Application of Coal Fly Ash to Replace Lime in the Management of Reactive Mine Tailings

A site-specific study is carried out to assess the suitability of utilizing Atikokan coal fly ash (AFA) as a buffering material to control and mitigate the generation of acid rock drainage from reactive Musselwhite Mine tailings. The physical, chemical, and mineralogical properties of the fly ash and mine tailings are determined via experiments, followed by six kinetic column permeation tests to monitor the leaching properties of the coal fly ash and coal fly ash mine tailings mixtures. The results of the experiments indicate that the hydraulic conductivities of high-calcium AFA and the ashtailings mixtures are significantly reduced upon contact with acidic drainage. The pH of the pore fluid has increased from acidic (pH 4) to alkaline (pH 8 and above). Chemical analyses after the kinetic column permeation tests further indicate that concentrations of regulated elements in the leachate from the ashtailings mixtures are well below the guideline limits set by the Ontario environmental authority for accelerated flow conditions.Key words: coal fly ash, mine tailings, hydraulic conductivity, pH, heavy metals, acid rock drainage.

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Characterisation of Industrial Side Streams and Their Application for the Production of Geopolymer Composites

Minerals ◽

10.3390/min11060593 ◽

2021 ◽

Vol 11 (6) ◽

pp. 593

Author(s):

Mehmet Emin Küçük ◽

Teemu Kinnarinen ◽

Juha Timonen ◽

Olli Mulari ◽

Antti Häkkinen

Keyword(s):

Fly Ash ◽

Mine Tailings ◽

Coal Fly Ash ◽

Steel Slag ◽

Bottom Ash ◽

Spherical Particles ◽

Green Liquor ◽

Green Liquor Dregs ◽

Biomass Fly Ash ◽

Geopolymer Composites

This study focuses on characterisation of side streams including biomass fly ash, biomass bottom ash, coal fly ash, green liquor dregs, limestone mine tailings, and electric arc furnace steel slag from different industrial locations in Finland. It was found that the fly ash samples contained the highest Al2O3 and SiO2 concentrations, a large number of spherical particles of small sizes and high specific surface areas. Fly ashes and steel slag were observed to contain higher amounts of amorphous phases compared to the other side streams. The high loss on ignition value of the coal fly ash and green liquor dregs was found to exceed the limitations for their application in geopolymer composites. Despite their relatively high concentrations in ashes and steel slag, the leaching tests have shown that no hazardous metal leached out from the streams. Finally, test specimens of geopolymer composites (GP2) were prepared by the application of biomass fly ash, bottom ash, and limestone mine tailings without any pre-treatment process, in addition to the ordinary Portland cement-(R) and metakaolin-based geopolymer composites (GP1). The measured compressive (14.1 MPa) and flexural strength (3.5 MPa) of GP2 suggest that it could be used in concrete kerbs and paving flags. The data has also shown that over 500% of the compressive strength was developed between 7 and 28 days in GP2, whereas in the case of reference concrete (R) and the metakaolin-based geopolymer composite (GP1) it was developed in the first 7 days.

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Lead-Zinc Mine Tailings Valorization Through Fly Ash-Based Geopolymer for Building Material: Synthesis, Microstructure, and Mechanical Properties

10.21203/rs.3.rs-996321/v1 ◽

2021 ◽

Author(s):

ALSENY BAH ◽

Andrea ORTIZ Ramos ◽

Feng Daolun ◽

jie Jin ◽

Alhassane Bah ◽

...

Keyword(s):

Compressive Strength ◽

Fly Ash ◽

Mine Tailings ◽

Unconfined Compressive Strength ◽

Building Materials ◽

Fourier Transforms ◽

Coal Fly Ash ◽

Environmentally Friendly ◽

Cement Industry ◽

Moderate Amount

Abstract Using geopolymerization to value mining wastes in order to meet construction demand is a sustainable and environmentally friendly strategy. Fly ash geopolymer materials have been developed to address environmental issues such as climate change caused by the emissions of CO2 from coal fly ash plants, mining, and cement industry into the atmosphere. The main objective of this study is to study the feasibility of using mine tailings to produce environmentally friendly building materials (so-called geopolymer products) with excellent mechanical strength through fly-based geopolymer technology. Fly ash (F.A.) and mine tailings (M.T.) were utilized as raw materials and gypsum (G.Y.) as additives. Sodium hydroxide (NaOH) at (5-10M) and sodium silicate (water glass) constituted the alkaline solution and were added separately to the mixture. The mechanical property and microstructure of the geopolymers were assessed by performing the Unconfined Compressive Strength (UCS), Scanning Electron Microscopy (SEM), X-ray diffractions (XRD), and Fourier transforms infrared (FTIR). A 24 MPa was achieved at 10M NaOH with 100% F.A. Besides, low UCS values were obtained with only M.T. as a binder. The SEM imaging analysis confirmed similar results showing that the geopolymer specimens cured with 100% of F.A. at 10M NaOH with a moderate amount of gypsum are denser than those prepared without gypsum at 5M. The findings revealed that F.A., MT, and gypsum, together with the alkali reagents, influenced the geopolymerisation process. These factors responded effectively to the microstructural performance(increasing density), resulting in increased unconfined compressive strength.

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