Preparation and Hydration Mechanism of Alkali-Activated Slag and Construction Demolition Waste Backfill Materials

Le résumé fourni par la source

This study investigates the feasibility of utilising alkali-activated slag (AAS) and construction demolition waste (CDW) as cemented paste backfill materials. The fluidity, unconfined compressive strength, bleeding rate, and sulfate resistance of AAS-CDW backfill systems were systematically analysed. Hydration mechanisms were characterised using SEM-EDS and XRD. A novel backfill system and application process were developed and implemented in Jining Coal Mine, Shandong Province. Results indicate that a 30% waste red brick addition enhances 28-day compressive strength by 9.3% and reduces the bleeding rate by 32%, while a 10% fly ash addition optimises slurry fluidity. Notably, the AAS-based backfill exhibits superior mechanical properties and sulfate resistance compared to ordinary Portland cement (OPC)-based systems. The 28-day compressive strength of the AAS backfill reached 5.31 MPa, which is 53.4% higher than that of the OPC backfill, and its strength loss rate after sulfate attack was reduced by 13%. The solid waste utilisation rate of the AAS backfill approaches 100%. Hydration products primarily comprise ettringite (Aft), C-A-S-H gel, and hydrotalcite (HT), resulting in higher compactness than OPC-RA mixtures.

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