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Application of alkali-activated industrial waste 365

Ahmari et al. (2015) studied the furnace smelting slag (SG) produced during the
primary copper smelting process which was managed in slag disposal areas at the
smelter site. This SG contained a very low CaO content (2.13%) and the main crys-

talline phases were magnetite and fayalite (iron silicate). Cured samples at 90 C for
7 days with SG activated by 15 M NaOH solution yielded more than 50 MPa in

compressive strength. For a curing temperature of 75 C, the strength increased to

75 MPa while at 60 C it decreased to 35 MPa.
Kalinkin et al. (2012) studied granulated Cu-Ni slags cooled with water. This
waste consists of magnesia-ferriferous glass (95% 98%) and contained high per-
centages of silicon, iron and magnesium oxides (the sum of these being more than
80%). The slag was ground under air and under CO 2 atmosphere. The reactivity of
the CO 2 -treated samples were higher (tested by isothermal conduction calorimetry
curves for slag activated using NaOH/water glass, Fig. 13.4), suggesting a signifi-
cant modification of the surface of the slag particles by intensive sorption of CO 2
molecules.
Ferronickel slags applied to AAMs were studied by different researchers
(Komnitsas et al., 2007; Maragkos et al., 2009; Sakkas et al., 2014). Ferronickel
alloy is prepared from lateritic ores, by reductive smelting by electric arc furnace
means. Separated slags from the alloy represent more than 80% of the raw materi-
als, which results in a huge quantity of waste and becomes a great environmental
problem. Usually, ferronickel slag is a low-calcium content material and contains
large percentages of silicon, aluminium and iron oxides. Table 13.1 summarises the
chemical composition for several studied slags.
Komnitsas et al. (2007) activated ferronickel slag by mixing 69% of it with 9%
kaolinite, 4.5% sodium silicate, 4.5% sodium hydroxide and 13% water, and the

systems were cured at 60 80 C, with a heating time of 24 48 h and 7 28 days
curing time. Achieved strengths were in the 10 15 MPa range. Despite

Figure 13.4 Isothermal conduction calorimetry curves of the Cu Ni slag mechanically
activated in air (dashed line) and in CO 2 (solid line) using SiO 2 /Na 2 O molar ratio of 2.0
(Kalinkin et al., 2012).