Civil Engineering Reference
In-Depth Information
SiO
2
HBA
MBAMO
MBARE
MBABO
80%
20%
Class F
40%
60%
FA
Blast furnace slag (BFS)
Class C
40%
60%
20%
80%
Ordinary Portland
cement (OPC)
CaO
80%
60%
40%
20%
Al
2
O
3
12.2
Comparison of MSWI fly ashes ('MBA...') and hospital
incinerator waste ('HBA') with conventional cementitious materials.
After Filliponi et al. (2003).
production. To understand why this is so, the composition of each of these
materials should be considered in more detail.
12.3.1 Bottom ashes
These solids comprise around 80% of MWI combustion products (Chimenos
et al. 1999) and consist of both glassy and crystalline particles, the latter
containing diamagnetic and paramagnetic particles of metal. Approximately
10
9
tonnes of MSWI bottom ash are produced in europe each year, but only
46% of this is re-used; the remainder poses a disposal problem. (Tiruta-
Barna et al. 2007). This fraction is much coarser than the others; particles
from 0.1 to 10 mm diameter being dominant (Ginés et al. 2009; Chimenos
et al. 1999 - see Fig. 12.3). Johnson et al. (1995) compares bottom ashes to
basic igneous rocks, as their bulk chemistry is dominated by Si, Ca, Al and
Fe (see also Belevi et al. 1992) and describes them as 'composed of equal
amounts of fine ash material and melted components, over half of which have
crystallized, small quantities of metallic components, ceramics and stones',
citing Lichtensteiger (1992) as a corroboration. She goes on to list some
of the major crystalline components, such as calcite, ettringite, haematite,
quartz, gypsum and silicate minerals (e.g. pyroxene, Fig. 12.4). Chimenos
et al. (1999) add gypsum, feldspar (anorthite, CaAl
2
Si
2
O
8
) and quick lime
(CaO) to this list and describe the many residual ceramic materials such as
