Note: Descriptions are shown in the official language in which they were submitted.
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i
[DESCRIPTION]
[Invention Title]
PULP SLUDGE ASH COMPOSITION FOR.PRODUCING BUILDING MATERIALS
[Technical Field]
<1> The present invention relates to a pulp sludge 'ash composition for
producing building materials. More particularly, the present invention
relates to a pulp sludge ash composition for producing building materials,
which comprises pulp sludge ash obtained by incineration of pulp sludge
generated from a paper manufacturing process after a wastewater treatment
step, and further comprises modified sodium silicate having an acidic group.
The pulp sludge ash composition according to the present invention allows
frt curing with no need for additional baking or sintering. Additionally,
the above pulp sludge ash composition further comprising a polymer emulsion
shows excellent strength and water resistance.
,
[Background Art]
<2> In gen'eral, pulp sludge is generated from a paper manufacturing process
after
a wastewater treatment step, in a great amount. Most of the pulp sludge has
been discarded in a landfill. However, pulp sludge itself is not suitable to
be discarded as landfill because it is not solidified with ease due to its
high water content. Therefore, a recent tendency has been for pulp sludge to-
be dumped in the sea.
<3> To solve the above-mentioned problem, there has been an attempt to
subject pulp sludge to incineration so as to recover any remaining heat
energy from pulp sludge and to reduce the amount of waste to be discarded in
a landfill. Pulp sludge ash generated from such incineration has been thought
to have low industrial applicability, and thus has been utilized in limited
use (for example, a supplementary additive for cement).
<4> Additionally, many attempts have been made to develop use of pulp
sludge ash. For example, Korean Patent Publication No. 1989-0002566 discloses
a method for producing building materials using ash generated from the
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incineration of paper-manufacturing sludge. More particularly, the method
comprises adding slaked lime, asbestos, paper-manufacturing sludge, or the
like to the pulp sludge ash, further adding sodium silicate thereto to
accomplish preliminary bonding, and curing the resultant product with steam
under high temperature and high pressure conditions to provide building
materials. The method permits the initial molding work to be performed
quickly due to the curing reaction of metal oxides and sodium silicate added
to the pulp sludge ash. However, there is a problem in that because sodium
silicate per se has poor water resistance, the bonding force between sodium
silicate and metal oxides is weakened after curing of the pulp sludge ash,
due to the absorption of ambient water or moistures into the cured material.
There is another problem embedded in this method because it includes a steam-
curing step performed at high temperature, which is not cost-efficient and
has low industrial applicability.
<5> Therefore, there is a continuous need for a method for recycling pulp
sludge ash. This may be in the form of the creation of a pulp sludge ash
composition,,which has excellent bonding strength and water resistance and is
cost-efficient, or in the form of the same pulp sludge ash composition.
<6>
'[Disclosure]
[Technical Problem]
<7> Therefore, the present invention has been made iri view of the above-
mentioned
problems. It is an object of the present invention to provide a pulp sludge
ash composition for producing building materials, wherein the pulp sl,udge ash
composition comprises pulp sludge ash and modifi-ed sodium silicate having an
acidic group added thereto, allows fast curing with no need for additional
baking or sintering, and shows excellent strength and water resistance.
<8> It is another object of the present invention to provide a pulp sludge
ash composition for producing building materials, which uses sodium'silicate
modified to provide improved water resistance, so that the water absorptivity
can be reduced significantly.
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<9> It is still another object of the present invention to provide a pulp
sludge ash composition for producing building materials, which comprises
modified sodium silicate having an acidic group, combined with aggregate or
light aggregate, and thus shows more improved strength or significantly
reduced specific gravity.
<10>
(Technical Solution]
<11> According to an aspect of the present invention, there is provided a pulp
sludge ash composition for producing building materials, which is obtained by
mixing pulp sludge ash with modified sodium silicate having an acidic group.
<12> According to another aspect of the present invention, there is
provided a pulp sludge ash composition for producing building materials,
which is obtained by mixing pulp sludge ash with modified sodium silicate
having an acidic group, combined with a polymer emulsion.
<13> Particularly, the modified sodium silicate having an acidic group is
obtained by mixing sodium silicate with any one selected from the group
consisting of: aqueous sodium sulfate, copper sulfate, iron sulfate, aluminum.
sulfate, magnesium sulfate, potassium bicarbonate, chrome alum, sulfuric acid
and hydrochloric acid solutions; and mixtures thereof; and then adding
caustic soda thereto as a catalyst.
<14> In a preferred embodiment of the present invention, the modified
sodium silicate having an acidic group is obtained by introducing sodium
silicate and each aqueous solution of copper sulfate, sodium sulfate, caustic
soda and chrome alum into'an agitator, followed by agitation.
<15> In another preferred embodiment of the, present.invention, the modified
sodium silicate having an acidic group is obtained by introducing sodium
silicate, 10% aqueous sodium lauryl sulfate solution, caustic soda and
aqueous sulfuric acid solution into an agitator, followed by agitation.
<16> Particularly, the polymer emulsion is any one selected from the group
consisting of latex, silicone resin, gum arabic, acrylic resins and epoxy
resins.
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<17> In the pulp sludge ash composition according to the present invention,
the pulp sludge ash and the modified sodium silicate having an acidic group
are mixed in a ratio of 1: 1.2-2.
<18> To increase the strength, the pulp sludge ash composition may further
comprise any one selected from the group consisting of-dust, fly ash, sand,
slag, gypsum, lime and molding sand.
<19> To reduce the specific gravity, the pulp sludge ash composition may
further comprise any one light-weight additive selected from the group
consisting of wood powder, pearlite, vermiculite, Styrofoam particles and a
foaming agent.
<20> When the above-mentioned additives are added to the pulp sludge ash
composition, organic bentonite or methyl cellulose is further added thereto
in order to accomplish a uniform distribution.
<21> Additionally, to improve the bending strength, the pulp sludge ash
composition may further comprise any one selected from the group consisting-
of wire mesh, waste fiber and fiber.
<22>
[Advantageous Effects]
<23> As can be seen from the foregoing, the cement-like composition according
to the present invention, which comprises pulp sludge ash and the modified
sodium silicate, shows excellent water resistance and strength, and thus is
useful for various industrial fields as a building material, etc. The
composition may further comprise various kinds of additives, if desired, to
conform to the particular use thereof. Additionally, it is possible to
transform various kinds of industrial wastes into the composition according
to the present invention. Therefore, the present invention contributes to
recycling of wastes and the protection of environment, and is cost-efficient
and time-efficient.
<24> While this invention has been described in connection with what is
presently considered to be the most practical and preferred embodiment, it is
to be understood that the invention is not limited to the disclosed
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embodiment and the drawings. On the contrary, it is intended to cover various
modifications and variations within the spirit and scope of the appended
claims.
<25>
[Description of Drawings]
<26> The foregoing and other objects, features and advantages of the present
invention will become more apparent from the following detailed description
when taken in conjunction with the accompanying drawings in which:
<27> FIG. 1 is a photograph showing various building materials obtained
from the pulp sludge ash compositions according to preferred embodiments of
the present invention.
<28>
[Best Nlode]
<29> Hereinafter, the present invention will be explained in more detail.
<30> The present inventors have found that addition of an aqueous acidic
solution to pulp sludge ash results in fast curing within a time of 1 hour or
less. Based on this finding, there is provided modified sodium silicate to
improve the strength of a pulp sludge ash composition, wherein the modified
sodium silicate is obtained by adding sodium silicate to an acidic solution,
such as an aqueous solution of sodium sulfate, copper sulfate, iron sulfate,
aluminum sulfate, magnesium sulfate, potassium bicarbonate, chrome alum,
sulfuric acid or hydrochloric acid solutions. Additionally, caustic soda
(sodium hydroxide) is added to the pulp sludge ash composition, as a catalyst
that helps blending of pulp sludge with the aqueous acidic solution.
<31> Due to the acidic group contained in the modified sodium silicate,
pulp sludge ash can be cured quickly and the modified sodium silicate shows
more improved water resistance compared to non-modified sodium silicate.
<32> Particular examples of the aqueous acidic solution that may be used to
provide the modified sodium silicate include aqueous solutions with pH 7 or
less, such as an aqueous sodium sulfate, copper sulfate, iron sulfate,
aluminum sulfate, magnesium sulfate, potassium bicarbonate, chrome alum,
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sulfuric acid and hydrochloric acid solutions, and mixtures thereof.
<33> Although various combinations of the above aqueous acidic solutions
may be used to provide modified sodium silicate, it is preferable to use
modified sodium silicate 1 and modified sodium silicate 2 as described
hereinafter so as to improve the water resistance to.the highest degree.
<34> (1) Modified Sodium Silicate 1
<35> Modified sodium silicate 1 having an acidic group is obtained by
introducing sodium silicate, copper sulfate, sodium sulfate and chrome alum
into an agitator in a mixing ratio of 30:4:3:20, further introducing caustic
soda into the agitator in the same proportion as chrome alum, and agitating
the resultant mixture for 30 minutes.
<36> (2) Modified Sodium Silicate 2
<37> Modified sodium silicate 2 having an acidic group is obtained by
adding 10% aqueous sodium lauryl sulfate solution and caustic soda to sodium
silicate, agitating the resultant mixture for 30 minutes, and further adding
aqueous sulfuric acid solution thereto with stirring. Preferably, sodium
silicate, 10% aqueous sodium lauryl sulfate solution, caustic soda and
aqueous sulfuric acid solution are mixed in a ratio of 10:3:10:3.
<38> The modified sodium silicate having an acidic group, obtained as
described above, is added to pulp sludge ash to provide the composition for
producing building materials according to the present invention. Preferably,
the pulp sludge ash has a fine size of 150 mesh or less, and the mixing ratio
of pulp sludge ash to the modified sodium silicate is 1: 1.2-2, on the
weight basis.
<39> Additionally, the cement-like composition according to the present
invention, comprising pulp sludge ash and the modified sodium silicate having
an acidic group, may further comprise various additives, so as to improve the
water resistance, to prevent deformation such as shrinkage, to increase the
strength, to reduce the specific gravity, or to improve the bending strength.
<40> More particularly, in order to improve the water resistance, the
composition optionally further comprises a polymer emulsion selected from the
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group consisting of latex, silicone oil, gum arabic, acrylic resins and epoxy
resins; in addition to the modified sodium silicate having an acidic group.
<41> For example, 3-25 g of latex, as a polymer emulsion, may be further
added to 100 g of the above "Aodified sodium silicate 1 having an acidic
group with stirring, and then, the resultant combination may be added to pulp
sludge ash. However, addition of the latex in an amount of 25 g or more
inhibits fast curing.
<42> In a variant, 0.3 --15 g of silicone oil, as a polymer emulsion, may be
further added to 100 g of the above %Oodified sodium silicate 1 having an
acidic group with stirring, and then the resultant combination may.be added
to pulp sludge ash. However, addition of the silicone oil in an amount of 15
g or more inhibits fast curing.
<43> In another variant, 5-V15 g of gum arabic and 0.5-3g of silicone oil,
as polymer emulsions, may be further added to 100 g of the above ~a odified
sodium silicate 1 having an acidic group -with stirring, and then the
resultant combination may be added to pulp sludge ash. However, addition of
the gum arabic in an amount of 15 g or more inhibits fast curing.
<44> In still another variant, 5-25 g of an acrylic resin and 0.5-3 g of
silicone oil, as polymer emulsions, may be further added to 100 g of the
above "Aodified sodium silicate 1 having an acidic group with stirring, and
then the resultant combination may be added to pulp sludge ash. However,
addition of the acrylic resin in an amount of 25 g or more inhibits fast
curing.
<45> Meanwhile, in order to prevent deformation such as shrinkage, the
cement-like compositiori, comprising pulp sludge ash and the modified sodium
silicate having an acidic group, may further comprise calcium carbonate,
lime, a metal oxide such as magnesium oxide or zinc oxide, or the like.
<46> In order to increase the strength, the cement-like composition,
comprising pulp sludge ash and the modified sodium silicate having an acidic
group, may further comprise dust, fly ash, sand, slag, gypsum, lime, molding
sand, or the like.
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<47> In order to reduce the specific gravity, the cement-like composition,
comprising pulp sludge ash and the modified sodium silicate having an acidic
group, may further comprise light-weight aggregate, such as wood powder,
pearlite, vermiculite or Styrofoam particles, or may be provided with air
bubbles obtained from pressurized air with a vegetable foaming agent. When
such light-weight aggregate or air bubbles are added to the composition, a
thickening agent such as organic bentonite or methyl cellulose may be further
added thereto so as to accomplish uniform blending.
<48> Additionally; in order to improve the bending strength, the cement-
like composition, comprising pulp sludge ash and the modified sodium silicate
having an acidic group, may further comprise wire mesh, waste fiber, fiber,
or the like.
<49>
[Mode for Invention]
<50> Reference will now be made in detail to the preferred embodiments of the
cement-like composition, comprising pulp sludge ash and the modified sodium
silicate having an acidic group, according to the present invention. Test
results for each composition are also provided.
<51> Example 1
<52> First, 60 parts of pulp sludge ash were provided. Next, 85 parts. of
modified sodium silicate were prepared by mixing 1,500g of sodium silicate
with an aqueous acidic solution with stirring. The acidic solution was
obtained by introducing 200g of copper sulfate, 150g of sodium sulfate,
1,000g of caustic soda and 1,000g of chrome alum into an agitator, each in
the form of an aqueous solution, and.agitating the materials for 30 minutes.
Then, 60 parts of pulp sludge were mixed with 85 parts of the modified sodium
silicate to obtain a cement-like composition.
<53> The pulp sludge ash composition was injected into a cylindrical mold
having a diameter of 50mm and a depth of 100 mm. Then, a bar having a weight
of lkg and a diameter of 10mm was placed on the mold at different times, and
determined the initial curing completion time, when the molded product showed
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no physical changes in its surface and permitted demolding and handling. The
composition removed from the mold was cured naturally for 7 days. Then, the
composition was measured for its weight and strength. Additionally, the
composition was dipped into a water bath for 24 hours and removed from the
water bath. Then, the composition was dried for 1 hour, and then was measured
for its weight and strength to determine the water absorptivity and strength
of the composition. The results are shown in the following Table 1.
<54> Examp l e 2
<55> First, 60 parts of pulp sludge ash were provided. Next, 85 parts of
modified sodium silicate were prepared by adding 300g of 10% aqueous sodium
lauryl sulfate solution and 1,000g of aqueous caustic soda to 1,000g of
sodium silicate, agitating the materials for 30 minutes and further adding
300g of 10% aqueous sulfuric acid solution thereto and further agitating the
materials. Then, 60 parts of pulp sludge were mixed with 85 parts of the
modified sodium silicate to obtain a cement-like composition.
<56> The composition obtained in this Example was tested in the same manner
as described in the above Example 1. The results are shown in the following
Table 1.
<57> Examp l e 3
<58> First, 60 parts of pulp sludge ash were provided. Next, 85 parts of
modified sodium silicate were prepared by mixing 1,500g of sodium silicate
with an aqueous acidic solution with stirring. The acidic solution was
obtained by introducing 200g of copper sulfate, 150g of sodium sulfate,
1,000g of caustic soda and 1,000g of chrome alum into an agitator, each in
the form of an aqueous solution, and agitating the materials for 30 minutes.
Further, 30g of latex and 3g of silicone oil were added to 1,000g of the
acidic solution. Then, 60 parts of pulp sludge were mixed with 85 parts of
the modified sodium silicate to obtain a cement-like composition.
<59> The composition obtained in this Example was tested in the same manner
as described in the above Example 1. The results are shown in the following
Table 1.
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<60> Example 4
<61> First, 60 parts of pulp sludge ash were provided. Next, 85 parts of
modified sodium silicate were prepared by mixing 1,500g of sodium silicate
with an aqueous acidic solution with stirring. The acidic solution was
obtained by introducing 200g of copper sulfate, 150g of sodium sulfate,
1,000g of caustic soda and 1,000g of chrome alum into an agitator, each in
the form of an aqueous solution, and agitating the materials for 30 minutes.
Further, 30g of silicone oil were added to 1,000g of the acidic solution.
Then, 60 parts of pulp sludge were mixed with 85 parts of the modified sodium
silicate to obtain a cement-like composition.
<62> The composition obtained in this Example was tested in the same manner
as described in the above Example 1. The results are shown in the following
Table 1.
<63> Examp l e 5
<64> First, 60 parts of pulp sludge ash were provided. Next, 85 parts of
modified sodium silicate were prepared by mixing 1,500g of sodium silicate
with an aqueous acidic solution with stirring. The acidic solution was
obtained by introducing 200g of copper sulfate, 150g of sodium sulfate,
1,000g of caustic soda and 1,000g of chrome alum into an- agitator, each in
the form of an aqueous solution, and agitating the materials for 30 minutes.
Further, 30g of an acrylic polymer emulsion and 3g of silicone oil were added
to 1,000g of the acidic solution. Then, 60 parts of pulp sludge were mixed
with 85 parts of the modified sodium silicate to obtain a cement-like
composition.
<65> The composition obtained in this Example was tested in the same manner
as described in the above Example 1. The results are shown in the following
Table 1.
<66> Comparative Example
<67> A composition was prepared by adding 100 parts of non-modified sodium
silicate solution to 60 parts of pulp sludge ash.
<68> The composition obtained in this Comparative Example.was tested in the
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same manner as described in the above Example 1. The results are shown in the
following Table 1.
<69> [Table 1]
<70> Test Results for Compositions Comprising Pulp Sludge Ash and Modified
Sodium Silicate
Sample Curing Weight Weight Strength Strength
time before after before after
(min.) dipping dipping dipping dipping
(g) (g) (kg/cmZ) (kg/cm2)
Ex. 1 21 301.6 358.9 93 89
Ex. 2 19 303.0 360.6 87 85
Ex. 3 32 302.1 311.6 118 104
Ex. 4 43 301.4 310.4 117 110
Ex. 5 36 301.5 320.0 135 130
Comp. Ex. 280 348.4 351.2 136 0
<71>
<72> As can be seen from Table 1, the compositions comprising pulp sludge
ash and the modified sodium silicate having an acidic group are capable of
fast curing within 1 hour, thereby providing products that can be demolded,
transported and loaded with ease. Such compositions are amenable to mass
production. After the water bath dipping test, it can be seen that addition
of a polymer emulsion can provide the compositions with excellent water
resistance, as compared to the sample free from a polymer emulsion, which
shows a relatively high water absorptivity and a relatively low strength. On
the contrary, the sample according to the above Comparative Example,
comprising non-modified sodium silicate, is not capable of fast curing and
causes cracking and deformation on the surface during drying. Moreover, the
comparative sample shows such poor water resistance that the sample may be
dissolved in the water bath dipping test, thereby making it impossible to
measure the strength after dipping. Therefore, it can be seen that the sample
according to the above Comparative Example has no industrial applicability.
<73> Meanwhile, in order to improve the water resistance of the composition
according to the present invention, it is also possible to apply a polymer
emulsion onto the surface of the composition.
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<74> Additionally, in order to determine whether harmful heavy metals
generally contained in pulp sludge ash are leached out of each composition
according to the above Examples and Comparative Examples, each composition
was crushed after measuring the compression strength, and then subjected to
the test methods for waste process evaluation. The results are shown in the
following Table 2.
<75> [Table 2]
<76> Results for Heavy Metal Leaching in the Inventive Compositions
Results (expressed in ppm units)
Item pH
Pb Cu As Hg Cd Cr Zn Ni Mn
Quality 7 3 3 1.5 0.005 0.3 1.5 3 3 3
Standard
Pulp sludge ash 5.8 52 43 0.01 ND 0.2 10 206 13 16
Ex. 1 10.5 0.03 0.01 ND ND ND ND 0.4 ND ND
Ex. 2 10.1 ND ND ND ND ND ND ND ND ND
Ex. 3 10.3 16 8 ND ND ND 0.04 34 0.01 0.02
Ex. 4 10.4 ND ND ND ND ND ND 0.03 ND 0.04
Ex. 5 10.0 ND ND ND ND ND ND 0.02 ND 0.01
Comn. Ex. 11.5 1.4 0.6 ND ND ND 0.03 3.5 ND 1.8
<77>
<78> As can be seen from Table 2, although pulp sludge ash contains a large
amount
of heavy metals such as lead, zinc, etc., the inventive composition
comprising the modified sodium silicate having an acidic group in addition to
pulp sludge ash does not allow the heavy metals to leach out of the
composition. On the contrary, the composition according to the Comparative
Example allows several heavy metals to leach out of the composition. As
demonstrated by the above results, the cement-like composition according to
the present invention is capable of fast 'curing and does not cause
environmental pollution. Therefore, it is thought that the present invention
may be applied to solidify any other heavy metal-containing industrial wastes
in a short time, or to transform the same wastes into industrially useful
products.
<79> Hereinafter, the composition comprising pulp sludge ash and the
modified sodium silicate, and further comprising various add-itives, if
desired, according to another preferred embodiment of the present invention
will be described.
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<80> Example 6: Composition Further Comprising Fly Ash
<81> First, 60 parts of pulp sludge ash was provided. Next, 130 parts of
modified sodium silicate having an acidic group was prepared by introducing
1,500g of sodium silicate No. 3, 200g of copper sulfate, 150g of sodium
sulfate, 1,000g of caustic soda and 1,000g of chrome alum, each dissolved in
hot water, into an agitator, stirring the materials for 30 minutes to provide
1,000g of an acidic solution, further adding lOOg of a polymer emulsion latex
and 3g . of silicone oil thereto with stirring. Then, 60 parts of pulp sludge
ash was mixed with 130 parts of the modified sodium silicate to obtain a
cement-like composition. Finally, 30 parts of fly ash was further added to
the cement-like composition.
<82> The final composition was injected into a cylindrical mold having a
diameter. of 100mm and a depth of 200 mm. Then, a bar having a weight of lkg
and a diameter of 10mm was placed on the mold at different times, and
determined the initial curing completion time, when the molded product showed
no physical changes in its surface and permitted demolding and handling. The
composition removed from the mold was cured naturally for 3 days. Then, the
composition was measured for its weight and strength. Additionally, the
composition was dipped into a water bath for 24 hours and removed from the
water bath, and then was measured for its weight and strength to determine
the water absorptivity and strength of the composition. The results are shown
in the following Table 3.
<83> Example 7: Composition Further Comprising Dust Generated from Steel-
Manufacturing Process
<84> A cement-like composition was prepared by mixing 60 parts of pulp sludge
ash with 120 parts of the modified sodium silicate having an acidic group,
obtained in the same manner as described in Example 6. Then, 100 parts of
dust generated from a steel-manufacturing process was added to the
composition. The composition was tested according to the method as described
in Example 6. The results are shown in the following Table 3.
<85> Example 8: Composition Further Comprising Iron Powder
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<86> A cement-like composition was prepared by mixing 60 parts of pulp sludge
ash with 120 parts of the modified sodiuni silicate having an acidic group,
obtained in the same manner as described in Example 6. Then, 300 parts of
iron powder generated after a surface treatment process for .iron panels was
added to the composition. The composition was tested according to the method
as described in Example 6. The results are shown in the following Table 3.
<87> Example 9: Composition Further Comprising Copper Slag
<88> A cement-like composition was prepared by mixing 60 parts of pulp
sludge ash with 120 parts of the modified sodium silicate-having an acidic
group, obtained in the same manner as described in Example 6. Then, 170 parts
of copper slag generated during a copper refining process was added to the
composition. The composition was tested according to the method as described
in Example 6. The results are shown in the following Table 3.
<89> Example 10: Composition Further Comprising Waste Molding Sand
<90> A cement-like composition was prepared by mixing 60 parts of pulp sludge
ash with 120 parts of the modified sodium silicate having an acidic group,
obtained in the same manner as described in Example 6. Then, 100 parts of
waste molding sand with a size of 7 mm or less, generated during a molding
process, was added to the composition. The composition was tested according
to the method as described in Example 6. The results are shown in the
following Table 3.
<91> [Table 3]
<92> Test Results for Physical Properties of Compositions Further Comprising
Various Kinds of Aggregate
Curing Weight Weight Strength Strength
Sample before after before after
time
(min) dipping dipping dipping dipping
(g) (g) (Kg/Cm) (Kg/cd)
Ex. 6 31 295.9 304.6 121 120
Ex. 7 28 364.6 375.1 126 130
Ex. 8 25 869.5 879.6 166 161
Ex. 9 30 469.1 473.8 181 180
Ex. 10 48 387.6 396.6 176 175
<93>
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<94> As can be seen from Table 3, each composition according to Examples 6-10
conform to the constitution of the cement-like composition according to the
present invention due to the presence of the modified sodium silicate in
addition to pulp sludge ash. However; addition of fly ash results in a
slightly delayed curing time. Therefore, it can be seen that addition of fly
ash controls the curing time. Also, it can be seen that addition of steel-
manufacturing dust and other aggregate contributes to realization of fast
curing and improved strength. Particularly, because industrial wastes such as
steel-manufacturing dust containing a large amount of heavy metals can be
incorporated into the composition according to the present invention, it is
-possible to recycle various types of harmful wastes into curable cement.
Meanwhile, besides the above-described wet process wherein mortar is injected
into a mold and cured therein, it is also possible to obtain a composition
according to the present invention via a pressurized molding process by
incorporating aggregate into the composition. The following Examples 11-13
illustrates the compositions further comprising light-weight aggregate for
the purpose of weight-down.
<95> Example 11: Composition Further Comprising Wood Powder
<96> A composition was prepared by mixing 80 parts of pulp sludge ash with
100 parts of the modified sodium silicate having an acidic group, obtained in
the same manner as described in Example 6. Then, 60 parts (based on the
weight of the above composition) of wood powder (sawdust), as light-weight
aggregate, was added to the composition, and 1.5 parts (based on the weight
of the above composition) of organic bentonite was further added thereto, so
that the light-weight aggregate can be distributed and blended uniformly in
the resultant mortar. The final composition was injected into a cylindrical
mold with a diameter of 50mm and a depth of 100mm. Then, the composition was
measured for its demoldable strength and initial curing time. Additionally,
the composition was cured naturally for 3 days and was measured for its
specific gravity. Also. The composition was measured for its weight before
and after dipping it into a water bath for 12 hours. The results are shown in
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the following Table 4.
<97> Example 12: Composition Further Comprising Pearlite
<98> A composition was prepared by mixing 80 parts of pulp sludge ash with
130 parts of the modified sodium silicate having an acidic group, obtained in
the same manner as described in Example 6. Then, 40 parts (based on the
weight of the above cement-like composition) of pearlite, as light-weight
aggregate, was added to the composition, and 1.5 parts (based on the weight
of the above composition) of organic bentonite was further added thereto. The
final composition was measured in the same manner as described in Example 11.
The results are shown in the following Table 4.
<99> Example 13: Composition Further Comprising Styrofoam Particles
<100> A composition was prepared by mixing 80 parts of pulp sludge ash with
130 parts of the modified sodium silicate having an acidic group, obtained in
the same manner as described in Example 6. Then, light-weight aggregate,
comprising 1,000cc of Styrofoam particles with a size of 3mm or less and 1.2
parts (based on the weight of the above cement-like composition) of methyl
cellulose, was added to the composition. The final composition was measured
in the same manner as described in Example 11. The results are shown in the
following Table 4.
<101> [Table 4]
<102> Test Results for Physical Properties of Compositions Further Comprising
Various Kinds of Light-Weight Aggregate
initial Specific Weight before Weight after
Sample curing time gravity dipping dipping
(min) (g) (g)
Ex. 11 60 8.9 211.4 231.8
Ex. 12 55 7.3 173.1 180.6
Ex. 13 50 6.8 162.5 180.0
<103>
<104> As can be seen from Table 4, each composition further comprising light-
weight
aggregate to reduce the weight also allows fast curing. Moreover, a greater
amount of light aggregate may be used to reduce the weight to a higher
degree, so that the composition is amenable to pressurized molding.
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Additionally, it can be seen that use of a thickening agent such as organic
bentonite or methyl cellulose permits uniform blending of light-weight
aggregate. In a variant, the composition according to the following Example
14 comprises air bubbles for the purpose of weight-down.
<105> Example 12: Composition Further Comprising Air Bubbles
<106> A pulp sludge ash composition was prepared by mixing 80 parts of pulp
sludge ash, containing 1.5 parts of methyl cellulose added thereto, with 100
parts of the modified sodium silicate having an acidic group, obtained in the
same manner as described in Example 6. Then, 1,000cc of air bubbles, obtained
from pressurized air with a vegetable foaming agent, were added .to the
composition with stirring to provide a final composition. The final
composition was injected into a cylindrical mold with a diameter of 50mm and
a depth of 100mm. Then, the composition was measured for its demoldable
strength and initial curing time. Additionally, the composition was cured
naturally for 3 days and was measured for its specific gravity. Also. The
composition was measured for its weight before and after dipping it into a
water bath for 12 hours. The results are shown in the following Table 5.
<107> [Table 5]
<108> Test Results for Physical Properties of Compositions Further Comprising
Air Bubbles
Initial Specific Weight before Weight after
Sample curing time gravity dipping dipping
(min) (g) (g)
Ex. 14 160 4.3 11.6 121.8
<109>
<110> As can be seen from Table 5, addition of air bubbles does not adversely
affect the composition according to the present invention.
<111> As described in the above Examples 1-14, addition of the modified sodium
silicate having an acidic group to pulpsludge ash can provide a cement-like
composition, which is capable of fast curing, and has excellent strength and
water resistance. Additionally, because the composition according to the
present invention may further comprise fly ash, aggregate, light-weight
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aggregate and air bubbles, it is possible to provide a cost-efficient
composition that can be used in various industrial fields, as a building
material, a civil engineering material, an interior material, a filler for a
safe, or the like. Particularly, the pulp sludge ash composition is useful
for solidifying harmful industrial wastes promptly. Further, the composition
may further comprise wire mesh, waste fiber, fiber or pulp sludge in order to
improve the bending strength. To prevent a shrinking phenomenon of the
composition, it is possible to add calcium carbonate, lime, a metal oxide
such as magnesium oxide or zinc oxide, or the like. Besides sodium silicate,
silicate salts (such as potassium silicate and lithium silicate) and modified
sodium silicate, obtained by adding boron, phosphoric acid or aluminum to
sodium silicate during its preparation, provide the same effect as sodium
silicate. Further, the composition may further comprise a dye, a pigment, an
additional waterproofing or water-repellant agent for Portland cement, or the
like, if desired.
<112>
