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Assessment of heat treatment on clays mixed with silica sand

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Australian Journal of Basic and Applied Sciences, 8(19) Special 2014, Pages: 310-314
AENSI Journals
Australian Journal of Basic and Applied Sciences
ISSN:1991-8178
Journal home page: www.ajbasweb.com
Corresponding Author: Mahmoud Bensaibi, National High School of Public Works, Algiers, Algeria.
+213 555 416 787; E-mail: bensaibim@yahoo.co.uk
Assessment of Heat Treatment on Clays Mixed with Silica Sand
A. Akbar Firoozi, M. R. Taha, A. Asghar Firoozi, Tanveer A.
Department of Civil and Environmental Engineering, University Kebangsan Malaysia, Malaysia.
A RT I CL E I NF O
A B ST RA CT
Article history:
Received 15 April 2014
Received in revised form 22 May
2014
Accepted 25 October 2014
Available online 10 November 2014
Key words:
Elastic-plastic; Bangalore; Mohr
Coulomb; PLAXIS 2D; Sheet
This study examines the effects of heat treatment on two types of clays mixed with
silica sand under laboratory conditions. Soils were subjected to three varied
temperatures, i.e. 100, 250 and 500oC. The soil properties studied were Atterberg limits,
optimum water content and unconfined compressive strength. Experimental results
showed that the temperature greater than 100oC resulted in a reduction in Atterberg’s
limits, optimum water content and unconfined compressive strength. For illite and silica
mixture heating the soils at 500oC decreased the liquid limit, plastic limit, optimum
water content and unconfined compressive strength reduced to 12%, 0%, 40% and 0%,
and for kaolinite and silica mixture the above characteristics reduced to 18%, 0%, 50%
and 0% respectively when matched to soil specimen’s properties at ambient
temperature. Whereas maximum dry density for illite and kaolinite increased by 5%
and 8% respectively for the two clays.
© 2014 AENSI Publisher All rights reserved.
To Cite This Article: A. Akbar Firoozi, M. R. Taha, A. Asghar Firoozi, Tanveer A., Assessment of Heat Treatment on Clays Mixed with
Silica Sand. Aust. J. Basic & Appl. Sci., 8(19): 310-314, 2014
INTRODUCTION
The temperature modifies the physical and mechanical properties of clays. When the clayey soils are treated
with heat, some of the changes in properties are permanent. The huge fires in the forests across the world have
brought the thought to measure the effect of heat on clayey soils (Alcocer, C. and H. Chowdhury, 1993).
Many researchers have investigated the effect of heat treatment on the clayey soils. Mitchell (1969) showed
that the heat treatment changed some of the physical properties of the clayey soils such as angle of friction,
cohesion and strength. Joshi et al. (1994) investigated the effect of the heat treatment on the strength of clayey
bricks at temperatures ranging from 300 to 700 oC. And it was found that an increase in strength was
accompanied with increase in temperature. Yang and Farouk (1995), Akinmusuru (1994) and Ma and Hueckel
(1992) investigated the effect of heat on the thermal conductivity of clayey bricks. Tanaka et al. (1997)
evaluated the stress-strain behaviors of the remodeled illite clay at different temperatures. It was found that peak
undrained strength was increased due to development of reduced pore water pressure during testing.
The main objective of this study was to investigate the effect of temperature on physical properties of
clayey soils. The parameters investigated in this study include Atterberg limits, optimum water content and
unconfined compressive strength.
Experimental Procedure:
The clay minerals used in this study were kaolinite and illite. Silt which was mixed with clay minerals in
the present study was silica sand with fine grained particles (45 μm). Kaolinite and illite clay minerals were
obtained from Kaolin (Malaysia) factory under the trade name “S-300” and “KM800” respectively. Table 1 & 2
present properties of kaolinite and illite, which were determined during this study by performing a series of
geotechnical laboratory experiments using procedures recommended by relevant ASTM standards. In Figure 1
and 2 scanning electronic microscope (SEM) images are given which show the kaolinite and illite layers.
Table 1: Physical property of materials
Kaolinite
Moisture content
Below 1.5%
Moisture content
Below 2.0%
pH
4.0
pH
4.5
100 mesh residue
Below 10%
325 mesh residue
Below 3.0%
60 mesh residue
Below 0.5%
Average particle size
2.5-5.0µm
Specific gravity (Gs)
ASTM D854
2.723
Specific gravity (Gs)
ASTM D854
2.701
311 Mahmoud Bensaibi et al, 2014
Australian Journal of Basic and Applied Sciences, 8(19) Special 2014, Pages: 310-314
Table 2: Chemical compositions of clay minerals and silica sand
Kaolinite
Illite
Silica Sand
Formula
Concentration (%)
Formula
Concentration (%)
Formula
Concentration (%)
SiO2
85.76
SiO2
29.43
SiO2
97.29
Al2O3
9.11
Al2O3
52.37
Al2O3
2.71
Fe2O3
0.38
Fe2O3
1.85
-
-
K2O
1.34
K2O
8.21
-
-
Heat loss
3.41
MgO
1.76
-
-
-
-
TiO2
1.36
-
-
-
-
Heat loss
5.02
-
-
Fig. 1: Kaolinite particles under SEM
Fig. 2: Illite particles under SEM
The mix selected for the test was, 50% clay (kaolinite / illite) + 50% silica sand. Physical properties
including plastic and liquid limits, maximum dry unit weight and optimum water content of untreated and
treated specimens were determined by using ASTM standards D4318-10 and D698 -12 respectively. For the
unconfined compressive strength experiment, soil samples were compacted with standard Proctor test (D698-12:
3 layers, 25 blows per layer) and then tested in accordance with ASTM D2166-06. Soil specimens were
compressed until failure under a strain rate of 1.5 mm/min. and deformations were noted during the whole test.
RESULTS AND DISCUSSION
The effect of temperature on liquid limit and plastic limit for kaolinite and illite are shown in Figure 3 & 4.
Liquid and plastic limits progressively decreased with increasing temperature and the plastic limit finally
reached a value of zero at 500oC. Liquid limit was decreased by a little up to 100oC, whereas plastic limit
remained almost same for this variation. Between 100oC and 250oC Atterberg limits decreased by more than
50% for both the samples. Beyond 250oC liquid limit appeared to get less affected by temperature rise to reach a
value of about 5% for the two specimens.
312 Mahmoud Bensaibi et al, 2014
Australian Journal of Basic and Applied Sciences, 8(19) Special 2014, Pages: 310-314
Fig. 3: Effect of heat treatment on liquid limit
Fig. 4: Effect of heat treatment on plastic limit
Figure 5 & 6 show the effect of temperature treatment on optimum water content and maximum dry
density, respectively. Optimum water content decreased with increasing temperature, though it was less affected
by temperature below 100oC. At a temperature of 500oC the optimum water content of illite and kaolinite
reduced to 40% and 50% respectively. A rise in maximum dry density was observed for both the clays reaching
the increase up to 5% and 8% for illite and kaolinite respectively at 500oC.
Fig. 5: Effect of heat treatment on optimum water content
313 Mahmoud Bensaibi et al, 2014
Australian Journal of Basic and Applied Sciences, 8(19) Special 2014, Pages: 310-314
Fig. 6: Effect of heat treatment on maximum dry density
The effect of temperature on the unconfined compressive strength of the two soil samples is shown in
Figure 7. Temperature increase beyond 100oC produced excessive decrease in unconfined compressive strength
for the two soils. And finally it reached to 0% at a temperature of 500oC.
Conclusion:
This study displayed that temperature has a significant effect on soil physical properties such as, Atterberg
limits, optimum water content and unconfined compressive strength. The relative change in these properties was
higher when temperature ranged from 100 to 500oC. Soils were normally not affected in great deal by
temperature below 100oC. Therefore it can be concluded that a temperature of 500oC brings drastic changes in
the mechanical properties of the two soils and transforming them into very weak soils.
Fig. 7: Effect of heat treatment on unconfined compressive strength
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Akinmusuru, J., 1994. Thermal conductivity of earth blocks, Journal of Materials in Civil Engineering, 6: 3-
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Joshi, R., A.C. Gopal, D. Horsfield, T. Nagaraj, 1994. Effect of heat treatment on strength of clays, Journal
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Australian Journal of Basic and Applied Sciences, 8(19) Special 2014, Pages: 310-314
Ma, C. and T. Hueckel, 1992. Effects of inter phase mass transfer in heated clays: a mixture theory,
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Yang, L. and B. Farouk, 1995. Modelling of solid particles flow and heat transfer in rotary kiln calciners,
30th National Heat Transfer Conference, American Society of Mechanical Engineers, p: 11.
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Temperature effects on the engineering properties and behaviour of soils, Highway Research Board, Special Report 103 Stress–strain behaviour of reconstituted illitic clay at different temperatures
  • J K Mitchell
  • N Tanaka
  • J Graham
  • T Crilly
Mitchell, J.K., 1969. Temperature effects on the engineering properties and behaviour of soils, Highway Research Board, Special Report 103. Tanaka, N., J. Graham and T. Crilly, 1997. Stress–strain behaviour of reconstituted illitic clay at different temperatures, Engineering Geology, 47: 339.