3178
Proceedings of the 18
th
International Conference on Soil Mechanics and Geotechnical Engineering, Paris 2013
6 CONCLUSIONS
FA
0
20
40
60
80
100
120
140
160
180
0
2
4
6
8
10
Horizontal displacement (mm)
Interface Stress (kPa)
200 kPa
100 kPa
50 kPa
Figure 10. Shear stress vs. horizontal displacement of manufactured
fly ash pellets.
Figure 11. Shear stress vs. vertical displacement of manufactured fly
ash pellets.
The shear stress vs. horizontal displacement and shear stress
vs. vertical displacement values of fly ash pellet aggregates are
presented in Figures 10 and 11 respectively. While dilation
behavior is observed under 50 and 100 kPa, contraction
behavior is seen under 200 kPa due to grain crushing.
5 SETTLEMENT BEHAVIOR OF PELLET AGGREGATES
The size of the silt sized powder wastes can be increased to sand
and gravel size by pelletization technique in large volumes and
low cost making the technique suitable for geotechnical
applications. In this study experience with self cementing fly
ash is presented, however the technique is applicable to other
silt sized powder wastes provided that adequate capillary forces
develop between the grains. For non self cementing fly ash,
binders like hydrated lime or cement can be used for
manufacturing. For higher performance needs the crushing
strength of the fly ash pellets can be improved by using lime or
cement additives. Surface treatment of pellets is possible using
water glass at reasonable cost. High water absorbtion values( 30
-35 per cent) place the manufactured granular material in an
unique place in clasical soil classification. The durability of the
aggregates is also satisfactory. With low unit weigh, free
draining behavior, and ease of compaction, the manufactured
soil has good potential for large volume utilization in
geotechnical applications. The geotechnical properties of the
manufactured soil ensures high stability. In addition to its
potential for utilization in large volumes, the manufactured soil
is a great tool for experimental research on crushable soils. It is
possible to control the size, shape, surface texture, roundness,
sphericity, crushing strength, unit weight, water absorption
properties of the powder materials to produce soil with target
engineering properties. This way by fixing one parameter at a
time it will be possible to study the effects of each parameter on
the engineering behaviour of natural soils. The cold bonding
pelletization technology is a low tech technology which requires
minimum capital investment and low operational costs. The
whole process can be automated. If the manufactured
aggregates are not used in a geotechnical application, a major
reduction in disposal costs is achieved by improving handling,
transportation, compaction and disposal in a dump site. Free
draining property, high stability and potential for reuse when
needed are other benefits of utilization.
FA
-0,5
-0,4
-0,3
-0,2
-0,1
0
0,1
0,2
0,3
0,4
0
2
4
6
8
10
Horizontal displacement (mm)
Vertical Displacement
(mm)
50 kPa
100 kPa
200 kPa
Manufactured fly ash pellet aggregates are placed in an
odometer and vertical stress of 25 to 1600 kPa is applied and
removed. The corresponding void ratio values vs. the applied
vertical stress are presented in Figure 12 (Erdurak 2011).
7 ACKNOWLEDGEMENTS
The studies presented above are conducted by PhD student Ata
Gurhan Doven; MSc students; Haydar Arslan, Egemen
Danyldz and Murat Cenk Erdurak with financial support
provided by Bogazici University Scientific Research Fund and
Turkish Scientific Research Council (TUBİTAK).
8 REFERENCES
Baykal G. And Doven A.G. 2000. Utilization of fly ash by pelletization
process; theory, application areas and research results.
Resources
Conservation and Recycling
30, 59-77.
Doven A.G. 1998. Lightweight fly ash aggregate production using cold
bonding technique. PhD Thesis. Bogazici University, İstanbul.
Erdurak M.C.2011. Artificial sand production for laboratory tests. MSc
Thesis Bogazici University, Istanbul
Danyldz E.2007. The interface behavior between granular soils and
concrete. MSc Thesis, Bogazici University. Istanbul.
Arslan H. 2003. The effect of grain crushing on the behavior of granular
materials. MSc Thesis. Bogazici University. Istanbul.
Figure 12. Odometer test results of fly ash pellets.
After the application of 100 kPa vertical stress the settlement
increases. Even for high embankment fills the settlement
magnitude is manageable.
