U.S. patent application number 10/971399 was filed with the patent office on 2005-03-10 for paving binders and manufacturing methods.
This patent application is currently assigned to Shell Canada Limited. Invention is credited to Bailey, William R., McBee, William C., Pugh, Norm D..
Application Number | 20050051056 10/971399 |
Document ID | / |
Family ID | 31946346 |
Filed Date | 2005-03-10 |
United States Patent
Application |
20050051056 |
Kind Code |
A1 |
Bailey, William R. ; et
al. |
March 10, 2005 |
Paving binders and manufacturing methods
Abstract
Solid, low-cost paving binder prepared by admixing sulfur,
paving grade asphalt (AC) asphalt, and a siliceous filler such as
fly ash and silica material, and solidifying the product into
preferably flaked, pellet or pastille forms. Carbon black is
another possible ingredient of the paving binder. The solid paving
binder has non-sick non-flow properties within a wide range of
ambient temperatures, and it can be stored solid for subsequent use
in paving applications. Properties such as the color,
radiation-resistance, and odor of the paving binder can be
controlled in the manufacturing process.
Inventors: |
Bailey, William R.;
(Vancouver, WA) ; Pugh, Norm D.; (Wilton, CA)
; McBee, William C.; (Lebanon, OR) |
Correspondence
Address: |
SENNIGER POWERS LEAVITT AND ROEDEL
ONE METROPOLITAN SQUARE
16TH FLOOR
ST LOUIS
MO
63102
US
|
Assignee: |
Shell Canada Limited
Calgary
CA
|
Family ID: |
31946346 |
Appl. No.: |
10/971399 |
Filed: |
October 22, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10971399 |
Oct 22, 2004 |
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10228660 |
Aug 26, 2002 |
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6824600 |
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10228660 |
Aug 26, 2002 |
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09576476 |
May 23, 2000 |
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6440205 |
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Current U.S.
Class: |
106/285 ;
106/275; 106/284.05; 106/287.32 |
Current CPC
Class: |
E01C 7/267 20130101;
C08K 3/34 20130101; C08K 3/04 20130101; C08L 95/00 20130101; C09D
195/00 20130101; C08L 95/00 20130101; C08L 95/00 20130101; C08L
2666/72 20130101; C08L 2666/74 20130101 |
Class at
Publication: |
106/285 ;
106/275; 106/284.05; 106/287.32 |
International
Class: |
C09D 001/00; C09D
195/00 |
Claims
What is claimed is:
1. A paving binder, comprising: a) a fine mineral constituent which
comprises ceramic clay; b) a hydrocarbon-based plasticizer which
comprises AC asphalt; and c) sulfur in a weight percentage of at
least about 60%, wherein said fine mineral constituent, said
hydrocarbon-based plasticizer and said sulfur are comprised in a
homogeneous single phase in the paving binder.
2. A paving binder as recited in claim 1 wherein said fine mineral
constituent further comprises at least one of fly ash and silica
material.
3. A paving binder as recited in claim 1, wherein said fine mineral
constituent is sized as to pass through a 200 mesh sieve.
4. A paving binder as recited in claim 1, wherein said
hydrocarbon-based plasticizer comprises at least one AC asphalt,
and at least one of tall oil pitch, cyclic saturated hydrocarbon,
cyclic unsaturated hydrocarbon, polycyclic saturated hydrocarbon,
polycyclic unsaturated hydrocarbon, tar, and mixtures thereof,
wherein said at least one AC asphalt substance is a majority
component in said plasticizer.
5. A paving binder as recited in claim 1, wherein said
hydrocarbon-based plasticizer comprises at least one an AC asphalt,
and at least one of furan, dihydrofuran, furfural, 3-(2-furyl)
acrolein, and mixtures thereof, wherein said at least one an AC
asphalt is a majority component in said plasticizer.
6. A paving binder as recited in claim 1, wherein said
hydrocarbon-based plasticizer comprises an AC asphalt, and at least
one of an aliphatic substance, an olefinic substance, an aromatic
substance, and mixtures thereof, wherein said AC asphalt is a
majority component in said plasticizer.
7. A paving binder, comprising: a) a fine mineral constituent that
comprises ceramic clay, wherein said fine mineral constituent is
sized as to pass through a 200 mesh sieve; b) a hydrocarbon-based
plasticizer which comprises AC asphalt, wherein said
hydrocarbon-based plasticizer is present in a weight percentage
amount within the range from about 1% to about 30%; and c) sulfur
in a weight percentage amount in the range from about 60% to about
98%, wherein said fine mineral constituent, said hydrocarbon-based
plasticizer and said sulfur are comprised in a homogeneous single
phase in the paving binder.
8. A paving binder as recited in claim 7 wherein said fine mineral
constituent further comprises at least one of fly ash and silica
material.
9. A paving binder as recited in claim 7, wherein said fine mineral
constituent is present in a weight percentage amount within the
range from about 1% to about 33%.
10. A paving binder, comprising: a) a fine mineral constituent
comprising ceramic clay, wherein said fine mineral constituent is
sized as to pass through a 200 mesh sieve; b) a hydrocarbon-based
plasticizer which comprises AC asphalt, wherein said
hydrocarbon-based plasticizer is present in a weight percentage
amount within the range from about 2.5% to about 20%; and c) sulfur
in a weight percentage amount in the range from about 70% to about
90%, wherein said fine mineral constituent, said hydrocarbon-based
plasticizer and said sulfur are comprised in a homogeneous single
phase in the paving binder.
11. A paving binder as recited in claim 10 wherein said fine
mineral constituent further comprises at least one of fly ash and
silica material.
12. A paving binder as recited in claim 10, wherein said fine
mineral constituent is present in a weight percentage amount within
the range from about 2.5% to about 20%.
13. A paving binder, comprising: a) a fine mineral constituent
comprising ceramic clay, wherein said fine mineral constituent is
sized as to pass through a 200 mesh sieve; b) a hydrocarbon-based
plasticizer which comprises AC asphalt, wherein said
hydrocarbon-based plasticizer is present in a weight percentage
amount within the range from about 5% to about 12%; and c) sulfur
in a weight percentage amount in the range from about 75% to about
90%, wherein said fine mineral constituent, said hydrocarbon-based
plasticizer and said sulfur are comprised in a homogeneous single
phase in the paving binder.
14. A paving binder as recited in claim 13 wherein said fine
mineral constituent further comprises at least one of fly ash and
silica material.
15. A paving binder as recited in claim 13, wherein said fine
mineral constituent is present in a weight percentage amount within
the range from about 5% to about 12%.
16. A method for manufacturing paving binder, comprising: a)
providing ingredients that comprise liquid sulfur, liquid
hydrocarbon-based plasticizer, and a fine mineral constituent,
wherein said fine mineral constituent comprises ceramic clay; b)
mixing said ingredients in controlled amounts, such that the weight
percentage of sulfur mixed is at least about 60% with respect to
all the ingredients in the mixture, so that said mixing provides a
homogeneous single phase mixture of said ingredients; and c)
cooling said mixture so that it becomes a solid.
17. A method as recited in claim 16 wherein said fine mineral
constituent further comprises at least one of fly ash and silica
material.
18. A method as recited in claim 16, further comprising comminuting
said solid into slates.
19. A method as recited in claim 16, further comprising comminuting
said solid into chips.
20. A method as recited in claim 16, further comprising pastilling
said mixture into solid pastilles.
21. A method as recited in claim 16, further comprising pelletizing
said mixture into solid pellets.
22. A method as recited in claim 16, wherein said mixing comprises
the mixing of said ingredients together in the same mixing
vessel.
23. A method as recited in claim 16, wherein said mixing comprises
the mixing of said liquid hydrocarbon-based plasticizer with said
fine mineral constituent to form a mastic material, and the mixing
of said mastic material with said liquid sulfur to form said
mixture.
24. A method as recited in claim 16, wherein said mixing comprises
the wetting of said fine mineral constituent and the subsequent
mixing with said liquid hydrocarbon-based plasticizer to form a
mastic material, and the mixing of said mastic material with said
liquid sulfur to form said mixture.
25. A method as recited in claim 16, further comprising
preplasticizing said liquid sulfur.
26. A method as recited in claim 16, further comprising
preplasticizing said liquid hydrocarbon-based plasticizer.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This patent application is a continuation of U.S. patent
application Ser. No. 10/228,660 filed Aug. 26, 2002, entitled
"Paving Binders and Manufacturing Methods" which is a
continuation-in-part of U.S. patent application Ser. No.
09/576,476, filed on May 23, 2000, entitled "Paving Binders and
Manufacturing Methods", both of which applications are incorporated
herein by reference in their entirety.
BACKGROUND OF THE INVENTION
[0002] 1. The Field of the Invention
[0003] The present invention relates generally to paving binder
compositions and methods for manufacturing such compositions. More
specifically, the present invention relates to high sulfur paving
binder compositions that contain a sulfur plasticizer such as
asphalt and which retain non-flow properties within a broad range
of ambient temperatures, and to methods for producing binders with
these compositions.
[0004] 2. Present State of the Art
[0005] Paving material typically 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 depend on the properties of the binder.
[0006] The binder component is generally an asphalt-based
composition that may include some additives. Asphalt is described
as a dark brown to black cementitious material, which has a solid,
semisolid or liquid consistency, 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. 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.
[0007] 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.
[0008] 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 the transport of
this type of conventional asphalt-based materials difficult or even
impossible, and it can also give rise to serious environmental
problems. Nevertheless, convenient transport of binder materials is
desirable because paving takes place at sites that are generally
far away from the locations where the asphalt is available.
Transporting binder materials in the form of smaller-sized, solid,
non-sticky and non-flowing materials facilitates the delivery of
paving binders even when they are transported to sites that are far
away from the asphalt sources.
[0009] Asphalt and sulfur are used in the manufacture of binders
and they are typically transported in liquid form. This type of
transport requires specialized containers and conditions. It is
desirable to manufacture binders that incorporate the required
amounts of asphalt and sulfur and they remain in solid, non-sticky
and non-flowing form over a wide range of ambient temperatures, so
that such binders can be conveniently transported over long
distances by conventional means of transportation for common
solids.
[0010] Asphalt additives are used to render the binder material
less flowable at ambient temperatures. In particular, 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. Some of these problems derive from
the different densities of asphalt and sulfur. In certain mixtures,
sulfur separates due to its greater density from the asphalt. As a
result, the sulfur depleted binder then retains the softening and
flowing properties of asphalt, which make the handling and
transportation of the binder difficult or impossible. Finely
divided calcium-based materials have also been used in an attempt
to keep the sulfur additive homogeneously dispersed in asphalt. For
example, crushed limestone has been used for this purpose. However,
the use of calcium-based materials is believed to lead to the
formation of calcium sulfides and polysulfides that are detrimental
to the pavement longevity.
[0011] Furthermore, it has been acknowledged 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. For
example, the sulfur concentration by weight in binders is not
significantly above 50%, and the art recognizes that a
sulfur-to-asphalt weight ratio greater than 1.5:1 increases the
cost and may make the binder so sulfur-rich as to detrimentally
affect the asphalt. Unless indicated otherwise, concentrations
given as percentages are hereinafter understood as being weight
percentages. Furthermore, sulfur-asphalt mixtures that contain more
than 52% of sulfur are conventionally described as being too
sensitive to compaction temperatures below 115.5.degree. C.
(240.degree. F.).
[0012] 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, such as
petroleum coke. 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 (32) years, a period during
which the price has risen from approximately $23/ton in 1968 to
approximately $1 52/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 asphalt paving binder that
can effectively replace high asphalt paving binders.
[0013] The use of sulfur often leads to acridity problems because
the smell of sulfur is generally considered unpleasant. This is so
even when sulfur applications do not lead to the formation of
products such as sulfides and sulfur oxides.
[0014] Because of its color, the addition of sulfur to mixtures
such as binders causes the manufactured binder to be paler than it
would otherwise be without sulfur. It is, however, desirable for
some applications to control the color of the binder. The ability
to control the binder's color permits the production of a binder
that can satisfy a wider range of customer expectations. For
example, some customers expect paved surfaces to be of a certain
color for aesthetic purposes. Other customers expect paved surfaces
to offer a certain appearance by displaying a color that is viewed
as harmonious with respect to other environmental factors.
[0015] Paved surfaces are typically exposed during long time
periods to solar radiation. Certain types of such radiation cause
the chemical transformation of binder components, and thus the
degradation of the pavement in which such binder is incorporated.
An example of such radiation is ultraviolet radiation, the exposure
to which causes asphalt embrittlement.
[0016] Accordingly, there is a need for paving binders which
include the following characteristics. First, these binders can be
manufactured in forms that are non-sticky and non-flowing within a
wide range of ambient temperatures at which storage and transport
is effectuated. Binders with these non-sticky and non-flowing
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, asphalt in these paving binders
should be incorporated at most as a minority component 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. Fourth, effects derived from the use of
sulfur, such as acridity and discoloration, should be controlled by
the use of appropriate binder components. Fifth, harmful radiation
protection should be provided to prevent or reduce asphalt
embrittlement. Finally, paving binders should include additives
which are not obtained at the cost of depleting resources that can
be used for other purposes, but which absorb waste substances that
would otherwise present disposal problems. The foregoing
characteristics should be achieved by the use of constituents that
are not incompatible amongst themselves and such that the
constituents combined properties preferably enhance the binder
properties.
BRIEF SUMMARY OF THE INVENTION
[0017] 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.
[0018] In accordance with the invention as embodied and broadly
described herein, paving binder compositions according to the
present invention comprise sulfur at a concentration of not less
than 60%, a carbon-based plasticizer such as asphalt, and a fine
mineral constituent such as fine silica material, fly ash and
mixtures thereof. Some embodiments of the paving binder according
to the present invention comprise a hydrocarbon-based plasticizer
that includes a mixture of asphalt and at least one organic
additive. According to the present invention paving binders are
manufactured by mixing at least sulfur, a hydrocarbon-based
plasticizer and a fine mineral constituent and solidifying the
fluid mixture to form paving binders in any one of a plurality of
forms such as pastilles and slates.
[0019] 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
[0020] 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:
[0021] FIG. 1 is a schematic block diagram of embodiments of the
methods for producing paving binders according to the present
invention.
[0022] FIG. 2 is a schematic block diagram of additional
embodiments of methods for producing paving binders that include
the use of carbon black according to the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0023] The present invention is directed to the production of
paving binders that contain sulfur and asphalt, where the asphalt
is a minority constituent when compared with the concentration of
sulfur. Paving binders according to the present invention also
contain a substance such as fly ash as stiffener and mastic
material former. Embodiments of the methods for manufacturing
paving binders according to the present invention comprise mixing
liquid asphalt and a substance such as fly ash and further mixing
with liquid sulfur, subsequently forming pastilles, slates,
pellets, chips, briquettes or other small forms of finished paving
binder product that are suitable for storage and transportation at
ambient temperature because of their non-flow properties within a
wide range of ambient temperatures. The finished paving binder
product 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, non-flowing, non-sticky and devoid of the emissions that
fluid asphalt or fluid sulfur would generate. Other embodiments of
the present invention include the incorporation of carbon black
into the manufacturing process.
[0024] Applications of embodiments of paving binders according to
the present invention include their use in hot mix plants where the
paving material such as asphalt concrete is produced for
transportation and delivery to the paving site. Other applications
of paving binders according to the present invention include its
use in road site paving operations, either alone or in combination
with other paving materials. Still another use comprises the
on-site or remote site storage. Storage of paving binders of this
invention permits its accumulation in large quantities so that it
can subsequently be shipped in large quantities to remote
locations. The properties of the various embodiments of paving
binders according to the present invention are such that paving
binders can effectively be shipped over long distances, such as by
transatlantic and transcontinental shipments by any one of a
variety of conventional means, such as rail cars, trucks, ships and
airplane. Properties that facilitate the storage and shipment of
the inventive paving binders in large quantities include the
non-sticky and non-flow properties according to the present
invention.
[0025] Some embodiments of binders according to the present
invention are provided with components that protect against
radiation-induced detrimental effects, thus preventing or reducing
undesirable effects of exposure to radiation, including prevention
or reduction of embrittlement of the binder and of the material to
which the binder is incorporated, such as the pavement itself. Some
embodiments of binders according to the present invention are
provided with components that permit to offset discoloration, such
as discoloration due to the presence of sulfur, a material that
typically presents itself as yellow or yellowish. Furthermore, some
embodiments of binders produced according to the present invention
are manufactured so that acrid odors in the manufacturing process
and/or in the manufactured product are eliminated or reduced.
[0026] FIG. 1 schematically shows a flow diagram of one possible
embodiment of a process for manufacturing paving binders according
to the present invention. In one embodiment, the paving binder
comprises fly ash, a fine mineral constituent, which is stored as
feed material in container 101; asphalt, a carbon-based
plasticizer, which is stored as liquid feed material in tank 102;
and sulfur, which is stored a liquid feed material in tank 104. It
is understood that tanks 102 and 104 are appropriately configured
for the storage and delivery of liquid asphalt and liquid sulfur,
respectively. 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 points of asphalt and sulfur
are well known and the devices for melting and keeping these
substances in liquid form are also well known in the art.
[0027] 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.
[0028] Fly ash is the preferred fine mineral constituent of the
paving binder of the present invention, but paving binders can also
be made according to the methods of the present invention with
other 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 F silica
material, and type F fly ash, and a ceramic clay such as
kaolin.
[0029] Asphalt is the preferred hydrocarbon-based plasticizer
according to the present invention, and asphalt cement is the most
preferred form for the plasticizer 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
plasticizers 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 plasticizers
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.
[0030] 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 these particular grades. Asphalt
characterized according to other designations, such as PG grades
are also envisaged with the scope of hydrocarbon-based plasticizers
according to the present invention. Furthermore, substances such as
bitumen and gilsonite are also envisaged as examples of
hydrocarbon-based plasticizers in the context of the present
invention.
[0031] It is envisaged that paving binders according to the present
invention can also be prepared with other hydrocarbon-based
plasticizers in which asphalt is the majority component added to
the plasticizer mixture. These plasticizers include, by way of
example and not limitation, the products of mixtures such as a
mixture 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.
[0032] Other hydrocarbon-based plasticizers 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 plasticizer 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.
[0033] Still other hydrocarbon-based plasticizers 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 plasticizer mixture.
In addition to furan and dihydrofuran, these heterocyclic compounds
include furfural, and 3-(2-furyl) acrolein.
[0034] Other hydrocarbon-based plasticizers 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.
[0035] In one embodiment, sulfur is most preferably elemental
sulfur, which can be commercial grade, crystalline or amorphous.
Sources that provide sulfur suitable for the compositions and
methods of the present invention include primary sulfur sources and
recovered sulfur sources.
[0036] In one embodiment depicted in FIG. 1, feed material from
container 101 is delivered through a weigh hopper with an auto-drop
feature 110 and subsequently by auger 112 to mixing unit 150. One
example of container 101 is a bulk silo, but other storage devices
that are configured for controllably delivering fine material are
envisaged to embody container 101. Auger 1 12 may be replaced in
other embodiments of the present invention by a suitable pump.
Further, other embodiments are contemplated to operate with a
combination of a pump and auger, depending on the size and flow
characteristics of the feed material in container 101. In one
embodiment of the present invention, the feed material that is
transported from container 101 to mixing unit 150 is circulated so
that the material flow interacts with measuring device 115, which
may in one embodiment be a metering device. Measuring device 115
may alternatively be embodied by a belt scale or an equivalent
measuring device. It will be appreciated by one skilled in the art
that measuring device 115 could be included as part of auger
112.
[0037] Feed material from tank 102 is delivered to mixing unit 150.
This delivery is accomplished in one embodiment with the aid of a
suitable pump 120, although liquid asphalt could also be delivered
as a gravity-driven fluid flow. As feed material is delivered from
tank 102 to mixing unit 150, the fluid flow is circulated so that
the material flow interacts with measuring device 125, such as a
mass-flow meter. In one embodiment, liquid asphalt is preferably
kept in tank 102 at a temperature range of about 115.degree. C.
(about 229.degree. F.) to about 180.degree. C. (about 356.degree.
F.). More preferably, tank 102 has a temperature range of about
140.degree. C. (about 284.degree. F.) to about 160.degree. C.
(about 320.degree. F.), and most preferably has a temperature of
about 149.degree. C. (about 300.degree. F.). It will be appreciated
by one of ordinary skill in the art that when feed material from
tank 102 at a temperature above about 310.degree. F. is mixed with
liquid sulfur, this operation may have to be performed in a
controlled environment, such as a sealed container, so that evolved
H.sub.2S.sub.(g) does not present safety problems. The liquid
asphalt in tank 102 is stirred with multiple agitators and the
temperature is maintained with the heat provided by a heater such
as a hot oil jacket surrounding tank 102.
[0038] In one embodiment, illustrated in FIG. 1, mixing unit 150 is
embodied by two subunits. In this embodiment, the material from
container 101 and the fluid from tank 102 are delivered to wetting
box 152, which in one embodiment is a gravity feed wetting box. The
mixture is subsequently transferred to mixer 154. One possible type
of mixer 154 is an in-line mixer such as the mixer known by the
name Komax. It will be appreciated that various other embodiments
of mixing unit 150, wetting box 152, and mixer 154 may be
utilized.
[0039] The mixture produced in mixing unit 150 is a type of
"asphalt mastic." As used herein, the term "asphalt mastic" is used
to describe a mixture of asphalt and fine mineral material in such
proportions that the material can be poured hot and compacted by
troweling, if so desired. The term "mastic material" refers herein
below to a mixture of a hydrocarbon-based plasticizer with a fine
mineral constituent that has properties such as those described for
asphalt mastic, which is an embodiment of a mastic material.
[0040] Feed material from tank 104 is further mixed with the
mixture produced in mixing unit 150. Delivery of this feed material
is accomplished in one embodiment with the aid of a suitable pump
130, although liquid sulfur could also be delivered as a
gravity-driven fluid flow. As feed material is delivered from tank
104, the fluid flow is preferably circulated so that the material
flow interacts with measuring device 127, such as a mass-flow
meter.
[0041] As known in the art, fluid materials such as liquid sulfur
and liquid asphalt 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.
[0042] In one embodiment of the present invention, in an optional
step, the feed material from tank 102 is preplasticized by adding
to such material in tank 102 a preplasticizing substance such as at
least one of the substances styrene monomer (vinyl toluene),
polyethylene terephthalate (PET), ethyl vinyl acetate (EVA), Exxon
101, and Exxon 103. In another embodiment of the present invention,
the feed material from tank 104 is optionally preplasticized by
adding to such material in tank 104 a preplasticizing substance
such as at least one of the substances styrene monomer (vinyl
toluene), PET, EVA, Exxon 101, and Exxon 103, which are proprietary
material, or other vinyl aromatics. Still in another embodiment of
the present invention, the feed material from tank 102 is
optionally preplasticized in tank 102 and the feed material from
tank 104 is preplasticized in tank 104 as indicated regarding the
preplasticization of each one of such feed materials. It will be
appreciated that adding the preplasticizer substance is an optional
step and can be omitted entirely.
[0043] The fluid mixture produced in mixing unit 150 is mixed with
the liquid sulfur from tank 104 in mixer 156. In one embodiment,
mixer 156 is an in-line mixer, such as the mixer known by the name
Komax.
[0044] Embodiments of the fine mineral constituent according to the
present invention are fillers for the fluid paving binder that
permit its solidification in a homogeneous form. Fluid paving
binder compositions according to the present invention are
preferably processed in a gel form that behaves as a thixotropic
fluid when mixed. Low to medium shear mixing is preferable to
maintain this preferred fluid condition, and high shear mixing
conditions generally cause the thixotropic characteristics to
deteriorate or even disappear. One advantage of the gel form of the
fluid paving binder is that no separation, or even development of
inhomogeneity due to settling of dense material, has been observed
for a period of up to two hours. Whereas losing the gel form is
believed not to be critically detrimental, the gel form is a very
advantageous feature of the new compositions according to the
present invention that greatly facilitates the handling of the
fluid paving binder and the subsequent formation of discrete solid
paving binder units with the strength, non-sick and non-flow
properties that characterize the paving binder compositions of the
present invention.
[0045] Mixer 156 produces a feed material that is used to form
finished paving binder in a variety of forms that includes, by way
of example and not limitation, pastilles, slates, pellets, chips,
briquettes or other forms of finished paving binder product that
are suitable for storage and transportation. In one embodiment,
these forms of finished paving binder product have a smaller
manageably size. By way of example only, in one embodiment the
finished paving binder products 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 paving binder products may be produced.
[0046] In one embodiment, feed material from mixer 156 is formed
into solid units such as, by way of example only, pellets,
pastilles, slates and chips. In contrast, conventional paving
binders are not known to be available in any of these useful forms.
Slates and chips are formed according to the embodiment shown in
FIG. 1 by circulating the feed material produced in mixer 156
through a cooling system 160, so that the fluid hardens as it is
transported by conveyor 158 into a brittle material that
subsequently breaks into discrete units, including units with a
fairly small size described above. Pastilles may be formed by
subjecting the fluid obtained from mixer 156 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 mixer 156 to treatment with conventional
pelletizers. Flakes are formed by subjecting the fluid obtained
from mixer 156 to treatment with conventional devices such as a
rubber, composite, or metal belt.
[0047] Paving binder according to the present invention is
preferably manufactured by mixing about 82% sulfur, about 9%
asphalt, and about 9% fine mineral constituent. Paving binders
according to the present invention are manufactured by mixing
sulfur in amounts that range from about 60% to about 98%, with
asphalt cement in amounts that range from about 1% to about 30%,
and fine mineral constituent such as fly ash, silica material, and
mixtures of fly ash and silica material, to balance, but generally
ranging from about 1% to about 33%. Preferable ranges are from
about 70% to about 90% of sulfur, from about 2.5% to about 20% of
asphalt, and fine mineral constituent to balance, but generally
ranging from about 2.5% to about 20%. More preferable ranges are
from about 75% to about .sup.900/o sulfur, from about 5% to about
12% of asphalt, and fine mineral material constituent to balance,
but generally ranging from about 5% to about 12%. Total
preplasticizing substance can range in embodiments of the present
invention from 0% to about 10%.
[0048] It is understood that material flow lines in the diagram
shown in FIG. 1 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 FIG. 1 are built with the suitable ports that are known
in the art. For example, the fluid mixture produced in mixing unit
150 may be fed into the liquid sulfur feed line through a
conventional vortex injector port.
[0049] Suitable combinations of compacting, crushing, comminuting
devices and other devices to further control and standardize the
size of the finished paving binder can be. implemented instead of
or in addition to conveyor 158 and cooling system 160.
Nevertheless, one of the advantages of the compositions and
processes of the present invention is that the finished paving
binder can be easily produced with a reduced set of devices and
with less equipment than it would otherwise be necessary for the
production of other binders.
[0050] In one embodiment of the process for making paving binder
according to this invention, cooling system 160 is a water-based
cooling system, including water baths and water flow systems, such
as a water sprinkling system, that lowers the temperature of the
fluid feed produced in mixer 156 as it is transported by conveyor
158. 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 the fluid paving binder
composition. This configuration can be achieved, for example, by
circulating the paving binder composition obtained from mixer 156
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 the fluid paving binder from mixer 156 is
fed to it, solidification is typically achieved in about 1 minute
to 10 minutes.
[0051] In one embodiment of the present invention, fluid feed
produced in mixer 156 is fed to a pelletizing unit, such as a
pelletizing drum unit, to produce solid paving binder in the form
of pellets.
[0052] Embodiments of the paving binder 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.).
[0053] Processes for manufacturing paving binders according to this
invention, such as the embodiment schematically shown in FIG. 1,
are preferably configured for an automated control of the amount of
constituents and process conditions. For example, FIG. 1 shows.
process control unit 129 that receives input from and provides
regulatory feedback to auger 112, pumps 120 and 130, measuring
devices 115,125 and 127, and auger and/or pump 112. The exchange of
signals to and from process control unit 129 that may be used to
implement the acquisition of information and provide the regulatory
feedback is generally represented in FIG. 1 by the dash lines. In
one embodiment, process control unit 129 may be a computerized
constituent ratio control unit. Automated process control can be
achieved in other embodiments by a process control unit that also
controls mixing unit 150, mixer 156, and the system for hardening
and sizing the fluid feed that is obtained from mixer 156 to form
finished paving binder product.
[0054] FIG. 2 schematically shows a block diagram of another
embodiment of paving binder production methodology that
incorporates the use of at least a substance such as carbon black
according to the present invention. Features already described with
reference to FIG. 1 and that are labeled with the same numerals are
not discussed again in the context of the block diagram shown in
FIG. 2.
[0055] As schematically shown in FIG. 2, carbon black is
incorporated into paving binder production according to the present
invention from a suitable storage and delivery container 170. The
delivery of carbon black is preferably controlled with the aid of a
measuring device 171, which in turn is preferably controlled with a
process control unit such as process control unit 129.
[0056] Carbon black is believed to cause sulfur dispersion and to
prevent the agglomeration of sulfur and thus the formation of pools
of sulfur in the asphalt. Lack of sulfur agglomeration was observed
in embodiments of this invention, particularly in the embodiments
which incorporated the use of carbon black in the binder
manufacturing process.
[0057] The incorporation of carbon black into paving binder
production according to the present invention can take place at any
one among a plurality of delivery stages. A preferred delivery
stage is shown in FIG. 2 as being the mixing of carbon black with
fluid sulfur prior to the mixing of sulfur with the product
obtained from mixing unit 150. Carbon black is added in embodiments
of the present invention in amounts in the range from about 0.2% to
about 15% of carbon black in the sulfur, more preferably in the
range from about 0.5% to about 10% of carbon black in the
sulfur.
[0058] It was observed in the practice of the preferred embodiment
for the incorporation of carbon black according to this invention
that the mixture of carbon black with sulfur at an early stage in
the paving binder manufacturing process reduced or even eliminated
the acridity otherwise attributable to the odor of sulfur. This
odor reduction or elimination was experienced during the
manufacturing process, and it was also observed as a characteristic
of paving binders manufactured according to the present
invention.
[0059] Mixing of carbon black with any other constituent according
to the present invention, such as mixing with sulfur, can take
place in a mixing unit 172 which is provided with flow control and
stirring elements to facilitate thorough mixing. In other
embodiments the mixing takes place upon the merging to the carbon
black delivery conduit with the conduit for whichever other
constituent is mixed with the carbon black.
[0060] Carbon black is provided by some sources in pelletized form.
It is then preferably comminuted, ground or otherwise reduced to
powder prior to its incorporation into the paving binder
compositions according to the present invention. Although not shown
in FIG. 2, it is understood that the appropriate equipment for such
operation is provided in the schematic flow chart shown in FIG. 2
as part of, for example, unit 172 and/or container 170.
[0061] Other embodiments of the present invention include the
incorporation of carbon black at other stages in the manufacturing
process, for example through mixing unit 150. Other embodiments
include the incorporation of carbon black into asphalt prior to the
mixing of asphalt in unit 150. Still other embodiments include the
incorporation of carbon black into material such as fly ash prior
to the mixing of such material with asphalt. Additional embodiments
include the incorporation of carbon black at a plurality of stages
such as those referred to hereinabove.
[0062] Sources of carbon black that can be used according to the
present invention include mining and manufacturing carbon black
sources. The latter sources include the oil-furnace black, the
thermal, the lamp black, the channel black, and the acetylene black
processes. Carbon black from sources such as any one of the
foregoing sources, from any other source, and from a combination
thereof, can be used in embodiments of this invention.
[0063] Carbon black characteristics in a wide range of elemental
carbon content, carbon black particle size, and carbon black
aggregate forms were used in a plurality of embodiments of the
present invention. By way of examples but not as limitations,
carbon black obtained from the oil-furnace process has particle
sizes typically characterized in the diameter range from about 10
nm to about 250 nm. Carbon black obtained from the thermal black
process has particle sizes typically characterized in the diameter
range from about 120 nm to about 500 nm. Carbon black aggregate
forms range from clusters to branched and to filamentous forms.
Paving binder compositions according to the present invention were
obtained with a great variety of carbon black materials from a
plurality of sources, including mined carbon black. Mined carbon
black and carbon black from the oil-furnace process are the more
available forms of carbon black that can be used in the context of
the present invention because these are presently the predominant
carbon black production forms.
[0064] The paving binder produced according to the compositions and
methods of the present invention is a high strength, durable, low
cost paving binder product that can be stored for future use in
paving applications. Paving binders 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 asphalt 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.
[0065] The strength of embodiments of the paving binder 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.
[0066] The strength of embodiments of the paving binder 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.
[0067] The paving binder 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 paving binder of the present invention
may also be used in a hot-mix plant by introducing them through the
recycled asphalt pavement (RAP) collar in a drum hot-mix plant or
pug mill in a batch process hot-mix plant, thus eliminating the
need for hot asphalt storage and heating. Consequently, emissions
from hot asphalt are also eliminated.
[0068] 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.
[0069] 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
availability of asphalt and sulfur.
[0070] The finished paving binder product 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
paving binder 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.
[0071] Embodiments of the paving binder according to the present
invention 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, these 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 paving binder 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 paving binder
according to the present invention provide for safer transportation
of the binder because of the solid nature of the paving binder,
thus eliminating the risk of hot asphalt transportation spills.
[0072] The use in the hot-mix plant of embodiments of the paving
binder according to the present invention eliminates the need for
stability testing during the hot-mix design process because the
paving binder produces a mix with stabilities that are higher than
can be measured with today's conventional testing equipment.
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 Superpave, as starting point.
[0073] One possible embodiment of a process according to the
present invention, as schematically shown in FIG. 1, displays a
configuration of devices to first mix asphalt and fine mineral
constituent, and subsequently incorporate sulfur into this mixture.
Mixing at each stage takes place to an extent that is sufficient to
thoroughly interdisperse the constituents in each mixture. In other
embodiments of this invention sulfur, asphalt and fine mineral
constituent are mixed together in a suitable vessel or apparatus 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 paving binder
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 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 150. Depending on the composition and characteristics of the
constituents, mixing in this batch mode can take from about 15
minutes to about 2 hours, and in any case, mixing is performed
until the constituents are thoroughly interdispersed in the mixture
and a gel is formed.
EXAMPLES
[0074] To date, numerous paving binder compositions have been
prepared and tested to develop and to offer exemplary embodiments
of the present invention. Below are specific examples of paving
binder compositions and tests of mixtures of paving binder
compositions 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 in the past tense,
while the hypothetical examples are written in the present tense in
order to distinguish between the two.
Example 1
[0075] 60% sulfur, 15% type F fly ash, and 25% AC-10 asphalt cement
were mixed together for a total time of one minute 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 paving binder was mixed with graded mineral aggregate in
relative amounts of about 5% of paving binder and 95% of aggregate,
and the mixture was formed into Marshall-type briquettes, which had
a stability of 3000 pounds and a flow of 8 at 50 blows.
Example 2
[0076] 80% sulfur, 10% type F silica flour, and 10% AC-10 asphalt
cement were mixed together for about one minute 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 paving binder was mixed with graded mineral aggregate in
relative amounts of about 5% of paving binder and 95% of aggregate,
and the mixture was formed into Marshall-type briquettes, which had
a stability of 5000 pounds and a flow of 8 at 2 blows.
Example 3
[0077] A composition like that described in Example 2 was prepared
with type A silica flour instead of type F silica flour.
Example 4
[0078] Compositions like those described in Examples 1-3 were
prepared with AC-20 asphalt instead of AC-10 asphalt.
Example 5
[0079] A composition was prepared as described in Example 1 with
65% sulfur, 12% type F fly ash, and 23% AC-10 asphalt.
Example 6
[0080] A composition was prepared as described in Example 3 with
85% sulfur, 8% type F silica material, and 7% AC-10 asphalt.
Example 7
[0081] A composition was prepared as described in Example 3 with
75% sulfur, 13% type F silica material, and 12% AC-10 asphalt.
Example 8
[0082] Compositions like those described in Examples 6-7 were
prepared with type A silica material instead of type F silica
material.
Example 9
[0083] Compositions like those described in Examples 5-8 were
prepared with AC-20 asphalt instead of AC-10 asphalt.
Example 10
[0084] Compositions like those described in Examples 1-2,4-7,9 are
prepared with the corresponding amount of fine mineral constituent
replaced by a 50-50 mixture of type F silica material and type F
fly ash.
Example 11
[0085] Compositions like those described in Examples 1-2,4-7,9 are
prepared with the corresponding amount of fine mineral constituent
replaced by a 50-50 mixture of type A silica material and type F
fly ash.
Example 12
[0086] 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
asphalts replacing AC-10 and AC-20 asphalts at the concentrations
described in the foregoing Examples.
Example 13
[0087] 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 a
plasticizer that is a mixture of crude oil with at least one of the
AC asphalts described herein above. These asphalts include
AC-1.75,AC-2.5,AC-5,AC-10,AC-20,AC-30,AC-40,AC-80, and AC-120
asphalts. The crude oil is a minority component in the plasticizer
with respect to the amount of asphalt, and the plasticizer
constituent is incorporated into the paving binder formulation at
concentrations such as the concentrations described in the
foregoing Examples.
Example 14
[0088] 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 a
plasticizer that is a mixture of an additive of the type described
below with at least one of the AC asphalts described herein above.
These asphalts include AC-1.75, AC-2.5, AC-5, AC-10, AC-20, AC-30,
AC-40, AC-80, and AC-120 asphalts. The additive is a minority
component in the plasticizer with respect to the amount of asphalt,
and the plasticizer constituent is incorporated into the paving
binder formulation at concentrations such as the concentrations
described in the foregoing Examples. The additive in the
formulations of this Example includes at least one of the following
substances: tall oil pitch, cyclic saturated hydrocarbons, cyclic
unsaturated hydrocarbons, polycyclic saturated hydrocarbons,
polycyclic unsaturated hydrocarbons, tar, and mixtures thereof.
Example 15
[0089] 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 a
plasticizer that is a mixture of a polymeric material or
polymerizable material of the type described below with at least
one of the AC asphalts described herein above. These asphalts
include AC-1.75, AC-2.5, AC-S, AC-10, AC-20, AC-30, AC-40, AC-80,
and AC-120 asphalts. The polymeric or polymerizable material is a
minority component in the plasticizer with respect to the amount of
asphalt, and the plasticizer constituent is incorporated into the
paving binder formulation at concentrations such as the
concentrations described in the foregoing Examples. The polymeric
or polymerizable material in the formulations of this Example
includes at least one of the following materials: PET, EVA, styrene
monomer (vinyl toluene), Exxon 101, and Exxon 103.
Example 16
[0090] 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 a
plasticizer that is a mixture of a heterocyclic material of the
type described below with at least one of the AC asphalts described
herein above. These asphalts include AC-1.75, AC-2.5, AC-5, AC-10,
AC-20, AC-30, AC-40, AC-80, and AC-120 asphalts. The heterocyclic
material is a minority component in the plasticizer with respect to
the amount of asphalt, and the plasticizer constituent is
incorporated into the paving binder formulation at concentrations
such as the concentrations described in the foregoing Examples. The
heterocyclic material in the formulations of this Example includes
at least one of the following materials: furan, dihydrofuran,
furfural, 3-(2-furyl) acrolein, derivatives thereof, and mixtures
thereof.
Example 17
[0091] 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 a
plasticizer that is a mixture of at least one aliphatic, olefinic,
or aromatic substance with at least one of the AC asphalts
described herein above. These asphalts include AC-1.75, AC-2.5,
AC-5, AC-10, AC-20, AC-30, AC-40, AC-80, and AC-120 asphalts. The
aliphatic, olefinic, aromatic or mixture thereof is a minority
component in the plasticizer with respect to the amount of asphalt,
and the plasticizer constituent is incorporated into the paving
binder formulation at concentrations such as the concentrations
described in the foregoing Examples.
Example 18
[0092] 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 1-9 included furthermore in
these additional formulations carbon black at a concentration in
the range from about 0.2% to about 15% with respect to the sulfur
present in such compositions.
Example 19
[0093] 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 10-17 include furthermore in
these additional formulations carbon black at a concentration in
the range from about 0.2% to about 15% with respect to the sulfur
present in such compositions.
[0094] The presence of carbon black in some embodiments of the
present invention permits the control of the color of the
manufactured binders from grey to black, and furthermore provides
binders that are typically less brittle than the carbon-black free
counterparts. This characteristic is believed to be due to the
protection from radiation provided by the carbon black. Absent such
protection, radiation such as ultraviolet radiation would cause
chemical changes that would eventually lead to more brittle forms
of binders.
[0095] Binders according to the present invention include
embodiments that comprise sulfur in at least about 60%,
plasticizer, such as hydrocarbon-based plasticizer, within the
range from about 2.5% to about 20%, and fine mineral constituent in
the range from about 1% to about 33%. Some of these embodiments
further contain carbon black in an amount within the range from
about 0.2% to about 15% with respect to the amount of sulfur.
[0096] Embodiments of the paving binders according to the present
invention have sulfur instead of asphalt as the majority
constituent. Because of the significant compositional difference
between asphalt binders and embodiments of the paving binders of
the present invention, some characteristics of these paving binders
are different from those of asphalt binders. In particular, the
range of viscoelastic behavior of asphalt binders does not
correspond with the behavior of embodiments of paving binders
according to the present invention.
[0097] Pavement failures include rutting, fatigue cracking, and
thermal cracking. These pavement failures are related to the
physical properties of the pavement binders. Furthermore, it has
also been recognized that hardening is a main factor in changing
asphalt properties during the pavement service life, thus affecting
performance. In addition, it has also been realized that asphalt
binders behave like viscoelastic materials. However, binder
properties are complex, and sound rheological methodology is needed
to study the behavior of binders. These testing and aging methods
include the dynamic shear rheometer (DSR), the bending beam
rheometer (BBR), and the pressure aging vessel (PAV), and the
parameters include the complex shear modulus (G*), phase angle (8),
creep stiffness (S), and logarithmic creep rate (m), or m-value.
These methods, parameters and functions thereof are believed to
provide a good description of viscoelastic materials, such as
asphalt binders.
[0098] The paving binders according to this invention, however,
contain sulfur as the majority component instead of asphalt, and
their viscoelastic behavior does not compare with that of asphalt
binders within the same temperature range. The differences in
behavior are particularly noticeable at low temperatures.
Nevertheless, the parameters referred to above are still applied to
embodiments of the present invention to provide reference data.
[0099] The characterization of the binder resistance to each one of
the main failure modes is outlined below in three separately
discussed contributions: (a) Contribution of the binder to rutting
resistance; (b) contribution of the binder to fatigue cracking
resistance; and (c) contribution of the binder to thermal cracking
resistance.
[0100] (a) Contribution of the Binder to Rutting Resistance
[0101] Rutting is the main failure mode at the high-temperature
range from about 45.degree. C. to about 85.degree. C. This
temperature range comprises the higher temperatures of most
pavements during summer. Higher G*-values imply high total
resistance to deformation and thus high rutting resistance. Lower
.delta.-values represent a more elastic (recoverable) component of
the total deformation and thus are associated with higher rutting
resistance. Consequently, the paving binder contribution to rutting
resistance can be increased by increasing its total resistance to
deformation (increasing G*) and/or by decreasing its non-elasticity
(sin .delta.). Instead of using G* and 8 separately, it is common
practice to use the ratio G*/sin .delta. to reflect the binder's
contribution to rutting resistance, so that when the ratio G*/sin
.delta. increases, rutting resistance also increases. This ratio is
typically given in units of Pa and standard multiples thereof.
Measurements are typically performed with DSR tests without
subjecting the material to aging ("original") or subjected to
simulated aging (typically in a rolling thin film oven
("RTFO")).
[0102] (b) Contribution of the Binder to Fatigue Cracking
Resistance
[0103] Fatigue cracking is the main failure mode at the
intermediate-temperature range from about 0.degree. C. to about
45.degree. C. Softer and more elastic paving binders are more
resistant to fatigue damage because the stress developed for a
given deformation is lower and the material is more capable of
recovering to its pre-loading condition. In terms of G* and
.delta., low G*-values are associated with softer binders which
deform without developing large stresses, and thus are more
resistant to fatigue cracking; low .delta.-values are associated
with more elastic binders, which are capable of recovering to their
original condition without dissipating energy in any fashion, thus
favoring fatigue cracking resistance. Instead of using G* and
.delta. separately, it is common practice to use the product G* sin
.delta. to reflect the binder's contribution to fatigue cracking
resistance, so that when the product G* sin .delta. decreases,
fatigue cracking resistance increases. This product is typically
given in units of Pa and standard multiples thereof. Measurements
are typically performed with DSR tests of material subjected to
aging (typically in a pressure aging vessel "PAV")).
[0104] (c) Contribution of the Binder to Thermal Cracking
Resistance
[0105] Fatigue cracking is the main failure mode at the
low-temperature range from about -50.degree. C. to about 0.degree.
C. Because stiffness is directly proportional to G*, lower
G*-values are associated with asphalt binders that offer a better
thermal cracking resistance. In contrast, thermal cracking
resistance increases as .delta. increases, because the rate of
relaxation is directly related to .delta. and a higher relaxation
rate is favorable to thermal cracking resistance. Measurements
regarding contribution of asphalt binder performance to thermal
cracking resistance are typically performed with BBR tests, but S
and m are typically given instead of G* and .delta..
[0106] Thermal cracking in pavements results from stresses
developed as a consequence of the thermal shrinkage that is caused
by a drop in temperature. During thermal cooling, binder stiffness
increases and stress builds up on the one hand because of restraint
on thermal shrinkage, but on the other hand, binder flow leads to
stress relaxation. Consequently, both stiffness (S) and stress
relaxation are important. The logarithmic creep rate, m, is
typically used as an indication of ability to flow, and thus as an
indication of stress dissipation ability. More specifically, a
higher m-value indicates a less elastic binder that can flow and
dissipate stresses. The m-value gives a measure of the rate of
stress relaxation by flow of the binder. High values of m are
associated with binders that have good resistance to thermal
cracking. Stiffness gives a measure of thermal stresses developed
in the pavement as a result of thermal shrinkage. As stiffness
increases, more stresses result from a thermal strain, such as
shrinkage. Low values of stiffness are associated with binders that
have good resistance to thermal cracking. Stiffness and m are
selected as indicators of binder contribution to pavement
performance at low temperatures. However, both stiffness and m are
functions of the loading time, and existing correlations with
thermal cracking are only available for impractically long times,
which would require impermissibly long tests. To avoid this problem
and to be able to run short-time tests, the time-temperature
superposition principle has been adopted as a standard practice, so
that the tests are performed at higher temperature but for shorter
loading times. In particular, it is known that a 10.degree. C.
increase in temperature is equivalent to a loading time shift from
7200 s to about 60 s. Accordingly, a specification criterion of a
minimum m-value of 0.30, and a maximum limit of 300 MPa on the
stiffness were selected as SHRP viscoelastic binder specifications,
where both values are taken at a loading time of 60 s.
[0107] The relationships between failure modes and viscoelastic
material characteristic parameters can be summarized as follows.
Increased G* values and lower .delta. values are favorable changes
with respect to rutting performance, but they are unfavorable for
thermal cracking performance. For fatigue cracking in viscoelastic
materials, the increase in S (or in G*) is not favorable, while the
decrease in m (or in .delta.) is generally favorable.
[0108] The foregoing discussion refers to aging in rotatory thin
film oven and in pressure aging vessel. Binder aging is briefly
discussed as follows. The asphaltic material in paving binders
typically hardens when the paving binder and the aggregate are
mixed in hot-mix plants. Tests have been devised to simulate this
hardening, and these tests include the Thin Film Oven (TFO) test,
ASTM D1754, and the Rolling Thin Film Oven (RTFO) test, ASTM D2872.
The RTFO test is currently more commonly used because it is
designed to produce in about 75 minutes results similar to those
produced by the TFO test in about 5 hours. In essence, these tests
simulate by oven aging the hardening that occurs in hbt-mix plants.
SHRP proposed the Pressure Aging Vessel (PAV) as an aging procedure
to simulate long-term field oxidative aging of asphalt binders.
[0109] Regarding compositions, Tables 1-3 display test results for
one embodiment of paving binder that had been manufactured
according to the present invention with 60% sulfur, 20% AC-20
asphalt from California Valley, and 20% fly ash.
1TABLE 1 T/.degree. C. m Stiffness/MPa -16 0.396 144 -22 0.321 355
-28 0.223 710
[0110]
2TABLE 2 (G*/sin .delta.)/kPa at three high temperatures Conditions
64.degree. C. 70.degree. C. 76.degree. C. ORIGINAL 4.49 2.10 1.04
RTFO 10.20 4.60 2.12
[0111]
3TABLE 3 (G* sin .delta.)/MPa at four intermediate temperatures
Conditions 31.degree. C. 28.degree. C. 25.degree. C. 22.degree. C.
PAV 2.24 3.31 4.66 6.61
[0112] Tables 4-5 display test results for an embodiment of paving
binder that had been manufactured according to the present
invention with 70% sulfur, 15% AC-20 asphalt from Cold Lake,
Canada, and 15% fly ash.
4TABLE 4 T/.degree. C. m Stiffness/MPa -16 0.281 365 -22 0.161 577
-28 0.173 972
[0113]
5TABLE 5 (G*/sin .delta.)/kPa at three high temperatures Conditions
70.degree. C. 76.degree. C. 82.degree. C. ORIGINAL 6.59 3.30 1.69
RTFO 9.77 5.26 2.69
[0114] Tables 6-8 display test results for an embodiment of paving
binder that had been manufactured according to the present
invention with 80% sulfur, 10% AC-20 asphalt from Cold Lake,
Canada, and 10% fly ash.
6TABLE 6 T/.degree. C. m Stiffness/MPa -16 0.338 150 -22 0.193 220
-28 0.018 48
[0115]
7TABLE 7 (G*/sin .delta.)/kPa at four high temperatures Conditions
52.degree. C. 58.degree. C. 64.degree. C. ORIGINAL 3.54 1.51 0.63
RTFO 18.3 7.88 3.31
[0116]
8TABLE 8 (G* sin .delta.)/MPa at three intermediate temperatures
Conditions 31.degree. C. 28.degree. C. 25.degree. C. PAV 3.12 4.43
5.76
[0117] Tables 9-11 display test results for an embodiment of paving
binder that had been manufactured according to the present
invention with 60% sulfur, 20% AC-20 asphalt from Gulf Coast,
Texas, and 20% fly ash.
9TABLE 9 T/.degree. C. m Stiffness/MPa -16 0.340 178 -22 0.198 217
-28 0.180 567
[0118]
10TABLE 10 (G*/sin .delta.)/kPa at three high temperatures
Conditions 52.degree. C. 58.degree. C. 64.degree. C. ORIGINAL 3.65
1.52 0.644 RTFO 10.1 4.14 1.67
[0119]
11TABLE 11 (G* sin .delta.)/MPa at three intermediate temperatures
Conditions 31.degree. C. 28.degree. C. 25.degree. C. PAV 3.46 4.91
7.01
[0120] Tables 1, 4, 6, and 9 display BBR test results at several
low temperatures, a temperature range at which thermal cracking is
considered to be the main failure mode. Tables 2, 5, 7, and 10
display DSR tests of materials under original and RTFO conditions
at several high temperatures, a temperature range at which rutting
is considered to be the main failure mode. Tables 3, 8, and 11
display DSR tests of materials under PAV conditions at several
intermediate temperatures, a temperature range at which fatigue
cracking is considered to be the main failure mode.
[0121] Values of the ratio G*/sin 8 shown in Tables 2, 5, 7, and 10
indicate that the paving binders according to the present invention
generally present good rutting resistance according to interpretive
criteria applied to viscoelastic materials.
[0122] Values of the product G* sin 8 shown in Tables 3, 8, and 11
indicate that the paving binders according to the present invention
generally present good fatigue cracking resistance according to
interpretive criteria applied to viscoelastic materials.
[0123] Stiffness and m-values shown in Tables 1, 4, 6, and 9 can be
interpreted as indicating that the paving binders according to the
present invention generally present good thermal cracking
resistance according to interpretive criteria applied to
viscoelastic materials for moderately low temperatures.
[0124] Embodiments of the paving binder of the present invention
confer good thermal cracking resistance to pavement in the low
temperature zone because of the high strength of these paving
binders. This strength prevents the development of cracks as a
consequence of stress accumulation upon cooling.
[0125] 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.
* * * * *