Civil Engineering Reference
In-Depth Information
and, more specifically, as artificial additions in cement manufacture (Douglas
and Malhotra, 1987). Nonetheless, research has focused primarily on slag
generated in copper metallurgy via fusion of primary minerals or copper-
based industrial waste. The end product is a shiny black, stable, vitreous,
compact, abrasive slag with variable particle size distribution (primarily
under 10 mm) (Fig. 5.2). Further to the data available worldwide, 27 Mt of
Cu slag are generated yearly, 700 000 t of which by Spanish industry.
The chemical composition of copper slag varies within a normal range,
depending primarily on the process and raw materials used. Cu slag consists
of Fe
2
o
3
(45-60%) and SiO
2
(20-36%), followed by Al
2
o
3
(2-7%) and ZnO
(1-8%). None of the remaining oxides present (CuO, CaO, MgO) comes
to 2% of the total weight of the sample. The sulphide content is lower
than 0.5%, with and LOI of 4 to 7% (weight gain), due to the presence of
oxidisable compounds. The main crystalline component, fayalite (SiO
4
Fe
2
),
is a member of the olivine family. XRD analysis has also identified traces
of iron oxides (FeO, Fe
2
o
3
and F
3
o
4
).
Pulverised coal combustion bottom ash (BA)
In addition to FA, well known for its pozzolanic properties (Sánchez de Rojas
and Frías, 1996) and included the world over in legislation on commercial
cement and concrete manufacture, other types of combustion wastes (bottom
ash, BA) are generated at coal-fired steam power plants and stockpiled in
open spaces, with the resulting adverse impact on the environment. Given its
characteristics, BA (Fig. 5.3) is presently being studied from the scientific,
technical and environmental standpoints for use alone or in combination
5.2
Morphological aspect of the Cu slag.
