Note: Descriptions are shown in the official language in which they were submitted.
CA 02915539 2015-12-21
MAGNESIUM PHOSPHATE BASED CEMENT, MORTAR AND CONCRETE COMPOSITIONS
WITH INCREASED WORKING TIME
FIELD OF THE INVENTION
The present invention is directed. to a fast setting cement, more specifically
a phosphate-based
cement using a source of low purity metal oxide, a phosphate component, a
retarder, sufficient water and,
optionally, calcium oxide containing material, having substantially high
amount of amorphous glass content.
BACKGROUND OF THE INVENTION
Known phosphate cements that have been discovered, including the one that was
done by Argonne
National Laboratories, pioneers in phosphate cements have been significantly
(ten times) expensive
compared to conventional cements and do not possess the required working time
for large volume placement.
This is due to the fact that these compositions Use as much as 30-45% of mono
potassium phosphate content
which is very expensive ($1900/ ton). and a very high purity metal oxide (more
than 95% purity). to the tune
of 10-15%. Hence the traditional phosphate cements have always been limited to
the application of concrete
road repair where the volume is less and more working time is not required.
To extend the.. working time of the phosphate cements would mean that it would
allow one to use
these type of cements- for larger area applications like underlayment or
overlayment of concrete floorings or
for normal construction of buildings itself. This concept was attempted
numerous times by different groups
by adopting different techniques like usage of retarders like borax or using
metal oxides calcined at higher
temperatures. However, all of these techniques failed to give a desired
working time because the resulting
cement set very fast which made them impractical to be used for large area
applications.
US patent No. 6,136,088 discloses ahigh early strength binder based on
phosphate cement utilizing a
maximum binder level of 58%, which avoids the evolution of ammonia gas in its
preparation by reacting
mono ammonium phosphate with potassium carbonate and a process for preparing a
.cementitious binder
useful in a quick setting mortar, whose utilityincludes a repair material for
cementitious structures. The
binding system is based on the formation of potassium struvite, by reacting a
source of high purity
magnesium oxide with potassium phosphate and water. Although still quick
setting, the set time of this
binder is slower than the set time of struvite.
US patent No. 7,001,860 discloses an inexpensive construction material,
adapted for use in warm
weather climates where styrofoam or other synthetic organic resin foams are
used as construction materials
and require a coating of a hard, dense material for a surface finish and a
method to coat styrofoam structures
with a material which cures or sets at room temperature and is easy to apply
in the field.
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US patent No. 7,204,880 discloses a cement formula utilizing the metal oxide
along with mono
potassium phosphate and mono ammonium phosphate but uses a very small amount
of it because of the use
of high purity metal oxide. lithe percentage of mono ammonium phosphate is
increased the final cement sets
faster making rendering it impractical for large area applications.
As seen from the above, some of the drawbacks of cements of the prior art
include quick setting and
less working time. llenee used for limited applications like road patching;
high cost (due to the use of high
quantities of expensive low solubility acid phosphates); and the sensitivity,
to increase in water/cement ratio.
In light of the prior art, there exists a need for a low cost phosphate-based
cement composition with
high mechanical properties and the present .invention relates to the method of
producing a structural material
with an improved workability to be used in the infrastructure development.
After years of experimentation
the inventors have found that the failure wasattributed to the purity of
magnesium oxide used.
It was unexpectedly and surprisingly found that by lowering the purity of
metal oxides by adding
other compounds like silicate or aluminate, the loading of metal oxides can be
increased and the loading of
phosphates can be decreased thereby reducing the cost of the final binder and
extend the working time of the
cement so that it can be used for many other applications other than road
repair. By replacing metal oxides
with metal silicates it is possible to extend the working time and replace
expensive a portion or all of the
mono potassium phosphate with a cheaper phosphate source such as mono ammonium
phosphate. Thereby
reducing the cost and achieving a greater working time to be able to be used
for wider applications as
compared to the disclosed prior art.
SUMMARY OF THE INVENTION
According to a preferred embodiment of the present invention, there is
provided a method of
producing fast setting phosphate-based cement, using a .source of low purity
metal oxide, a phosphate
component, a retarder, a sufficient quantity of water and optionally, a source
of calcium oxide containing
material having a substantially high amount of amorphous glass content.
According to a preferred embodiment of the present invention, the phosphate
cement comprising a
source of low purity metal oxides can also overcome the working time -issue by
using low purity metal oxides
in combination with retarders such as an alkali metal stannate or an alkali
metal fluoride. According to a
preferred embodiment of the present invention, the water resistance is
improved by the use of amorphous
calcium oxide containing material. According to a preferred embodiment of the
present invention, the use of
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a high amount of tow cost high solubility phosphate provides for a cost
effective cement composition.
According to a preferred embodiment; the mechanical properties of the cement
are improved by the use of
calcium oxide containing .fillers having amorphous glass content.
According to a preferred embodiment of the present invention, the novel cement
with good strength
coupled with improved flowability and increased working time and mechanical
properties is produced by
mixing the right proportions of metal oxide or a source of low purity metal
oxide, an industrial waste
containing a source of silica which can include fly ash, steel slag, ground
granulated blast furnace slag
(GGBFS), and a phosphate component, and a retarder with sufficient water. The
resulting cement does not
involve clinkering. More particularly, a preferred embodiment of the present
invention is directed to
overcoming the problem of poor water resistance, increased cost and lack of
working time of traditional
phosphate cements which has been the main hindrance to the widespread use of
such cements.
The setting time of the final cement depends upon the amount of metal cations
released from the
metal oxide to be able to react with phosphate anions when water is added to
the cement. If the amount of
metal cations released is higher in a given period of time then the cements
sets faster. If the release of the
cations can be controlled, the setting can be controlled. .One of the ways to
do it is by increasing the
calcination temperature of metal oxides or the having other compounds along
with the metal oxides which
will lower the amount of metal oxide getting released. Examples of such
compounds are silicates and
aluminates, which can be represented as IVIgSiO3 and .MgA1204. As far as the
chemical composition of the
metal oxide is concerned it is preferred to have a non stoichiometric metal
oxide silicates or aluminates in
order to obtain better results. The non stoichiometric metal oxide silicates
can be represented as MgO,Si02
0-20 and the metal oxide aluminate can be represented as MgO,Al2030,0.
Reactivity of magnesium oxide depends on its morphology and its chemical
composition. Highly
crystalline oxide is also the least soluble in the phosphate solution (the
crystals are called periclase) and it is
achieved by increasing the temperature of calcination. Due to the low
solubility of these crystals, the mixing
and application time of the resulting cement is expected to be longer than
that without this crystal
morphology. Using this lower purity (thus, less reactive) magnesium oxide or
magnesium silicate, it may be
then possible to reduce the content of the phosphate by increasing the content
of this magnesium oxide. By
reducing the content of the phosphate in the total binder the cost of the
cement is consequently reduced as the
former is a high cost component in the binder. The binder here is referred as
the combination of metal oxide
or metal silicate, metal aluminate and the phosphate component. The cement
forming reaction between 100%
magnesium oxide and mono potassium phosphate can be expressed as:
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MgO + KI-12PO4 + 5H20 Mgl(PO4.6H20 -------------------- = (I)
Based on the, above cement forming equation (1), the molecular weight ratio of
metal oxide:
phosphate would ideally have to be 40 grams: 136 grams (I 3.2). This ratio not
only makes the price of the
binder high but also results in a quick setting composition. In an effort to
reduce the price of the binder, a
slight increase (of as little as 10%) in the high purity metal oxide, weight
releases more cations in the mix
which renders the cement fast setting, hence unsuitable for certain practical
applications.
The cement forming reaction when using a low purity metal oxide with silicate
may be written as:
Mg0xSi02 0,0 + + 51120 -->MgO,Si02 (1.õ) KPO4.61420 (2).
- Magnesium potassium phosphate, the final product formed due to the chemical
reaction between
magnesium oxide and mono potassium phosphate has a solubility product constant
of 24X. I tr" and gets
converted into Mg3(PO4)2 when immersed in water for a prolonged period of time
accompanied by a drop in
the mechanical properties making. it unusable in areas where prolonged water
immersion is expected. It was
found after an extensive period of testing with various fillers along with
binder (magnesium silicate +
phosphate component) that by having a suitable magnesium oxide/silicate:
phosphate component ratio, the
water resistance of these phosphate cements are greatly increased.
DETAILED DESCRIPTION OF THE INVENTION
According to a preferred embodiment of the present invention, a preferred
embodiment of the
present invention comprises a source. of low purity metal oxide (<85% purity)
or similar material such as
magnesium silicate or magnesium aluminate. This source of low purity metal
oxide is preferably present in
the range of 20-55% by weight of the total composition. This source of low
purity metal oxide is more
preferably present in the range of 25-45%. This source of low purity metal
oxide is even more preferably
present in the range of 30-40%. The preferred form of metal oxide is magnesium
oxide.
The phosphate component is selected from the group consisting of: a low
solubility acid phosphate; a
high solubility acid phosphate, and combinations thereof. The low solubility
acid phosphate (such as mono
potassium phosphate) is preferably present in an amount ranging from I to 45%
by weight of the total
composition; and when present, the high solubility acid phosphate (such as
mono ammonium phosphate) is
preferably present in an amount ranging from I to 20% by weight of the total
composition, more preferably
from 1 to 15% and even more prefereably from 1 to 5%. Preferably, the total
content of phosphate
component will range of 20-55% by weight of the total composition. More
preferably, the phosphate
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component is present. in the range of 25-45%. Even more preferably, the
phosphate component is present in
the range of 30-40%.
Material containing calcium oxide in the range of 1-50% and having high
amorphous glass content
includes materials selected from the group consisting of: fly ash, ground
granulated blast furnace slag and
steel slag. More preferred is fly ash. When present, such material is
preferably present in an amount ranging
from 15 to 45% by weight of the total composition. More preferably, this
material is present from 15 to 25
A by weight of the total composition.
Preferably, the ratio of MgO:phosphate.component should range between 0.6: 1
to 1.5: 1.
According to a preferred embodiment of the present invention, fibers are added
to the cement
composition in order to increase the flexural strength of the resulting
cement. Preferably, the fibers are
selected from the group consisting of: glass fibers (preferably 3mm long);
polypropylene fibers; and basalt
fibers. Most preferred are glass fibers. Pigments such as titanium dioxide can
be added to impart a white
tone to the cement. Typically, the presence of pigments ranges from 1 to 5%
but can be reasonably adjusted
to more or less than this range in order to obtain the desired color or tone
while substantially maintaining the
physical characteristics required of the cement
To allow for longer working (setting) time, of cement compositions, retarders
are generally used.
According to a preferred embodiment of the present invention retarders are
selected from the group
consisting of: alkali metal fluoride; alkali metal stannate; borax and
combinations thereof'. More preferably,
an alkali metal fluoride such as sodium fluoride is used: in another preferred
embodiment, an alkali metal
stannate such as sodium stannate is used. When present as retarder, the alkali
metal fluoride such as sodium
fluoride is preferably present in an amount ranging from 0.1 to 10% by weight
of the total composition,
more preferably from I to 5%. When present as retarder, the alkali metal
stannate such as sodium stannate is
preferably present in an amount ranging from 0.1 to 10 % and more preferably
from 1 to 5% by weight of the
total composition. When present as retarder, borax is preferably present in an
amount ranging from 0.1 to 10
% and more preferably from Ito 5% by weight of the total composition.
As understood by the person of ordinary skill in the art, the amount of water
used in the cement
composition should generally be half the amount of hinder. Of course, the
person of ordinary skill in the art
will know that the amount of water can be varied within a reasonable range to
optimize the cement
pertbrmance (setting time and strength) without departing from the scope of
the present invention. Ideally,
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the working time of the cement according to a preferred embodiment of the
present invention will be ten
minutes or more.
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. These
include fine granular sand
such as quartz sand (of 3mm size) as well as rock aggregates (such as 20mm
stones). It is also understood
that the cements according to the present invention can be used to make,
mortars by the addition of various
types of .fine granular material such as sand 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 concrete comprising a cementitious composition according to a preferred
embodiment of the
present invention was prepared according to the following formula:
- Magnesium silicate having a MgO content of 84%
- and Si02 content of 12.5% ¨446 g =
- MKP-364 g
- M.AP ¨ 20 g
- Fly Ash ¨ 1.70 g
- Borax 20 g
- Sand ¨ 2000 g
- 20 mm Aggregates ¨ 4000 g
- Water ¨400 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 100 mm were cast, their setting times were recorded and the hardness
was measured. The
initial setting time was of 25 minutes and the final setting time was 40
minutes. The slump was recorded to
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be 160 mm. 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 I are listed below:
2 Hours ¨ 3.6 Mpa
Day¨ 1.8.4 Mpa
3 Days -19.8 Mpa
7 Days ¨23 Mpa
28 Days ¨27 MPti
Example 2
A concrete comprising a cetnentitious composition according to a preferred
embodiment of the
present invention was prepared according to the following formula:
Magnesium silicate having a MgO content of 84%
and Si02 content of 12.5% ¨400 g
MKP 380 g
MAP 20 g
Ely Ash ¨ 180 g-
Borax ¨ 20 g
Sand ¨ 1000 g (Quartz sand having 3 mm size)
Water ¨ 220 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 nun were cast, their .setting times were recorded and the
hardness was measured. The
initial setting time was of 3 minutes and 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 2 are listed below:
2 Hours ¨ 18 Mpa
1 Day ¨ 35 Mpa
3 Days -38.4 Mpa
7 Days ¨45 Mpa
28 Days ¨ 53A Mpa
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Example 3
A concrete comprising a cementitious composition according to a preferred
embodiment of the
present invention was prepared according to the following formula:
Magnesium silicate having a MgO content of 84%
and Si02 content of 12.5% ¨ 400 g
MKP-380 g
MAP¨ 20 g
Fly Ash ¨ 180 g
Sodium Stannate ¨50 g
Sand ¨ 1000 g
Water ¨220 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
initial setting time was of 10 minutes and 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 3 are listed below:
2 Hours ¨ 16.9 Mpa
I Day ¨ 34.5 .Mpa
3 Days ¨36 Mpa
7 Days 43.7 Mpa
28 Days ¨49.2 Mpa
Example 4
A concrete comprising a cementitious composition according to a preferred
embodiment of the
present invention was prepared according tothe following formula:
Magnesium silicate having a MgO content of 84%
and SiO2 content of 115% ¨ 400 g
= MKP ¨ 380 g
MAP 20 g
Fly Ash ¨ 180 g
Sodium Fluoride¨SO g
Sand ¨ 1000 g
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Water 220 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
initial setting time was of 12 minutes and 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 4 are listed below:
2 Hours ¨ 15.8 Mpa
.1 Day ¨ 31 Mpa
3 Days ¨37 Mpa
7 Days- 43.1 Mpa
28 Days ¨47 Mpa
Example 5
A concrete comprising a. cementitious composition according to a preferred
embodiment of the
present invention was prepared according to the following formula:
Magnesium silicate having a MgO content o114%
and Si02 content of 12.5% ¨230 g
M.KP ¨ 115 g
MAP¨ 115.g
Fly Ash 286g
Borax ¨8 g
Fibers.¨ 3 g
Ti02 ¨ 38 g
Sand¨ 1500 g
Water ¨210 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
initial setting time was of 5 minutes. and the final setting time was 10
minutes. The cement hardness was
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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:
3 Hours 18.6 Mpa
1 Day ¨ 24 Mpa
3 Days 26 Mpa
7 Days ¨ 28.9 Mpa
28 Days ¨ 37 Mpa
Example 6
A cementitious composition according to a preferred embodiment of the present
invention was
prepared according to the following formula:
Magnesium silicate having a MgO content of 84%
and Si02 content of 12.5% ¨ 253 g
M.KP ¨ 213 g
MAP 40 g
Fly Ash ¨433 g
Quartz sand powder ¨66 g
Water ¨ 210 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
initial setting time was of 3 minutes and the final setting time was 5
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 Hours ¨ 5 Mpa
I Day ¨ 16. Mpa
3 Days¨ 18.7 Mpa
7 Days ¨ 21.3 Mpa
28 Days 26 Mpa
Example 7
. A concrete comprising a cementitious composition according to a preferred
embodiment of the
present invention was prepared according to the following formula:
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Magnesium silicate having a MgO content of 84%
and a S102 content of 12.5% ¨ 245 g
MKP-410 g
Sand Powder ¨ 267 g
Borax ¨ 58 g
TDO- 20 g
Sand ¨ 2000 g
Water ¨ 260 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
initial setting time was of 20 minutes and the final setting time was 30
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 7 are listed below:
2 Hours ¨4 inpa
1 Day¨ 14.3 Mpa
3 Days 19.6 Mpa
7 Days 22 Mpa
28 Days ¨29.6 Mpa
Table 1 - Weight content of each component for the cement composition of
Examples 1 to 7 (in
grams)
component 1 2 3 4 5 6 7
Magnesium silicate
having a MgO content 446 400 400 400 230 253 245
of 84% and Si02
content of 12.5%
MKP 364 380 380 380 ¨ 115 213 410
MAP 20 20 20 20 115 40 X
Fly ash 170 180 180 180 286 433 X
Borax 20 20 X X 8 X 58
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-
Na Stannate X X 50 X X X X
NaF X X X 50 X X X
1
Fiber X X X X 3 X X
TD-6- X X X X 38 X 20
sand powder X ' X X X X 66 267
Total 1020 1.000 1030 1030 795 1005 1000
,
Table 2- Percentage content of each component of the cement composition
of Examples 1 to 7
Component 1 2 3 4 5 6 7
Magnesium silicate
having a MgO Content of
43.73 40.00 38.83 38.83 28.93 25.17 24.50
84% and Si% content of
12.5%
MKP 35.69 ' 38.00 36.89 36.89 14.47 21.19
41.00
MAP 1.96 2.00 1.94 1.94 14.47 3.98 0.00
Fly aih------ 16.67 18.00 17.48 17.48 ' 35.97 43.08 '
0.00
Borax ' 1.96 - 2.00 ' 0.00 0.00 1.01 0.00 5.80
Na Stannate 0.00 0.00 4.85 ' 0.00 0.00 0.00
0.00
....____
NaF 0.00 0.00 0.00 4.85 0.00 0.00 0.00
Fiber 0.00 0.00 0.00 0.00 4 0.38 0.00 0.00
iDo 0.00 0.00 0,00 0.00 4.78 0.00 2.00
sand powder 0.00 ' 0.00 0.00 0.00 0.00 6.57 26.70
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