01-07-2014, 12:29 PM
GLAZED SLUDGE TILE
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Abstract
In this article, glaze with different
colorants was applied to tile specimens
manufactured by incinerated sewage sludge ash
(ISSA) and Clay. Improvements using different
amounts of colorants, and glaze components
and concentrations on tile bodies were
investigated. Three different proportions of clay
(by weight ratio) were replaced by ISSA. Tiles
of size 10cm *10cm*1 cm were made and left
in an electric furnace to make biscuit tiles at
800°C. Afterwards, four colorants, Fe2O3 (red),
V2O5 (yellow), and CoCO3 (blue) and three
different glaze concentrations were applied on
biscuit tile specimens. These specimens were
later sintered into glazed tiles at 1050°C. The
study shows that replacement of clay by sludge
ash had adverse effects on properties of tiles.
Water absorption increased and bending
strength reduced with increased amounts of
sludge ash. However, both water absorption and
bending strength improved for glazed ash tiles.
Abrasion of grazed tiles reduced noticeably
from 0.001 to 0.002 g. This implies glaze can
enhance abrasion resistance of tiles.
Introduction
Since Chennai city is extending its zones
for the growth of heavy population, the
government in TN has been very positive in the
construction of sanitary sewer and wastewater
treatment plants. With this increases in house
connections, the amounts of wastewater and
sewage sludge will likely increase as well. It is
becoming harder to find land to be used as
sanitary landfill for dry sludge cakes in Chennai
city. As a result, how to efficiently reclaim
from sewage sludge is important, the sewage is
incinerated which reduces its volume building
bricks are also manufactured by mixing dry
sewage sludge with clay comprising 30-40% of
dry sludge seen as the optimum amount. The
properties such as bending strength and
abrasion of ash bricks met the standards and
properties of sludge bricks were found to be
way below average. Using sewage sludge as
construction materials are commonly seen in
research. However, high-priced tiles
manufactured by sewage sludge and clay were
studied less. Bio-solid ash was used to make
tiles which showed water absorption and
bending strength met the requirements of
standard specifications. But when different
amounts of ISSA were added to clay to
manufacture biscuit tiles, shortcomings such as
higher water absorption, abrasion, and
excessive pores were noticed. In order to solve
such shortcomings, we mix ISSA with clay to
make glazed tiles. Results indicated that
application of glaze to biscuit tiles could
improve drawbacks such as water absorption
and abrasion. It also slightly increased the
bending strength of tiles. In addition, bending
strengths of tiles with various amounts of ash
added when sintered at same temperature also
proved good. When glazes were applied on the
surface of ash tiles, a hard dense impermeable
layer formed after being fired in a kiln at high
temperature. This layer provided glazed ash
tiles with better resistance in physical and
Methods and materials
Dewatered sewage sludge samples were
obtained from a local municipal wastewater
treatment plant. These samples are dried at
room temperature and incinerated at kiln at
800°C.Incinerated sludge ash passing a
#200mm sieve was collected and properties
such as unit weight (2.71 g/cm3), specific
weight (2.67), specific surface area (4860
cm2/g), and pH values (5.97–6.02) were
obtained. The specific weight (2.52) and
specific surface area (5398 cm2/g) of clay were
also determined. The plasticity index of clay,
which is decided by the Atterberg Limits test,
was 19.11 and reduced to 16.94 when 30% of
ash was mixed with clay. This indicated that
ash can lower the plasticity of mixture. Further,
both chemical components of clay and ISSA are
shown in Table1. As seen in the table, the
quantities of each component in ISSA were
more than those in clay, with the exceptions of
Si. In this study, the procedure of making
glazed ash tile is shown diagrammatically in
Fig. 2. Four different proportions of ash, 0%,
30% and 45% were prepared for mixing with
clay. The optimum amount of water for a
mixture was determined by a standard
compaction test. Air in the mixture was
expelled using a De-airing vacuum pug mill
Penetration test
To help investigate the effects of ash
replacement on water when used in making a
mixture of ash clay paste, penetration tests were
performed on specimens of mixture (150 mm in
height) with 0% and 30% ash added. If the
amount of water applied was higher than 45%,
liquefied phenomena were noticed in the
mixtures and 150 mm of penetration depth was
easily reached. The depth of penetration for the
mixture with 30% ash added was less when the
same amount of water was used. This implies
that the replacement of ash could reduce the
plasticity of mixture and lead specimens to a
semi-solid state.
Tile water absorption
Water absorption is used to estimate the
pore ratio of tile specimens. High water
absorption in tile is characterized by a high pore
ratio. The water absorption of tile earthenware
should be less than 16%. Water absorption of
tiles increased by about 3–4% with the addition
of ash, However, glaze formed a thin film,
which helped protect the surface and reduce
water absorption of ash tiles. The water
absorption for 30% ash tile specimens was 13%
before glaze was applied, and became less than
10% with the application of glaze. It also
indicates that water absorption decreased with
the increase of glaze concentration application.
Furthermore, all glaze colors tested helped
reduce more than 2–3% of water absorption.
Performances of different colors were closely
related to components of glaze as well as
degrees of crystallization during the firing
process.
Abrasion of tile surface
The durability and hardness of tiles are
determined by abrasion, which is influenced by
daily human activities. Abrasion types such as
drag motion, friction, and impact are commonly
seen in daily life. Hence, requirements for tile
abrasion are decided by locations and
frequencies of different activities. The abrasion
of tile earthenware should be less than 0.1 g.
The abrasion of tile with 30% ash added was
twice that of the controlled group (clay tile with
no glaze).This indicates that simply replacing
part of the clay with ash in tiles was insufficient
for resisting abrasion and weathering process.
After application of different glazes on ash
tiles, abrasion resistance of tiles improved about
10–20 times more than ash tiles without glaze
applied. This result matched closely to tiles
with glaze applied in the controlled group. It
can be seen that application of glazes to ash
tiles was important in abrasion resistance.
Further, different glaze colors had similar
effects on abrasion resistance, even though the
red color was slightly better.
Tile weight loss on ignition
Weight loss on ignition is to measure
the weight differences in tile specimens before
and after firing. As stated before, sewage sludge
was incinerated at about 800°C before applying
it to manufacture tiles. In this manner, organic
materials in sludge samples were burnt away.
The only source of organic materials came from
Bending strength of tile
Bending strength is affected by the pore
distributions and the vitrification level of the
tile body. Different bending strengths of tiles
are listed in regulations according to the
location and frequency of application. For
example, bending strengths of wall tile
earthenware ranges from 60 to 100 kgf/cm2 and
100 kgf/cm2 for floor tile earthenware.
Theoretically, if glazes were applied to tiles,
bending strength would reduce with increased
thickness. However, bending strengths of
glazed tiles improved to about 5–10 (kgf/cm2).
Glazes melted tightly into tile bodies in the
sintering process at high temperatures. After
crystallizations were rearranged, melted glazes
formed a hard layer on the surfaces of tile,
which could improve the bending strength of
tiles. By comparing the effects of different
glaze colors on bending strength, red glaze
gives a better performance.
Break Strength
Tiles used on floors and walls must be
able to withstand the expected load bearing
capacity of various installations. In order to
determine the strength and durability of the tile,
a standard test method is used to evaluate
individual pieces. A force is applied to an
unsupported portion of the tile specimen until
the breakage occurs. The ultimate breaking
strength is then recorded in pounds per square
inch. Final selection of the tile should be based
upon the breaking strength and the appropriate
installation method
Conclusions
In this study, results obtained on the
basis of experimental data are directed towards
comparing various amount of ISSA added to
the tile body, as well as different colorants and
quantities of glaze concentration applied to the
surface of biscuit tile bodies. The results are
summarized as follows:
1. Test results indicate that glaze formed a thin
film that could protect the surface and reduce
water absorption in ash tiles. They also show
that water absorption decreased with an
increase in glaze concentration applied.
However, different colorants had very small
effects on weight loss on ignition.
2. Comparison of the effects of different glaze
colors on bending strength showed that red
glaze gave a better performance. Since red
colorant contains iron oxide thereby lowering
the sintering temperature, interface adhesion
between red glaze and tile bodies improved
most. As a result, bending strength also
increased.
3. In this study, red glazed ash tiles were most
stable in ageing resistance tests, followed by
blue, yellow. With the help of iron oxide, red
glaze makes glaze crystallization better. A more
excellent light fastness of ash tiles surfaces was
produced.