Item – Thèses Canada

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Numéro d'OCLC
300581249
Lien(s) vers le texte intégral
Exemplaire de BAC
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Auteur
Fried, Éliane,1981-
Titre
Étude du phénomène d'hy[d]ratation et du comportement à la lixiviation des remblais miniers en pâte cimentés.
Diplôme
Thèse (M. Sc. A.)--École polytechnique de Montréal, 2007.
Éditeur
Ottawa : Library and Archives Canada = Bibliothèque et Archives Canada, [2008]
Description
3 microfiches
Notes
Étude du phénomène d'hyratation et du comportement à la lixiviation des remblais miniers en pâte cimentés
Comprend des références bibliographiques
Résumé
The use of cemented paste backfill (CPB) technology for underground mine has become a common practice worldwide in the mining industry. This method is similar to a solidification/stabilization process using hydraulic binders. Indeed, paste backfill is produced by mixing mine tailings with a hydraulic binder and water to obtain a paste consistency, making the transport to the stopes easier. The binder gives mechanical resistance to the CPB after curing. The filled stopes participate to the ground support that allows maximizing orebody extraction. Moreover, the binder may induce physical retention of metals by entrapment in the hydrated phases. Sulfide oxidation by oxygen and water produces acidity, sulfates and metals in solution. However, it was demonstrated that this reaction is limited in CPB. The cement phases contribute to acid neutralization (if generated) and to metal retention by different mechanisms. The stabilized materials have particular mechanical and hydraulic properties. Several analytical methods used to characterize the cement phases in the CPB were studied. The most common analysis that are used in this study are spectroscopic and thermogravimetric methods. The most efficient method to reveal the speciation of metals in a cement matrix is the X-ray absorption spectrometry (EXAFS). However, it is a very expensive and inaccessible method. To study the leaching behaviour of stabilized materials and the speciation of metals in cement phases, a summary of the existing methods was realized. The most common leaching method is the batch test. There are a lot of different types of leaching experiments and leaching set-up. Two others methods were found: the selective dissolution method and the method of retention isotherms. A laboratory procedure was implemented consisting in the preparation of various paste backfill mixtures using sulphide-rich and sulphide-free materials, different types of binder, and mixing waters having various sulphates, copper and zinc concentrations. After curing, mechanical strength and porosity were measured and the pore water was extracted and analysed. The cement phases mineralogy characterization was made using different methods: Scanning Electron Microscope coupled to Energy Dispersive Spectrometry (SEM-EDS), Fourier Transform InfraRed spectrometry (FTIR), X-Ray Diffractometry (XRD) and Differential thermal analysis and ThermoGravimetric analysis (DTA-TGA). The study of the leaching behaviour and the metal speciation in CPB was made by measuring its neutralization potential, performing some column leaching tests and selective dissolution tests. The compression tests showed that the Portland cement and blast furnace slag composite binder based CPB has a higher mechanical strength that Portland cement composite based CPB. If metals are added in the mixing water, the strength is improved. The pore water analysis reveals that few metals are remaining in solution. As for the CPB mineralogy, the synthesis of all the results obtained from the different analytical methods allows us to follow the cement phases evolution. Thus, we can observe that the quantity of portlandite increases with curing time but decreases with the increase of sulphates in the mixing water of the CPB made of cement Portland cement based CPB. It was possible to analyse the behaviour of each cement phases with regard to the variation of the different parameters of this study. The leaching test results indicate that the CPB samples underwent a strong decalcification. Copper remains trapped in the solid. Zinc is released in higher quantity in Portland cement and blast furnace slag composite binder based mixes than in other mixes. This zinc mobilization is simultaneous to the dissolution of a phase containing silica, magnesium and calcium. It is possible that zinc is retained in the CPB by calcium silicate hydrates (CSH) and magnesium silicate hydrates (MSH). The results of the selective dissolution test tend to confirm this hypothesis. Moreover, it can be observed another zinc mobilization at pH 6,5 with a simultaneous calcium and magnesium leaching. This can be due to a second retention mode for zinc that may involve carbonates.
ISBN
9780494292334
0494292334