Authors: Kermani, M; Hassani, FP; Nokken, M; Aflaki, E

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Kermani, M, Hassani, FP, Nokken, M & Aflaki, E 2014, 'An investigation into the addition of sodium silicate into mine backfill, Gelfill', in Y Potvin & T Grice (eds), Proceedings of the Eleventh International Symposium on Mining with Backfill, Australian Centre for Geomechanics, Perth, pp. 271-280,

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Physical and mechanical properties of cemented hydraulic backfill (CHF) made with and without sodium silicate are investigated in this paper. Sodium silicate is an alkali activator and has been successfully used to stimulate the reactions of pozzolanic materials such as fly ash and blast furnace slag (BFS). A series of CHF samples made with various concentrations of sodium silicate were prepared and cured over 28 days. The mechanical properties of samples were analysed by conducting uniaxial and triaxial compression tests. The microstructure of selected samples was also investigated by conducting mercury intrusion porosimetry (MIP) test and scanning electron microscopy (SEM). The results demonstrate that CHF made with an appropriate amount of sodium silicate can have stronger mechanical properties in comparison to those without the additive. Moreover, the rate of strength gain in samples made with sodium silicate is faster than samples without sodium silicate over 28 days of curing period. However, an elevated amount of sodium silicate may have a detrimental effect on the strength of samples due to the increase of the total porosity. The MIP test shows that the total porosity and pore structure are different for the two types of backfills. The SEM micrographs taken from samples made with and without sodium silicate revealed that the addition of sodium silicate caused the formation of more calcium-silicate-hydrate (C-S-H) gel.

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