Effect of overflow tailings properties on cemented paste backfill

Area of Science:

• Geotechnical Engineering
• Materials Science
• Environmental Science

Background:

• Overflow tailings (OFT) are a byproduct of mining operations.
• Cemented paste backfill (CPB) is used to fill underground voids.
• The properties of OFT can impact the performance of CPB.

Purpose of the Study:

• To evaluate the unconfined compressive strength (UCS), indirect tensile strength (ITS), microstructural properties, and environmental impacts of OFT-based CPB.
• To determine the suitability of OFT as a backfill material.
• To identify methods for improving CPB mechanical properties.

Main Methods:

• Experimental testing of CPB samples with OFT.
• Measurement of UCS and ITS.
• Microstructural analysis using Scanning Electron Microscopy (SEM) and Energy Dispersive Spectrometry (EDS).
• Nuclear Magnetic Resonance (NMR) for porosity assessment.

Main Results:

• OFT contains fine particles (<20 μm) and high oxide/sulfide content.
• CPB with OFT showed low UCS (<2 MPa) and ITS (<0.5 MPa) after 28 days.
• Sulfate content negatively affected strength by dissolving C-S-H gel and forming gypsum/ettringite.
• High porosity (25.0–33.1%) in CPB due to fine OFT negatively impacted UCS.
• Increasing cement content and solid concentration improved mechanical properties.

Conclusions:

• OFT can be used as backfill material, but its fine particle size and sulfate content present challenges.
• Sulfate-induced secondary products (gypsum, ettringite) reduce CPB strength and integrity.
• Optimizing cement content and solid concentration is crucial for enhancing OFT-based CPB performance.
• Further research may be needed to mitigate negative impacts of OFT properties on CPB.