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Application of alkali-activated industrial waste 393

Passuello et al., 2017). Geraldo et al. (2017) studied the activation of binary blends
of MK and water treatment sludge which were activated with RHA-NaOH.
Torres-Carrasco and Puertas (2015) described the preparation of the activating
solution from glass waste: NaOH 10 M and glass waste were mixed and magneti-

cally stirred at 80 C for 6 h. The mixture was subsequently filtered. The obtained
liquid was used as activating reagent in FA based geopolymers. Similar strength
was reached for 7 and 28 days cured samples when an alternative activator and
NaOH-sodium silicate were compared (Fig. 13.25). Comparison between alternative
activating solutions prepared with RHA and waste glass was done: compressive test
showed better results for waste glass in MK-based geopolymer (Tchakoute ´ et al.,
2017a, 2016c).
Different mineral materials have been alternatively used as silica source in geo-
polymers: nanosilica from olivine (Gao et al., 2017, 2018), SF (Villaquira ´n-Caicedo
et al., 2015) or diatomaceous earth. Mejı ´a et al. (2016) used spent diatomaceous
earth (SDE) from a brewery company as silica source in FA/MK geopolymers. The

SDE was calcined at 400 C for 3 h in order to remove organic matter. The com-
pressive strength of geopolymers activated by means SDE alkali solution yielded
much lower than control geopolymer prepared with sodium silicate (50% diminu-
tion). Font et al., 2018 have developed FCC geopolymers prepared with activating
systems containing four types of diatomite: commercial diatomite (CD), a residual
diatomite from the beer industry (BD), and two residual diatomite from the wine
industry, as-received waste residue (WD) and the same one calcined at 650 C for

Figure 13.25 Compressive strength development for FA activated geopolymers with 8 M
NaOH solution, 10 M NaOH plus glass waste and 10 M NaOH solution plus waterglass
(Torres-Carrasco and Puertas, 2015). FA, Fly ash.