L’objectif de la thèse est de comprendre le comportement géochimique de l’arsenic dans les remblais miniers en pâte cimentés. Cette technique est employée depuis plusieurs années pour remblayer les galeries de mine exploitées à l’aide des rejets de concentrateurs. Pour cette étude, deux types de remblais sont élaborés en laboratoire : des échantillons de remblai minier en pâte synthétiques, fabriqués à partir de silice et enrichis artificiellement en arsenic, et des remblais miniers en pâte élaborés à partir de rejets miniers arséniés. Dans les deux cas, différents liants cimentaires sont testés. Plusieurs types d’investigations sont menés sur les échantillons de remblai en pâte cimentés. Une caractérisation minéralogique est effectuée à l’aide de divers outils. En parallèle, les échantillons de remblais sont soumis à différents tests de lixiviation complémentaires, afin d’évaluer la mobilité/rétention de l’arsenic dans ces matrices. Enfin, une modélisation géochimique est mise en œuvre à partir des résultats issus des deux études précédentes, afin d’affiner les connaissances sur la nature et la stabilité des composés arséniés dans les remblais étudiés. Les résultats obtenus indiquent que l’arsenic est mieux stabilisé dans les matrices à base de ciment Portland et de laitier de haut-fourneau que dans les remblais à base de cendres volantes. Le comportement à la lixiviation variable d’une matrice à l’autre s’explique par des spéciations et des mécanismes de piégeage de l’arsenic variés. L’arsenic peut précipiter sous forme de minéraux arséniés, principalement sous forme d’arséniates de calcium, mais aussi de divers autres composés secondaires variables d’une matrice à l’autre. Un piégeage physique des grains de rejets miniers arséniés par les hydrates cimentaires peut aussi avoir lieu, par formation d’un revêtement limitant l’oxydation des sulfures porteurs d’arsenic. Tous ces mécanismes interviennent dans la stabilisation/solidification de l’arsenic. / The objective of this study is to understand the geochemical behaviour of arsenic in cemented paste backfills. This technique consists in transporting the tailings in the mine openings. Two types of backfills are prepared in the laboratory for this study. First, synthetic cemented paste backfills artificially spiked with arsenic are synthesized, using silica in replacement of the tailings. In parallel, other cemented paste backfill specimens are prepared with arsenic-rich tailings. In the two cases, various types of hydraulic binders are tested. Several types of investigations are conducted on the cemented paste backfill specimens. A mineralogical characterization is carried out with the help of specific tools. At the same time, cemented paste backfill samples are submitted to several complementary leaching tests, to assess the mobility/immobilization potential of arsenic in these matrices. Finally, geochemical modeling is implemented, based on the results of the two previous studies, in order to refine the understanding of the nature and stability of the arsenic compounds. The results show that arsenic is better immobilized in Portland cement and slag-based matrices, rather than in fly ash-based matrices. The variable leaching behaviour from a given matrix to another is due to different arsenic trapping mechanisms. Arsenic can precipitate and form several arsenic minerals, mainly calcium arsenates, but also various other secondary compounds, which are different from a matrix to another. Physical entrapment of the tailings grains by the cementitious minerals can also occur, by formation of a coating around the grains, limiting the oxidation and dissolution of arsenic-bearing sulfides (passivation). These mechanisms are involved in the stabilization/solidification of arsenic by cemented paste backfills.

The purpose of this study was to develop a conceptual integrated online visual merchandising framework containing online visual merchandising themes that South African apparel e-tailers could use when developing an effective apparel e-store, with the main aim of possibly influencing consumer purchasing behaviour. The study adopted a consumer-centred response approach to online visual merchandising in an attempt to holistically consider this area of the South African e-tail industry from the consumer’s perspective. The study followed a pragmatic paradigm that implemented a mixed-method approach. The qualitative section of the mixed-method approach primarily comprised four focus group interviews as the main data-collection instrument. The data obtained during the qualitative section was analysed by Tesch’s inductive descriptive coding technique, better known as thematic analysis. The findings obtained during the qualitative section were used as the basis for the quantitative section of the mixed-method approach, which implemented a self-administered web-based questionnaire as the data-collection instrument. The data was analysed by means of the Statistical Package for Social Science (SPSS) version 23. The findings of the study delivered a conceptual integrated online visual merchandising framework that consists of 13 themes and 82 items. This conceptual integrated online visual merchandising framework will contribute to the South African apparel retail and e-tail industry, as both apparel brick-and-mortar retailers and apparel e-tailers in South Africa can benefit from using the conceptual integrated framework as a guideline. The value of the conceptual integrated framework lies in the fact that it includes consumers’ views regarding the online visual merchandising themes. Therefore, apparel e-tailers, as well as brick-and-mortar retailers that want to develop an e-store, or update an existing e-store, can use this conceptual integrated framework as a guideline to make their online offering as attractive as possible. This way involves the least possible online risks to ensure that online trust is created, and ultimately, that consumer purchasing behaviour has been influenced. / Business Management / D. Phil. (Management Studies)

Department of Ecology and Resource Management / MENVSC