Mechanical Transformation of Fly Ash toward Its Utilization in Cemented Paste Backfill

Haijun Wang,Yun Duan,Piti Sukontasukkul

doi:10.1155/2021/5492272

Abstract

Fly ash (FA) showed low reactivity when being used to prepare the binder for cemented paste backfill (CPB). In the present work, wet-grinding treatment was used to increase the pozzolanic reactivity of FA and promote its sustainable utilization. The results showed that wet-grinding could be a suitable and efficient technology for FA pretreatment. Wet-grinding strongly modified the structure of FA by decreasing the crystalline phase content and the binding energy of Si 2p and Al 2p, contributing to the increase in pozzolanic reactivity of FA. The performance of CPB samples prepared by wet-ground FA was then optimized. This was reflected by the acceleration in the sample setting and increase in the strength development. The compressive strength of the CPB samples prepared by wet-ground FA for 120 min was increased by around 40% after curing for 28 d compared with the control samples.

Highlights

Coal is the most abundant natural mineral resources on the earth, and it is one of the main energy sources used by all countries [1,2,3]
Mechanical activation could decrease the particle size and increase the specific surface area and increase the contact area between the reactive substances [40]. erefore, in the present work, wet-grinding was used to pretreat Fly ash (FA) with the aim of increase its pozzolanic reactivity. e effect of wetgrinding was evaluated via physical structure, mineralogical modification, and dissolution behavior. e wet-ground FA was used in cemented paste backfill (CPB). e reaction kinetic, setting time, compressive strength development, and pore structure of the CPB samples were investigated
Wet-grinding significantly promoted the initial setting of the CPB samples. e reduction of the initial setting time was approximately 39.2% and 33.3% when the FA was ground for 120 h. is phenomenon was in line with the calorimetry test results, where the reaction was promoted by the wet-grinding, leading to faster formation of hydration gels. is would promote the samples setting

Summary

Introduction

Coal is the most abundant natural mineral resources on the earth, and it is one of the main energy sources used by all countries [1,2,3]. Flexural and compressive strength of 20% FA replaced mortar specimens cured in water, NaCl and MgSO4 solutions were higher compared with 50% FA replaced the mortar specimens For this regard, the replacement level of FA in concrete is typically limited in the range of 15–25% [31], which restricts the large scale utilization of FA. Liu et al [36] studied the consequences of temperature on the physical and mechanical properties and microstructure of CGFB when using FA in CPB at a mass ratio of cement: coal gangue: fly ash of 1 : 2:5. Cavusoglu et al [18] studied the effect of sodium silicate as an accelerator on early age mechanical and microstructure properties of cemented coal fly ash backfill (CCB). Mechanical activation could decrease the particle size and increase the specific surface area and increase the contact area between the reactive substances [40]. erefore, in the present work, wet-grinding was used to pretreat FA with the aim of increase its pozzolanic reactivity. e effect of wetgrinding was evaluated via physical structure, mineralogical modification, and dissolution behavior. e wet-ground FA was used in CPB. e reaction kinetic, setting time, compressive strength development, and pore structure of the CPB samples were investigated

Materials and Methods

Experiments

Results and Discussion

Mechanical Transformation of Fly Ash

Utilization of the Mechanically Treated Fly Ash in Cemented Paste Backfill