Effects of Kaolin Addition on Mechanical Properties for Cemented Coal Gangue-Fly Ash Backfill under Uniaxial Loading

Faxin Li, Dawei Yin, Chun Zhu, Feng Wang, Ning Jiang and Zhen Zhang
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Faxin Li: State Key Laboratory of Mine Disaster Prevention and Control, Shandong University of Science and Technology, Qianwangang Road 579, Qingdao 266590, China
Dawei Yin: State Key Laboratory of Mine Disaster Prevention and Control, Shandong University of Science and Technology, Qianwangang Road 579, Qingdao 266590, China
Chun Zhu: School of Earth Sciences and Engineering, Hohai University, Xikang Road 1, Nanjing 210098, China
Feng Wang: State Key Laboratory of Mine Disaster Prevention and Control, Shandong University of Science and Technology, Qianwangang Road 579, Qingdao 266590, China
Ning Jiang: State Key Laboratory of Mine Disaster Prevention and Control, Shandong University of Science and Technology, Qianwangang Road 579, Qingdao 266590, China
Zhen Zhang: State Key Laboratory of Mine Disaster Prevention and Control, Shandong University of Science and Technology, Qianwangang Road 579, Qingdao 266590, China

Energies, 2021, vol. 14, issue 12, 1-18

Abstract: In this investigation, six groups of cemented coal gangue-fly ash backfill (CGFB) samples with varying amounts of kaolin (0, 10, 20, 30, 40, and 50%) instead of cement are prepared, and their mechanical properties are analyzed using uniaxial compression, acoustic emission, scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. The uniaxial compressive strength, peak strain, and elastic modulus of CGFB samples decreased with the kaolin content. The average uniaxial compressive strength, elastic modulus, and peak strain of CGFB samples with 10% amount of kaolin are close to that of CGFB samples with no kaolin. The contribution of kaolin hydration to the strength of CGFB sample is lower than that of cement hydration, and the hydration products such as ettringite and calcium-silicate-hydrate gel decrease, thereby reducing strength, which mainly plays a role in filling pores. The contents of kaolin affect the failure characteristics of CGFB samples, which show tensile failure accompanied by local shear failure, and the failure degree increases with the kaolin content. The porosity of the fracture surface shows a decreasing trend as a whole. When the amount of kaolin instead of cement is 10%, the mechanical properties of CGFB samples are slightly different from those of CGFB samples without kaolin, and CGFB can meet the demand of filling strength. The research results provide a theoretical basis for the application of kaolin admixture in fill mining.

Keywords: kaolin; cemented coal gangue-fly ash backfill sample; mechanical properties; macroscopic failure; microstructure (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2021
References: View complete reference list from CitEc
Citations: View citations in EconPapers (3)

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