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Returning waste material underground, as backfill, has been practiced for many years so as to improve the economical and environmental performance of underground mining operations. A specific type of backfill, which is used to fill mined areas that will not be exposed to further mining, is called hydraulic backfill. Cemented backfill has also been used to provide mechanical support for underground mining. Such backfill has allowed mining companies to extract more ore, while simultaneously improving working and environmental conditions. Cemented backfill, however, represents 50 to 85 percent of operating costs compared with the 5 to 10 percent that hydraulic backfill consumes. / The objective of this thesis is to investigate use of sodium silicate as a partial or total replacement for cement in stabilised backfill. Sodium silicate is a viscous material that is usually used to activate pozzolanic materials such as slag and fly ash. The chemical compound has many applications, namely, in waste treatment, cement and other construction materials. / In order to determine the influence of sodium silicate on backfill performance, a series of laboratory experiments were carried out on samples with different binder compositions, such as: cement; slag and cement; slag, cement and sodium silicate; and slag and sodium silicate. Additionally, the effects of mixing time and addition order on the backfill samples' performance were studied. The subsequent thesis focuses mainly on the strength of paste and slurry backfill samples containing sodium silicate in addition to the observation of a number of experimental variables, which include: pulp density (relative amount of water), curing time, and binder dosage. In order to investigate the overall suitability of sodium silicate for use in stabilised backfill, other properties such as porosity, elastic modulus, and trends of water release are also studied. / The results of the research endeavour demonstrate that sodium silicate-fortified backfill materials behave favourably compared with cemented backfills. Sodium silicate, thus, has potential as a backfill binder or additive.

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Thesis (MAppSc in Chemical Technology)--University of South Australia, 1997

Geopolymerisation can transfer A1 and Si containing wastes into geopolymers with a high mechanical strength and high fire, acid and bacteria resistances. This thesis investigates the geopolymerisation of natural aluminosilicate minerals which cover a wide range of structures, minerals groups, hardness, densities and A12O3 and SiO2 contents. The study of fifteen selected A1-Si minerals shows that the framework structured A1-Si minerals with a high CaO content and a lower K2O content, have a higher potential to undergo geopolymerisation in KOH solution with resulting geopolymers possessing a higher compressive strength. The NaOH solution is observed to leach more A1 and Si complexes from the solid reactants than KOH solution, while KOH solution produces geopolymers with a higher mechanical strength than NaOH solution does. (For complete abstract open document)

Thesis (B. Sc. Hons.) - Dept. of Geology, University of Adelaide, 1975. / Typescript (photocopy).