U.S. patent application number 17/164401 was filed with the patent office on 2021-08-05 for composite mineralizers/fluxes for the production of alite/calcium sulfoaluminate clinkers.
The applicant listed for this patent is University of Kentucky Research Foundation. Invention is credited to Tristana Duvallet, Robert Jewell, Thomas Robl.
Application Number | 20210238090 17/164401 |
Document ID | / |
Family ID | 1000005401503 |
Filed Date | 2021-08-05 |
United States Patent
Application |
20210238090 |
Kind Code |
A1 |
Duvallet; Tristana ; et
al. |
August 5, 2021 |
COMPOSITE MINERALIZERS/FLUXES FOR THE PRODUCTION OF ALITE/CALCIUM
SULFOALUMINATE CLINKERS
Abstract
A cement clinker composition incorporates calcium fluoride and
iron oxide to reduce firing temperatures and increase strength.
High fly ash, aluminum dross, aluminum scrap, high aluminum clays
and combinations thereof may also be substituted for bauxite in the
cement clinker composition
Inventors: |
Duvallet; Tristana;
(Lexington, KY) ; Robl; Thomas; (Sadieville,
KY) ; Jewell; Robert; (Lexington, KY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
University of Kentucky Research Foundation |
Lexington |
KY |
US |
|
|
Family ID: |
1000005401503 |
Appl. No.: |
17/164401 |
Filed: |
February 1, 2021 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
62967625 |
Jan 30, 2020 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C04B 7/323 20130101;
C04B 7/3456 20130101; C04B 7/26 20130101 |
International
Class: |
C04B 7/32 20060101
C04B007/32; C04B 7/26 20060101 C04B007/26; C04B 7/345 20060101
C04B007/345 |
Claims
1. A cement clinker composition defined by oxide content,
comprising: 42-65 wt % CaO; 5-20 wt % SiO.sub.2; 10-40 wt %
Al.sub.2O.sub.3; 0.5-5 wt % Fe.sub.2O.sub.3; and 2-13 wt %
SO.sub.3.
2. The cement clinker composition of claim 1, including: 50-55 wt %
CaO; 9-13 wt % SiO.sub.2; 20-30 wt % Al.sub.2O.sub.3; 0.5-3 wt %
Fe.sub.2O.sub.3; and 5-10 wt % SO.sub.3.
3. A cement clinker composition of claim 2, including between about
0.1 and 3 wt % fluoride compound and between about 0.5 and about 5
wt % Fe.sub.2O.sub.3.
4. The cement clinker of claim 3, further including between about
10-35 wt % of a bauxite substitute selected from a group consisting
of high fly ash alumina, aluminum dross, aluminum scrap, high
alumina clays, kaolin, metakaolin, 1:1 silica to alumina clays and
combinations thereof.
5. The cement clinker composition of claim 1, including between
about 0.1 and 3 wt % fluoride compound and between about 0.5 and
about 5 wt % Fe.sub.2O.sub.3.
6. The cement clinker of claim 5, further including between about
10-35 wt % of a bauxite substitute selected from a group consisting
of high fly ash alumina, aluminum dross, aluminum scrap, high
alumina clays and combinations thereof.
7. A cement clinker composition, comprising; 15-40 wt % C.sub.3S;
20-60 wt % C.sub.4A.sub.3 ; 5-30 wt % C.sub.2S; 1-10 wt %
C.sub.4AF; and 0.4-1.0 wt % CaF.sub.2 as present in
fluorellestadite and fluormayenite clinker phases fired at
1150-1350.degree. C.
8. The cement clinker of claim 7, further including between about
0.5-2.0 wt % Fe.sub.2O.sub.3.
9. The cement clinker of claim 8, further including between about
10-35 wt % of a bauxite substitute selected from a group consisting
of high fly ash alumina, aluminum dross, aluminum scrap, high
alumina clays and combinations thereof.
10. The cement clinker of claim 7, further including between about
10-35 wt % of a bauxite substitute selected from a group consisting
of high fly ash alumina, aluminum dross, aluminum scrap, high
alumina clays and combinations thereof
11. The cement clinker composition of claim 7, including: 20-35 wt
% C.sub.3S; 40-55 wt % C.sub.4A.sub.3 ; 10-25 wt % C.sub.2S; 1-4 wt
% C.sub.4AF; and 0.6-0.8 wt % CaF.sub.2 as present in
fluorellestadite and fluormayenite clinker phases fired at
1200-1300.degree. C.
12. The cement clinker of claim 5, further including between about
0.5-2.0 wt % Fe.sub.2O.sub.3.
13. The cement clinker of claim 12, further including between about
10-35 wt % of a bauxite substitute selected from a group consisting
of high fly ash alumina, aluminum dross, aluminum scrap, high
alumina clays, kaolin, metakaolin, 1:1 silica to alumina clays and
combinations thereof.
14. The cement clinker of claim 11, further including between about
10-35 wt % of a bauxite substitute selected from a group consisting
of high fly ash alumina, aluminum dross, aluminum scrap, high
alumina clays and combinations thereof.
15. A cement clinker composition, comprising between about 0.1 and
about 3.0 wt % fluoride compound and between about 0.5 and about
5.0 wt % Fe.sub.2O.sub.3 and after firing at between about
1150.degree. C. and 1350.degree. C. including between about 15 and
about 40 wt % alite and between about 20 and about 60 wt % calcium
sulfoaluminate.
16. The cement clinker of claim 15, further including between about
10-35 wt % of a bauxite substitute selected from a group consisting
of high fly ash alumina, aluminum dross, aluminum scrap, high
alumina clays, kaolin, metakaolin, 1:1 silica to alumina clays and
combinations thereof.
17. The cement clinker of claim 15, after firing at between
1200.degree. C. and 1300.degree. C.
Description
RELATED APPLICATION
[0001] This application claims priority to U.S. Provisional Patent
Application Ser. No. 62/967,625 filed on Jan. 30, 2020 which is
hereby incorporated by reference in its entirety.
TECHNICAL FIELD
[0002] This document generally relates to the cement industry and,
more particularly, to an alite/calcium sulfoaluminate (A/CSA)
cement clinker incorporating a novel composite of
mineralizers/fluxes.
BACKGROUND
[0003] The cement industry is the third-largest consumer of
industrial energy and the second-largest emitter of industrial
carbon dioxide. With the global population growing every year,
there is a need for further construction materials in order to meet
infrastructure requirements. Ordinary Portland cement (OPC) is the
most widely used type of cement material for construction purposes,
and it has been estimated that the production of cement is
responsible for approximately 7-8% of anthropogenic carbon dioxide
emissions worldwide.
[0004] The production of OPC requires natural resources as
ingredients, such as limestone, marl or chalk as a source of
calcium; and clay or shales as a source of silicate and alumina.
The raw materials are ground and fired at 1450-1500.degree. C. to
obtain the OPC clinker and mixed with 5 wt. % gypsum to obtain the
final OPC cement. There are two main processes in cement production
responsible for the CO.sub.2 emissions. The first source of
CO.sub.2 emissions is the calcination of limestone, while the
second source is the combustion of fossil fuels to produce clinker
at high firing temperature. This high firing temperature is
necessary for the formation of alite, a high calcium demanding
clinker phase, responsible for most of the strength development in
OPC cement.
[0005] For the past decades, various alternative cementitious
binders with lower CO.sub.2 emissions than OPC have been proposed.
These alternative binders are produced at a lower firing
temperature than OPC but do not contain alite and do not perform on
a par with it. They include calcium aluminate cements (CAC),
belite-calcium sulfoaluminate cement (BCSA), alkali-activated
materials (AAM), supersulfated cement, calcium sulfoaluminate
belite ferrite cement (CSABF), etc. However, these possible
alternative solutions encounter issues, ranging from loss of
strength over time due to carbonation for CAC, to costly raw
materials in CSAB, to highly caustic and costly activators for AAM,
and special curing methods (supersulfated and other cements).
[0006] The production of a successful commercial alternative binder
should be able to seamlessly replace current commercial OPC
production methods in cement plants. For example, the same rotary
kilns used to produce OPC should be used to produce alternative
cements but at a lower firing temperature to reduce the CO.sub.2
emissions from the decarbonation of limestone and the fossil fuels.
Alternative materials to limestone should be targeted, with
emphasis on industrial wastes and by-products. As an example, it
has been widespread that CSA cement cannot be widely produced due
to the necessity to use bauxite, an abundant but not regionally
available material, making it costly. However, the novel cement
clinker composition set forth herein demonstrates that an
industrial by-product, a high fly ash alumina, may be used as a
source of alumina and can completely replace the use of bauxite.
Other materials of this type include aluminium dross and scrap as
well as high alumina clays such as kaolin.
SUMMARY
[0007] In accordance with the purposes and benefits set forth
herein, a new and improved cement clinker composition defined by
oxide content comprises: 42-65 wt % CaO; 5-20 wt % SiO.sub.2; 10-40
wt % Al.sub.2O.sub.3; 0.5-5 wt % Fe.sub.2O.sub.3; and 2-13 wt %
SO.sub.3. More specifically, the new and improved clinker
composition may comprise: 50-55 wt % CaO; 9-13 wt % SiO.sub.2;
20-30 wt % Al.sub.2O.sub.3; 0.5-3 wt % Fe.sub.2O.sub.3; and 5-10 wt
% SO.sub.3.
[0008] In accordance with yet another aspect, a new and improved
cement clinker composition comprises between about 0.1 and 3.0 wt %
fluoride compound and between about 0.5 and about 5.0 wt %
Fe.sub.2O.sub.3. Such a composition may be fired at a temperature
of between about 1150-1350.degree. C. More preferably such a cement
clinker composition is fired at temperature of between
1200-1300.degree. C. After firing, such a composition provides
between about 15 and 40 wt % alite and between about 20 and about
60 wt % calcium sulfoaluminate.
[0009] In accordance with an additional aspect, the new and
improved cement clinker composition comprises: 15-40 wt % C.sub.3S;
20-60 wt % C.sub.4A.sub.3 ; 5-30 wt % C.sub.2S; 1-10 wt %
C.sub.4AF; and 0.4-1.0 wt % CaF.sub.2 as present in
fluorellestadite and fluormayenite clinker phases fired at
1150-1350.degree. C. and more particularly 1200-1300.degree. C.
More specifically, the new and improved cement clinker composition
comprises: 20-35 wt % C.sub.3S; 40-55 wt % C C.sub.4A.sub.3 ; 10-25
wt % C.sub.2S; 1-4 wt % C.sub.4AF; and 0.6-0.8 wt % CaF.sub.2 as
present in fluorellestadite and fluormayenite clinker phases fired
at 1150-1350.degree. and more particularly 1200-1300.degree. C.
[0010] In the following description, there are shown and described
several preferred embodiments of the cement clinker composition. As
it should be realized, the cement clinker composition is capable of
other, different embodiments and its several details are capable of
modification in various, obvious aspects all without departing from
the composition as set forth and described in the following claims.
Accordingly, the drawings and descriptions should be regarded as
illustrative in nature and not as restrictive.
BRIEF DESCRIPTION OF THE DRAWING FIGURES
[0011] The accompanying drawing figures incorporated herein and
forming a part of the patent specification, illustrate several
aspects of the cement clinker composition and together with the
description serve to explain certain principles thereof.
[0012] FIG. 1 is graph of DSC/TGA (SDT) data illustrating the
influence of fluorellestadite and ferrite within A/CSA
clinkers.
[0013] FIG. 2 is a bar graph of resistivity as a function of time
for cement made with the new and improved clinker composition
compared to commercial cements.
[0014] FIG. 3 is a bar graph of compressive strength as a function
of time for cement made with the new and improved clinker
composition compared to commercial cements.
[0015] FIG. 4 is a line graph of length change as a function of
time for cement made with the new and improved clinker composition
compared to commercial cements.
DETAILED DESCRIPTION
[0016] Cement Notation used throughout this document:
TABLE-US-00001 Chemical Formula Cement Notation CaO C SiO.sub.2 S
Al.sub.2O.sub.3 A Fe.sub.2O.sub.3 F SO.sub.3 M MgO
[0017] The alternative binder presented in this novel cement
clinker composition is alite-calcium sulfoaluminate (A-CSA) cement.
A-CSA clinker combines alite (C.sub.3S) and calcium sulfoaluminate
(CSA, ye'elimite or C.sub.4A.sub.3 ) phases. These are the phases
responsible for most of the strength development in OPC and CSA
cements, respectively. Until recently, A-CSA clinker was not
considered practical due to the perceived incompatible coexistence
of both clinker phases. Alite forms at 1450-1500.degree. C., while
CSA decomposes at 1300-1350.degree. C. [3-5] The introduction of
mineralizers and fluxes, such as calcium fluoride and calcium
sulfate [6-13], barium and strontium [14-16], or other elements
such as titanium [17], partly resolved this issue, however
improvements in this field were needed.
[0018] This document demonstrates that the use of both calcium
fluoride and iron oxide in the production of A/CSA clinker reduces
the melting temperature and increases the formation of alite.
Previously, it was found that the presence of sulfate hinder the
formation of alite, but as this document demonstrates the
production of increased levels of alite (30 wt. %) with high levels
of calcium sulfoaluminate (50 wt. %) in the clinker. This binder
formulation exhibits superior mechanical properties to both
commercial OPC and CSA cement, including higher compressive
strength, high resistivity, and high dimensional stability.
[0019] The new and improved cement clinker composition as defined
by oxide content incorporates about 42-65 wt % CaO; about 5-20 wt %
SiO.sub.2; about 10-40 wt % Al.sub.2O.sub.3; about 0.5-5 wt %
Fe.sub.2O.sub.3; and about 2-13 wt % SO.sub.3. In at least one
particularly useful embodiment, the new and improved clinker
composition incorporates about 50-55 wt % CaO; about 9-13 wt %
SiO.sub.2; about 20-30 wt % Al.sub.2O.sub.3; about 0.5-3.0 wt %
Fe.sub.2O.sub.3; and about 5-10 wt % SO.sub.3.
[0020] In one or more embodiments, the cement clinker composition
includes between about 0.1 and about 3.0 wt % fluoride compound and
between about 0.5 and about 5.0 wt % Fe.sub.2O.sub.3. The fluoride
compound may comprise, for example, calcium fluoride (CaF.sub.2),
pickling liquor sludge containing fluoride and the like.
[0021] In one or more embodiments, the cement clinker composition
includes between about 10-35 wt % of a bauxite substitute selected
from a group consisting of high fly ash alumina, aluminum dross,
aluminum scrap, high alumina clays and combinations thereof. For
purposes of this document, "high fly ash alumina" means a fly ash
containing at least 20 wt. % of Al.sub.2O.sub.3, and more
preferably at least 40 wt. % of Al.sub.2O.sub.3. For purposes of
this document, "high alumina clays" means a clay containing at
least 10 wt. % of Al.sub.2O.sub.3, and more preferably at least 20
wt. % of Al.sub.2O.sub.3, such as kaolin compound.
[0022] In one or more embodiments, the cement clinker composition
incorporates about 15-40 wt % C.sub.3S; about 20-60 wt %
C.sub.4A.sub.3 ; about 5-30 wt % C.sub.2S; about 1-10 wt %
C.sub.4AF; and about 0.4-1.0 wt % CaF.sub.2 as present in
fluorellestadite and fluormayenite clinker phases fired at about
1150-1350.degree. C., 1200-1300.degree. C. or 1225-1275.degree. C.
More specifically, the new and improved cement clinker composition
incorporates about 20-35 wt % C.sub.3S; about 40-55 wt %
C.sub.4A.sub.3 ; about 10-25 wt % C.sub.2S; about 1-4 wt %
C.sub.4AF; and about 0.6-0.8 wt % CaF.sub.2 as present in
fluorellestadite and fluormayenite clinker phases fired at about
1150-1350.degree. C. or 1200-1300.degree. C. In one or more
embodiments, the cement clinker composition is fired at about
1225-1275.degree. C.
[0023] In one or more embodiments, the cement clinker composition
further includes between about 0.5-2.0 wt % Fe.sub.2O.sub.3. In one
or more embodiments, that cement clinker composition also includes
between about 10-35 wt % of a bauxite substitute selected from a
group consisting of high fly ash alumina, aluminum dross, aluminum
scrap, high alumina clays and combinations thereof.
[0024] In one or more of the many possible embodiments, the new and
improved cement clinker composition comprises between about 0.1 and
3.0 wt % of a fluoride compound, such as CaF.sub.2, pickling liquor
sludge including fluoride or the like, and between about 0.5 and
about 5.0 wt % Fe.sub.2O.sub.3. Such a composition may be fired at
a temperature of between about 1150-1350.degree. C. or
1200-1300.degree. C. More preferably such a cement clinker
composition is fired at temperature of between 1225-1275.degree. C.
Further, such a cement clinker composition may include between
about 10-35 wt % of a bauxite substitute selected from a group
consisting of high fly ash alumina, aluminum dross, aluminum scrap,
high alumina clays and combinations thereof.
EXPERIMENTAL SECTION
[0025] A calculated clinker composition composed of 50 wt. % alite
and 50 wt. % calcium sulfoaluminate was investigated. Four
compositions were tested: #1 with no additions of CaF.sub.2 or iron
oxide; #2 with addition of only CaF.sub.2; #3 with addition of only
iron oxide; and #4 with additions of both CaF.sub.2 and iron oxide.
The compositions were produced from reagent chemicals, as presented
in Table 1. Fe.sub.2O.sub.3 was added at a percentage of 1.3 wt. %
to obtain approximately 5 wt. % of ferrite (C.sub.4AF) in the final
clinker composition. Regarding the addition of CaF.sub.2, the
target was to produce approximately 10 wt. % of fluorellestadite, a
liquid phase. The calculated clinker compositions are presented in
Table 2.
TABLE-US-00002 TABLE 1 Mixtures of chemicals used to produce A/CSA
#1 to A/CSA #4 in weight percentages Mixtures Reagent Chemicals
A/CSA Comments Ca(OH).sub.2 SiO.sub.2 Al(OH).sub.3 Fe.sub.2O.sub.3
CaSO.sub.4 0.5H2O CaF.sub.2 #1 No fluorellestadite 51.54 9.86 29.6
-- 9.0 -- or ferrite #2 Only 51.235 9.815 29.4 -- 8.95 0.6
fluorellestadite #3 Only ferrite 50.89 9.21 29.6 1.3 9.0 -- #4 Both
fluorellestadite 50.57 9.13 29.5 1.3 8.895 0.605 or ferrite
TABLE-US-00003 TABLE 2 Calculated clinker compositions in wt. % for
A/CSA #1 to A/CSA #4 Calculated Clinker Compositions (in wt.%)
Mixtures C.sub.3S C.sub.2S C.sub.4A.sub.3 C.sub.4AF C CaF.sub.2
A/CSA #1 48.5 -- 49.9 -- -- -- A/CSA #2 48.0 0.1 49.5 -- -- 0.78
A/CSA #3 45.0 0.1 47.7 5.0 0.5 -- A/CSA #4 44.7 -- 47.4 5.0 0.4
0.78
[0026] A/CSA #1 to A/CSA #4 were produced by mixing the raw
materials with the quantities as described in Table 1 with an
additional 10 wt. % of deionized water in a mortar and pestle until
a homogenized powder was obtained. A part of the powder was kept
for SDT analyses. A few 28.times.7 mm pellets were formed using a
load of 25000 lbs, and dried overnight in an oven at 60.degree. C.
The pellets were then fired in a box furnace, and followed the
firing program: 1--heat from room temperature to 800.degree. C. at
7.5.degree. C./min; 2--dwell at 800.degree. C. for 30 min; 3--heat
from 800.degree. C. to 1250.degree. C. at 5.0.degree. C./min;
4--dwell at 1150/1200/1250.degree. C. for 60 min; and 5--quench
rapidly in air. The clinker pellets were then crushed in a shatter
box until a fine powder was obtained.
[0027] Results:
[0028] About the A/CSA Clinker
[0029] Evidence about the Reduction of the Melting Temperature:
[0030] The influence of additions of CaF.sub.2 (to form
fluorellestadite) and iron oxide (to form ferrite) on A/CSA
clinkers was studied through Simultaneous Different Scanning
calorimetry and Thermogravimetry Analysis (SDT). The experiments
were performed with a TA Instruments SDT Q600, under air atmosphere
at a rate of 100 mL/min, from 50.degree. C. to 1400.degree. C., at
a heating rate of 10.degree. C./min. The results are presented in
FIG. 1.
[0031] Below 600.degree. C., all four A/CSA samples present the
same SDT results, where three main peaks are present: at around
100.degree. C. referring to the release of water; at around
300.degree. C. referring to the decomposition of aluminium
hydroxide; and at around 450.degree. C. referring to the
decomposition of calcium hydroxide. The weight losses for all three
peaks are confirmed by the TGA results. The SDT curves of the four
A/CSA clinkers differ above 600.degree. C. Compositions A/CSA #1
(no fluorellestadite or ferrite formed) and A/CSA #3 (only ferrite
formed) showed melting temperatures at 1259.degree. C. and
1249.degree. C., respectively. The formation of 5 wt. % of ferrite
within A/CSA #3 clinker did not considerably decrease the melting
temperature of A/CSA clinkers. On the other hand, A/CSA #2 (only
fluorellestadite formed) and A/CSA #4 (fluorellestadite and ferrite
formed) exhibited lower melting temperatures, at 1194.degree. C.
and 1187.degree. C., respectively. Compared to the composition
A/CSA #1, the melting temperature decreased by 65.degree. C. when
fluorellestadite was formed, and by 72.degree. C. when both
fluorellestadite and ferrite were formed. Based on these SDT
results, the influence of both fluorellestadite and ferrite within
the formation of A/CSA clinkers increased the reduction of the
melting temperature.
[0032] Evidence about the Formation of High Alite and High Calcium
Sulfoaluminate Clinker:
[0033] The influence of adding fluorellestadite and ferrite to the
raw mix of A/CSA clinkers was determined by XRD/Rietveld analyses.
The same compositions as presented in Table 1 and studied through
SDT analyses were fired at different temperatures of 1150.degree.
C., 1200.degree. C., and 1250.degree. C. for 60 minutes. The
results are presented below in Table 3.
TABLE-US-00004 TABLE 3 Clinker compositions determined by Rietveld
for A/CSA #1 to A/CSA #4 fired at 1150.degree., 1200.degree., and
1250.degree. C. for 60 minutes. Rietveld parameters to ensure
accuracy of the results are added: Rexp = Expected R Factor; Rp =
Residual of Least-Squares Refinement; Rwp = Weighted Profile
R-Factor; and GoF = Goodness of Fit. Clinker phases A/CSA #1 A/CSA
#2 A/CSA #3 A/CSA #4 Firing Temperature (.degree. C.) 1150 1200
1250 1150 1200 1250 1150 1200 1250 1150 1200 1250 C.sub.3S 1.1 1.3
-- -- 1.3 21.4 -- -- 3.1 -- 3.6 26.9 C.sub.2S 40.5 39.1 39.7 38.9
38.7 21.7 35.0 37.0 36.4 35.5 33.4 14.4 C.sub.4A.sub.3 36.5 47.1
47.7 43 41.8 50.4 44.8 48.2 47.7 42.3 44.3 50.5 C.sub.4AF -- 2.7
1.5 -- 0.6 -- 3.9 4.7 4.2 4 4.4 3.2 C 2.9 -- -- -- -- 0.1 -- -- --
-- -- 0.1 C 11.5 7.9 10.3 10.6 9 4.6 11.1 9 8.4 10 6.2 2.8 M 0.2
0.4 0.7 0.4 0.3 0.1 0.4 0.4 0.3 0.4 0.6 0.2 C.sub.12A.sub.7 5.2 --
-- -- -- -- -- -- -- -- -- -- CA 2.2 -- -- -- -- -- -- -- -- -- --
-- C.sub.3A -- -- -- -- -- -- -- -- -- -- -- --
C.sub.11A.sub.7CaF.sub.2 -- 1.5 -- 3.8 7.2 1.5 1.3 0.7 -- 5.3 6.8
1.9 3C.sub.2S 3C CaF.sub.2 -- -- -- 3.3 1.1 -- -- -- -- 2.6 0.8 --
Rexp 3.29 3.34 3.27 3.29 3.30 3.27 3.14 3.11 3.12 3.12 3.14 3.13 Rp
5.54 5.62 5.60 4.88 5.11 5.41 4.94 5.05 4.82 4.55 4.55 4.79 Rwp
8.06 8.19 8.25 7.07 7.38 7.96 7.15 7.48 7.13 6.54 6.58 6.94 GoF
6.00 6.02 6.35 4.63 5.01 5.94 5.20 5.76 5.24 4.39 4.39 4.92
[0034] The composition A/CSA #1 without the formation of
fluorellestadite or ferrite, did not form any measurable alite, at
all three firing temperatures. Formation of belite was constant for
all three firing temperatures, at around 40 wt. %. The formation of
ye' elimite increased with the firing temperature, especially
between 1150.degree. C. and 1200.degree. C., from 36.5 to 47.1 wt.
%. Instead of forming essentially ye'elimite at 1150.degree. C.,
other clinker phases were present, such as mayenite (5.2 wt. %),
calcium aluminate (2.2 wt. %) and anhydrite (2.9 wt. %). At
1200.degree. C., mayenite, calcium aluminate, and anhydrite were no
longer present, while more ye'elimite had been formed. The free
lime content decreased with the increasing firing temperature, from
11.5, to 7.9, and 10.3 wt. %, at 1150, 1200, and 1250.degree.
C.
[0035] The composition A/CSA #2 (only CaF.sub.2 added) contained a
significant amount of alite when fired at 1250.degree. C., at 21.4
wt. %, and 4.6 wt. % of free lime. At lower firing temperatures,
mostly belite and ye'elimite were present, with free lime,
C.sub.11A.sub.7CaF.sub.2, and fluorellestadite. As studied
previously in other works, the addition of calcium fluoride does
provide benefit in reducing the firing temperature by forming a
liquid phase, fluorellestadite, at a low temperature.
Fluorellestadite does contribute to the formation of alite at a low
firing temperature of 1250.degree. C.
[0036] The composition A/CSA #3 (only iron oxide added) contained a
small amount of alite (3.1 wt. %), only at 1250.degree. C. As
expected, belite and ye'elimite are the major clinker phases
present and ferrite is present at around 4.0-4.5 wt. % at all three
firing temperatures. In addition, the free lime content does not
seem to decrease significantly, even at high firing temperature of
1250.degree. C., with a content of 8.4 wt. %. In OPC, the clinker
ferrite is known to form a liquid phase promoting the formation of
alite via a flux mechanism. Recent work by Lu et al. discusses the
influence of ferrite on the formation and coexistence of ye'elimite
and alite. They demonstrated that the addition of 20 wt. % of
ferrite within an A/CSA clinker (from calculation: 15 wt. %
C.sub.3S, 42 wt. % C.sub.2S, 23 wt. % C.sub.4A.sub.3 , and 20 wt. %
C.sub.4AF) facilitated the coexistence of both phases at
1350.degree. C. A/CSA #3 clinker confirms their results, that the
addition of a small amount of ferrite, here 5 wt. %, does
contribute to the formation of alite in small quantity.
[0037] The final composition, A/CSA #4 (CaF.sub.2 and iron oxide
added), contained a significant amount of alite and ye'elimite, of
26.9 wt. % and 50.5 wt. % respectively, and a low amount of free
lime, (2.8 wt. %), when fired at 1250.degree. C. At low firing
temperatures of 1150.degree. C. and 1200.degree. C., almost no
alite was present, and only belite, ye'elimite and free lime. Even
though this composition, when fired at 1250.degree. C., still
contains free lime at a level above our target of 2.0%, it proves
that the addition of both fluorellestadite and ferrite in
combination improves the clinkering process by decreasing the
firing temperature needed to form A/CSA clinkers and forming a
significant amount of alite and ye' elimite.
[0038] As mentioned earlier, other works have demonstrated the
production of A/CSA clinkers, but with much lower quantities of
alite. As a few examples, Londono-Zuluaga et al. produced a A/CSA
clinker with 60 wt. % belite, 14 wt. % ye'elimite, and 10 wt. %
alite, by adding 0.9 wt. % CaF.sub.2 to the raw mixture, and
sintering at 1300.degree. C. for 15 minutes. In another work by Ma
et al., they demonstrated a two stage process for the production of
a A/CSA clinker based on a OPC clinker, containing in the final
clinker less than 4 wt. % ye'elimite, when fired at 1250.degree.
C.
[0039] While first interpreting the SDT data, it did not seem that
the formation of both fluorellestadite and ferrite together within
A/CSA clinker effectively improved the reduction in the firing
temperature, when compared with only the addition of
fluorellestadite as only a 7.degree. C. difference in temperature
was observed between A/CSA #2 and A/CSA #4. However, when
interpreting the Rietveld data, the results unequivocally
demonstrated that presence of both phases successfully enhanced the
formation of alite, reduced the firing temperature, and free lime
content.
[0040] Experiments were run again at 1250.degree. C. and this time,
the difference of adding only CaF.sub.2 and adding both CaF.sub.2
and iron oxide was obvious, as presented in Table 4.
TABLE-US-00005 TABLE 4 Calculated clinker compositions in wt. % for
A/CSA #1 to A/CSA #4 by following the equations of established by
Dr. Zhou [23]. Clinker compositions of samples presented in Tables
1 and 2, characterized by Rietveld method. A-CSA A-CSA A-CSA A-CSA
#1 #2 #3 #4 Expected/Calculated C.sub.3S 48.5 48.0 45 44.7
Compositions C.sub.2S 0 0.1 0.1 0 C.sub.4A.sub.3 49.9 49.5 47.7
47.4 C.sub.4AF 0 0 5.0 5.0 C 0 0 0.5 0.4 Mineralizers/ Fl* &
Fluxes present None Fl* Ferrite Ferrite Rietveld Compositions
C.sub.3S 0.4 13.4 4.0 24.5 C.sub.2S 45.6 33.1 42.6 22.6
C.sub.4A.sub.3 40.5 42.6 39.3 42.8 C.sub.4AF 0.9 0.6 4.6 3.7 C 0.1
0.0 0.2 0.1 C 8.4 5.6 7.2 2.8 M 0.2 0.1 0.2 -- C.sub.12A.sub.7 0.1
-- 0.5 2.8 CA 1.9 -- -- -- C.sub.11A.sub.7CaF.sub.2 1.8 -- 1.4 0.5
Fl* -- 4.5 -- -- (Fl* = fluorellestadite)
[0041] About the A/CSA Cement
[0042] An A/CSA clinker was produced from 55.7 wt. % of
agricultural lime, 12.3 wt. % of FGD gypsum, 31.38 wt. % of high
alumina ash, and 0.62 wt. % of calcium fluoride. In terms of oxide
contents within the raw mix, the composition is: 52.6 wt. % CaO,
11.5 wt. % SiO.sub.2, 25.3 wt. % Al.sub.2O.sub.3, 1.3 wt. %
Fe.sub.2O.sub.3, and 7.5 wt. % SO.sub.3, and minor compounds. The
raw materials used can be easily replaced with current raw
materials, such as limestone, marl/clay, bauxite, aluminium dross,
and pickling liquor sludge. Other raw materials can also be
introduced, as long as the oxide content of the final clinker is
similar to the composition described above. Similar A/CSA clinker
compositions with various available raw materials are presented in
Table 5. The raw materials were milled together and fired at
1250.degree. C. for 60 minutes, and ground to a particle size d(50)
of around 13-14 .mu.m. The final clinker was analysed by
XRD/Rietveld and contained: 29.6 wt. % alite (C.sub.3S), 9.4 wt. %
belite (C.sub.2S), 1.5 wt. % ferrite (C.sub.4AF), 50.8 wt. %
ye'elimite (C.sub.4A.sub.3 ), 0.6 wt. % anhydrite (C ), and 0.3 wt.
% free lime. The other clinker phases are minor phases.
TABLE-US-00006 TABLE 5 Possible alternative raw materials for the
production of A/CSA clinkers (not limiting in scope) Raw Exemplary
Alternative Alternative Materials in wt. % Embodiment-A/CSA #1 #2
Agriculture Lime 55.7 -- -- FGD Gypsum 12.3 9 9 CaF.sub.2 0.62 --
-- High alumina Ash 31.38 -- -- Aluminum Dross -- -- 20 Limestone
-- 62 62 Bauxite -- 21.5 -- Pickle liquor sludge -- 1.5 1.5
Marl/Clay -- 6 7.5
[0043] Mechanical properties of A/CSA cements were tested alongside
two commercial cements, an OPC Type I from Cemex and a CSA cement
from Buzzi. The composition of the A/CSA cements with gypsum
(CSA-NM-20G) and anhydrite (CSA-NM-15.8A) are presented in Table
6.
TABLE-US-00007 TABLE 6 Compositions of mortar samples in grams
Materials OPC CSA CSA-NM-20G CSA-NM-15.8A OPC Type I (Cemex) 450 --
-- -- CSA Cement (Buzzi) -- 450 -- -- A/CSA clinker -- -- 360 378.9
FGD Gypsum -- -- 90 -- Anhydrite -- -- -- 71.1 Sodium Citrate --
4.5 4.5 4.5 European Sand (EN-196) 1350 1350 1350 1350 DI Water 225
225 225 225
[0044] European standard EN 196 was followed to produce mortar
samples for compressive strength, resistivity, and dimensional
stability measurements. Following the production of mortar samples,
the samples were stored in a 100% humidity chamber, demolded after
24 hours, and tested after 1, 7, 14, 21, 28, 56, and 91 day. At
each test day, the samples were tested for resistivity with the
Resipod from Proceq, for dimensional stability by measuring the
length, and for compressive strength.
[0045] Evidence about the high resistivity of A/CSA cement compared
to commercial cements:
[0046] The resistivity data (see FIG. 2) demonstrate that the A/CSA
cement exhibits much higher resistivity compared to OPC cement at
all ages. Compared to CSA cement, A/CSA cement is lower initially
but increases to a similar level at 91 days. Resistivity is
relatable to the level of interconnected pores and in a measure of
durability.
[0047] Evidence about the High Compressive Strength A/CSA Cement
Compared to Commercial Cements:
[0048] The compressive strength data (see FIG. 3) demonstrate that
after one day the new and improved A/CSA cement is 2-3 times
stronger than OPC and 145% stronger than CSA with A/CSA with
anhydrite. For the first 14 days, A/CSA with anhydrite is the
strongest.
[0049] Evidence about the High Stability in High Humidity Curing
Room of A/CSA Cement Compared to Commercial Cements:
[0050] The mortar samples were stable compared to the commercial
cements meeting all requirements, with expansion and/or shrinkage
of less than 0.08%, as can be seen from FIG. 4.
[0051] The following methods are also provided.
[0052] Bullet List of the Method Steps for the Production of
Clinker:
[0053] 1. Select the raw materials that satisfies the chemical
composition described in the following claims, especially the
amounts of iron oxide and calcium fluoride;
[0054] 2. For our exemplary embodiment--A/CSA, mix 55.7 wt. %
agricultural lime, 12.3 wt. % FGD gypsum, 31.38 wt. % of high
alumina ash (includes sufficient iron oxide), and 0.62 wt. %
calcium fluoride;
[0055] 3. Produce pellets by mixing raw mix with 10 wt. % of
deionized water in a mortar and pestle until complete
homogenization is obtained and pressing the raw mix using a 25000
lbs load;
[0056] 4. Dry the pellets in an oven at 60.degree. C.
overnight;
[0057] 5. Fire the pellets in a box furnace following the firing
procedure: 1--ramp from room temperature to 800.degree. C. at 7.5
C/min; 2--dwell for 30 min at 800.degree. C.; 3--ramp from
800.degree. C. to 1250.degree. C. at 5 C/min; 4--dwell at
1250.degree. C. for 60 min; 5--rapid quenching of the pellets;
[0058] 6. Grind the pellets in a shatter box or ball mill until a
particle size d(50) of around 5-15 .mu.m is obtained, and
preferably around 8-12 .mu.m.
[0059] 7. Verify the clinker composition by XRD/Rietveld
analyses.
[0060] Bullet List of the Method Steps for the Production of
Cement:
[0061] 1. Mix the A/CSA clinker with 20 wt. % FGD gypsum or 15.8
wt. % anhydrite until complete homogenization is obtained;
[0062] 2. Follow EN-196 for the production and testing of mortar
samples.
[0063] Each of the following terms written in singular grammatical
form: "a", "an", and the", as used herein, means "at least one", or
"one or more". Use of the phrase One or more" herein does not alter
this intended meaning of "a", "an", or "the". Accordingly, the
terms "a", "an", and "the", as used herein, may also refer to, and
encompass, a plurality of the stated entity or object, unless
otherwise specifically defined or stated herein, or, unless the
context clearly dictates otherwise. For example, the phrases: "a
unit", "a device", "an assembly", "a mechanism", "a component, "an
element", and "a step or procedure", as used herein, may also refer
to, and encompass, a plurality of units, a plurality of devices, a
plurality of assemblies, a plurality of mechanisms, a plurality of
components, a plurality of elements, and, a plurality of steps or
procedures, respectively.
[0064] Each of the following terms: "includes", "including", "has",
"having", "comprises", and "comprising", and, their
linguistic/grammatical variants, derivatives, or/and conjugates, as
used herein, means "including, but not limited to", and is to be
taken as specifying the stated component(s), feature(s),
characteristic(s), parameter(s), integer(s), or step(s), and does
not preclude addition of one or more additional component(s),
feature(s), characteristic(s), parameter(s), integer(s), step(s),
or groups thereof. Each of these terms is considered equivalent in
meaning to the phrase "consisting essentially of". Each of the
phrases "consisting of" and "consists of, as used herein, means
"including and limited to". The phrase "consisting essentially of
means that the stated entity or item (system, system unit, system
sub-unit device, assembly, sub-assembly, mechanism, structure,
component element or, peripheral equipment utility, accessory, or
material, method or process, step or procedure, sub-step or
sub-procedure), which is an entirety or part of an exemplary
embodiment of the disclosed invention, or/and which is used for
implementing an exemplary embodiment of the disclosed invention,
may include at least one additional feature or characteristic"
being a system unit system sub-unit device, assembly, sub-assembly,
mechanism, structure, component or element or, peripheral equipment
utility, accessory, or material, step or procedure, sub-step or
sub-procedure), but only if each such additional feature or
characteristic" does not materially alter the basic novel and
inventive characteristics or special technical features, of the
claimed item.
[0065] The term "method", as used herein, refers to steps,
procedures, manners, means, or/and techniques, for accomplishing a
given task including, but not limited to, those steps, procedures,
manners, means, or/and techniques, either known to, or readily
developed from known steps, procedures, manners, means, or/and
techniques, by practitioners in the relevant field(s) of the
disclosed invention.
[0066] Terms of approximation, such as the terms about,
substantially, approximately, etc., as used herein, refers to
.+-.10% of the stated numerical value. Use of the terms parallel or
perpendicular are meant to mean approximately meeting this
condition, unless otherwise specified.
[0067] It is to be fully understood that certain aspects,
characteristics, and features, of the cement clinker composition
and method of making the same, which are, for clarity,
illustratively described and presented in the context or format of
a plurality of separate embodiments, may also be illustratively
described and presented in any suitable combination or
sub-combination in the context or format of a single embodiment.
Conversely, various aspects, characteristics, and features, of the
cement clinker composition and method of making the same which are
illustratively described and presented in combination or
sub-combination in the context or format of a single embodiment may
also be illustratively described and presented in the context or
format of a plurality of separate embodiments.
[0068] Although the cement clinker composition and method of making
the same have been illustratively described and presented by way of
specific exemplary embodiments, and examples thereof, it is evident
that many alternatives, modifications, or/and variations, thereof,
will be apparent to those skilled in the art. The cement clinker
compositions described above and in the following claims may also
be accurately expressed as "consisting of" rather than "comprising"
the formulations indicated in the body of the following claims.
Accordingly, it is intended that all such alternatives,
modifications, or/and variations, fall within the spirit of, and
are encompassed by, the broad scope of the appended claims.
[0069] The foregoing has been presented for purposes of
illustration and description. It is not intended to be exhaustive
or to limit the embodiments to the precise form disclosed. Obvious
modifications and variations are possible in light of the above
teachings. All such modifications and variations are within the
scope of the appended claims when interpreted in accordance with
the breadth to which they are fairly, legally and equitably
entitled.
* * * * *