3270
Proceedings of the 18
th
International Conference on Soil Mechanics and Geotechnical Engineering, Paris 2013
(Ferguson 1993, Zia and Fox 2000, Çokça 2001, Nalbantoglu
and Gucbilmez 2002, Ramadas and Kumar 2012).
5
CONCLUSIONS
Although many scientific results show that Class F fly ash
cannot be used for soil stabilization without addition of cement
or lime, laboratory tests performed in this research have shown
that fly ash from thermal power plant "Kolubara" is effective
material for soil stabilization. Main conclusions of this research
are as follows:
Additon of KFA decreases the plasticity index of medium
and high plasticity soils (type A).
KFA impacts moisture-density relation of tested soils –
optimum moisture content increases and maximum dry density
decreases.
For soil A, based on UCS gain, amount of 15% KFA is
identified as optimum. Strength gain was approximately 20%.
There wasn't UCS gain for low plasticity soil B.
For both soil types, long term friction angle almost doesn't
change with addition of KFA, while effective cohesion
significantly increases with time for all tested mixtures.
CBR values increased around 260-380% for mixtures with
15% of KFA, which is adopted as optimum. This is main
stabilization effect for soil B and very important effect for soil
A.
Compressibility modulus for both soil types increase with
addition of fly ash, without influence of time. Overall increase
is around 15-35%.
Swell potential of very expansive soil A reduced with
addition of 15% KFA. Swell deformation decreased from
ε=8.6% to ε=1.8-3.1%.
Despite shown positive effects, the universal principle of soil
stabilization using fly ash cannot be easily defined. It is
necessary to perform detailed laboratory investigations, with
certain types of ash and soil. It is the only possible way to
precisely determine the optimal percentage of ash to be added,
to determine strength gain and define the technology operations.
The presented results of laboratory tests have confirmed the
need to develop a research program in this field for Serbia,
bearing in mind that the average annual production of fly ash
that will be disposed on landfills is around 7 million tons.
6
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