Experimental Study on Mechanical Properties of Paste Backfill with Flue-Gas Desulphurisation Gypsum under Combined Action of Dry–Wet Cycles and Chloride Erosion

Sheng Wang,Dawei Yin,Feng Wang,Zhen Zhang,Tianqi Jiang

doi:10.3390/min11080882

Abstract

Flue-gas desulphurisation gypsum—a solid waste from power plants—can be used to prepare paste backfill for reducing costs. Most paste backfills are exposed to dry–wet cycles and chloride salt-rich water in mines. Therefore, the mechanical properties and damage mechanisms of paste backfill with desulphurised gypsum under the coupling action of erosion due to chloride with different concentrations and dry–wet cycles were investigated using methods such as visual observation, mass measurement, uniaxial compression, acoustic emission, Fourier-transform infrared spectroscopy, X-ray diffraction analysis, and field-emission scanning electron microscopy. With an increasing number of dry–wet cycles, the mass, elastic modulus, and strength of the paste backfill exhibited the trend of increasing first and then decreasing. The failure mechanism changed from mainly vertical fractures to the alternating development of vertical and horizontal fractures. The surface denudation effect of the specimens in a solution with a higher concentration was more severe under the same number of dry–wet cycles. In this study, the laws governing the mass change, strength change, degree of surface denudation, and failure pattern of desulphurised gypsum-filled specimens under different concentrations of chloride salt and different numbers of dry–wet cycles were derived.

Highlights

Mining with backfilling has been adopted by many mines because of the ability to control mine subsidence and reduce ecological damage [1,2], but the cost of filling restricts its widespread application
Chen et al [5] studied various mechanical properties of red mud after it was added to filling paste using macroscopic and mesoscopic test methods, and the results provided a basis for the reasonable use of red mud
The results revealed the mechanical properties and damage mechanisms of paste backfill with desulphurised gypsum under the coupled effects of erosion due to chloride at different concentrations and dry–wet cycles

Summary

Introduction

Mining with backfilling has been adopted by many mines because of the ability to control mine subsidence and reduce ecological damage [1,2], but the cost of filling restricts its widespread application. No studies have been performed on the mechanical properties and deterioration of paste backfill with desulphurised gypsum under the coupled effects of dry–wet cycles [33] and chloride erosion [34]. The results revealed the mechanical properties and damage mechanisms of paste backfill with desulphurised gypsum under the coupled effects of erosion due to chloride at different concentrations and dry–wet cycles. The uniaxial compressive strength and elastic modulus of the paste backfill with desulphurised gypsum exhibited an overall pattern of a short increase followed by a sharp decrease under the coupled effects of chloride erosion and dry–wet cycles. This caused deterioration of the internal structures of the specimens, which wa1s1 of 23 reflected by reductions in the elastic moduli

AE Characteristics

Crystal Calibration Analysis with XRD Diffraction

Findings

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Conclusions