6th
International Science, Social Sciences, Engineering and Energy Conference
17-19 December, 2014, Prajaktra Design Hotel, Udon Thani, Thailand
I-SEEC 2014
http//iseec2014.udru.ac.th
Property Modification of Vitreous Ceramic Sanitaryware
Using Pottery Stone as Raw Materials
Sirilara,e1, Charoenyingb,e2, Bootpengc,e3, Naksopond,e4 , Ariyajinnoe,e5
a-e
e1
Program of Ceramics Engineering Technology, Faculty of Industrial Technology, Loei Rajabhat University,
234 Loei-Chiangkarn Rd., Muang, Loei, 42000, THAILAND
pakawadee.si@lru.ac.th, e2na_din@outlook.co.th, e3pirondbudpang@hotmail.com, e4Yut007@hotmail.com, e5felspa@gmail.com
Abstract
Pottery stone is raw materials weathering from rhyolite rock containing combination of alumina,
alkali oxide and silica in appropriated ratio that will accelerate vitrification of ceramic body without
dunting or cracking. The objectives of this work were to modify ceramic sanitaryware body by replacing
pottery stone to kaolin clay, feldspar and silica and to compare technological property of conventional
and modified body. Sampling of seven proportional formulations by replacing two types of materials with
0, 50 and 100% replacement were used and all formulations were prepared by wet milling. Casting
properties were tested and analyzed, and then the samples were formed by plaster mold solid casting.
After that, high temperature firing at 1175, 1200 and 1225 ๐ C were conducted. Technological property
follows ASTM C326-09, ASTM C373-88, ASTM C674-88 and ASTM C372-94 has been study. XRD
and SEM were used to investigate crystal structure and microstructure of selected formulations.
The results found that, important property of body with replacing pottery stone to kaolin clay,
feldspar and silica was significantly different at the .05 level. The property with 100% replacing pottery
stone to silica after 1200 fired was suitable to manufacture in sanitaryware industry that as follows;
total shrinkage 9.27%, water absorption 0.17%, bending strength 60.09 MPa, crystal structure consists of
41% mullite, microstructure apparent surface connected homogeneous, porous approximately spherical
shape looks off less than 10 and is distributed uniformly porous, linear thermal expansion 0.34%,
thermal expansion coefficient 7.07x10-6/°C and linear thermal expansion different between body and
glaze 0.02% at temperature of 500°C. The body with 100% replacing pottery stone to silica tend to reduce
vitrification temperature without dunting or cracking because conversion or inversion of quartz by free
silica controlled mechanism.
Keywords: ceramic body, pottery stone, vitrification, water absorption, thermal expansion
1. Introduction
Vitreous sanitaryware body is conventional triaxial body that manufactured from blends
consisting of clays (plastic materials), quartz (filler) and feldspar (flux). Because of high coefficient of
thermal expansion (COE) of quartz and its inversion, / crystal structure transition at 573๐ C,
that shows cracking of body or crazing of body-glaze that are important problems for many ceramic
industries. Common compositions of pottery stone are quartz, mica or sericite, kaolinite, feldspar and
montmorillonite. In several years ago this stone is ejected from clay mining but now the stone is used in
the industries such as tile, white ware and sanitaryware. Composition of pottery stone is K2O-Na2O
combination and firing temperature range is 1100-1260๐ C. Modifying of ceramic sanitaryware body by
materials replacement can be lower firing temperature with good technological property and improve
thermal expansion of body-glaze fit.
2. Experimental procedures
In this work, sanitaryware body formulations were prepared by used pottery stone as main
raw materials mixed with kaolin, clay, feldspar and quartz. The chemical compositions of these raw
materials were determined by XRF analyzer in table 1. Seven different formulations were designed and
denoted P1-P7, that P1 was a conventional formulation. Raw materials compositions of all formulations
were in table 2.
Table1 Chemical composition of raw materials.
Chemical
composition (%)
SiO2
Al2O3
K2O
Na2O
Fe2O3
CaO
MgO
TiO2
MnO
SO3
Rb2O
CuO
ZrO2
SrO
PbO
Nb2O5
ZnO
Y2O3
Ga2O3
BaO
V2O5
P2O5
Total
Pottery
stone
76.3
15.5
2.72
4.17
0.647
0.147
0.102
0.0350
0.129
0.0786
0.00584
0.00939
0.00172
0.00930
0.0208
0.00989
0.00482
100
Kaolin-1
Kaolin-2
Kaolin-3
Clay
Feldspar
Quartz
69.3
22.8
3.59
1.77
1.31
0.429
0.373
0.123
0.0596
0.0353
0.0298
0.0127
0.00819
0.0123
100
57.4
34.3
5.71
0.588
1.29
0.2
0.262
0.0755
0.155
0.0459
0.119
0.0171
0.0501
0.0306
0.0131
0.00989
0.00882
100
53.3
43.2
1.75
1.20
0.0264
0.0550
0.0664
0.0467
0.0695
0.0124
0.0097
0.011
0.0103
0.0137
100
64.4
27.3
3.02
0.189
2.39
0.404
0.582
0.963
0.165
0.0207
0.0117
0.0362
0.023
0.0192
0.0569
0.032
100
67.6
18.0
7.45
1.04
0.504
3.12
1.02
0.396
0.0205
0.0108
0.0343
0.0439
0.00636
0.245
100
98.9
0.526
0.163
0.118
0.0344
0.0388
0.0121
100
Table 2 Raw materials composition of ceramic body formulations.
Formulations
Pottery stone
Kaolin-mixed
Clay
Feldspar
Quartz
Total
P1
P2
P3
P4
P5
P6
P7
0
22
44
7.5
15
16
32
44
22
0
44
44
44
44
9
9
9
9
9
9
9
15
15
15
7.5
0
15
15
32
32
32
32
32
16
0
100
100
100
100
100
100
100
Homogenization of all slips were conducted by wet milling for 12 hrs with 45% water,
0.3% NaSiO3 and 0.1% NaCO3 added plus 250 mesh sieving. The specimens were formed using solid
casting method in plaster molds after measured viscosity, thixotropy and specific gravity of the slips.
To determined technological property of the bodies, rectangle-shaped specimens were fired at 1175, 1200
and 1225๐ C with firing rate of 41๐ C/min and 60 min soaked. Total shrinkage (TS), water absorption
(WA) and modulus of rupture (MOR) of all formulations were investigated follows ASTM C326-09,
ASTM C373-88 and ASTM C674-88 (Eq. (1),(2),(3)), respectively where Lp is the plastic length, Lf is the
fired length, M is the saturated mass, D is the dry mass, P is the load at rupture, L is the distance between
supports, b is the width and d is the thickness of specimen.
%Total shrinkage
(S t ) 
%Water absorption
( A) 
Modulus of rupture
Lp  L f
Lp
 100
M D
 100
D
8 PL
( MOR ) 
bd 2
(1)
(2)
(3)
Linear thermal expansion and coefficient of selected specimens were analyzed by dilatometer
method according to the ASTM C372-9. The microstructural evolution of selected fired specimens,
that prepared by polishing and etched in 3% HF acid solution for 10 min were observed by using SEM
in combination with EDX spectroscopy. The crystalline phases of fired specimens were determined using
XRD analyzer.
3. Results and discussion
3.1 Technological property of modified body
Water absorption and modulus of rupture for all formulations depended on firing temperature.
Fig.1 (a) lower water absorption was found in P2-P3 and P6-P7, which using pottery stone replaced
feldspar and quartz for 50-100%, respectively. On the other hand, fig.1 (b) higher modulus of rupture was
found in P2-P3 and P6-P7 for all firing temperature. P3 and P7 had WA lower than 0.5% and only P7 had
very high MOR after 1200 and 1225๐C fired, which are concerning for sanitaryware use. Because fineness
particle size of the ground materials has larger surface area that leaded bodies denser [1, 2]. The presences
of K2O+Na2O in pottery stone accelerating vitrification for the bodies [3]. The formulation P7 shows
good technological property, 0.17% WA and MOR 60.09 MPa at lowest firing temperature, 1200๐C.
P1
P2
P3
P4
P5
P6
P7
P1
(a)
P2
P3
P4
P5
P6
P7
(b)
Figure 1 Technological property of specimens after 1175, 1200 and 1225 ๐C fired (a) WA and (b) MOR.
3.2 Comparison of mullite formation and microstructure
The comparison of mullite proportion between conventional sanitaryware body, P1 and the
selected one, P7 was in table 3. The XRD analysis showed the combination of two major phases in the
bodies, quartz and mullite. For pottery stone modified body, P7 (42%), the result showed that mullite
proportion was higher than the convention one, P1 (23%). In fact, mullite forms from two mechanisms,
decomposition from pure kaolinite and interaction of feldspar, quartz and clay at high temperature, which
controlled mechanical behavior of body [4-6].
Table 3 Phase analysis of modification body after 1200๐C fired.
Phase proportion (%)
Quartz
Mullite
P1
77
23
P7
59
41
Microstructure in fig.2 shows the linked pores larger than 10 m in P1 (fig.2 (a)) and
coalescence pores whose diameter was about 3-5 m in P7 (fig.2 (c)). Primary mullite (PM), secondary
mullite (SM) and quartz grain were occurred in both specimens (fig.2 (b-d)). Because of lower volume of
feldspar in P1 than P7, leads it lower densification [6]. Smaller diameter of pores and no interconnecting
channels in P7 which explains the zero water absorption [7]. At about 990 ๐ C (eutectic point), quartz
dissolution was occurred and mullite was formed until 1150 ๐ C [4]. During firing, feldspar fusibility and
ability to form eutectics reach a high densification [8].
Q
SM
PM
(a)
(b)
SM
PM
Q
(c)
(d)
๐
Figure 2 Microstructures of body P1 (a-b) and P7 (c-d) after 1200 C fired at 500X and 1,500X, respectively.
3.3 Body-glaze fit
High volume of quartz increases thermal expansion, since it does not all enter into the glassy
phase on firing [9]. Lower free quartz trend to lower thermal expansion coefficient and risk of
microcracking of body [10]. At about 500๐C, the greater rate of glass expansion zone [11]. Figure 3 shows
linear thermal expansion curve of bodies and conventional glaze (G), that the curve of glaze G were
closed to the curve of body P7 more than P1. The glaze curve was superimposed on body P7. Shrinkage
differences of glaze and bodies at 500๐ C in figure 4 shows that the differences of G-P7 was better than
G-P1, which about 0.02% difference in the range for sanitaryware.
Table 4 Linear thermal expansion analysis of body-glaze fit at 500๐C.
Specimens
P1
P7
Conventional Glaze
dL/L0 (%)
0.41
0.34
0.32
 (x10-6/๐C)
8.47
7.07
6.72
Linear thermal expansion: dL/L0 (%)
P1
P7
G
Figure 3 Linear thermal expansion of bodied P1 and P7 compared with conventional glaze (G).
4. Conclusions
Using of pottery stone as sanitaryware raw materials replaced feldspar and quartz can be
modified vitreous ceramic body with near zero water absorption, very high bending strength, lower
thermal expansion and trend to decrease dunting effect at firing temperature lower to 1200 ๐ C. Thermal
expansion coefficient of modified body can be decreased and body-glaze fit can be improved.
Acknowledgments
This project was supported by annual government statement of expenditure from Loei Rajabhat
University. The authors gratefully acknowledge Khonkaen ceramic Co., Ltd., Khonkaen, Thailand and
Kiwlom Co., Ltd, Lampang, Thailand for providing raw materials.
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