U.S. patent number RE44,080 [Application Number 11/716,066] was granted by the patent office on 2013-03-19 for sulfur additives for paving binders and manufacturing methods.
This patent grant is currently assigned to Shell Oil Company. The grantee listed for this patent is William R. Bailey, Norm D. Pugh. Invention is credited to William R. Bailey, Norm D. Pugh.
United States Patent |
RE44,080 |
Bailey , et al. |
March 19, 2013 |
Sulfur additives for paving binders and manufacturing methods
Abstract
Sulfur, useable in as an additive to asphalt in the preparation
of asphalt binders can be plasticized by addition of carbon and
further treated with amyl acetate. This plasticized sulfur can be
formed into solid particles and then added to asphalt as either a
minority or majority component to create desired paving binder
compositions. The solid plasticized sulfur has non-stick non-flow
properties within a wide range of ambient temperatures, and it can
be stored solid for subsequent use in paving applications.
Inventors: |
Bailey; William R. (Las Vegas,
NV), Pugh; Norm D. (Wilton, CA) |
Applicant: |
Name |
City |
State |
Country |
Type |
Bailey; William R.
Pugh; Norm D. |
Las Vegas
Wilton |
NV
CA |
US
US |
|
|
Assignee: |
Shell Oil Company (Houston,
TX)
|
Family
ID: |
26909704 |
Appl.
No.: |
11/716,066 |
Filed: |
March 8, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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60311419 |
Aug 9, 2001 |
|
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Reissue of: |
10215111 |
Aug 8, 2002 |
6863724 |
Mar 8, 2005 |
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Current U.S.
Class: |
106/287.32;
106/275; 106/287.24; 106/286.8; 106/274; 106/285 |
Current CPC
Class: |
C08L
95/00 (20130101); C08L 95/00 (20130101); C08L
2666/72 (20130101) |
Current International
Class: |
C01B
17/02 (20060101); C04B 28/36 (20060101); C09D
195/00 (20060101) |
Field of
Search: |
;106/274,275,281.1,284.05,285,286.8,287.24,287.32 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1 528 384 |
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Oct 1978 |
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GB |
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202763 |
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Nov 1967 |
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SU |
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1528760 |
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Sep 1989 |
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SU |
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1528760 |
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Dec 1989 |
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SU |
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Other References
William C. McBee, "Potential and Properties of Sulfur Asphalt
Paving," Fourth International Symposium, Sulphur Markets (Mar.
23-25, 1994). cited by applicant .
G. Mohammed Memon, John G. Boone, and Brian H. Chollar, "Furfural
Substitutes For Chemical Modification of Asphalt," Physical
Properties Asphalt Cement Binders, STP 1241 (1995). cited by
applicant .
H.U. Bahia and D.A. Anderson, "The New Proposed Rheological
Porperties of Asphalt Binders: Why Are They Required and How Do
They Compare To Conventional Properties," Physical Properties Of
Asphalt Cement Binders, STP 1241 (1995). cited by applicant .
Hussain U. Bahia and David A. Anderson, "The Development of the
Bending Beam Rheometer; Basics and Critical Evaluation of the
Rheometer," Physical Properties Of Asphalt Cement Binders, STP 1241
(1995). cited by applicant.
|
Primary Examiner: Brunsman; David M
Attorney, Agent or Firm: Stewart; Charles W.
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of U.S. Provisional Application
No. 60/311,419, filed Aug. 9, 2001 and entitled "Sulfur Additives
for Paving Binders and Manufacturing Methods," which is hereby
incorporated by reference.
Claims
What is claimed and desired to be secured by United States Letters
Patent is:
.[.1. A plasticized sulfur product, comprising: a plasticized
sulfur composition obtained by mixing liquid sulfur with carbon and
amyl acetate, wherein at least a portion of said liquid sulfur is
plasticized..].
.[.2. A plasticized sulfur product according to claim 1 wherein
said carbon is added at a weight percent concentration above about
0.25%..].
.[.3. A plasticized sulfur product according to claim 1 wherein
said carbon is added at a weight percent concentration between
about 0.25% and about 1.0%..].
.[.4. A plasticized sulfur product according to claim 1 wherein
said carbon is added at a weight percent concentration between
about 0.4% and about 0.8%..].
.[.5. A plasticized sulfur product according to claim 1 wherein
said amyl acetate is added at a weight percent concentration above
about 0.08%..].
.[.6. A plasticized sulfur product according to claim 1 wherein
said amyl acetate is added at a weight percent concentration
between about 0.1% and about 1.5%..].
.[.7. A plasticized sulfur product according to claim 1 wherein
said amyl acetate is added at a weight percent concentration
between about 0.2% and about 0.4%..].
8. A process .[.for plasticizing sulfur.]., comprising:
.[.mixing.]. .Iadd.making solid particles of a plasticized sulfur
composition by forming a mixture consisting essentially of
.Iaddend.liquid sulfur .[.with.]. .Iadd.and a .Iaddend.carbon and
allowing said sulfur to polymerize .Iadd.to form said solid
particles.Iaddend..
9. A process .[.for plasticizing sulfur.]. according to claim 8
wherein said sulfur.[.,.]. is maintained .Iadd.during the forming
step .Iaddend.at a temperature of between about 120.degree. .[.F.].
.Iadd.C.Iaddend.. and about 150.degree. .[.F.].
.Iadd.C.Iaddend..
10. A process .[.for plasticizing sulfur.]. according to claim 8
wherein said process further comprises cooling said plasticized
sulfur into .Iadd.said .Iaddend.solid particles.
11. A process .[.for plasticizing sulfur.]. according to claim 10
wherein said solid particles exhibit no agglomeration at
temperatures under 175.degree. F.
12. A sulfur-rich paving binder obtained by mixing the substances
comprising: (a) hydrocarbon-based material; (b) a fine mineral
constituent; and (c) a plasticized sulfur product obtained by
.[.mixing.]. .Iadd.forming a mixture consisting essentially of
.Iaddend.liquid sulfur .[.with.]. .Iadd.and .Iaddend.carbon and
allowing said .Iadd.liquid .Iaddend.sulfur to polymerize.
13. A sulfur-rich paving binder according to claim 12 wherein said
plasticized sulfur .Iadd.product .Iaddend.is incorporated into the
.[.mixture.]. .Iadd.sulfur-rich paving binder .Iaddend.in a weight
percentage of at least 60%.
.[.14. A sulfur-rich paving binder according to claim 12 wherein
said fine mineral constituent comprises at least one of the
materials in the group consisting of fly ash, silica material, and
mixtures thereof..].
15. A sulfur-rich paving binder .[.according to claim 12.].
.Iadd.obtained by forming a mixture by mixing the substances
comprising a hydrocarbon-based material; a fine mineral
constituent; and a plasticized sulfur product obtained by mixing
liquid sulfur with a plasticizer consisting essentially of carbon
and allowing said sulfur to polymerize .Iaddend.wherein said
plasticized sulfur .Iadd.product .Iaddend.is incorporated into
.[.the.]. .Iadd.said .Iaddend.mixture in a weight percentage of
.[.about 70%.]. .Iadd.at least 60%.Iaddend., said hydrocarbon-based
material is incorporated into .[.the.]. .Iadd.said .Iaddend.mixture
in a weight percentage of .[.about 15%.]. .Iadd.at least 10%
.Iaddend.and said fine mineral constituent is incorporated into the
mixture in a weight percentage of .[.about 15%.]. .Iadd.at least
10%.Iaddend..
.[.16. A sulfur-rich paving binder according to claim 15 wherein
said solid particles exhibit no agglomeration at temperatures under
175.degree. F..].
17. A sulfur-rich paving binder according to claim 12 wherein said
.Iadd.sulfur-rich paving .Iaddend.binder is formed into solid
particles.
.[.18. A sulfur-rich paving binder according to claim 12, wherein
the plasticized sulfur product further comprises amyl acetate,
wherein the amyl acetate improves the handling and odor
characteristics of the plasticized sulfur product..].
19. A paving product obtained by mixing substances comprising: (a)
a plasticized sulfur product obtained by .[.mixing.]. .Iadd.forming
a mixture consisting essentially of .Iaddend.liquid sulfur
.[.with.]. .Iadd.and .Iaddend.carbon and allowing said .Iadd.liquid
.Iaddend.sulfur to polymerize; and (b) hydrocarbon-based
material.
.[.20. A sulfur-rich paving binder according to claim 19, wherein
the plasticized sulfur product further comprises amyl acetate,
wherein the amyl acetate improves the handling and odor
characteristics of the plasticized sulfur product..].
.Iadd.21. A sulfur-rich paving binder obtained by forming a mixture
by mixing (a) a hydrocarbon-based material; (b) a fine mineral
constituent; and (c) a plasticized sulfur product obtained by
mixing liquid sulfur with carbon and allowing said sulfur to
polymerize and to form solid particles, wherein said plasticized
sulfur product is incorporated into said mixture in a weight
percentage of at least 60%, said hydrocarbon-based material is
incorporated into said mixture in a weight percentage of at least
10% and said fine mineral constituent is incorporated into the
mixture in a weight percentage of at least 10%, and wherein said
solid particles exhibit no agglomeration at temperatures below
175.degree. F..Iaddend.
.Iadd.22. A sulfur-rich paving binder obtained by mixing the
substances comprising: (a) hydrocarbon-based material; (b) a fine
mineral constituent; and (c) a plasticized sulfur product obtained
by mixing liquid sulfur with carbon and allowing said sulfur to
polymerize, wherein the plasticized sulfur product further
comprises amyl acetate, wherein the amyl acetate improves the
handling and odor characteristics of the plasticized sulfur
product..Iaddend.
.Iadd.23. A paving product obtained by mixing substances
comprising: (a) a plasticized sulfur product obtained by mixing
liquid sulfur with carbon and allowing said sulfur to polymerize;
(b) hydrocarbon-based material, and (c) amyl acetate, wherein the
amyl acetate improves the handling and odor characteristics of the
plasticized sulfur product..Iaddend.
.Iadd.24. A composition, comprising: a plasticized sulfur product
obtained by forming a mixture by mixing liquid sulfur and an amount
of carbon, wherein said amount of carbon is in the range of from
about 0.25% to about 1.0% of said mixture and allowing
plasticization of at least a portion of said liquid sulfur, and
wherein said forming of said mixture further includes mixing an
amount of amyl acetate with said liquid sulfur and said amount of
carbon, wherein said amount of amyl acetate is in the range of at
least about 0.08% of said mixture..Iaddend.
.Iadd.25. A composition as recited in claim 24, wherein said amount
of amyl acetate is in the range of from about 0.1% to about 1.5% of
said mixture..Iaddend.
.Iadd.26. A composition as recited in claim 25, wherein said amount
of amyl acetate is in the range of from about 0.2% to about 0.4% of
said mixture..Iaddend.
.Iadd.27. A composition as recited in claim 26, wherein said liquid
sulfur of said forming step is at a temperature in the range of
from about 120.degree. C. to about 150.degree. C..Iaddend.
.Iadd.28. A composition as recited in claim 27, wherein said
forming step further includes cooling said mixture having at least
a portion of said liquid sulfur that is plasticized to thereby form
solid particles of said plasticized sulfur product..Iaddend.
.Iadd.29. A composition as recited in claim 28, wherein said solid
particles have characteristics such as to exhibit no agglomeration
at temperatures under 79.degree. C. (175.degree. F.)..Iaddend.
.Iadd.30. A composition as recited in any one of claims 24 through
29, further comprising: a hydrocarbon-based material and a fine
mineral constituent..Iaddend.
.Iadd.31. A composition as recited in any one of claims 24 through
29, further comprising: a hydrocarbon-based material and a fine
mineral constituent, wherein said plasticized sulfur product is
present in said composition in an amount of at least 60 weight
percent of said composition, wherein said hydrocarbon-based
material is present in said composition in an amount of at least 10
weight percent of said composition, and wherein said fine mineral
constituent is present in said composition in an amount of at least
10 weight percent..Iaddend.
.Iadd.32. A composition as recited in any one of claims 24 through
29, further comprising a hydrocarbon-based material and a fine
mineral constituent selected from the group of aggregates
consisting of fly ash and silica material, and wherein said
plasticized sulfur product is present in said composition in an
amount of at least 60 weight percent of said composition, wherein
said hydrocarbon-based material is present in said composition in
an amount of at least 10 weight percent of said composition, and
wherein said fine mineral constituent is present in said
composition in an amount of at least 10 weight
percent..Iaddend.
.Iadd.33. A composition, comprising: a plasticized sulfur product
obtained by forming a mixture by mixing liquid sulfur and an amount
of carbon, wherein said amount of carbon is in the range of from
about 0.25% to about 1.0% of said mixture and allowing
plasticization of at least a portion of said liquid sulfur; a
hydrocarbon-based material; and a fine mineral constituent, wherein
said plasticized sulfur product is present in said composition in
an amount of at least 60 weight percent of said composition,
wherein said hydrocarbon-based material is present in said
composition in an amount of at least 10 weight percent of said
composition, and wherein said fine mineral constituent is present
in said composition in an amount of at least 10 weight
percent..Iaddend.
.Iadd.34. A composition as recited in claim 33, wherein said
forming of said mixture further includes mixing an amount of amyl
acetate with liquid sulfur and said amount of carbon, wherein said
amount of amyl acetate is in the range of at least about 0.08% of
said mixture..Iaddend.
.Iadd.35. A composition as recited in claim 34, wherein said amount
of amyl acetate is in the range of from about 0.1% to about 1.5% of
said mixture..Iaddend.
.Iadd.36. A composition as recited in claim 35, wherein said amount
of amyl acetate is in the range of from about 0.2% to about 0.4% of
said mixture..Iaddend.
.Iadd.37. A composition as recited in claim 36, wherein said liquid
sulfur of said forming step is at a temperature in the range of
from about 120.degree. C. to about 150.degree. C..Iaddend.
.Iadd.38. A composition as recited in claim 37, wherein said
forming step further includes cooling said mixture having at least
a portion of said liquid sulfur that is plasticized to thereby form
solid particles of said plasticized sulfur product..Iaddend.
.Iadd.39. A composition as recited in claim 38, wherein said solid
particles have characteristics such as to exhibit no agglomeration
at temperatures under 79.degree. C. (175.degree. F.)..Iaddend.
.Iadd.40. A composition, comprising: a plasticized sulfur product
obtained by forming a mixture by mixing liquid sulfur and an amount
of carbon, wherein said amount of carbon is in the range of from
about 0.25% to about 1.0% of said mixture and allowing
plasticization of at least a portion of said liquid sulfur; a
hydrocarbon-based material; and a fine mineral constituent selected
from the group of aggregates consisting of fly ash and silica
material, and wherein said plasticized sulfur product is present in
said composition in an amount of at least 60 weight percent of said
composition, wherein said hydrocarbon-based material is present in
said composition in an amount of at least 10 weight percent of said
composition, and wherein said fine mineral constituent is present
in said composition in an amount of at least 10 weight
percent..Iaddend.
.Iadd.41. A composition as recited in claim 40, wherein said
forming of said mixture further includes mixing an amount of amyl
acetate with liquid sulfur and said amount of carbon, wherein said
amount of amyl acetate is in the range of at least about 0.08% of
said mixture..Iaddend.
.Iadd.42. A composition as recited in claim 41, wherein said amount
of amyl acetate is in the range of from about 0.1% to about 1.5% of
said mixture..Iaddend.
.Iadd.43. A composition as recited in claim 42, wherein said amount
of amyl acetate is in the range of from about 0.2% to about 0.4% of
said mixture..Iaddend.
.Iadd.44. A composition as recited in claim 43, wherein said liquid
sulfur of said forming step is at a temperature in the range of
from about 120.degree. C. to about 150.degree. C..Iaddend.
.Iadd.45. A composition as recited in claim 44, wherein said
forming step further includes cooling said mixture having at least
a portion of said liquid sulfur that is plasticized to thereby form
solid particles of said plasticized sulfur product..Iaddend.
.Iadd.46. A composition as recited in claim 45, wherein said solid
particles have characteristics such as to exhibit no agglomeration
at temperatures under 79.degree. C. (175.degree. F.)..Iaddend.
.Iadd.47. A composition as recited in claim 46, wherein said
concentration of carbon is 0.4 weight % to about 0.8 weight
%..Iaddend.
.Iadd.48. A composition as recited in claim 47, wherein said
composition mixture further comprises a hydrocarbon-based
material..Iaddend.
.Iadd.49. A composition as recited in claim 48, wherein said
composition further comprises an aggregate having been mixed with
said composition mixture in liquefied form..Iaddend.
.Iadd.50. A composition as recited in claim 49, wherein said
hydrocarbon-based material is selected from the group consisting of
asphalt, heavy crude oil, and fuel oil..Iaddend.
.Iadd.51. A composition as recited in claim 46, wherein said solid
particles are of the type that includes pastilles, slates, pellets,
chips, and briquettes..Iaddend.
.Iadd.52. A composition as recited in claim 51, wherein said
composition mixture further comprises a hydrocarbon-based
material..Iaddend.
.Iadd.53. A composition as recited in claim 52, wherein said
composition further comprises an aggregate having been mixed with
said composition mixture in liquefied form..Iaddend.
.Iadd.54. A composition as recited in claim 53, wherein said
composition has a concentration of carbon of at least 0.25 weight
%, with the weight % being based on the weight of said plasticized
sulfur composition..Iaddend.
.Iadd.55. A composition as recited in claim 54, further comprising
aggregate..Iaddend.
.Iadd.56. A composition as recited in claim 53, wherein said
composition has a concentration of carbon of from about 0.25 weight
% to about 1.0 weight %, with the weight % being based on the
weight of said plasticized sulfur composition..Iaddend.
.Iadd.57. A composition as recited in claim 56, further comprising
aggregate..Iaddend.
.Iadd.58. A composition as recited in claim 53, wherein said
composition has a concentration of carbon of from about 0.4 weight
% to about 0.8 weight %, with the weight % being based on the
weight of said plasticized sulfur composition..Iaddend.
.Iadd.59. A composition as recited in claim 58, further comprising
aggregate..Iaddend.
.Iadd.60. A composition as recited in claim 53, wherein said
composition contains between about 20 weight % and 60 weight % of
said plasticized sulfur composition based on the weight of said
plasticized sulfur composition and said hydrocarbon-based
material..Iaddend.
.Iadd.61. A composition as recited in claim 53, further comprising
aggregate..Iaddend.
.Iadd.62. A composition as recited in claim 46, wherein said solid
particles are of the size that units thereof expose a surface area
within the range of from about 0.25 in.sup.2 to about 4
in.sup.2..Iaddend.
.Iadd.63. A composition as recited in claim 46, wherein said
composition mixture includes between about 20% and 60% said
plasticized sulfur composition..Iaddend.
.Iadd.64. A composition as recited in claim 63, wherein said
hydrocarbon-based material is selected from the group consisting of
asphalt, heavy crude oil, and fuel oil..Iaddend.
.Iadd.65. A composition as recited in claim 46, wherein said
composition mixture further comprises a hydrocarbon-based
material..Iaddend.
.Iadd.66. A composition as recited in claim 65, wherein said
composition further comprises an aggregate having been mixed with
said composition mixture in liquefied form..Iaddend.
.Iadd.67. A composition as recited in claim 66, wherein said
hydrocarbon-based material is selected from the group consisting of
asphalt, heavy crude oil, and fuel oil..Iaddend.
.Iadd.68. A composition, comprising: a plasticized sulfur
composition obtained by forming a mixture comprising liquid sulfur
and a concentration of carbon, under conditions wherein at least a
portion of said liquid sulfur is plasticized, to thereby provide
said plasticized sulfur composition; and a hydrocarbon-based
material selected from the group consisting of asphalt, heavy crude
oil, and fuel oil..Iaddend.
.Iadd.69. A composition as recited in claim 68, further comprising
aggregate..Iaddend.
.Iadd.70. A composition, comprising: a composition mixture
comprising solid particles of a plasticized sulfur composition
obtained by forming a sulfur mixture consisting essentially of
liquid sulfur and a concentration of carbon of from about 0.25
weight % to about 1.0 weight %, with the weight % being based on
the weight of said plasticized sulfur composition, under conditions
wherein at least a portion of said liquid sulfur is plasticized to
thereby provide said plasticized sulfur composition, and wherein
said solid particles are formed from said plasticized sulfur
composition..Iaddend.
.Iadd.71. A composition as recited in claim 70, wherein said
composition mixture further comprises a hydrocarbon-based
material..Iaddend.
.Iadd.72. A composition as recited in claim 71, wherein said
composition further comprises an aggregate having been mixed with
said composition mixture in liquefied form..Iaddend.
.Iadd.73. A composition as recited in claim 72, wherein said
hydrocarbon-based material is selected from the group consisting of
asphalt, heavy crude oil, and fuel oil..Iaddend.
Description
BACKGROUND OF THE INVENTION
1. The Field of the Invention
The present invention relates generally to plasticized sulfur
materials usable in paving binder compositions and methods for
manufacturing such compositions. More specifically, the present
invention relates to the preparation of a plasticized sulfur
composition which can be then added to asphalt and an aggregate.
This plasticized sulfur material can be prepared independent of the
asphalt into which it is added and can be shipped to locations
where asphalt is available for preparation of a modified
asphalt-based paving binder. Additionally, for remote locations
where asphalt, and more particularly quality asphalt, is not
readily available, this plasticized sulfur material can be mixed
with asphalt and a fine mineral constituent to create a usable
asphalt-based binder that will retain non-flow properties within a
broad range of ambient temperatures. The present invention also
relates to the methods for producing the plasticized sulfur
compositions and the asphalt-based paving binders with these
compositions.
2. The Relevant Technology
Paving material usually includes a binder and an aggregate.
Although the binder is typically the minority component in paving
materials, most of the pavement properties that relate to its
longevity and performance depend on the properties of the
binder.
The binder component is generally an asphalt-based composition that
may include various additives. Asphalt is described as a dark brown
to black cementitious material, which has a solid, semisolid or
liquid consistency, and in which the predominant constituents are
bitumens that occur in nature as such or which are obtained as
residue in refining petroleum. Natural deposits in which asphalt
occurs within porous rocks are known as rock asphalts or tar sands.
Petroleum asphalt is part of the residue that is obtained in the
distillation of petroleum. In particular, asphalt cement is
petroleum asphalt that is refined to meet specifications for
paving, industrial, and special purposes.
The aggregate component of paving material is typically any hard,
inert, mineral material that is used for mixing in graduated
fragments. The aggregate component may include sand, gravel,
crushed stone, coral, and slag.
One of the limitations to the use of asphalt as a binder for paving
materials is that it softens and flows within a wide range of
ambient temperatures. This limitation makes transporting this type
of conventional asphalt-based material difficult and can also give
rise to serious environmental problems. Further, because of the
asphalt's tendency to soften, even at ambient temperatures,
modification of the asphalt by the incorporation of various
additives has long been known in the art. Asphalt additives are
typically used to render the binder material less flowable at
ambient temperatures.
Sulfur is one of such additives that has been incorporated into the
binder as a minority binder constituent. Mixing asphalt with
sulfur, however, presents a number of problems. In order for the
sulfur to effectively modify the asphalt, the sulfur must be
effectively plasticized or polymerized. This plasticization may
occur when the sulfur is mixed with the hot asphalt. However,
problems with the plasticization of the sulfur often result as the
liquid sulfur, liquid asphalt and aggregate are mixed.
In certain mixtures, the sulfur and asphalt can separate due to the
differences in their respective densities which tend to cause an
uneven dispersion of the plasticized sulfur. As a result, the
sulfur-depleted portions of the binder then retain the softening
and flowing properties of asphalt. Not only does the presence of
sulfur-depleted portions of binder diminish the overall
effectiveness of the asphalt as a binder, but handling and
transporting the binder remains difficult. Chemicals such as
dicyclopentidiene and heptane have also been used in an attempt to
keep the sulfur homogeneously dispersed in asphalt. Further,
crushed limestone has been used for this purpose. However, the use
of calcium-based materials leads to the formation of calcium
sulfides and polysulfides that are detrimental to the pavement
longevity.
Additionally, where liquid sulfur, liquid asphalt and aggregate are
mixed simultaneously or nearly simultaneously, even with other
components, additional problems with the plasticization of the
sulfur can occur. Specifically, where part of the liquid sulfur
reacts with the aggregate before being completely plasticized by
the asphalt, the nonplasticized sulfur bonds with the aggregate
rather than completing its plasticization reaction. This
non-plasticized sulfur works to weaken rather than strengthen the
overall material strength.
Even where the final sulfur-modified asphalt binder is successfully
prepared, this process requires the handling of liquid sulfur on
site. The presence of liquid sulfur creates potential environmental
and material handling concerns.
It has been long believed that sulfur-rich binders may
detrimentally affect the quality and longevity of the paving
material. In addition, sulfur has been viewed as a constituent that
would unacceptably increase the cost of binder materials to the
point of rendering them prohibitively expensive if the amount of
sulfur in the binder exceeded a certain limit.
In addition to economic considerations regarding the use of sulfur
as an additive in paving binders, the use of asphalt is also
related to economic factors. For example, the use of asphalt as the
major constituent in paving binders is negatively affected by the
often fluctuating petroleum production patterns. Further, limited
petroleum supplies may threaten, in the long term, the viability of
paving binders in which asphalt is a major constituent. Profitable
utilization of petroleum products is another factor that
detrimentally affects the use of asphalt as a majority constituent
in paving binders. For example, maintaining, renovating and
protecting the surfaced highways and streets in the United States
requires approximately thirty (30) million tons of asphalt cement
annually. Asphalt cement was available in the past at a reasonable
cost because asphalt cement is a residue in petroleum refining and
certain petroleum refining residues could only be economically
utilized for the production of asphalt cement. However, higher
percentages of petroleum are utilized nowadays for the production
of other more profitable forms of petroleum products. As this trend
continues, the price of asphalt cement is expected to increase even
under constant demand. This expectation is supported by the
evolution of the average price of asphalt cement over the past
thirty-two years, a period during which the price has risen from
approximately $23/ton in 1968 to approximately $152/ton in 2000
(through February), an increase of about 561%. It is generally
recognized, however, that there is currently no economical paving
binder that can be substituted for asphalt cement, and that there
is no low priced asphalt paving binder that can effectively replace
high priced asphalt paving binders.
Therefore, there is a need to be able to provide a solid,
pre-plasticized sulfur which can be readily mixed with the asphalt
to effectively modify the asphalt. Such a pre-plasticized sulfur
modifier can reduce the complexity of binder preparation, eliminate
the need for handling liquid sulfur in conjunction with liquid
asphalt, and provide increased uniformity of binder without concern
that non-plasticized sulfur may weaken the paving material.
Further, the ability to transport the solid, pre-plasticized sulfur
additive material that is in the form of a smaller sized,
non-sticky, non-flowing, and non-melting material facilitates the
delivery of the pre-plasticized sulfur additive materials to
locations where it can be readily mixed with asphalt to create a
material acceptable for the specific project specifications. It is
desirable to manufacture a binder additive that incorporates
pre-plasticized sulfur and which remains in solid, non-sticky,
non-flowing and non-melting form over a wide range of ambient
temperatures, so that such binder additive can be conveniently
transported over long distances by conventional means of
transportation for common solids.
Accordingly, there is also a need for improved paving binders
which, while still utilizing asphalt, that provide increased
performance over asphalt alone. These paving binders should be
readily made by incorporating additives into the asphalt. These
additive materials would include the following characteristics.
First, these additive materials come ready to use without the need
of further reaction or modification. These additive materials can
also be manufactured in forms that are non-sticky, non-melting, and
non-flowing within a wide range of ambient temperatures at which
storage and transport is effectuated. Additive materials with these
non-sticky, non-flowing, and non-melting properties can be
conveniently transported over long distances while avoiding
pollution problems that would derive from the emissions and spills
of other forms of binders that soften and flow at ambient
temperatures. Second, when utilized, these additive materials
should substantially reduce the quantity of asphalt in the final
paving binders to reduce petroleum dependency and cost. Third, the
additives used in the paving binders should not substantially
incorporate constituents that, whether directly or when combined
with other binder constituents, are known to detrimentally affect
the quality and longevity of the pavement.
It is also desirable to manufacture finished plasticized sulfur
plus asphalt-based binder compositions in which the sulfur is a
majority component and which can be readily shipped to remote
locations because the composition remains in solid, non-sticky,
non-flowing, and non-melting form over a wide range of ambient
temperatures. This material also should impart improvements to the
pavement's performance and strength.
BRIEF SUMMARY OF THE INVENTION
The present invention has been developed in response to the present
state of the art and, in particular, in response to problems and
needs that have not been solved heretofore.
In accordance with the invention as embodied and broadly described
herein, liquid sulfur is plasticized by the addition of carbon at a
concentration of at least 0.25% and the plasticized sulfur can be
further treated with amyl acetate at a concentration of at least
about 0.08% and to produce an even more manageable plasticized
sulfur additive. Once the plasticized sulfur is prepared it can be
formed into usable solid particles, typically small particles such
as pellets or briquettes. These solid particles do not flow or melt
and do not stick at temperatures within a wide range of ambient
temperatures and, consequently, can be readily shipped to any given
location where they can then be mixed with hot asphalt cement to
create a modified asphalt-based binder hot mix paving material.
Likewise, once prepared, the plasticized sulfur can be mixed
(either immediately or after being formed into solid particles) as
a majority component with an asphalt-based material and a fine
mineral constituent such as fly ash or fine silica to create a
complete binder material, which sulfur-rich binder material can
itself be formed into usable solid particles, typically small
particles such as pellets or briquettes. This sulfur-rich solid
binder material does not flow or melt and docs not stick at
temperatures within a wide range of ambient temperatures.
Consequently, the sulfur-rich solid binder can be readily shipped
to any given location where it can be mixed with any given
aggregate without the need to ship either the liquid asphalt or
liquid sulfur. These and other objects, features, and advantages of
the present invention will become more fully apparent from the
following description, drawings, and appended claims, or may be
learned by the practice of the invention as set forth
hereinafter.
BRIEF DESCRIPTION OF THE DRAWINGS
In order that the manner in which the above recited and other
advantages and objects of the invention are obtained, a more
particular description of the invention briefly described above
will be rendered by reference to specific embodiments thereof which
are illustrated in the appended drawings. Understanding that these
drawings depict only typical embodiments of the invention and are
not therefore to be considered to be limiting of its scope, the
invention will be described and explained with additional
specificity and detail through the use of the accompanying drawings
in which:
FIG. 1 is a schematic block diagram of one embodiment of the
methods for producing a plasticized sulfur additive material to be
used in the production paving binders according to the present
invention.
FIG. 2 is a schematic block diagram of one embodiment of the
methods for producing a sulfur-rich binder material.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention is directed to the manufacture and use of a
plasticized sulfur additive which can be used to create improved
asphalt or hydrocarbon-based paving binders. The plasticized sulfur
additive according to the present invention is prepared by the
addition of carbon which serve to plasticize (or polymerize) the
liquid sulfur. Further, amyl acetate can also be added to the
composition to improve the handling and odor characteristics of the
plasticized sulfur. This plasticized sulfur can then be mixed with
various concentrations of an asphalt-based material during the
mixing cycle with aggregate, sand or other materials to create the
desired product characteristics.
Once created, the plasticized sulfur additive can be formed into
pastilles, slates, pellets, chips, briquettes or other small forms
of product that are suitable for storage and transportation at
ambient temperature because of their non-flow, non-melt, and
non-stick properties within a wide range of ambient temperatures.
This allows for the solid product to be stacked or piled without
concern that the individual pastilles, slates, pellets, chips or
briquettes will fuse or otherwise stick together and create a
single, unmanageable mass of product. The finished plasticized
sulfur additive according to the present invention can be stored at
the production site or at a remote site and can be transported and
stored in piles or within containers such as sacs, tanks, and
barrels while the individual small forms of finished product remain
loose and non-sticky and devoid of the emissions that liquid sulfur
would generate.
FIG. 1 schematically shows a flow diagram of one possible preferred
embodiment of a process for manufacturing a plasticized sulfur
additive material for use in paving binders according to the
present invention. In this embodiment, the plasticized sulfur
additive material comprises sulfur, which is placed into a mixing
tank 102 and heated to form liquid sulfur; carbon, which is stored
as feed material in container 104; and amyl acetate which is stored
as feed material in container 106. It is understood that containers
104 and 106 are appropriately configured for the storage and
delivery of carbon and amyl acetate respectively and that mixing
tank 102 is appropriately configured to allow for the mixing of the
sulfur, carbon and amyl acetate therein. Accordingly, these tanks
can be provided with stirrers and heating systems that are not
shown in the embodiment depicted in FIG. 1 because the melting
point of sulfur is well known and the devices for melting and
keeping these substances at the appropriate temperatures and mixing
them are also well known in the art.
In one embodiment, the sulfur utilized is, by way of example and
not limitation, preferably elemental sulfur, which can be
commercial grade, crystalline or amorphous. By way of example and
not limitation, sources that provide sulfur suitable for the
compositions and methods of the present invention include primary
sulfur sources and recovered sulfur sources.
Carbon, also known as carbon black, is also available from multiple
sources. In one presently preferred embodiment, again by way of
example and not limitation, particle or fibrous type carbon
material found in natural occurring, mined carbon black may be
used. In addition, another possible source of carbon is
manufactured carbon, such as the material created during
combustion, or carbon synthetically reacted. Examples of such
carbon include natural carbon material, fuel residue material, and
carbon 60 through carbon 69, known as bucky balls.
Likewise, one skilled in the art will recognize that amyl acetate
is readily available in commercial form, and that while relatively
pure forms of amyl acetate are, in one embodiment, most preferable,
that it is within the scope of the present invention to utilize
amyl acetate added to the sulfur in conjunction with other
compounds including acetate-containing organic compounds.
In one embodiment of the present invention, depicted in FIG. 1, the
sulfur held in the mixing tank 102 is preferably maintained at a
temperature sufficient to bring or keep the sulfur in liquid form,
e.g. between approximately about 120.degree. C. to about
150.degree. C. Whether the sulfur is delivered into the mixing tank
102 as a solid or liquid form is simply a matter of convenience. As
known in the art, fluid materials such as liquid sulfur can be
circulated as such fluids by maintaining the appropriate
temperature and pressure conditions in the pipes. These conditions
are achieved in most environments by properly insulating or heat
tracing the pipes through which these liquids circulate. Other
measures that can be adopted to achieve the same goal are well
known in the art.
Carbon from container 104 is added to mixing tank 102 at a
concentration of at least about 0.25%. While any concentration of
carbon black above about 0.25% can create the desired polymerizing
effect on the sulfur, excess carbon can increase the overall binder
cost. Consequently, a preferred concentration of carbon would be
between about 0.25% to about 5%, with a more preferred
concentration from about 0.25% to about 1.0%, and an even more
preferred concentration from about 0.4% to about 0.8%. The carbon
facilitates the plasticization reaction with the sulfur.
Additionally, the carbon creates an ultraviolet light shield which
helps to prevent ultraviolet degradation of the final asphalt plus
aggregate product. As previously stated, this percentage is a
weight percent of the carbon in the final plasticized sulfur
composition.
The amyl acetate held in container 106 will preferably be added to
the sulfur/carbon mixture and will also be maintained at ambient
temperature. Therefore, it is preferred that the amyl acetate in
container 106 be held at ambient temperature range. FIG. 1
illustrates that in this embodiment the amyl acetate from container
106 also feeds into mixing tank 102. In one embodiment, it is
preferred that the amyl acetate will be added to the sulfur at a
concentration of at least about 0.08% to help eliminate or at least
reduce unwanted odors from the product and thereby improve its
overall handling. As previously stated, this percentage is a weight
percent of the amyl acetate in the final plasticized sulfur
composition. While any concentration of amyl acetate above about
0.08% can create the desired effect on the plasticized sulfur
product, excess amyl acetate can increase the overall binder cost.
Consequently, a more preferred concentration would be between about
0.1% to about 1.5%, and an even more preferred concentration would
be from between about 0.2% to about 0.4%.
During the addition of the amyl acetate and the carbon (which can
occur simultaneously or in any sequential order), the liquid sulfur
in mixing tank 102 is stirred or otherwise mixed until the reaction
becomes complete at which point the amyl acetate and carbon will
have created plasticized sulfur. Visual observation of a change of
the liquid sulfur from a light color to a gray or black (depending
on the concentration of carbon added) provides an easy method for
determining the completion of the reaction. Typically, the reaction
time will be between about a half minute to about 5 minutes once
both the carbon and amyl acetate have been added.
Further, while the above description of the process as illustrated
in FIG. 1 shows a batch process, one skilled in the art will
recognize that a continuous process will produce the same result
and is encompassed within the scope of the present invention.
Once the plasticization of the sulfur has occurred, the plasticized
sulfur can then either be immediately mixed with a
hydrocarbon-based material such as asphalt, to produce the desired
pavement, forming and structure material or composite binder, or be
formed into any type of relatively small, solid particles and
shipped to any given location to be used at a latter time to create
the desired binder. These relatively small, solid particles could
include, by way of example and not limitation, pastilles, slates,
pellets, chips, briquettes or other forms of product that are
suitable for storage and transportation. In one embodiment, these
forms of finished plasticized sulfur additive material have a
smaller manageable size. By way of example only, in one embodiment,
the finished plasticized sulfur additive material are sized so that
each unit exposes a surface area within the range from about 0.25
in.sup.2 to about 4 in.sup.2. It is contemplated that various other
sizes and forms of finished plasticized sulfur additive material
may be produced.
FIG. 1 also illustrates, by way of example and not limitation, how
the plasticized sulfur material can be formed into in a variety of
solid forms that include, for example, pastilles, slates, pellets,
chips, briquettes or other forms of finished paving binder product
that are suitable for storage and transportation. Slates and chips
are formed according to the embodiment shown in FIG. 1 by
circulating the plasticized sulfur produced in mixing tank 102
through a cooling system 150, so that the fluid hardens as it is
transported by conveyor 152 into a brittle material that
subsequently breaks or is chopped into discrete units, including
units with a fairly small size described above. Pastilles may be
formed by subjecting the fluid obtained from mixing tank 102 to
known pastille-making processes such as rotoforming, and processing
with pastille making devices such as the devices known by the name
AccuDrop and Sandvik rotoformer. Pellets are formed by subjecting
the fluid obtained from mixing tank 102 to treatment with
conventional pelletizers. Flakes are formed by subjecting the fluid
obtained from mixing tank 102 to treatment with conventional
devices such as a rubber, composite, or metal belt.
Whether the plasticized sulfur is formed into small particles for
shipment or immediately added to the asphalt constituents to create
the desired material, the process for combination of the asphalt
and plasticized sulfur is the same.
By way of example and not limitation, asphalt is the preferred
hydrocarbon-based material into which the plasticized sulfur is
mixed according to the present invention, and asphalt cement is the
presently preferred form of hydrocarbon-based material used in the
embodiments of paving binder according to the present invention.
Asphalt cement is commonly abbreviated with the terms AC-xx
asphalt, and it is provided by petroleum companies. The notation
"xx" in the description of an AC asphalt represents a numeral
related to the asphalt viscosity. Asphalts such as AC-20 and AC-10
asphalts are preferred forms of asphalt to be used as
hydrocarbon-based material according to the present invention.
Other forms of asphalt that are envisaged as constituents in paving
binder formulations according to the present invention include, by
way of example and not limitation, AC-1.75, AC-2.5, AC-5, AC-30,
AC-40, AC-80, and AC-120 asphalts. Other hydrocarbon-based
materials that are envisaged as constituents in paving binder
formulations according to the present invention include, by way of
example and not limitation, heavy crude oil, fuel oil, and mixtures
of substances such as heavy crude oil and fuel oil with at least
one of the AC asphalts referred to above.
The use of the AC-xx grading system to designate exemplary
embodiments of asphalt that can be used in the context of the
present invention is provided as an example and is not intended to
limit the types of asphalt to this particular grade. Asphalt
characterized according to other designations, such as PG grades
are also envisaged with the scope of hydrocarbon-based materials
according to the present invention. Furthermore, substances such as
bitumen and gilsonite are also envisaged as examples of
hydrocarbon-based materials in the context of the present
invention.
It is envisaged that paving binders according to the present
invention can also be prepared with other hydrocarbon-based
materials in which asphalt is the majority component added to the
plasticized sulfur mixture. These hydrocarbon-based materials
include, by way of example and not limitation, products resulting
from mixtures of asphalt and tall oil pitch, mixtures of asphalt
and cyclic saturated hydrocarbons, mixtures of asphalt and cyclic
unsaturated hydrocarbons, mixtures of asphalt and polycyclic
saturated hydrocarbons, mixtures of asphalt and unsaturated
polycyclic hydrocarbons, and mixtures of asphalt and tar.
Other hydrocarbon-based materials that are envisaged as
constituents in paving binder formulations according to the present
invention include, without limitation, the products of mixtures of
at least one of the asphalts referred to above and polymeric or
polymerizable materials in which asphalt is the majority component
added to the plasticized sulfur mixture. Examples of such polymeric
or polymerizable materials include, by way of example and not
limitation, styrene monomer (vinyl toluene), polyethylene
terephthalate (PET), ethyl vinyl acetate (EVA), Exxon 101, and
Exxon 103, which are proprietary materials, or other vinyl
aromatics.
Still other hydrocarbon-based materials that are envisaged as
constituents in paving binder formulations according to the present
invention include, by way of example only, the products of mixtures
of at least one of the AC asphalts referred to above and at least
one heterocyclic compound such as furan, dihydrofuran, and
derivatives of such heterocyclic compounds, where asphalt is the
majority component added to the plasticizes sulfur mixture. In
addition to furan and dihydrofuran, these heterocyclic compounds
include furfural, and 3-(2-furyl) acrolein.
Other hydrocarbon-based materials that are envisaged as
constituents in paving binder formulations according to the present
invention include the products of mixtures of at least one of the
AC asphalts referred to above and at least one aliphatic, olefinic
or aromatic substance.
In order to combine the plasticized sulfur with the
hydrocarbon-based asphalt material to create the desired binder or
final product, both the plasticized sulfur and the asphalt must
simply be liquefied and mixed with aggregate. This mixing and
liquefying of the plasticized sulfur with the asphalt and aggregate
can be accomplished in almost any order of mixing. For example, it
can be accomplished by combining the plasticized sulfur with the
asphalt followed by the combination sulfur-asphalt binder with the
aggregate as well as by initially combining the asphalt and
aggregate followed by the plasticized sulfur as well as by a
combination of all three elements at once.
Where asphalt is relatively accessible, the plasticized sulfur can
be shipped to the specific location and mixed with the asphalt to
create the desired paving material. Typically, the plasticized
sulfur will be added to the asphalt at not much more than a 50%
weight percentage concentration and in the presently preferred
embodiment, the plasticized sulfur will constitute between about
20% and 60% of the final binder material. While it is generally
believed or recognized that a concentration of less than 20%
plasticized sulfur provides little strength enhancement or
modification to the asphalt, the plasticized sulfur can still be
utilized at concentrations less than 20% in order to extend the
amount of asphalt required.
One skilled in the art will recognize that the typical hot mix
plant components capable of heating asphalt into liquid form and
mixing the liquefied asphalt with aggregate will allow simple
addition of the solid plasticized sulfur particles into the asphalt
for creation of the desired final paving binder. Further, the scope
of the present invention additionally extends to the use of the
plasticized sulfur in conjunction with other additive and/or
modifiers used with a given asphalt to produce a desired
binder.
Another use for the plasticized sulfur is in the creation of a
complete binder composition which itself can be added directly to
aggregate without requiring any additional materials, such as
asphalt. This complete binder composition is particularly useful
for applications in more relatively remote locations where supplies
of asphalt, and more particularly quality asphalt, may not be
readily available, or where shipment of asphalt is difficult. In
order to create this complete binder composition, the plasticized
sulfur can be mixed as a majority component with asphalt and a fine
mineral constituent to produce a final sulfur-rich paving binder
which has the necessary hot mix properties. This sulfur-rich paving
binder also possesses the non-stick and non-flow properties at
temperatures within a wide range of ambient temperatures which
allow it to be effectively shipped to any given location.
One possible embodiment of a process to create this sulfur-rich
paving binder according to the present invention, as schematically
shown in FIG. 2, displays a configuration of devices to first mix
asphalt (from tank 200) and a fine mineral constituent (from tank
202) into tank 204. Subsequently the plasticized sulfur (from input
pipe 206) can be introduced into the asphalt/mineral constituent
combination and the final product mixed in tank 208. The
plasticized sulfur could be introduced directly from the mixing
tank 102 of FIG. 1 or may be solid or reliquified plasticized
sulfur particles. Mixing at each stage takes place to an extent
that is sufficient to thoroughly interdisperse the constituents in
each mixture. Once complete, the final sulfur-rich paving binder
material can be made into solid particles through the same or
similar process as discussed above in reference to FIG. 1.
In other embodiments of this invention the plasticized sulfur,
asphalt and fine mineral constituent are mixed simultaneously
together. Regardless of the order of introduction of materials, one
skilled in the art will recognize that in order to liquefy and
adequately mix the asphalt with the plasticized sulfur, these
materials will need to be heated and maintained in suitable vessels
at a temperature range of about 93.degree. C. (about 200.degree.
F.) to about 204.degree. C. (about 400.degree. F.) for a sufficient
time to ensure thorough mixing and interaction of the constituents.
More preferably, the temperature range in which sulfur, asphalt,
and fine mineral constituents are mixed together in a suitable
vessel or apparatus is in a temperature range of about 121.degree.
C. (about 250.degree. F.) to about 160.degree. C. (about
320.degree. F.). Most preferably, the temperature range is from
about 132.degree. C. (about 270.degree. F.) to about 149.degree. C.
(about 300.degree. F.). These ranges of mixing temperatures also
apply to the temperatures at which constituents are mixed in mixing
unit 200 Depending on the composition and characteristics of the
constituents, mixing in this batch mode can take about 15 minutes,
and in any case, mixing is performed until the constituents are
thoroughly interdispersed in the mixture and a gel is formed.
Fly ash is a finely divided mineral residue that is obtained as a
waste in power plants that burn pulverized bituminous coal. Coal
consuming electrical power plants are a prime producer of fly ash
in the United States. These plants have to dispose of an enormous
amount of fly ash every year, which increases the costs of
producing electricity and also generates disposal problems. The
paving binders and manufacturing methods of the present invention
effectively absorb the fly ash that is produced in plants that
generate electricity by burning coal, and use the fly ash as a
constituent in paving binders. While fly ash is the preferred fine
mineral constituent of the paving binder of the present invention,
final paving binders can also be made according to the methods of
the present invention with another fine mineral constituents, such
as silica-based materials, and in particular with silica material
and with mixtures of fly ash and silica material. Although fine
mineral constituents with a wide range of particle size can be used
in the paving binders and the manufacturing methods according to
the present invention, a particle size characterized by the
fraction that passes through a sieve with a mesh number 200 or
finer is preferred, such as, by way of example and not limitation,
silica flour. Examples of such fine mineral constituents are type A
silica material, type silica material, and type F fly ash, and a
ceramic clay such as kaolin.
Such a final sulfur-rich paving binder material would contain at
least 60% plasticized sulfur and at least 10% of asphalt and at
least 10% of the fine mineral constituent. In the presently
preferred embodiment a composition of 70% plasticized sulfur, 15%
asphalt and 15% fly ash have been found to produce the desired
results. Once the plasticized sulfur, asphalt and fly ash have been
thoroughly combined, this final paving binder material can itself
be formed into any desired solid particle as already described in
FIG. 1. Again, while a batch process is shown in FIG. 2, one
skilled in the art will recognize that a continuous process is also
within the scope of the present invention. Further, while the
embodiment shown in FIG. 2 utilizes a process where the asphalt and
fine mineral constituent are initially mixed prior to addition of
the plasticized sulfur, the order of mixing these components is not
critical to the invention and whether these components are mixed
together in a different order or all simultaneously together, the
same type of product will be produced.
It is understood that material flow lines in the diagram shown in
FIGS. 1 and 2 are, in practice, embodied by an auger system or
equivalent device when the rheology of the circulating fluid
requires such devices to cause or facilitate the circulation.
Furthermore, material flow line connections in the embodiment
sketched in FIGS. 1 and 2 are built with the suitable ports that
are known in the art. For example, the fluid mixture produced in
mixing unit 204 may be fed into the liquid plasticized sulfur
through a conventional vortex injector port.
Suitable combinations of compacting, crushing, comminuting devices
and other devices to further control and standardize the size of
the plasticized sulfur material can be implemented instead of or in
addition to conveyor 152 and cooling system 160 shown in FIG.
1.
In one embodiment of the process for making either the solid
plasticized sulfur particles or final sulfur-rich paving binder
materials according to this invention, cooling system 160 (shown in
FIG. 1) is a water-based cooling system, including water baths and
a water flow systems, such as a water sprinkling system, that
lowers the temperature of the fluid feed produced in tank 102 or
208 as it is transported by conveyor 152. In one embodiment, the
water based cooling system is configured in a way such that the
cooling water is not substantially in direct contact with either
the plasticized sulfur or final sulfur-rich paving binder
composition. This configuration can be achieved, for example, by
circulating either the plasticized sulfur or final paving binder
composition obtained from tank 102 or 208 along a conveyor, so that
the outer bottom portion of the conveyor is in contact with the
cooling water. Heat is then transferred from the binder composition
within the conveyor to the cooling water through the conveyor
material. Examples of conveyors that are used in the context of
this invention include U-shaped conveyors, flat conveyors,
stainless steel belt conveyors, and rubber conveyors. In addition,
a fan or plurality of fans can also be used as part of the cooling
system. Depending on the specific embodiment of the cooling system
and how either the plasticized sulfur or final paving binder
composition from tank 102 or 208 is fed to it, solidification is
typically achieved in about 1 minute to 10 minutes.
In one embodiment of the present invention, fluid feed produced in
tank 102 or 208 is fed to a palletizing unit, such as a palletizing
drum unit, to produce solid particles in the form of pellets.
Embodiments of the plasticized sulfur particles produced according
to the present invention have excellent non-flow behavior at
temperatures below about 77.degree. C. (about 170.degree. F.), and
no agglomeration of the individual units, such as pastilles,
slates, pellets or other forms, of the paving binder of this
invention have been observed at temperatures as high as about
79.degree. C. (about 175.degree. F.). Although the melting point of
the paving binder of the present invention depends on the
composition of each embodiment, the melting point is generally
above about 93.degree. C. (about 200.degree. F.).
Embodiments of the final sulfur-rich paving binder shown in FIG. 2
where the plasticized sulfur constitutes a majority of the overall
product composition produced according to the present invention
have excellent non-flow behavior at temperatures below about
77.degree. C. (about 170.degree. F.), and no agglomeration of the
individual units, such as pastilles, slates, pellets or other
forms, of the paving binder of this invention have been observed at
temperatures as high as about 79.degree. C. (about 175.degree. F.).
Although the melting point of the paving binder of the present
invention depends on the composition of each embodiment, the
melting point is generally above about 82.degree. C. (about
180.degree. F.).
The plasticized sulfur or final sulfur-rich paving binder
composition produced according to the compositions and methods of
the present invention are high strength, durable, low cost products
that can be stored for future use in paving applications. The
plasticized sulfur or final sulfur-rich paving binder composition
according to the present invention achieve high strength in the
aggregate mixture upon cooling to ambient temperatures and the
strength further increases upon aging. A possible explanation of
this increase in strength upon aging is believed to be based on
solid state nucleation and growth of sulfur crystals in the
material. Furthermore, the plasticizer effects of these materials
are believed to impede the development of crystals whose presence
would be detrimental to the pavement into which binder with such
crystals had been incorporated.
The strength of embodiments of the plasticized sulfur or final
sulfur-rich paving binder composition according to this invention
is already very high upon solidification, reaching generally about
80% of the ultimate strength after a period of about 24 hours after
solidification. The resulting strength permits the various
embodiments of the paving binder of this invention to be stored in
stockpiles up to approximately 12 m (40 feet) high.
The strength of embodiments of the plasticized sulfur or final
sulfur-rich paving binder composition according to the present
invention also provides excellent resistance to thermal cracking.
As discussed more extensively below, thermal cracking is the
predominant failure mode at temperatures near and below 0.degree.
C., and pavement resistance to thermal cracking depends mostly on
the resistance to thermal cracking of the binder that is utilized
in the pavement manufacture. Because of the high internal strength
of the paving binder of the present invention, resistance to
thermal cracking of pavements that incorporate paving binder
according to the present invention is also high.
The plasticized sulfur or final sulfur-rich paving binder
composition of the present invention is manufactured and delivered
to the hot-mix plant in any one of the solid forms discussed herein
above in lieu of the conventional hot liquid state. Embodiments of
the final paving binder composition of the present invention may
also be used in a hot-mix plant by introducing them through the
recycled asphalt pavement collar in a drum hot-mix plant or pug
mill in a batch process hot-mix plant, thus reducing the need for
hot asphalt storage and heating. Consequently, emissions from hot
asphalt are also reduced.
The compositions and manufacturing methods of the present invention
permit the effective use of fly ash and sulfur supplies that would
otherwise present disposal problems. For example, sulfur is a
by-product from petroleum refining and natural gas processing that
is obtained to offer fuels that comply with environmental
regulations and specifications for other manufacturing processes.
Recovered sulfur production has increased steadily over the past
twenty-five years and currently is creating an imbalance between
sulfur supply and demand which results in an excess of available
sulfur. Because of this imbalance and future recovery operations,
and in contrast with the prices expected regarding the price of
asphalt, the price of sulfur is expected to follow a decreasing
trend. Since 1970, the cost of recovered sulfur has remained below
56% of the price of asphalt, a cost ratio that is considered the
break-even point for substitution of asphalt for sulfur. A
significant price differential currently exists with the average
price of recovered sulfur approximately 35% of the price of
asphalt. These average prices are obtained from surveys, which
report generally widely varying prices depending on location.
The foregoing discussion of the prices of asphalt and sulfur and
their respective expected trends indicate that the present
invention solves the compositional and manufacturing problems of a
new form of paving binder. This solution is such that it
beneficially utilizes the economic factors regarding the objection
of asphalt and sulfur.
The finished plasticized sulfur or final sulfur-rich paving binder
composition products can subsequently be stored at or near the
production site or at a remote site, it can be used alone or in
combination with additional paving material at road sites, and it
can be shipped to a hot mix plant where the plasticized sulfur or
final sulfur-rich paving binder composition of this invention is
mixed with additional paving materials to manufacture asphalt
pavements and surface treating materials. Among the asphalt
pavements, asphalt concrete is a high quality, thoroughly
controlled hot mixture of asphalt cement and well-graded, high
quality aggregate that is thoroughly compacted into a uniform dense
mass.
Embodiments of the plasticized sulfur or final sulfur-rich paving
binder composition according to the present invention each have a
very long shelf life in storage sites because of the solid nature
of these embodiments and the lack of a temperature control system.
Furthermore, the final sulfur-rich paving binder composition
embodiments are a convenient choice of binder to be used at remote
sites because transporting liquid asphalt to remote sites is
generally expensive and difficult. Embodiments of the plasticized
sulfur or final sulfur-rich paving binder composition according to
the present invention can be shipped conventionally by rail, truck,
ship or air over long distances, such as by transatlantic and
transcontinental shipments. Embodiments of the plasticized sulfur
or final sulfur-rich paving binder composition according to the
present invention provide for safer transportation of these
materials because of their solid nature, thus eliminating the risk
of hot asphalt transportation spills.
The use of the plasticized sulfur to modify asphalt in the hot-mix
plant in preparation of the embodiments of the paving binder
according to the present invention reduces the need for stability
testing during the hot-mix design process because the paving binder
produced by the mixture of the plasticized sulfur and asphalt
creates a mix with stabilities that are higher than conventional
sulfur-modified asphalt. Furthermore, because of the ongoing
compatibility of the constituents introduced by the paving binder
and the other elements in the hot mix, the stabilities continue to
increase over time without losing hot and cold temperature
properties. Hot-mix stability, however, is not a design
characteristic that can be conveniently measured. As a result, the
hot mix is typically designed for voids and workability, using
conventional designs, such as Marshall, Hveem and Super pave, as
starting point.
EXAMPLES
To date, numerous plasticized sulfur compositions have been
prepared then mixed with various types of asphalt and tested to
develop and to offer exemplary embodiments of the present
invention. Below are specific examples of plasticized sulfur
compositions and tests of mixtures of plasticized sulfur plus
asphalt (and in some cases plus fine constituent material)
compositions which are then mixed with aggregate material to form
asphalt cement and other paving materials. Additionally, a number
of hypothetical, or "prophetic", examples have been included based
on actual paving binder compositions that have been designed or
which would be expected, based on experience, to possess the
properties described hereinafter. The actual examples are written
the past tense, while the hypothetical examples are written in the
present tense in order to distinguish between the two.
Example 1
Sulfur was heated and liquefied at a temperature of 140.degree. C.
(about 284.degree. F.). The liquefied sulfur was treated with 0.25%
amyl acetate and 0.5% carbon and within about five minutes the
composition turned a shiny dark gray color indicating completion of
the plasticization reaction of the sulfur. This plasticized sulfur
was then cast into slate approximately 0.63 cm (about 0.25 in)
thick. After cooling, the slate was broken up into pieces not
bigger than forms which would have their length and width
approximately equal to their thickness. AC-20 asphalt cement,
aggregate and the plasticized sulfur were mixed with the overall
composition of the asphalt cement containing approximately 2.7%
AC-20 asphalt cement, 3.0% plasticized sulfur and 94.3% aggregate,
and the mixture was found to have a stability of over 5400 pounds
and a flow of 12 at 50 blows.
Example 2
Plasticized sulfur was prepared as described in Example 1. AC-20
asphalt, aggregate and the plasticized sulfur were mixed with the
overall composition of the asphalt cement containing approximately
2.0% AC-20 asphalt, 2.0% plasticized sulfur and 96% aggregate, and
the mixture was found to have a stability of over 5800 pounds and a
flow of 12 at 50 blows.
Example 3
Plasticized sulfur was prepared as described in Example 1. AC-10
asphalt, aggregate and the plasticized sulfur were mixed with the
overall composition of the asphalt cement containing approximately
3.0% AC-10 asphalt, 1.5% plasticized sulfur and 95.5%
aggregate.
Example 4
Plasticized sulfur was prepared as described in Example 1.
Subsequently 70% plasticized sulfur, 15% type F silica flour, and
15% AC-10 asphalt cement were mixed together for about three
minutes at about 140.degree. C. (about 284.degree. F.) and then
cast into slate approximately 0.63 cm (about 0.25 in) thick. After
cooling, the slate was broken up into pieces not bigger than forms
which would have their length and width approximately equal to
their thickness. This sulfur-rich paving binder is mixed with
graded mineral aggregate in relative amounts of about 5% of
sulfur-rich paving binder and 95% of aggregate, and the mixture was
found to have a stability of about 5000 pounds and a flow of about
8 at 2 blows.
Example 5
A sulfur-rich paving binder was prepared as described in Example 4.
This sulfur-rich paving binder is mixed with graded mineral
aggregate in relative amounts of about 10% of sulfur-rich paving
binder and 90% of aggregate, and the mixture was found to have a
stability of about 10000 pounds and a flow of about 8 at 2
blows.
Example 6
Plasticized sulfur was prepared by adding 0.25% carbon and 0.1%
amyl acetate to liquefied sulfur at 140.degree. C. (about
284.degree. F.). Within less than three minutes the composition
turned a shiny gray color indicating completion of the
plasticization reaction of the sulfur.
Example 7
Plasticized sulfur is prepared by adding 1.5% carbon and 1.0% amyl
acetate to liquefied sulfur at 140.degree. C. (about 284.degree.
F.). Within less than three minutes the composition turns a dark
gray color indicating completion of the plasticization reaction of
the sulfur.
Example 8
A sulfur-rich paving binder composition was prepared as described
in Example 4 with 70% plasticized sulfur, 15% fly ash, and 15%
AC-10 asphalt.
Example 9
Plasticized sulfur is prepared by adding 1.5% carbon to liquefied
sulfur at 140.degree. C. (about 284.degree. F.). Within less than
three minutes the composition turns a dark gray color indicating
completion of the plasticization reaction of the sulfur.
Example 10
This example describes a set of formulations that refer to a
variety of asphalt cement types. Compositions such as those
described in the foregoing examples in which the asphalt
constituent is AC-10 or AC-20 asphalt are prepared with at least
one of AC-1.75, AC-2.5, AC-5, AC-30, AC-40, AC-80, and AC-120
graded asphalts replacing AC-10 and AC-20 asphalts at the
concentrations described in the foregoing Examples.
The present invention may be embodied in other specific forms
without departing from its spirit or essential characteristics. The
described embodiments are to be considered in all respects only as
illustrative and not restrictive. The scope of the invention is,
therefore, indicated by the appended claims rather than by the
foregoing description. All changes which come within the meaning
and range of equivalency of the claims are to be embraced within
their scope.
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