Early-age strength property improvement and stability analysis of unclassified tailing paste backfill materials
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Early-age strength property improvement and stability analysis of unclassified tailing paste backfill materials Qian Zhou 1), Juan-hong Liu 1,2,3), Ai-xiang Wu 1,3), and Hong-jiang Wang 1,3) 1) School of Civil and Resource Engineering, University of Science and Technology Beijing, Beijing 100083, China 2) Beijing Key Laboratory of Urban Underground Space Engineering, University of Science and Technology Beijing, Beijing 100083, China 3) Key Laboratory of High-Efficient Mining and Safety of Metal, Ministry of Education, University of Science and Technology Beijing, Beijing 100083, China (Received: 23 October 2019; revised: 26 December 2019; accepted: 26 December 2019)
Abstract: High-density tailings, small cementitious materials, and additives are used for backfill materials with poor early compressive strength (ECS), which may greatly affect the mining and backfill cycle, to prepare paste backfill materials (PBMs) with a high ECS. The effects and mechanisms of different early strength agents on the property of PBM are investigated. The action mechanism of additives on the properties of PBM is also analyzed through X-ray diffraction, scanning electron microscope, and energy dispersive spectrometry. Results show that the effects of single-component additives 1, 3, and 6 are better than those of the other additives, and their optimal dosages are 3wt%, 1wt%, and 3wt%, respectively. The optimum multicomponent combinations are 1wt% of additive 1 and 1.5wt% of additive 6. The ECS of the paste with additive 10 increases to a greater extent than that of the other pastes because of the synergistic action of additive 1 with additive 6. The hydration product of Ca(OH)2 is consumed, and more C –S –H gels are generated with the addition of additives to paste. Tailings particles, ettringite crystals, and gels intertwined with one another form a dense net-like structure that fills the pores. This structure can significantly improve the ECS of PBM. Keywords: paste backfill; unclassified tailings; binder powder; early-age strength; microstructure
1. Introduction The solid waste of tailings produced from metallic ore not only occupies a large area of surface resources but also easily causes mud-rock flow and tailings dam failure. The existence of a large number of underground voids threatens the safety of underground mining operations and likely induces mining earthquakes and surface subsidence [1–6]. With cemented paste backfill technology, surface solid waste can be formed into paste that can be placed into underground voids. It can solve environmental pollution, security flaws, and resource wastage caused by exploitation. Paste technology has been widely accepted and applied worldwide because of its advantages, including safety, environmental protection, economic value, and high efficiency [7–10]. A paste backfill material (PBM) is a toothpaste-like fluid with good fluidity, plasticity, and stability; it is an engineered mixture frequently consisting of thi
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