Page 203 - New Trends in Eco efficient and Recycled Concrete

174 New Trends in Eco-efficient and Recycled Concrete

Figure 7.6 Ladle furnace slag.
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usually above 3.5 g/cm . It is estimated that for each tonne of steel produced in this
furnace, between 110 and 150 kg of EAFS are generated (UNESID, 2018). When
they are used as aggregates, after slow cooling, they have high compressive strength
and skid resistance. EAFS have been shown to be high-performance aggregates in
high-strength concrete and in road layers.
LFS, see Fig. 7.6, is commonly generated in the production of low-alloy steels
and after air cooling and weathering over several days, this material is completely
ground into fine white particles (Manso et al., 2005, 2013). Depending on the type
of process, two types of LFS can be found. Those saturated with alumina
(Tossavainen et al., 2007; Adolfsson et al., 2007; Nicolae et al., 2007; Yildirim and
Prezzi, 2011) and those saturated in silica (Manso et al., 2013; Qian et al., 2002;
Papayianni and Anastasiou, 2006, 2010; Branca et al., 2009; Rodriguez et al., 2009;
Setie ´n et al., 2009; Montenegro et al., 2013). They differ in their composition, hav-
ing either a higher content of aluminium oxides or a higher content of silica oxide.
LFS can be used as raw material in the production of cement, although special care
should be taken with the content of fluorine and chlorine, which could adversely
affect the properties of the clinker. It accounts for between 10% and 20% of EAFS
production (UNESID, 2018).
SS can be used in many applications. In most cases, the valorisation and use of
these by-products prevent landfill, reduce energy consumption, reduce CO 2 emis-
sions and help preserve natural resources.

7.2 Steel slags from electric arc furnace

During the process of scrap-based steel production, two different types of slag are
produced. In the first stage, or primary metallurgy, during the oxidation inside the
EAF, the fluxes combine with incompatible non-metallic scrap and steel compo-
nents to form the slag. The slag presents a lower density than steel and in liquid