Transcript عرض تقديمي من PowerPoint

‫بسم هللا الرحمن الرحيم‬
‫قالوا سبحانك العلم لنا االماعلمتنا‬
‫انك أنت العليم الحكيم‬
‫صدق هللا العظيم‬
Assessment of the Egyptian Clayey Deposits for
Ceramic Industries
Mohammed A. Serry
Department of Refractories, Ceramics and
Building Materials, National Research Centre,
12622-Dokki, Cairo, Egypt
[email protected]
Aim of the Research work
• Reviewing most of the studies published during the last 50 years
on geology and assessment of the Egyptian clayey deposits for
ceramic industries
• Discussing the relationship between nature and ceramic
properties of these clays and their chemical, mineral and particlesize composition
• Colour, compactness and rate of slaking in water represent nature
of the clays, whereas their ceramic properties are represented by
plasticity as well as drying and firing behaviour
• Accordingly, the Egyptian clayey deposits are classified into three
main categories; namely, kaolinite- smectite- and illite rich clays.
• What are Clayey Deposits?
Clayey Deposits are soft plastic sedimentary
rocks, mainly compose of variable amounts of clay
and non-clay minerals
Clay minerals are mainly:
Kaolinite, illite and smectite ( or montmorillonite)
Non-clay minerals are mainly:
Quartz, feldspars, micas, calcite, gypsum, goethite,
limonite, alunite and others
• Crystal Structure and properties of clay minerals:
Clay minerals are generally hydrated aluminosilicates with characteristic layer crystal structure
(Figure 1), based on different combinations of SiO4tetrahedral layers with AlO6-octahedral layers at
their corners.
Such structure leads to formation of fine, platy
and charged particles with variable rates of slaking in
water and plasticity as well as drying and firing
behaviour.
Figure 1: Crystal structure of the kaolinite, illite and
smectite clay minerals
The physical properties of clay minerals are
directly related to their crystal structure:
- Kaolinite clay mineral has high particle sizes
(2-10 um), Al2O3 content (~40%) and
vitrification range (>1400oC), with low cationexchange capacity, impurity oxides (<5%), rate
of slaking in water and plasticity as well as
drying and firing shrinkage.
In contrast, smectite clay mineral has ultralow particle sizes (<2 um), Al2O3 content (<20%)
and vitrification range (<1000oC), with high
cation-exchange capacity, impurity oxides (up to
20%), rate of slaking in water and plasticity as
well as drying and firing shrinkage.
Meanwhile, illite clay mineral always shows
intermediate levels of all physical properties
between those of kaolinite and smectite
• Summary of Previous Relevant
Research Work
Amer et al. (1970) have assessed the
clayey deposits existing at some localities
around the Nile Valley and Gulf of Suez for
ceramic industries.
They
have
investigated
geology,
petrography and chemistry of these clays
and generally summarized their suitability
for ceramic industries.
In 1974, Hegab has studied in detail geology,
petrography and mineralogy of many clay deposits
exposed at the Nile Valley as well as Eastern and
Western deserts.
He also outlined the prospective application
fields of the studied clays according to their
chemical and mineral composition.
Gindy (1983) has generally classified the Egyptian clays and
marls into three major clay-mineral provinces as follows (Figure 2):
• Kaolinite-rich clays, exposed south of Egypt and formed by
chemical weathering and leaching of the Precambrian granite
masses, during Paleozoic-Cretaceous times
•
Kaolinite-illite rich clays, exists around Gulf of Suez and formed
due to effect of hydrothermal fluids associated the tectonic and
volcanic activity, during Carboniferous time
•
The sedimentary smectite (or montmorillonite)-rich clays, covering
most of Eastern and Western deserts and formed under marine
conditions since Mid-Cretaceous time as well as by continental
deposition from Mid-Eocene to Pliocene times and thereafter, the
River Nile becomes the chief source up to the present time
Figure 2: Distribution of the three major clay-mineral
provinces allover Egypt as given by Gindy, 1983
According to the clay mineral composition, previously
characterized by many authors, for the Egyptian clayey deposits
the following classification could be done as shown in Figure 3:
• Kaolinite-rich clays, mainly exist around Suez Gulf and Aswan
areas
• Smectite-rich clays, existing around the Nile valley in most of
Eastern and Western Deserts
• Illite-rich clays, mainly occur in El-Bahariya Oasis, Western Desert
Figure 3: Location map of the Egyptian kaolinite-, smectiteand illite- rich clay deposits allover the country
Chemical and Mineral Composition
of the Egyptian Clays in Relation to
their Ceramic Properties
1- Kaolinite-Rich Clays
Figure 4: DTA curves of the Gulf of Suez kaolinite-rich clays
exposed at El-Tieh, Qiseib and Khaboba
Figure 5: DTA curves of Aswan kaolinite-rich clays exposed at
Abu El-Riesh, Abu Sbera and Kalabsha
Table 1: Mean values of physical properties, particle- size distribution and major mineral
composition of kaolinite rich clays representing Aswan and Gulf of Suez Provinces
Province
Gulf of
Suez
Aswan
Locality
Rate of
slaking
in
water
Water of
plasticity
(%)
Particle-size distribution,,
(mm), (%)
Major mineral composition,
(%)
Sand
2.0 0.063
Silt
0.063 0.002
Clay
- 0.002
Kaolinite
Illite
Quartz
El-Tieh
slow
23
5
50
50
90
5
5
Qiseib
slow
21
12
40
48
85
5
10
Abu ElRiesh
slow
28
2
48
50
65
15
20
Kalabsh
a
slow
23
5
45
50
95
--
5
Table 2: Mean values of chemical constitution as well as vitrification range and linear drying & firing
shrinkage of the kaolinite-rich clays representing Aswan and Gulf of Suez districts
Area
Gulf
Of
Suez
Aswan
locality
Chemical constitution, (%)
Vitrificat
ion
range,
(0C)
from- to
Linear
drying
shrinkage
(%)
Linear
firing
shrinkage
after
vitriication
(%)
SiO2
Al2O3
Fe2O3
TiO2
CaO
MgO
Na2O
K2O
El-Tieh
45.60
36.90
0.80
2.30
0.40
0.30
0.20
0.40
1250 1500
3.5
12.30
Qiseib
48.80
35.20
0.80
1.90
0.10
0.10
0.10
0.50
1250 1500
2.3
4.90
Abu ElRiesh
55.30
27.10
4.20
1.70
0.40
0.40
0.20
0.40
1100 1300
4.8
8.50
Kalabsh
a
44.10
36.70
1.40
2.90
0.20
0.20
0.10
0.10
1250 –
1500
3.6
11.80
Figure 6: XRD pattern and DTA curve of A Tushka kaoliniterich clay exposed at Sinn El-Kaddab Plateau
2- Smectite-Rich Clays
Figure 7: DTA curves of the Western Desert smectite-rich clays
exposed at Wadi El-Natrun, El-Fayoum and El-Kharga
Table 3: Mean values of physical properties, particle -size distribution and claymineral composition of smectite-rich clays of the Eastern and Western Deserts
Desert
Eastern
Desert
Western
Desert
Localit
y
Physical properties
Particle size
distribution, (mm)
( %)
Clay-mineral composition,
( %)
Rate of
slaking
in water
Water of
plasticity
, (%)
Sand
(2.0 0.063)
Silt
(0.063
0.002)
Clay
(0.002)
Kaolinit
e
Illite
smectite
ElTebbin
V. Fast
27
41
32
27
25
12
63
ElMinia
V. Fast
42
25
30
45
27
7
66
Wadi
El
Natrun
V. Fast
65
6
20
74
23
5
72
ElFayum
V. Fast
55
11
32
57
20
5
75
Table 4: Mean values of chemical constitution as well as vitrification range and total drying and firing
shrinkage of smectite-rich clays of the Eastern and Western Deserts
Desert
East
Desert
West
Desert
locality
Chemical constitution, (%)
Vitrification
range,
(oC)
from - to
Total
drying and
firing
shrinkage after
vitrification,,
(%)
at
10000C
and (12500C)
SiO2
Al2O3
Fe2O3
TiO2
CaO
MgO
Na2O
K2O
ElTebbin
59.7
14.7
8.9
1.4
2.0
1.5
1.9
1.2
850 - 1000
11.2
(Bloated)
ElMinia
53.6
19.9
8.8
0.7
1.6
1.2
1.1
1.3
850 - 1000
14.0
(Bloated)
Wadi
ElNatrun
56.2
17.8
4.4
1.5
1.5
2.2
2.7
1.8
850 -1000
15.7
Bloated
ElFayum
55.3
17.9
5.1
1.5
1.2
2.6
1.8
1.4
850 -1000
15.9
Bloated
• Mechanism of bloating of the smectite-rich clays at 1000-1250oC:
-
Formation of excessive amount of viscous silicate liquid phase due to the fluxing
effect of their high impurity oxide content (15-20%) on their high SiO2 (50-60%)
and low Al2O3 (15-20%) contents.
-
Gradual reduction of Fe2O3 into FeO with the evolution of O2 gas, with
simultaneous development of sufficient amount of the viscous silicate phase to trap
the oxygen gas and formation of the black magnetite (FeO.Fe2O3 ) spinel.
-
This results to produce brown, rounded and lightweight bloated clay aggregate
with variable sizes and very low bulk density (~0.5 g/cm3).
-
These aggregates are greatly demanded for processing insulating building and
refractory concretes for application up to 1000oC instead of the more expensive
vermiculite, perlite and diatomite lightweight materials, currently imported for
this purpose.
-
Figure 8 confirms the location of the chemical composition plots of all clays in
terms of their SiO2 , Al2O3 and total fluxing oxides (TFO) content, on calcined basis,
within the area of bloated clays as defined by Riley (1951).
Figure 8: Ternary Al2O3-SiO2-total fluxing oxides composition diagram showing the
chemical constitution of Tushka as well as Eastern and Western Deserts Clays, on
calcined basis plotted and existed within the bloated clays area [after Riley (1951)]
3- Illite-Rich Clays
Figure 9: XRD paterrns of the raw illite-rich clays exposed at El-Gedida iron
ore mine, El-Bahriya Oasis (a) and its vitrified product (b)
Table 5: Mean values of physical properties, particle-size distribution, clay-mineral composition,
chemical constitution as well as vitrification range and total linear shrinkage after vitrification of ElBahariya illite-rich clays.
Sam
ple
Rate of
slaking in
water
Water of
plasticity
(%)
1
Fast
2
Fast
Sampl
e
Particle- size distribution, (mm), (%)
Clay mineral composition, (%)
Sand
(2.0 -0.063)
Silt
(0.063 0.002)
Clay
(- 0.002)
Kaolinite
Illite
37
33
32
35
35
65
-
38
10
32
58
16
84
-
Chemical constitution, (%)
SiO2
Al2O
Fe2O3
TiO2
CaO
MgO
Na2O
K2O
Smectite
L.O.I.
(%)
T.F.O
(%)
Vitrifi
cation
range
(oC)
from
to
3
1
52.00
14.0
0
16.00
0.40
0.50
1.50
1.70
4.30
10.50
24.30
950 1150
2
48.40
15.0
0
15.60
0.20
0.10
1.60
1.80
6.10
10.50
25.30
950 1060
Total
linear
shrinka
ge after
vitrifica
tion
(%)
14.00
15.50