Experimental Study on Performance Optimization of Grouting Backfill Material Based on Mechanically Ground Coal Gangue...

Area of Science:

• Materials Science
• Geotechnical Engineering
• Environmental Science

Background:

• Grouting backfill controls mining-induced ground movement.
• Coal gangue (CG) is abundant but underutilized in backfill due to its properties.
• Existing backfill often relies on fly ash or clay, increasing costs and environmental concerns.

Purpose of the Study:

• To develop novel cemented grouting backfill materials (GBMs) using ground coal gangue (CG) powder as a primary component.
• To investigate the effects of grinding time, urea, and quicklime on CG powder properties and GBM performance.
• To optimize GBM formulations for improved slurry transportability and compressive strength, reducing reliance on fine aggregates.

Main Methods:

• Coal gangue was ground with and without urea for varying durations to alter particle size and phase composition.
• Slurry transportability (bleeding rate, slump flow) and compressive strength of GBMs were evaluated based on grinding time, solid concentration, and additive dosages.
• The influence of urea on hydrogen bonding and quicklime on pozzolanic reactions was analyzed.

Main Results:

• Grinding CG for 30-90 minutes significantly reduced particle size and induced crystal deformation.
• Urea addition improved slurry flowability by reducing water absorption and releasing encapsulated water.
• Quicklime enhanced GBM strength through accelerated pozzolanic reactions.
• A specific formulation (G60U3-based GBM-B2 with 5% quicklime) achieved a 1.25% bleeding rate, 205 mm slump flow, and 1.51 MPa seven-day unconfined compressive strength (UCS).

Conclusions:

• Ground CG powder can effectively replace traditional fine aggregates in GBMs.
• Urea and quicklime are effective additives for optimizing CG-based GBMs' performance.
• The developed GBMs offer a promising, sustainable solution for coal gangue utilization and mine subsidence control.