Influence of Particle Size on the Basic and Time-Dependent Rheological Behaviors of Cemented Paste Backfill
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Influence of Particle Size on the Basic and Time-Dependent Rheological Behaviors of Cemented Paste Backfill X.J. Deng, B. Klein, D.J. Hallbom, B. de Wit, and J.X. Zhang (Submitted September 17, 2016; in revised form May 6, 2018) The rheological properties of cemented paste backfill (CPB) significantly influence the materials transportability, and these properties are strongly affected by the materials particle size. This paper mainly focuses on the influence of particles size on the basic and time-dependent rheological behaviors of CPB. The rheology tests and microstructure analysis were conducted using multiple CPB samples with different solid contents, cement contents, and particle sizes. Results show that the CPB samples with finer particle sizes have a lower apparent maximum packing density compared to the CPB samples with larger particle sizes. Fresh CPB mixture samples exhibit shear thinning characteristics which are more pronounced in samples with larger particle sizes and higher volume fraction to apparent maximum packing density (/=/m ) ratios. When the /=/m ratio is lower than 0.875, the samples with finer particle sizes display a higher yield stress but less time-dependent rheological behavior than coarser samples. In all CPB samples that contained cement, the shear stress decreases first and then increases over the shearing time when samples are sheared at a constant shear rate. In the CPB samples without cement, samples with finer particle sizes show lower apparent viscosities, and it is observed in the sample with the finest particles that the shear stress only decreases over the shearing time. Moreover, it is found that the number of hydration products and the rate of particle sedimentation are both higher in samples with larger particle sizes, which result in these samples having higher apparent viscosities. Keywords
apparent maximum packing density, cemented paste backfill, particle size, rheological behavior, timedependent, yield plastic
1. Introduction The mining industry has seen a much greater emphasis placed on safety and sustainability in recent years (Ref 1, 2), and one technology being used by mines to improve their practices in these areas is backfill (Ref 3). Cemented paste backfill (CPB) technology (Ref 4-8) is widely used across the industry for filling excavated stopes with a mixture of mine waste materials such as tailings, slags, and water (Ref 9, 10). Normally, CPB is prepared in a backfill plant located on the surface of a mine and is transported underground to mine stopes by pumps and/or gravity through a network of pipelines (Ref
X.J. Deng, College of Resources and Safety Engineering, China University of Mining and Technology, Beijing 100083, China; and State Key Laboratory of Coal Resources and Safe Mining, China University of Mining and Technology, Xuzhou 221116, China; B. Klein and B. de Wit, Norman B. Keevil Institute of Mining Engineering, University of British Columbia, 517C Frank Forward, 6350 Stores Road, Vancouver, BC V6T 1Z4, Canada; and D.J.
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