Page 407 - New Trends in Eco efficient and Recycled Concrete

362 New Trends in Eco-efficient and Recycled Concrete

Figure 13.1 Traditional and new alkali-activated systems.
Source: Jordi Paya ´.
et al., 2015; Seiffarth et al., 2013). In some cases, the precursor may be thermally
or mechano-chemically activated (Almalkawi et al., 2017).
In this section, the state-of-the-art is focussed on precursors based on waste from
urban, metallurgical, ceramic, construction, demolition and agro-industry activities.
Regarding the activating solution, the state-of-the-art is also focussed on waste-
derived reagents, differentiating between the cases in which the activating solution
was prepared totally or partially from waste.

13.2.1 Precursors based on wastes
13.2.1.1 Metallurgical activities
Several wastes from metallurgical activities have been tested in alkali-activated sys-
tems. In most cases, slags from pyro-metallurgical extraction of any metal or alloys
from different ores are used, such as Cu-Ni, Mn and Pb, etc. In other cases, these
slags are obtained from pyro-metallurgical purification processes in steel produc-
tion. Another interesting waste used in AAMs applications is the red mud (RM)
produced as a by-product in the aluminium industry.
Zinc slag produced from the imperial smelting process is usually dumped in
landfills. Alex et al. (2013) reused this waste by geopolymerisation of finely ground
zinc slag (about 6 μm median particle diameter). In this work, the main elements of
Zinc slags are described, presenting iron, calcium, aluminium, silicium and zinc in
the oxide forms. This type of slag is amorphous and contains wustite (FeO) as a
crystalline phase. In this research, the powder fraction of slag was activated by
means of a NaOH solution (6 M) and the water:slag ratio applied in the paste was