Rapport 867.pdf - Svenska EnergiAskor AB

VÄRMEFORSK
To enable the use of and encourage the acceptances of bottom ashes as a construction
material it is important to show that the requirements above are fulfilled. The situation
is complicated regarding the fact that fixed numerical values for functional
requirements above are missing except for the frost heave and heat conductivity (if the
construction is built according to ATB VÄG 2003 [7]. This means that new knowledge
about bottom ashes for the other functional requirements have to be evaluated through a
comparison with current the knowledge about the functional requirements in general
(the appropriate level of the requirements for different applications). When it is possible
the report suggests suitable levels for different functional requirements. What functional
requirements that is valid for a certain application depends on the character of the
application. The testing methods, which are needed to confirm the above functional
requirements, are a combination of established methods (for traditional materials) and
newer methods for the ashes.
For ashes bearing capacity, stability, settling and compression should be tested with
cyclic load triaxial test combined with some kind of more simple test, for example the
compression test. Special attention should be payed to water absorption, since it is
considerable for ashes and has been more or less neglected earlier. A correct
measurement of the water absorption is important for testing of frost resistance (which
should be performed with freeze-thaw-testing), frost heave and heat conductivity (to
avoid slippery road surfaces). The frost heave can be tested with established methods if
correct water content is achieved. The heat conductivity can be tested with the same
method for ashes as for traditional materials considered a correct conditioning of the
materials.
The particle size distribution should be tested with careful variants of established
methods, and that changes in particle size distribution should be checked when other
testing is performed. A special crushing method (developed for light weight aggregate)
to test resistance to mechanical action, can also be used to test ashes.
Concerning compaction, established methods can presumably be used. The methods,
that treat the materials in a careful manner, are recommended, i.e. standard proctor or
vibro table. The measurement of permeability is not that dependent of the kind of
materials that are going to be tested, i.e. some of the established methods can be used.
Also for capillarity, established methods can be used. For porous materials as ashes, the
result can however be a combination of absorption as a result of capillarity and
absorption as a result of ordinary absorption in the particles.
Organic content is an important parameter in the ashes since this has influence on the
stability. A method which measures only organic material and is up-to-date should be
used, for example SS-EN13137.
The experience of bottom ashes within the field of civil construction in Sweden is
limited. The relatively largest experience from technical point of view is about MSWIash
(Municipal Solid Waste Incinerator) and also to some extent for coal bottom ash.
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