Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02913306 2015-11-26
CHEMICALLY ACTIVATED CEMENT USING INDUSTRIAL WASTE
FIELD OF THE INVENTION
This invention relates to process and composition of producing high
performance cement using
industrial wastes, more specifically, cements incorporating fly ash.
BACKGROUND OF THE INVENTION
Disposal of industrial waste such as Ground Granulated Blast Furnace Slag
(GGBFS), Cement Kiln
Dust, Fly Ash, etc have been a major problem and concern for the industry. The
above industrial wastes have
alkali metal oxides like lime, silica, alumina, iron, etc., the combination of
which react with calcium to
produce pozzolans. Ordinary Portland Cement (OPC) having ingredients required
for concrete, mortar and
stucco is obtained by grinding Portland cement clinkers and Calcium Sulphate
to form a hydraulic material
that hardens by reacting with water and forms water resistant product.
However, the process to make
Portland cement clinkers requires heating the raw materials to sintering
temperatures. Large amounts of CO2
are released in the making of such preparation which have deleterious effects
on the environment. It is
estimated that the production of OPC utilizes 2% of all the global energy used
and 5% of industrial energy
consumed.
Moreover, the production of a single ton of OPC results in the production of
at least 3/4 ton of green
house gases (of which CO, accounts for 1/2 ton) is emitted that is a major
pollutant that spoils the
environment. The OPC so produced has several drawbacks like cracks due to
shrinkage, expansion because
of sulfate attack, expansion due to the presence of alkalis in the aggregates
etc.
Fly ash is a pozzolan. Class C fly ash contains silica, aluminium and calcium
in combinations which
makes it cementitious and self hardening and has been used as a strengthening
additive in Portland cement.
Class C fly ash is sub-bituminous and has higher sulphur content. The chemical
attributes of the Class C fly
ash are defined in ASTM C-618 which a person of ordinary skilled in the art is
knowledgeable about.
Adding water to Class C fly ash causes it to harden, but the same does not
have significant strength.
Similarly, when Class C fly ash is mixed with Portland cement there are
limitations to the quantity that can
be added.
US Patent No. 4,997,484 as well as US Patent No. 7,288,148 disclose a
composition of fly ash with
acid-base reacting system utilizing the combined effect of citric acid and
alkali hydroxide or metal carbonate.
The composition does not exhibit the required working time and releases lot of
heat during the setting of the
cement which, in turn, causes durability issues.
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US Patent No. 8,016,937 discloses a composition containing industrial pozzolan
powder with a
neutral pH activator without the use of any hydrocarboxylic acids like citric
acid or metal carbonate or alkali
metal stannate or alkali metal chloride in a weight proportion greater than
50% of total activator content of
its cement composition and less than 30% by weight content of acidic activator
in association with 95 parts
of Class C fly ash to achieve high strength in short time.
The use of increased percentage alkali metal salt of citric acid to achieve
setting not only results in
increasing the cost of the final cement but also results in the quick setting
of the cement creating several
drawbacks, for example quick loss of slump associated with such setting. As a
result, the present invention
cannot be used for many applications except for rapid concrete repairs.
Some of the drawbacks of the prior art include: cements having quick setting
time and hence limited
applications; the use of hazardous alkalis such as potasium hydroxide; the
quick loss of flowability resulting
in difficult placement; the inability to use Class C fly ash having low amount
of calcium oxide; the creation
of expansive forces during setting making the cement self stressing; the
difficulty in using fly ashes having
high water absorption; and the high cost.
The inventors after years of trials have surprisingly and unexpectedly
discovered that with the use of
alkali metal stannate or alkali metal chloride or alkali metal phosphate along
with alkali metal salt of hydro
carboxylic acid in the cement composition, the working time of the cement can
extend beyond three hours
depending on the composition of the fly ash. This enables the cement to be
used for normal construction
uses.
Despite the prior art, there still exists a need for a workable, practical and
economical cement
composition having increased percentage of fly ash which can be manufactured
by simple powder blending
process.
SUMMARY OF THE INVENTION
More specifically, this invention relates to a process and product of an
activated cement composition
comprising: industrial waste such as ground granulated blast furnace slag,
cement kiln dust, lime kiln dust,
and Class C fly ash having a specific surface area between 2500-7000 cm2/gram
and/or high alumina cement;
an alkali metal hydroxide; an alkali metal salt of hydro carboxylic acid
and/or a source of alkali salt of hydro
carboxylic acid; alkali metal fluoride; alkali metal chloride such as MgC12,
NaC1 and KC1, preferred is
MgCl2; a retarder such as an alkali metal phosphate and/or an alkali metal
stannate; and nano alkali metal
carbonate that does not require clinkering and can be used for a broad range
of applications. Preferably, the
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required surface area of the industrial byproducts can be obtained by
mechanical grinding followed by
classification of same.
According to one aspect of the present invention, there is provided a rapid
setting hydraulic cement
composition comprising:
- an industrial byproduct containing calcium oxide ranging from 5 to 50 wt
%;
- optionally, an alkali metal hydroxide;
- an alkali metal salt of an hydrocarboxylic acid or an alkali
metal fluoride;
- an alkali metal oxide; and
- an alkali metal carbonate.
According to one aspect of the present invention, there is provided a
controlled setting hydraulic
cement composition comprising:
- an industrial byproduct containing calcium oxide ranging from 5 to 50 wt
%;
- optionally, an alkali metal hydroxide;
- an alkali metal salt of an hydrocarboxylic acid or an alkali
metal fluoride;
- a retarder selected from the group consisting of: an alkali
metal phosphate
an alkali metal stannate, alkali metal titanate and combinations thereof;
- an alkali metal chloride; and
- optionally, an alkali metal carbonate.
According to one aspect of the present invention, there is provided a rapid
setting hydraulic cement
composition for use in concrete road repair comprising :
- an industrial byproduct containing calcium oxide ranging from 5 to 50 wt %;
- optionally, an alkali metal hydroxide;
- an alkali metal salt of an hydrocarboxylic acid or an alkali metal
fluoride;
- an alkali metal oxide;
- an alkali metal carbonate; and
- a sand (such as quartz sand).
According to one aspect of the present invention, there is provided a
controlled setting hydraulic
cement composition comprising:
- an industrial byproduct containing calcium oxide ranging
from 5 to 50 wt %;
- optionally, an alkali metal hydroxide;
- an alkali metal salt of an hydrocarboxylic acid or an alkali metal
fluoride;
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- a retarder selected from the group consisting of: an alkali
metal phosphate
an alkali metal stannate, and combinations thereof;
- an alkali metal chloride;
- optionally, an alkali metal carbonate; and
- a sand (such as quartz sand).
According to an object of the present invention, there is provided a cement
composition comprising
fly ash and the use of an activator such as a fluoride. Preferably, the
fluoride is sodium fluoride.
According to a preferred embodiment of the present invention, there is
provided a cement
composition comprising fly ash and retarders to prevent a sudden loss in
flowability. Preferably, the cement
composition of the present invention uses chlorides as retarders as they are
cheaper than borates or tartrates.
According to a preferred embodiment of the present invention, the cement
composition comprising fly ash
has an extended working time through the use of low cost retarders such as
magnesium chloride.
According to an object of the present invention, there is provided a cement
composition comprising
fly ash and a retarder selected form the group consisting of: alkali metal
phosphate, alkali metal stannate and
a combination thereof.
According to an object of the present invention, there is provided a cement
composition comprising
fly ash and which does not require the use of harsh alkalis.
According to a preferred embodiment of the present invention, there is
provided a cement
composition comprising fly ash having low calcium oxide in combination with
calcium aluminate cement.
According to a preferred embodiment of the present invention, there is
provided a cement
composition comprising fly ash whereby the self stressing nature thereof is
prevented or limited by using of
quartz sand powder as additive.
According to a preferred embodiment of the present invention, there is
provided a cement
composition comprising fly ash having high water absorption which is ground
and classified and mixed with
water reducing agents such as polycarboxylate ethers.
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DETAILED DESCRIPTION OF THE INVENTION
The present invention provides for the use of industrial waste such as fly ash
to prepare both rapid
setting cement composition and controlled setting cement composition.
Preferably, the rapid setting hydraulic cement composition for use in concrete
road repair comprising
=
- an industrial byproduct containing calcium oxide ranging from 5 to 50 wt
%;
- optionally, an alkali metal hydroxide;
- an alkali metal salt of an hydrocarboxylic acid or an alkali
metal fluoride;
- an alkali metal oxide;
- an alkali metal carbonate;
- a granular material such as sand (preferably quartz sand)
and water.
Preferably as well, the controlled setting hydraulic cement composition
comprising:
- an industrial byproduct containing calcium oxide ranging from 5 to 50 wt %;
- optionally, an alkali metal hydroxide;
- an alkali metal salt of an hydrocarboxylic acid or an alkali
metal fluoride;
- a retarder selected from the group consisting of: an alkali metal
phosphate
an alkali metal stannate, and combinations thereof;
- an alkali metal chloride;
- optionally, an alkali metal carbonate;
- a granular material such as sand (preferably quartz sand)
and water.
According to a preferred embodiment, the cement composition has a setting time
ranging between 3
minutes to 5 hours depending on the composition chosen.
The industrial byproducts containing lime may be selected from the group of
Class C fly ash, Ground
Granulated Blast Furnace Slag (GGBFS), Cement Kiln Dust or Lime Kiln Dust.
According to a preferred
embodiment, Class F fly ash can used in combination with any one of Ground
Granulated Blast Furnace Slag
(GGBFS), Cement Kiln Dust and Lime Kiln Dust. Preferably, the composition of
the present invention will
be free of portland cement but may require the addition of up to a maximum of
20% by weight of the
composition of calcium aluminate cement in certain cases when the Aluminum
Saturation Index (AS!) of the
fly ash measured by the formula ASI. (A1203)/(Ca0+Mg0+Na70+K20) increases
beyond 0.9.
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Industrial waste having calcium oxide in the range of 5-50% having a specific
surface area between
2500- 7000 cm2/g is preferably present in an amount ranging from 80 to 95% by
weight of the total
composition; quartz sand powder is preferably present in an amount ranging
from 0.1 to 20% by weight of
the total composition; alkali metal oxide is preferably present in an amount
ranging from 0.1 to 5% by weight
of the total composition; nano alkali metal carbonate is preferably present in
an amount ranging from 0.1 to
4% by weight of the total composition; alkali metal of hydrocarboxylic acid is
preferably present in an
amount ranging from 0.1 to 7% by weight of the total composition; alkali metal
fluoride is preferably present
in an amount ranging from 0.1 to 5% by weight of the total composition; alkali
metal phosphate is preferably
present in an amount ranging from 0.1 to 7% by weight of the total
composition; alkali metal chloride is
preferably present in an amount ranging from 0.1 to 3% by weight of the total
composition; hydrocarboxylic
acid is preferably present in an amount ranging from 0.1 to 5% by weight of
the total composition; alkali
metal stannate is preferably present in an amount ranging from 0.1 to 4% by
weight of the total composition
and/or alkali metal titanate is preferably present in an amount ranging from
0.1 to 4% by weight of the total
composition.
The surface area of the unclassified fly ash used ranged from 2000- 4000
cm2/gram. The classified
fly ash preferably has a surface area ranging from 3300 to 4000 cm2/gram. It
is preferable to use fly ash
within those particle size ranges as uniform particle size distribution is
preferable for the performance of the
cement.
It is understood that the cements according to the present invention can be
used to make concretes by
the addition of various types of aggregates commonly used in the field. The
purposes disclosed herein are
understood to be examples of the breadth of use the present invention can be
applied and should not be
construed to be limited to such.
The following examples are included to illustrate the present invention and
are not to be considered
limiting thereof. In each of the examples, the amount of water was carefully
controlled, as would be
understood by the person of ordinary skill in the art, to ensure an efficient
mixing and reaction and also to
ensure that the cement created was of sufficient strength. The person skilled
in the art will understand the
scope of the invention is defined by the claims appended hereto.
Example 1
A cementitious composition was prepared according to the following
composition:
Classified Class C ¨ Ash ¨ 923g
Sodium Citrate ¨ 55g
Lime Powder ¨20 g
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Lithium Carbonate ¨ 2 g
Quartz Sand (3mm Size) ¨ 1000 g
Water ¨320 ml
All the powder components were mixed first and water was then added and mixed
in a mixer. Then
sand was then added and the resulting mixture was mixed for another 10
minutes.
Cubes of 70.6 mm were cast, their setting times were recorded and the hardness
was measured. The
final setting time was 10 minutes. The cement hardness was monitored and
recorded over a range of time of
up to 4 weeks. The results of the hardness testing for example 1 are listed
below:
2 Hrs ¨ 15 Mpa
24 Hrs ¨ 20 Mpa
3 days ¨21.4 Mpa
7 days ¨ 24.8 Mpa
28 days - 28.9 Mpa
Example 2
A cementitious composition was prepared according to the following
composition:
Classified Class C ¨Fly Ash ¨ 903 g
Sodium Citrate ¨55 g
Lime Powder ¨20 g
Lithium Carbonate ¨ 2 g
MgC12¨ 20 g
Sand ¨ 1000 g
Water ¨320 ml
The final setting time was 2 hours. The cement hardness was monitored and
recorded over a range
of time of up to 4 weeks. The results of the hardness testing for example 2
are listed below:
2 Hrs ¨ 13 Mpa
24 Hrs ¨ 22 Mpa
3 days ¨ 26.4 Mpa
7 days ¨ 28.9 Mpa
28 days - 34 Mpa
Example 3
A cementitious composition was prepared according to the following
composition:
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C - Ash ¨ 903 g
Sodium Citrate ¨ 55g
Lime Powder ¨ 20g
Lithium Carbonate ¨ 2g
Citric Acid- 20g
Sand ¨ 1000 g
Water ¨ 360 ml
The final setting time was 24 minutes. The cement hardness was monitored and
recorded over a
range of time of up to 4 weeks. The results of the hardness testing for
example 3 are listed below:
2 Hrs ¨ 12.4 Mpa
24 Hrs ¨19.8 Mpa
3 days ¨ 22.4 Mpa
7 days ¨ 26 Mpa
28 days - 30 Mpa
Example 4
A cementitious composition was prepared according to the following
composition:
Ash ¨ 710 g
Sodium Citrate ¨ 64g
Lime Powder- 24g
Lithium Carbonate ¨ 2g
Calcium Aluminatc Cement ¨ 200g
Sand ¨ 1000g
Water ¨ 325 ml
The final setting time was 15 minutes. The cement hardness was monitored and
recorded over a
range of time of up to 4 weeks. The results of the hardness testing for
example 4 are listed below:
2 Hrs ¨ 20 Mpa
24 Hrs ¨30 Mpa
3 days ¨34.4 Mpa
7 days ¨ 38.7 Mpa
28 days ¨42.3 Mpa
Example 5
A cementitious composition was prepared according to the following
composition:
C - Ash ¨ 710 g
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Sodium Citrate ¨ 64 g
Lime Powder ¨24 g
Lithium Carbonate ¨2 g
Calcium Aluminate Cement ¨ 200g
Sand ¨ 1000g
Water ¨325 ml
The final setting time was 15 minutes. The cement hardness was monitored and
recorded over a
range of time of up to 4 weeks. The results of the hardness testing for
example 5 are listed below:
2 Hrs ¨ 4 Mpa
24 Hrs ¨ 15 Mpa
3 days ¨ 17 Mpa
7 days - 22 Mpa
28 days - 27 Mpa
Example 6
A cementitious composition was prepared according to the following
composition:
C ¨ Ash ¨903 g
Sodium Citrate ¨ 55g
Lime Powder ¨20 g
Nano Calcium Carbonate ¨20 g (Particle size between 5 to 10 microns)
Lithium Carbonate ¨ 2g
Sand ¨ 1000 g
Water ¨ 340 ml
The final setting time was 12 minutes. The cement hardness was monitored and
recorded over a
range of time of up to 4 weeks. The results of the hardness testing for
example 6 are listed below:
2 Hrs ¨ 9 Mpa
24 Hrs ¨ 16 Mpa
3 days ¨20.4 Mpa
7 days - 22.9 Mpa
28 days - 26.4 Mpa
Example 7
A cementitious composition was prepared according to the following
composition:
C ¨ Ash ¨ 900 g
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Sodium Citrate ¨ 55g
Lime Powder¨ 30g
Lithium Carbonate ¨ 2 g
Mono Ammonium Phosphate ¨ 10 g
Sand ¨ 1000 g
Water ¨335 ml
The final setting time was 2 hours. The cement hardness was monitored and
recorded over a range
of time of up to 4 weeks. The results of the hardness testing for example 7
are listed below:
4 Hrs ¨ 13 Mpa
24 Hrs ¨ 28.4 Mpa
3 days ¨ 27.5 Mpa
7 days - 32 Mpa
28 days - 38.9 Mpa
Example 8
A cementitious composition was prepared according to the following
composition:
C ¨ Ash ¨ 903 g
Sodium Citrate ¨ 55g
Lime Powder ¨ 20g
Lithium Carbonate ¨ 2g
Mono Potasium Phosphate ¨ 10g
Sand ¨ 1000 g
Water ¨ 385 ml
The final setting time was 2 hours. The cement hardness was monitored and
recorded over a range
of time of up to 4 weeks. The results of the hardness testing for example 8
are listed below:
24 Hrs ¨ 21.5 Mpa
3 days ¨25 Mpa
7 days - 34 Mpa
28 days - 37.6 Mpa
Example 9
A cementitious composition was prepared according to the following
composition:
C ¨ Ash ¨ 923 g
Sodium Fluoride -55 g
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Lime Powder ¨20 g
Lithium Carbonate ¨ 2 g
Sand ¨ 1000 g
Water ¨450 ml
The final setting time was 20 minutes. The cement hardness was monitored and
recorded over a
range of time of up to 4 weeks. The results of the hardness testing for
example 9 are listed below:
2 hrs ¨5 Mpa
24 hrs ¨9.4 Mpa
3 days ¨ 13.2 Mpa
7 days ¨ 17.1 Mpa
28 days ¨19.8 Mpa
Example 10
A cementitious binder was prepared according to the following composition:
Classified Class C ¨ Ash ¨ 903g
Sodium Citrate ¨ 55g
Lime Powder ¨20 g
Lithium Carbonate ¨2 g
Sodium Stannate ¨20 g
Quartz Sand (3mm Size) ¨ 1000 g
Water ¨320 ml
The final setting time was 4 hours. The cement hardness was monitored and
recorded over a range
of time of up to 4 weeks. The results of the hardness testing for example 10
are listed below:
24 Hrs ¨ 18 Mpa
3 Days ¨ 23.2 Mpa
7 Days ¨ 26 Mpa
28 Days- 32 Mpa
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