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Application of alkali-activated industrial waste 395

from Muja, 4% of Ca(OH) 2 addition let to produce materials with more than
40 MPa in compression. The addition of slag in 4.1% only achieved 25 MPa at
room temperature. The authors conclude that the effectivity of calcium addition
was significantly higher for Ca(OH) 2 than for slag.
Choo et al. (2016) used RM as a solid alkali activator in the geopolymerisation
of high carbon FA. Five FAs, with LOI values in the range 7.50% 19.70%, were
activated with different proportions of solid RM (0% 60% by mass). In this way,
one-part AAMs were designed. The pH of the pastes was raised when the RM con-
tent was increased (Fig. 13.26). The compressive strength of the FA/RM one-part
alkali AAMs was very low ( 1 MPa) and consequently, their application was lim-
ited to low strength requirement construction sites.
Shirley and Black (2011) used an aluminium-containing waste caustic (WC)
solution produced from an industrial cleaning process. They studied the potential
treatment by solidification/stabilisation of APC residues, which were mixed with
FA and WC. Solidification occurred very slowly at room temperature but a signifi-
cant reduction in setting time was reached when increasing the curing temperature.
Ferna ´ndez-Jime ´nez et al. (2017) analysed the potential application of a waste solu-
tion used to wash moulds from the aluminium casting industry. This waste cleaning
solution (CS) contained 20% of dissolved solids: 7.14% Al 2 O 3 , 12.13% Na 2 O and
1.18% SO 3 . Similar compressive strength ( 16 MPa) was found for FA geopoly-
mer activated with 8 M NaOH and activated with CS after 28 days of curing.
Ban et al. (2017); Cheah et al. (2015) studied a high calcium WA (HCWA)
obtained from the use of wood biomass as fuel in the boiler. The biomass mainly
contained dominantly Malaysian rubber wood species Hevea brasiliensis. The

Figure 13.26 Variation of pH fly ash pastes as a function of the red mud content by mass
(Choo et al., 2016).