Micro-mechanism on strength development and failure mode of cemented ultra-fine tailing backfill: Influence of binder

Authors：Cheng, Aiping^*; Xie, Sihang; Ji, Maowei; Huang, Shibing; Ye, Zuyang

Source：CONSTRUCTION AND BUILDING MATERIALS, 2023, 394: 132245.

DOI：10.1016/j.conbuildmat.2023.132245

• Cemented ultra-fine tailings backfill
• Hydration product
• Microstructure
• Mechanical properties

As cemented ultra-fine tailings filling method gains popularity, the demands for more economical and environment friendly binders rise. In order to better understand the influence of different binders on the mechanical properties of cemented ultra-fine tailings backfills (CUTBs), the CUTBs with solid materials of 72% for 3, 7, 14, 21 and 28d respectively were made by the water-quenched slag binder (WSB) and ordinary Portland cement (OPC). The microstructure characteristics and macro-mechanical properties of WSB-CUTB and OPC-CUTB at different ages were compared by uniaxial compressive strength (UCS), thermo-gravimetry (TG), X-ray diffraction (XRD) and surface electron microscope (SEM) tests. The results show that the strength development process of CUTBs with different binders has obvious phased characteristics, which can be divided into the initial germination (IG) stage, rapid growth (RG) stage and slow growth (SG) stage: the UCS of WSB-CUTB increases quicker than UCS of OPC-CUTB at the IG and RG stages, while the UCS of OPC-CUTB increases faster than UCS of WSBCUTB at the SG stage. The micro-mechanism on strength development of CUTBs with different binders was revealed by the evolutional characteristics in the amounts and shapes of hydration products: the amount and shape of AFt are the primary factors which impact the strength development at the IG and RG stages, while the amount and shape of C-S-H are the primary factors which impact the strength development at the SG stage. As the age increases, WSB-CUTB transitions from brittle failure to brittle-ductile failure, while OPC-CUTB transitions from ductile failure to brittle-ductile failure. The micro-mechanism on the failure modes of CUTBs with different binders was revealed by the different characteristics in the skeleton composed of hydration products: the CUTBs with AFt-dominated skeleton will transition from brittle failure to brittle-ductile failure, while the CUTBs with CS-H-dominated skeleton will transition from ductile failure to brittle-ductile failure. The research results provided theoretical guidance for applying CUTBs using WS as a binder.