Page 432 - New Trends in Eco efficient and Recycled Concrete

Application of alkali-activated industrial waste 385

NaOH showed the best mechanical behaviour (27 MPa) when cured for 56 days at

38 C. Badanoiu et al. (2011) also studied this CKD/FA system and found that the
decrease of liquid/solid ratio (from 0.25 to 0.15) led to improving the strength in
98 200%. Good behaviour also was found for 20% CKD systems when cured for

28 days at 85 C(Cabrera-Fuentes et al., 2011). A comparison between different
mineral additions was carried out by mixing CKD and slag, FA, inert calcite filler
and MK (Buchwald and Schulz, 2005). The best results were observed for 1:1
CKD/slag system, finding a compressive strength higher than 20 MPa. Geopolymer
bricks were manufactured by activation with NaOH (10 to 15 M) of a mixture of
CKD and copper mine tailings (Ahmari and Zhang, 2013).
Spent FCC catalyst was studied as a precursor for geopolymer synthesis. This
residue is composed of a mixture of Al 2 O 3 and SiO 2 . Tashima et al. (2012b) discov-
ered the high reactivity of FCC by mixing with NaOH/Na 2 SiO 3 solutions.
Fig. 13.19 shows that applying 1.19 SiO 2 /Na 2 O molar ratio, 68 MPa were reached
after curing for 3 days at 65 C. Different studies were carried out in order to find

optimum dosage (silica modulus, water/binder ratio) for different curing conditions
(thermal curing, room temperature) (Tashima et al., 2013c, 2014; Rodriguez et al.,
2013; Trochez et al., 2015). Very good strength development was found for mortars
cured at room temperature, for both sodium- and potassium-activated systems
(Tashima et al., 2014). Cellular concrete was prepared by alkali activation of FCC
in 0.2% of metallic powdered aluminium presence (Font et al., 2017a,b).
Residue from calcium carbide (CCR) produced in the acetylene production was
also used as a co-precursor. CCR contains Ca(OH) 2 and when mixed with FA and

Figure 13.19 Compressive and flexural strengths of spent FCC activated with different
activating solutions and cured for 3 days at 65 C(Tashima et al., 2012b). FCC, fluid

catalytic cracking.