cement type I with NaCl concentrations ranging from 0 to 300 g/L.
• Unconfined compressive strength (UCS) was measured over time.
• Self-desiccation was assessed through suction and volumetric water content measurements.

Main Results:

• Low NaCl concentrations (10-35 g/L) moderately increased UCS, while high concentrations (≥100 g/L) decreased it.
• High salinity (100-300 g/L) inhibited self-desiccation and cement hydration, negatively impacting UCS.
• Slag replacement (≥50%) with Portland cement enhanced UCS in saline CPB.

Conclusions:

• Saline water can be used in CPB, but optimal concentrations are crucial for strength development.
• Binder selection, particularly incorporating slag, can mitigate negative effects of salinity.
• Understanding salinity impacts is vital for sustainable and mechanically stable CPB.