Mahlaba, SJ & Pretorius, PC 2006, 'Exploring Paste Technology as a Co-Disposal Option for Fly Ash and Brines', in R Jewell, S Lawson & P Newman (eds), Paste 2006: Proceedings of the Ninth International Seminar on Paste and Thickened Tailings, Australian Centre for Geomechanics, Perth, pp. 181-189, https://doi.org/10.36487/ACG_repo/663_16
(https://papers.acg.uwa.edu.au/p/663_16_Mahlaba/)
Abstract: Water is a scarce resource in many parts of the world resulting in a drive towards the reuse of industrial effluents 
(Gordon, 2001; McPhail et al., 2004). A common feature in most cases where saline water is re-used to any 
significant degree is the use of desalination technologies. A disadvantage of the desalination technologies is the 
production of concentrated salt streams (brines) that are difficult to handle (Ahmed, et al., 2001; Buckley et al.,
1987). The brines pose an environmental risk (Hoepner and Lattemann, 2002; Mabrook, 1994; Purnalna et al., 
2003; Tsiourtis, 2001) and their treatment is costly (Al-Handaly et al., 2003; Vedavyasan, 2001). Salt disposal is 
usually perceived as a problem mainly for the inland industries (Khordagui, 1997) as coastal facilities 
conventionally dispose of their salts in the sea using pipelines (Gordon, 2001; Khordagui, 1997).  
On the other hand the coal processing facilities such as power utilities produce vast quantities of ash. However, a 
considerable amount of work has been reported on basic fly ash composition in addition to its physical and 
chemical behaviour with an intention of extending its applications beyond the cement industry (Raghavendra 
et al., 2002). The physical (particle size distribution) and chemical (pozzolanic) properties of fly ash make it 
possible to dispose of it as a paste (Asavapisit and Cosanavit, 2004; Bergeson et al., 1988). Brines and ash pose 
an environmental threat within the context of sustainable development (Scheetz, 2005 Joshi et al., 1994; 
Khordagui, 1997). 
The use of paste technology to dispose of tailings through dewatering of slurry is well documented in literature 
(Jewell et al., 2002; Stropnik and Južni , 1988; McPhail et al., 2004; Yilmaz et al., 2004; Theriault et al., 2005). 
A case study conducted in Iowa reports on a paste prepared by mixing dry fly ash and water and showed the 
existence of hydration products (secondary minerals) which were dependent on particle size distribution and 
chemical composition of the fly ash (Bergeson et al., 1988). The existence of these secondary minerals served as 
the motivation for this study as it presents an opportunity to stabilise the ionic components of brines in a fly ash 
paste. The work reported here represents an attempt to explore paste technology as an alternative solution for the 
co-disposal of brines and fly ash. Laboratory experiments were conducted to explore the fundamental properties 
of pastes prepared from fly ash and brines (FABPs). The investigation focused on the effect of the physical 
properties of the fly ash (e.g. loss on ignition and particle size distribution) on slumping as well as the effect of 
the salinity of the liquid medium on the physical properties of the resulting paste. 
Paste2006–R.J.Jewell,S.Lawson,P.Newman(eds)
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