Influence of water loss on mechanical properties of superfine tailing-blast-furnace slag backfill

In this study, two types of solid waste, namely superfine tailings and blast-furnace slag, were used to prepare backfills for filling mined-out void and to prevent surface subsidence in a mine in China. The tailing, binder, and paste were investigated using laser particle size analyzer, X-ray diffraction, and scanning electron microscopy, respectively. The backfills' strength with different water loss content was tested by uniaxial compressive tests and split Hopkinson pressure bar (SHPB) tests at strain rates ranging from 100 to 140 s(-1). A high-speed camera, digital image correlation (DIC), and numerical simulation were used to analyze the failure process of backfills. Results indicate that the static/dynamic strength of this backfill decreased because of considerable water loss, which may be related to the shrinkage of hydration products, such as C-(A)-S-H gels. Numerical simulations reproduced the failure process of the backfill in SHPB tests in comparison with the strain field calculated by DIC, including micro crack initiation at early stage of loading. (C) 2020 Elsevier Ltd. All rights reserved.