Note: Descriptions are shown in the official language in which they were submitted.
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PORTLAND CEMENT FREE ACTIVATION OF GROUND GRANULATED BLAST
FURNACE SLAG
FIELD OF INVENTION
The present invention relates to a new cement composition which is more
environmentally friendly
than traditional Portland cement, more specifically, the novel cement
comprises a high proportion of ground
granulated blast furnace slag.
BACKGROUND OF THE INVENTION
Blast furnace slag is the non-metallic by-product of iron production,
generally consisting of silicon,
calcium, aluminum, magnesium and oxygen. When iron is manufactured using a
blast furnace, two products
collect in the hearth - molten iron and slag. The slag floats on top of the
iron and is skimmed off to be fed to
a granulator. In the granulator the molten slag is rapid quenched with water.
The resulting granules are
essentially glassy, non-metallic silicates and alumino silicates of calcium.
The glass content of the slag
generally determines its cementitious character or suitability for use in
hydraulic cement¨the higher the glass
content the greater the cementitious properties.
Significant quantities of this blast furnace by-product are produced annually.
Disposal of blast
furnace slag had been problematic until subsidiary uses for the slag were
developed. For instance, ground
granulated blast furnace slag (GGBFS) may be added to cement clinker and
calcium sulfate and inter-ground
to create a modified Portland slag cement.
Manufacturing Portland cement through a dry method is a very energy intensive
process. After
quarrying the principal raw materials such as limestone, clay, and other
materials, the rock is crushed. This is
done is multiple steps. The first step reduces the rock to a maximum size of
about 6 inches. Subsequent
crushing steps reduce the rocks to a size of about 3 inches or smaller. At
that point the rocks are combined
with other ingredients such as iron ore or fly ash and ground further and
mixed and added to a cement kiln.
The cement kiln heats the mixture to a temperature ranging from about 2,700 to
about 3000 degrees
Fahrenheit. The finely ground raw material or slurry is led into the elevated
end of the kiln. At the other end
of the kiln are the flames produced by the burning of powdered coal, oil,
alternative fuels, or other
combustible material. The high temperature calcines the chemically combined
water and carbon dioxide
from the raw materials which comes out at the higher end of the kiln and forms
new compounds such as
tricalcium silicate, dicalcium silicate, tricalcium aluminate and tetracalcium
aluminoferrite) which forms the
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clinker that comes out at the lower end of the kiln. This clinker is in the
form of marble sized balls. Clinker
coming out of the kiln is cooled, ground and 'nixed small amounts of gypsum
and limestone.
EP 0 553 131 discloses method of converting latent hydraulic ground granulated
amorphous blast-
furnace slag to a hydraulic binder which will act directly when water is
added, by improved activation of a
slag activated with an activator comprising magnesium oxide and phosphate. The
description states that
improved activation is obtained by mixing the slag and the activator with a
combination of additional
activators which include alkali and calcium, wherein alkali is present in an
amount of less than 4 percent by
weight, based on the amount of binder present, and calcium is present in the
form of a Portland cement and
optionally calcium oxide.
US Patent No. 5,411,092 teaches a method for cementing a well, comprising:
combining constituents
comprising water, blast furnace slag having a particle size within the range
of 2,000 to 15,000 cm2 /g, and an
activator comprising trisodium phosphate, to form a cement slurry; displacing
the cement slurry into the
well; and allowing the cement slurry to set. The description states that the
activator can include a citrate ion
containing compound such as sodium citrate, calcium citrate and potassium
citrate.
US patent application No. 2014/0264140 teaches a product comprising: a
geopolymer composite
binder comprising: one or more Class F fly ash materials; one or more gelation
enhancers, and one or more
hardening enhancers which includes ground granulated blast furnace slag in an
amount ranging from about 5
to about 92 wt. 'Yo.
US patent No. 5,026,215 teaches a method of grouting formations with a
ccmentitious material
comprising microtine ground slag is useful for stabilizing and strengthening
soil and rock formations as well
as underground structures associated with buildings, tunnels and dams. A
composition is provided which
comprises water, a dispersant, slag and an accelerator to activate the slag.
US patent No.4,018,616 discloses a water glass composition comprising a water-
soluble or water-
dispersible silicate binder and an inorganic phosphate curing agent, wherein
said inorganic phosphate curing
agent is composed of an inorganic solid fine powder comprising as the main
ingredient a silicon
polyphosphate or its metal salt and said curing agent. Slag is mentioned as
one of the potential filler additive.
US patent application No. 2014/0343194 teaches stabilized aqueous suspensions
include aluminous
cement and/or calcium sulfoaluminous cement and binding compositions including
the aqueous suspension
in combination with organic binders, which are stable at room temperature and
at high temperature as well as
methods for preparing the same are described.
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US patent No. 8,703,659 discloses a sealant composition for servicing a
wellbore comprising at least
one gel system, a loss prevention material and water, wherein the at least one
gel system comprises a
crosslinking agent such as polyethylene amine, wherein the loss prevention
material comprises a particulate
material which comprises silica flour. it is stated that in addition to the
gel system comprising the pumpable,
corrosion resistant, hardenable epoxy described, certain hydraulic cements
such as, Portland cement may be
desirable as components of this sealant composition.
US Patent No. 4,761,183 discloses a grouting composition comprising a very
small particle size slag,
an equal or greater weight of water and the optional components cement, alkali
silicate, anionic dispersant, a
source of orthophosphate ions, sodium hydroxide and sodium carbonate.
US patent No. 8,722,772 teaches a hydraulically setting sealing composition
based on a) a
- hydraulically setting compound from the group comprising high-alumina
cement, ordinary portland cement,
blast furnace slag, b) protective-colloid stabilized polymer of one or more
ethylcnically unsaturated
monomers in form of an aqueous polymer dispersion or a water-redispersible
polymer powder, and c) one or
more fillers.
US patent No. 5,673,753 teaches a drilling mud for in situ conversion to
cement by addition of blast
furnace slag. The description states that the purpose of the invention is
achieved through the in situ
solidification of water-base drilling fluids through the addition of blast
furnace slag, set-time control
additives, and rheology modifying additives. The blast furnace slag is said to
be added in an amount
equivalent from about 50 to 400 pounds of slag per standard (42-gallon) barrel
of drilling fluid. It is also
stated that the composition is particularly useful for the solidification of
drilling fluids containing polyhydrie
alcohols.
WO 2015/082585 discloses a binder composition for improved mortars and
coatings, comprising
first standard mineral constituent and a second constituent based on
pulverulent calcium hydroxide, wherein
said second constituent based on pulverulent calcium hydroxide has a specific
surface calculated according
to the BET method which is lower than 12 m2/g. The description states that
among the cements that can be
selected ground blast furnace slag and fly ash can be used.
One of the issues with the addition of slag to Portland cement is that
increasing the amount of slag
addition increases the setting time of the final cement. The early strength
gain of the cement considerably
decreases thus making the cement unusable. Currently, the addition of slag to
Portland cement has been
limited to a maximum of 50% depending on the fineness and glass content of the
slag. Consequently, there is
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still a need to increase the percentage of slag loading without compromising
on the early and final strength of
the final cement and, more advantageously, to remove altogether the presence
of Portland cement in the
cementitious binder composition.
Some of the problems of prior art cements include: slow setting and decreased
early strength when
slag percentage is increased; the use of high pH and harsh alkalis like sodium
hydroxide and sodium silicate;
and the mandatory use or Portland cement and high amount of calcium sulfate.
The inventors have discovered that cement made according to a preferred
embodiment of the present
invention promotes the reaction between lime and phosphate and hence provides
a more durable cement than
previously used or known cements.
SUMMARY OF THE INVENTION
According to an aspect of the present invention, there is provided a method of
producing blast
furnace slag cement that does not involve any addition of Portland cement and
hence requires very less
energy to make and does not release green house. gases during its production.
According to a second aspect of the present invention, there is provided an
activator composition for
combining with hydraulically-active materials comprising ground granulated
blast furnace slag (GGLIFS)
and/or pulverised fuel ash (PFA) to form a cementitious binder, methods for
using such activator
compositions and methods of forming cementitious binders.
According to a preferred embodiment of the present invention, there is
provided a cementitious
binder composition comprising at least 80 % by weight of a hydraulically-
active material comprising ground
granulated blast furnace slag (GGBFS) and/or fly ash having a surface area
ranging between 2500-12000
cm2/g, preferably of approximately 4000 em2/g; at least 0.5 % by weight of
lime; at least 0.5% of nano
calcium carbonate having a particle size of 5-10 micron meter; at least 0.5%
by weight of alkali metal
fluoride; at least 0.5% by weight of an alkali metal sulfate; optionally, 0.1%
by weight of a hydrocolloid as
water retention agent; and at least 0.1% by weight of acid and/or alkali metal
phosphate as part of cement
composition for the hydraulically-active material. The cementitious binder
composition according to an
aspect of the present invention does not comprise any Portland cement and is,
therefore, more
environmentally friendly. The resulting cement does not involve clinkering.
According to an aspect of the present invention, there is provided a concrete,
mortar, grout, screed or
render formed by mixing the cementitious binder composition according to the
present invention with
aggregate particles, water and a superploticiser. The particles of slag must
preferably be within the
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specified ranges or if too coarse. the particles will have fewer chemical
reactions with other components of
the binder and therefore lead to a cement with reduced strength.
According to another aspect of the present invention, there is provided the
use ol'an alkali metal poly
phosphate such as sodium hexa meta phosphate as activator which was heretofore
not known to the
inventors. The cement according to preferred embodiments of the present
invention provides for a strength
gain comparable to Portland cement compositions.
According to another aspect of the present invention, there is provided the
use of an increased
percentage in the use of slag as well as higher strength because of the use of
mechanically activated GGBI'S
or fly ash.
According to a preferred embodiment of the present invention, a curing agent
can be added to the
cement composition in order to provide a cement which does not need to undergo
the complex process of
curing. The curing agent used in a preferred embodiment of present invention
can be a hydrocolloid such as
sodium polyacrylate.
DETAILED DESCRIPTION OF THE INVENTION
It is known in the prior art to combine (.36131'S, lime and other harsh
alkalis like sodium hydroxide or
sodium silicate to form a cementitious binder. In the prior art, a high
proportion of lime has been used and a
cement prepared using such a binder has low initial strength and a slow
setting time. Previously phosphate
has been used as retarder for slag cements containing a high amount of calcium
sulfate to prevent the flash
setting of the cements.
The inventors have unexpectedly and surprisingly found that in combining
ground granulated blast
furnace slag (GORES) with lime, nano alkali metal carbonate, a source of
alkali metal fluoride, a source of
alkali metal phosphate as accelerator and alkali metal sulfate one could
obtain a cement having comparable
characteristics with Portland cement.
The inventors have now determined that concretes with improved durability can
be prepared using a
cementitious binder comprising _a high proportion of GGI.31:S and/or ITA and a
low proportion of
combination of CaO, or lime, alkali metal phosphate, alkali metal fluoride,
nano calcium carbonate, and
alkali metal sulfate as described herein.
Preferably, ground granulated blast furnace slag can be used in an amount
ranging from 80 to 90%
by weight in the cement composition. Preferably, the alkali metal oxide is
present in an amount ranging from
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0. I to 0 %. Preferably, the alkali metal oxide is lime. According to a
preferred embodiment, the nano alkali
metal carbonate is nano calcium carbonate and is present in an amount ranging
from 0.1 to 10%. Preferably,
alkali metal fluoride such as sodium fluoride is present in an amount ranging
from 0.1 to 5%. Preferably,
acid phosphate is present in an amount ranging from 0.1 to 5%. Preferably,
alkali metal phosphate such as
sodium hexa meta phosphate is present in an amount ranging from 0.1 to 10%.
Preferably, alkali metal
sulfate such as sodium sulfate is present in an amount ranging from 0.1 to
10%. Preferably, hydrocolloids are
present in an amount ranging from 0.1 to 0.5%. Preferred hydrocolloids are
selected from the group
consisting of poly acrylates, alginates, starch, and polyacronitrile. Most
preferred is sodium polyacrylate.
Example 1
Concrete containing cement according to an embodiment of the present invention
was made having
the following components:
Slag -- 864 g
Lime 50 g
SHMP - 50g
Sodium Sulfate -30 g
Sodium Fluoride - 5 g
Sodium Polyacrylate - 1 g
Sand 2000 g
Aggregates - 2875 g
Water 500 ml
All the powder components were mixed first and water is added and mixed in a
mixer. Then sand
and aggregates were added and the resulting mixture was mixed lbr another 10
minutes.
For the compressive strength testing, 100 mm concrete cubes were .cast using
the above mix for
testing of compressive strength. The compressive strength was tested at 1, 3,
7 and 28 days. The results arc
provided in the respective tables below.
Table 1 - Testing data of the compressive strength of the concrete made in
Example 1
Duration Compressive
(days) Strength (Mpa)
20
- 7 26
28 33
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Example 2
Concrete containing cement according to an embodiment of the present invention
was made having
the following components:
Slag ¨ 864 g
Lime ¨ 50 g
SFIMP - 30g
Sodium Sulfate ¨ 30 g
Sodium Fluoride ¨ 5 g
Sodium Poly acrylate ¨ 1 g
Nano Calcium Carbonate 20 g
Sand ¨ 2000 g
Aggregates 2875 g
Water ¨ 500 ml
Table 2 ¨ Testing data of the compressive strength of the concrete made
in Example 2
Duration Compressive
Strength (Mpa)
8
3 19
7 27
28 31
Example 3
Concrete containing cement according to an embodiment of the present invention
was made having
the following components:
Slag ¨ 874 g
iimc ¨ 50 g
SIIMP - 20g
Sodium Sulfate ¨ 30 g
Sodium Fluoride ¨ 5 g
Sodium Poly aerylate 1 g
Nano Calcium Carbonate ¨ 20 g
Sand ¨2000 g
Aggregates ¨ 2875 g
Water ¨500 ml
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Table 3 - Testing data of the compressive strength of the concrete made
in Example 3
Duration Compressive
1
Strength (Mpa)
I 6.4
. _______________________________________________________ _
3 17.8
7 25
28 29 -
- ___________________________
Examples 4 through 11
Preparation of concrete made with cement according to examples 4 to 1] was
made as follows. All
the powder components (referring to Table 4 for components and quantities)
were mixed first in the above
mentioned ratio and the cement was made. Concrete was then made using the
ratio of 1 : 2 : 2.87 for Cement
: Sand : Aggregate.
The water:cement ratio was maintained as 0.5 in each example.
All the components cement, sand, aggregate and water were mixed for about 10
minutes and 100
mm cubes were casted. All of the cube samples were water cured except for the
composition of Example 6
where an internal curing agent, sodium polyacrylate, was added to the mixture.
Table 4- Effect of Various additives on Compressive strength of Slag Cement
Ex. Slag SH M P LP SS SF PS NCC SPA ID 31) 7D 281)
No (wt %) Mpa Mpa Mpa Mpa
4 86.5 5 5 3 0.5 0 0 0 6.7
17.5 23.4 31.8
5 84.5 5 5 3 0.5 0 2 0 10.1
23.2 27.9 35.3
6 86.4 5 5 3 - 0.5 0 0 0.1 9.8 20.1 25.8
33.1
7 87 5 5 3 0 0 0 0 12.3
20.4 22.0 17.4
.. _______ -___., ... __
8 87 0 5 3 0 5 0 0 3.5 4.5 5.7 6.6
9 84 5 5 3 ' 0 3 0 0 4.2 14.6 19.0
21.7
10 90 5 5 0 0 0 0 0 8.5 13.1 18.6
12.6
11 80 10 10 0 0 0 0 0 10.6
19.6 28.4 35.6
_______________________________________________________________________ J
SHIV1P- Sodium hexa meta phosphate
LP- Lime Powder (CaO)
SS- Sodium Sulfate
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SF ¨ Sodium fluoride
PS ¨ Potasium Silicate
NCC ¨ Nano Calcium Carbonate
SPA- Sodium Poly acrylate
Observations
By looking at examples 10 and 11, a net hardening reaction was observed which
was caused by the
reaction of lime and sodium hexa meta phosphate.
By referring to examples 7 and 19, one notices that the addition of sodium
sulphate has an impact in
increasing the strength across all test points (I day, 3 days, 7 days and 28
days).
By comparing examples 4 and 5, one can establish the positive impact of the
addition of nano
calcium carbonate in the increase of the concrete strength across all test
points.
Example 6 provides an indication that the addition of 0.1% of hydrocolloids
allows to make a cement
which does not require curing.
Examples 8 and 9 illustrate that the addition of potassium silicate alone or
in the presence of a
phosphate additive such as SHNIP decreases the strength of the cured
composition.
Concrete made with pozzolona portland cement undergoing the same test have
compression
data as follows: I day: 8.1 Mpa; 3 days: 14.6 Mpa; 7 days: 21.1 Mpa; and 28
days: 31.6 Mpa.
The terms and descriptions used herein are set forth by way of illustration
only and are not meant as
limitations unless otherwise specifically indicated. Those skilled in the art
will recognize that many
variations arc possible within the scope of the invention as defined in the
following claims, and their
equivalents, in which all terms arc to be understood in their broadest
possible sense unless otherwise
specifically indicated. While the examples shown and described in detail
herein are capable of attaining the
above-described aspects of the invention, the person skilled in the art will
understand that these are but
preferred embodiments ()Utile present invention and the invention is not to be
limited to those embodiments.
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