Civil Engineering Reference
In-Depth Information
12
Municipal solid waste incinerator (MSWI)
concrete
M. Tyrer, Mineral Industry research Organisation, UK
DOI
: 10.1533/9780857098993.3.273
Abstract
: The potential to use municipal waste incineration products in
concrete has been examined over many years, both as a source of aggregates
and as supplementary cementitious materials (SCM). With an understanding
of the chemical evolution of these materials in the cement environment, both
applications provide routes to the re-use of these materials in construction.
Fly ashes and air pollution control residues must be washed to remove their
considerable chloride content before use, after which, the remaining solids
(largely aluminosilicates) may replace some fraction of the cementitious
binder. Care must be taken when using these materials as SCMs, as volatile
heavy metals present in the original waste may be concentrated in the fly
ash. The bottom ashes from municipal solid waste (MSW) incineration also
show sufficient pozzolanic reactivity when finely ground, to replace some
cement in the binder phase. They may also serve directly as aggregate in
concrete, although the irregular and angular particle shape may reduce its
workability somewhat. Most MSW bottom ashes contain sufficient free
aluminium to disrupt the setting reactions of the binder through hydrolysis
reactions at high pH. Consequently, this must be removed or reacted by pre-
treatment, prior to use in concrete and means of doing so are described here.
Slower detrimental reactions are also known, such as alkali silca reaction,
especially of container-glass fragments and these are considered here.
Lastly, the use of MSW incineration products in manufactured aggregates
is described, comparing sintering, melting and recrystallization, and plasma
processing, with low temperature methods such as rapid carbonation
technology.
Key words
: municipal solid waste (MSW), municipal solid waste incinerator
(MSWI), fly ash, bottom ash, air pollution control (APC) residues, plasma
processing, accelerated carbonation.
12.1 Introduction
The global trend towards incineration of municipal solid waste (MSW)
reflects two important drivers. There is a widely recognized need to reduce
the volumes of waste sent to landfills and this is especially true of highly
industrialized and densely populated countries such as Japan and the United
Kingdom, but is of wider global concern. Incineration of municipal waste
offers two advantages over conventional landfill disposal; the first is volume
reduction; typically around 90% of the original volume, equivalent to >70%
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