U.S. patent application number 13/094362 was filed with the patent office on 2012-11-01 for destabilized bituminous bonding layer.
This patent application is currently assigned to ROAD SCIENCE, LLC. Invention is credited to Marvin K. Exline.
Application Number | 20120275860 13/094362 |
Document ID | / |
Family ID | 47068003 |
Filed Date | 2012-11-01 |
United States Patent
Application |
20120275860 |
Kind Code |
A1 |
Exline; Marvin K. |
November 1, 2012 |
DESTABILIZED BITUMINOUS BONDING LAYER
Abstract
A method of applying a new surface to an existing surface. The
method comprises applying a bituminous emulsion bonding layer to
the existing surface; destabilizing the bituminous emulsion bonding
layer; and applying a bituminous mixture to the bituminous emulsion
bonding layer.
Inventors: |
Exline; Marvin K.; (Terre
Haute, IN) |
Assignee: |
ROAD SCIENCE, LLC
Tulsa
OK
|
Family ID: |
47068003 |
Appl. No.: |
13/094362 |
Filed: |
April 26, 2011 |
Current U.S.
Class: |
404/31 ;
404/82 |
Current CPC
Class: |
C08L 95/005 20130101;
E01C 7/353 20130101; E01C 11/005 20130101 |
Class at
Publication: |
404/31 ;
404/82 |
International
Class: |
E01C 11/00 20060101
E01C011/00; E01C 19/46 20060101 E01C019/46 |
Claims
1. A method of applying a new surface to an existing surface, the
method comprising: applying a bituminous emulsion bonding layer to
the existing surface; destabilizing the bituminous emulsion bonding
layer; and applying a bituminous mixture to the bituminous emulsion
bonding layer.
2. The method of claim 1 where the step of destabilizing the
bituminous emulsion bonding layer occurs within 15 seconds of
applying the bituminous emulsion bonding layer to the existing
surface.
3. The method of claim 1 where the step of destabilizing the
bituminous emulsion bonding layer occurs within 5 seconds of
applying the bituminous emulsion bonding layer to the existing
surface.
4. The method of claim 1 where the bituminous mixture is a
cold-applied bituminous mixture.
5. The method of claim 4 where the bituminous mixture is applied
with a thickness of less than 4.5 cm.
6. The method of claim 4 where the bituminous mixture is applied
with a thickness of less than 2.5 cm.
7. The method of claim 1 where the bituminous emulsion bonding
layer and the bituminous mixture are applied with a spray
paver.
8. The method of claim 1 where the step of applying the bituminous
mixture to the bituminous emulsion bonding layer occurs within 5
seconds of the step of applying the bituminous emulsion bonding
layer to the existing surface.
9. The method of claim 1 where the bituminous emulsion bonding
layer is destabilized with a destabilization agent and the
destabilization agent is selected based on the bituminous emulsion
bonding layer.
10. The method of claim 1 where the step of destabilizing the
bituminous emulsion bonding layer is achieved by counter ion
attack, destabilization chemicals, pH change, temperature change,
precipitation of a surfactant system, driers, chemical or physical
dehydration, or HLB imbalance causing phase inversion.
11. The method of claim 1 where the bituminous emulsion bonding
layer is a cationic emulsion and where the step of destabilizing
the bituminous emulsion bonding layer comprises applying an anionic
surfactant solution to the cationic emulsion.
12. The method of claim 11 where the anionic surfactant solution
has a concentration and the concentration is increased to
accelerate the step of destabilizing the bituminous emulsion
bonding layer.
13. The method of claim 11 where the anionic surfactant solution is
a sulfonate mixed with water.
14. The method of claim 13 where the anionic surfactant solution
has a concentration of at least about 0.05% of a sulfonate by
weight of the water.
15. The method of claim 1 where the bituminous emulsion bonding
layer is a cationic emulsion with a pH and where the step of
destabilizing the bituminous emulsion bonding layer comprises
changing the pH of the cationic emulsion.
16. The method of claim 15 where changing the pH of the cationic
emulsion comprises creating a destabilization solution by mixing an
alkali in water.
17. The method of claim 16 where the alkali is sodium hydroxide at
a concentration of at least about 0.01% by weight of the water.
18. The method of claim 1 where the bituminous emulsion bonding
layer is an anionic emulsion and where the step of destabilizing
the bituminous emulsion bonding layer comprises applying a cationic
surfactant solution to the anionic emulsion.
19. The method of claim 18 where the cationic surfactant solution
has a concentration and the concentration is increased to
accelerate the step of destabilizing the bituminous emulsion
bonding layer.
20. The method of claim 18 where the cationic surfactant solution
is fatty acid imidazoline mixed with water.
21. The method of claim 20 where the cationic surfactant solution
has a concentration of at least about 0.05% of fatty acid
imidazoline by weight of the water.
22. The method of claim 1 where the bituminous emulsion bonding
layer is an anionic emulsion with a pH and where the step of
destabilizing the bituminous emulsion bonding layer comprises
changing the pH of the anionic emulsion.
23. The method of claim 22 where changing the pH of the anionic
emulsion comprises creating a destabilization solution by mixing an
acid in water.
24. The method of claim 23 where the acid is acetic acid at a
concentration of at least about 0.01% by weight of the water.
25. The method of claim 1 where the bituminous emulsion bonding
layer is an anionic emulsion with an anionic fatty acid salt and
where the step of destabilizing the bituminous emulsion bonding
layer comprises precipitating the anionic fatty acid salt with a
divalent metal ion in water solution.
26. The method of claim 25 where the divalent metal ion in water
solution is at least about 0.01% Calcium Chloride by weight.
27. The method of claim 1 where the bituminous emulsion bonding
layer comprises water and the step of destabilizing the bituminous
emulsion bonding layer comprises sequestering the water in the
bituminous emulsion bonding layer, rendering the bituminous
emulsion bonding layer unstable.
28. The method of claim 27 where sequestering the water in the
bituminous emulsion bonding layer comprises applying sequestering
agents to the bituminous emulsion bonding layer.
29. The method of claim 28 where the sequestering agents comprise
silica gels, chalk, clay-based desiccant, Portland cement, fly ash,
or combinations thereof.
30. The method of claim 28 where the sequestering agents are
applied to the bituminous emulsion bonding layer before, during, or
immediately after the application of the bituminous emulsion to the
existing surface.
31. The method of claim 1 where the step of destabilizing the
bituminous emulsion bonding layer comprises engineering a
destabilization component into the bituminous emulsion bonding
layer.
32. The method of claim 31 where the destabilization component is a
surfactant that has a high cloud point, turbidity point, phase
inversion temperature, or combination thereof.
33. The method of claim 31 where the destabilization component is a
nonionic surfactant that becomes insoluble in water under normal
road surface temperatures.
34. The method of claim 33 where the destabilization component
comprises a polyoxyethylene group.
35. The method of claim 1 where the bituminous emulsion bonding
layer is a cationic emulsion and the step of destabilizing the
bituminous emulsion bonding layer comprises applying an anionic
bituminous emulsion to the bituminous emulsion bonding layer.
36. The method of claim 1 where the bituminous emulsion bonding
layer is a cationic emulsion and the step of destabilizing the
bituminous emulsion bonding layer comprises applying anionic SBR
latex to the bituminous emulsion bonding layer.
37. The method of claim 1 where the step of destabilizing the
bituminous emulsion bonding layer occurs before, during, or after
the step of applying the bituminous emulsion bonding layer to the
existing surface, or a combination thereof.
38. A surface layer comprising: an existing surface; a destabilized
bituminous emulsion bonding layer applied to the existing surface;
and a bituminous mixture applied to the destabilized bituminous
emulsion bonding layer.
39. The surface layer of claim 38 where the bituminous mixture is
cold-applied bituminous mixture.
40. The surface layer of claim 38 where the bituminous mixture has
a thickness of less than 4.5 cm.
41. The surface layer of claim 38 where the bituminous mixture has
a thickness of less than 2.5 cm.
42. The surface layer of claim 38 where the destabilized bituminous
emulsion bonding layer comprises a bituminous emulsion and a
destabilization agent.
43. The surface layer of claim 42 where the destabilization agent
was applied to the bituminous emulsion within 15 seconds after the
bituminous emulsion was applied to the existing surface.
44. The surface layer of claim 42 where the destabilization agent
was applied to the bituminous emulsion within 5 seconds after the
bituminous emulsion was applied to the existing surface.
45. The surface layer of claim 42 where the bituminous emulsion is
a cationic emulsion and the destabilization agent is an anionic
surfactant solution or an alkali solution.
46. The surface layer of claim 42 where the anionic surfactant
solution is a sulfonate mixed with water.
47. The surface layer of claim 46 where the anionic surfactant
solution has a concentration of at least about 0.05% of a sulfonate
by weight of the water.
48. The surface layer of claim 45 where the alkali solution is
sodium hydroxide mixed with water at a concentration of at least
about 0.01% by weight of the water.
49. The surface layer of claim 42 where the bituminous emulsion is
an anionic emulsion and the destabilization agent is a cationic
surfactant solution or an acidic solution.
50. The surface layer of claim 49 where the cationic surfactant
solution is fatty acid imidazoline mixed with water.
51. The surface layer of claim 50 where the cationic surfactant
solution has a concentration of at least 0.05% of fatty acid
imidazoline by weight of the water.
52. The surface layer of claim 48 where the acidic solution is
acetic acid mixed with water at a concentration of at least about
0.01% by weight of the water.
53. The surface layer of claim 42 where the destabilization agent
is a sequestering agent.
54. The surface layer of claim 53 where the sequestering agent is
silica gel, chalk, clay-based desiccant, Portland cement, fly ash,
or combinations thereof.
55. The surface layer of claim 42 where the destabilization agent
is a surfactant that has a high cloud point, turbidity point, phase
inversion temperature, or combination thereof.
56. The surface layer of claim 42 where the destabilization agent
is a nonionic surfactant that becomes insoluble in water under
normal road surface temperatures.
57. The surface layer of claim 42 where the destabilization agent
comprises a polyoxyethylene group.
58. The surface layer of claim 42 where the bituminous emulsion is
a cationic emulsion and the destabilization agent is an anionic
bituminous emulsion utilizing a sodium salt of a fatty acid.
59. The surface layer of claim 42 where the bituminous emulsion is
a cationic emulsion and the destabilization agent is anionic SBR
latex.
Description
CROSS REFERENCE
[0001] Not Applicable.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This invention relates generally to a method of applying a
bituminous mixture to an existing surface, and more particularly,
but not by way of limitation, to a method of applying a bituminous
emulsion bonding layer and a thin layer of cold-applied bituminous
mixture to an existing surface by destabilizing the bituminous
emulsion bonding layer immediately before applying the bituminous
mixture.
[0004] 2. Description of the Related Art
[0005] It is often desirable to place a new layer on an existing
surface, such as a road, to improve the ride and serviceability of
the surface. The dominant materials of choice for the construction,
repair, and maintenance of roads are hot mix bituminous
mixtures.
[0006] Hot mix bituminous mixtures are generally produced in a
central location and transported to the application site. As any
hot bituminous products are transported, they lose heat. If the
temperature of a hot mix bituminous mixture becomes too low, the
mixture becomes difficult to handle and place and it becomes
difficult to achieve a durable surface. Thus, there are limits as
to how far hot mix bituminous mixtures can be transported.
[0007] Hot mix plants heat one or more aggregates to temperatures
generally in excess of 150.degree. C. Hot bituminous materials are
added to the aggregates and mixed. The resultant hot bituminous
mixture is transported to the road upon which it is to be applied.
The hot mix bituminous mixture may be additionally heated prior to
transportation to further elevate the temperature to account for
cooling that will inevitably occur during transportation. However,
there is an effective upper limit on mixture temperatures, either
due to the cost to heat the mixture or the degradation of the hot
bituminous product.
[0008] Areas beyond the maximum haul distances for hot mix
bituminous mixtures have few options for the construction, repair,
and maintenance of roads. One option is the use of cold-applied
bituminous mixtures, which utilize similar aggregates as those used
in hot mix bituminous mixtures, but preferentially use emulsified
binders. These cold-applied bituminous mixtures may be produced on
site for immediate use, obviating excessive haul distances.
[0009] Cold-applied bituminous mixtures utilize an aggregate system
generally known in the art. This aggregate system is mixed with a
suitable quantity of bituminous binder. The bituminous binder may
be either emulsified or solvent cut back. The bituminous emulsions
may also contain additives and/or solvents to increase the
workability or other desirable properties of the resultant mixture.
Cold-applied bituminous mixtures may be applied to a surface, such
as a road, by conventional equipment, including any mixture
application equipment known to those skilled in the art.
[0010] Cold-applied bituminous mixtures are much more difficult to
apply to a surface, such as a road, than hot mix bituminous
mixtures. A cold-applied bituminous mixture may have less lubricity
than a similar hot mix bituminous mixture, and may thus require
greater shearing forces to be suitably applied, as lower lubricity
requires higher shearing forces to handle and place the product. To
better utilize bituminous cold-applied mixtures, specialized
equipment has been developed to apply these stiffer mixtures. U.S.
Pat. No. 7,316,520 issued to Grubba on Jan. 8, 2008 describes a low
area shearing device better capable to apply cold-applied
bituminous products. Likewise, U.S. Pat. No. 6,543,962 issued to
Wells on Apr. 8, 2003 details an apparatus similar to traditional
paving screeds, but has the added capability of placing extra
pressure on the mixture, enabling better use of cold-applied
bituminous mixtures. The '520 patent and the '962 patent are
incorporated herein by reference.
[0011] Lubricity can be altered in cold-applied bituminous
mixtures. Generally, increasing amounts of solvent in the mixture
may increase lubricity and allow easier handling and placement. The
disadvantage to increasing solvent is that it results in a tender
mixture until a sufficient amount of solvent evaporates. Also,
solvent emissions produce a negative environmental impact.
Therefore, an ideal cold-applied bituminous mixture contains no
solvents.
[0012] Lubricity of the mixture may also be somewhat aided by the
utilization of very soft asphalts. Although handling and laydown
may be enhanced, however, the ultimate rheological properties of
the mixture may be compromised. The bituminous mixture may remain
soft and may push, shove, or rut while in service.
[0013] A bonding layer may be used to ensure an adequate bond
between the road surface and the cold-applied bituminous product.
Generally, a bituminous bonding layer is used to increase adhesion
between a road surface and the mixture to be applied. These
bituminous bonding layers may be applied hot, as solvent diluted,
or emulsified.
[0014] Bituminous emulsions are routinely used to bond bituminous
mixtures to the road. Typically, the bituminous emulsion bonding
layer is applied to a road and allowed to partially or completely
dry. This drying allows coalescence of the dispersed bituminous
component and eventually builds toughness of the layer. Next, the
mixture application equipment and support vehicles enter the
roadway to apply the bituminous mixture. The tires of these
vehicles tend to adhere to the bituminous bonding layer and
transport it to undesirable adjacent areas. This loss of bituminous
bonding layer may degrade the desirable bond between the surface
and the bituminous mixture.
[0015] A bituminous emulsion bonding layer tends to be extremely
slick or slippery when first applied to a roadway. In conventional
applications, the bituminous emulsion bonding layer is applied and
allowed to partially or completely dry before a bituminous mixture
is applied. The partially or completely dried bituminous emulsion
bonding layer provides sufficient adhesion to the road surface and
suitable internal cohesion whereby the placement of the bituminous
mixture is not hindered.
[0016] Specialized equipment has been developed to apply both a
bituminous product, like a bituminous emulsion bonding layer, as
well as a bituminous mixture. This concurrent application
eliminates any equipment or support vehicle tires from contacting
the bituminous bonding layer. One such device is described in U.S.
Pat. No. 5,069,578 issued to Bense et al. on Dec. 3, 1991, which
patent is incorporated herein by reference.
[0017] The apparatus of the '578 patent is better known as a spray
paver and has been used successfully with hot mix bituminous
mixtures for many years. The spray paver helps build a better bond
between the road surface and the bituminous mixture. A preferred
use of the '578 spray paver is the combination of a bituminous
emulsion bonding layer that is sprayed on the road surface
immediately before a hot bituminous product. The water-laden
bituminous emulsion bonding layer, when in contact with the hot
bituminous product, partially boils and builds a suitable adhesive
bond between the road surface and the bituminous mixture. However,
the apparatus of the '578 patent is not as successful with
cold-applied bituminous mixtures.
[0018] The '578 spray paver does not allow the bituminous emulsion
bonding layer to partially or completely dry before application of
the bituminous mixture, which is applied within five (5) seconds of
the application of the bituminous emulsion bonding layer. A hot
bituminous mixture will boil off some of the water in the
bituminous emulsion bonding layer and greatly accelerate the
cohesive build of the bituminous emulsion bonding layer, thereby
eliminating any application problems of the bituminous mixture. The
use of a cold-applied bituminous mixture with the '578 spray paver
is more problematic. The combination of the non-dried bituminous
emulsion bonding layer, which is very slick, and the cold-applied
bituminous mixture, which has lower lubricity, produces a situation
where the mixture has a propensity to slide on the bonding layer.
This slippage is a result of the high shearing forces required to
apply the cold-applied bituminous mixture and the low frictional
component of the slick bituminous bond layer.
[0019] To remedy this phenomenon, the thickness or weight of the
mixture is increased until no tearing occurs. Applying a greater
mixture layer thickness may increase the weight per unit area of
the cold-applied bituminous mixture, and this extra material
increases the normal force, resulting in a greater frictional
coefficient between the mixture and the bonding layer. There may be
a point where a sufficient amount of mixture is applied such that
the mix can withstand the shearing forces exerted by the
application equipment without slipping on the bonding layer and
creating tears in the surface. Thus, cold-applied bituminous
mixture may be successfully applied at high application rates, but
extra material is costly. As the application equipment attempts to
apply thinner and thinner layers of cold-applied bituminous
mixture, the mixture will tear as it slides on the slick bituminous
emulsion bonding layer. Increasing the thickness of the
cold-applied bituminous mixture is valuable for remote areas not
suitably served by central bituminous hot mix plants, but the cost
of the resulting surface is excessively high.
[0020] Additionally, when a cold-applied bituminous mixture is
applied while the bituminous emulsion bonding layer is not
sufficiently coalesced, the mixture may move under post placement
compaction. This pushing and shoving may produce a surface that is
not sufficiently dense and the desired thickness and smoothness may
be compromised.
[0021] Combining the '578 spray paver with either the '520 patent
or the '962 patent does not remedy the application inabilities. The
problem is a combination of the slick bituminous emulsion bonding
layer and the stiff cold-applied bituminous mixture, which tends to
slide on the slick bituminous emulsion bonding layer. Applying a
greater shearing force to the bituminous mixture only increases the
slippage and creates greater tearing of the cold-applied bituminous
layer.
[0022] Although the '578 patent discusses the use of the spray
paver with a bituminous emulsion bonding layer and cold-applied
bituminous mixtures, the only successful method to create such a
surface is to apply a sufficiently thick layer of the cold-applied
bituminous mixture. The drawback is the excessive amounts of
materials that are required to produce a paved surface that can be
applied without tearing, shoving, or sliding either during
application by a spray paver or by post placement compaction.
[0023] Based on the foregoing, it is desirable to utilize a spray
paver with a bituminous emulsion bonding layer and a cold-applied
bituminous mixture at minimal thickness without tearing, shoving,
or pushing of the layer.
SUMMARY OF THE INVENTION
[0024] In general, in a first aspect, the invention relates to a
method of applying a new surface to an existing surface. The method
comprises applying a bituminous emulsion bonding layer to the
existing surface; destabilizing the bituminous emulsion bonding
layer; and applying a bituminous mixture to the bituminous emulsion
bonding layer.
[0025] The step of destabilizing the bituminous emulsion bonding
layer may occur within 15 seconds or within 5 seconds of applying
the bituminous emulsion bonding layer to the existing surface. The
step of destabilizing the bituminous emulsion bonding layer may
occur before, during, or after the step of applying the bituminous
emulsion bonding layer to the existing surface, or a combination
thereof. The bituminous mixture may be a cold-applied bituminous
mixture. The bituminous mixture may be applied with a thickness of
less than 4.5 cm or less than 2.5 cm. The bituminous emulsion
bonding layer and the bituminous mixture may be applied with a
spray paver. The step of applying the bituminous mixture to the
bituminous emulsion bonding layer may occur within 5 seconds of the
step of applying the bituminous emulsion bonding layer to the
existing surface.
[0026] The bituminous emulsion bonding layer may be destabilized
with a destabilization agent and the destabilization agent may be
selected based on the bituminous emulsion bonding layer. The step
of destabilizing the bituminous emulsion bonding layer may be
achieved by counter ion attack, destabilization chemicals, pH
change, temperature change, precipitation of a surfactant system,
driers, chemical or physical dehydration, or HLB imbalance causing
phase inversion, and the like.
[0027] The bituminous emulsion bonding layer may be a cationic
emulsion and the step of destabilizing the bituminous emulsion
bonding layer may comprise applying an anionic surfactant solution
to the cationic emulsion. The anionic surfactant solution may have
a concentration that is increased to accelerate the step of
destabilizing the bituminous emulsion bonding layer. The anionic
surfactant solution may be a sulfonate mixed with water. The
anionic surfactant solution may have a concentration of at least
about 0.05% of a sulfonate by weight of the water.
[0028] The bituminous emulsion bonding layer may be a cationic
emulsion with a pH and the step of destabilizing the bituminous
emulsion bonding layer may comprise changing the pH of the cationic
emulsion. Changing the pH of the cationic emulsion may comprise
creating a destabilization solution by mixing an alkali in water.
The alkali may be sodium hydroxide at a concentration of at least
about 0.01% by weight of the water.
[0029] The bituminous emulsion bonding layer may be an anionic
emulsion and the step of destabilizing the bituminous emulsion
bonding layer may comprise applying a cationic surfactant solution
to the anionic emulsion. The cationic surfactant solution may have
a concentration that is increased to accelerate the step of
destabilizing the bituminous emulsion bonding layer. The cationic
surfactant solution may be fatty acid imidazoline mixed with water.
The cationic surfactant solution may have a concentration of at
least about 0.05% of fatty acid imidazoline by weight of the
water.
[0030] The bituminous emulsion bonding layer may be an anionic
emulsion with a pH and the step of destabilizing the bituminous
emulsion bonding layer may comprise changing the pH of the anionic
emulsion. Changing the pH of the anionic emulsion may comprise
creating a destabilization solution by mixing an acid in water. The
acid may be acetic acid at a concentration of at least about 0.01%
by weight of the water.
[0031] The bituminous emulsion bonding layer may be an anionic
emulsion with an anionic fatty acid salt and the step of
destabilizing the bituminous emulsion bonding layer may comprise
precipitating the anionic fatty acid salt with a divalent metal ion
in water solution. The divalent metal ion in water solution may be
at least about 0.01% Calcium Chloride by weight.
[0032] The bituminous emulsion bonding layer may comprise water and
the step of destabilizing the bituminous emulsion bonding layer may
comprise sequestering the water in the bituminous emulsion bonding
layer, rendering the bituminous emulsion bonding layer unstable.
Sequestering the water in the bituminous emulsion bonding layer may
comprise applying sequestering agents to the bituminous emulsion
bonding layer. The sequestering agents may comprise silica gels,
chalk, clay-based desiccant, Portland cement, fly ash, or
combinations thereof. The sequestering agents may be applied to the
bituminous emulsion bonding layer before, during, or immediately
after the application of the bituminous emulsion to the existing
surface.
[0033] The step of destabilizing the bituminous emulsion bonding
layer may comprise engineering a destabilization component into the
bituminous emulsion bonding layer. The destabilization component
may be a surfactant that has a high cloud point, turbidity point,
phase inversion temperature, or combination thereof. The
destabilization component may be a nonionic surfactant that becomes
insoluble in water under normal road surface temperatures. The
destabilization component may comprise a polyoxyethylene group.
[0034] The bituminous emulsion bonding layer may be a cationic
emulsion and the step of destabilizing the bituminous emulsion
bonding layer may comprise applying an anionic bituminous emulsion
utilizing a sodium salt of a fatty acid to the bituminous emulsion
bonding layer. The bituminous emulsion bonding layer may be a
cationic emulsion and the step of destabilizing the bituminous
emulsion bonding layer may comprise applying anionic SBR latex to
the bituminous emulsion bonding layer.
[0035] In a second aspect, the invention relates to a surface layer
comprising: an existing surface; a destabilized bituminous emulsion
bonding layer applied to the existing surface; and a bituminous
mixture applied to the destabilized bituminous emulsion bonding
layer. The bituminous mixture may be cold-applied bituminous
mixture. The bituminous mixture may have a thickness of less than
4.5 cm or of less than 2.5 cm.
[0036] The destabilized bituminous emulsion bonding layer may
comprise a bituminous emulsion and a destabilization agent. The
destabilization agent may be applied to the bituminous emulsion
within 15 seconds or within 5 seconds after the bituminous emulsion
was applied to the existing surface.
[0037] The bituminous emulsion may be a cationic emulsion and the
destabilization agent may be an anionic surfactant solution and/or
an alkali solution. The anionic surfactant solution may be a
sulfonate mixed with water. The anionic surfactant solution may
have a concentration of at least about 0.05% of a sulfonate by
weight of the water. The alkali solution may be sodium hydroxide
mixed with water at a concentration of at least about 0.01% by
weight of the water.
[0038] The bituminous emulsion may be an anionic emulsion and the
destabilization agent may be a cationic surfactant solution and/or
an acidic solution. The cationic surfactant solution may be fatty
acid imidazoline mixed with water. The cationic surfactant solution
may have a concentration of at least 0.05% of fatty acid
imidazoline by weight of the water. The acidic solution may be
acetic acid mixed with water at a concentration of at least about
0.01% by weight of the water.
[0039] The destabilization agent may be a sequestering agent. The
sequestering agent may be silica gel, chalk, clay-based desiccant,
Portland cement, fly ash, or combinations thereof. The
destabilization agent may be a surfactant that has a high cloud
point, turbidity point, phase inversion temperature, or combination
thereof. The destabilization agent may be a nonionic surfactant
that becomes insoluble in water under normal road surface
temperatures. The destabilization agent may comprise a
polyoxyethylene group. The bituminous emulsion may be a cationic
emulsion and the destabilization agent may be an anionic bituminous
emulsion utilizing a sodium salt of a fatty acid. The bituminous
emulsion may be a cationic emulsion and the destabilization agent
may be anionic SBR latex.
DETAILED DESCRIPTION OF THE INVENTION
[0040] The devices, compositions, and methods discussed herein are
merely illustrative of specific manners in which to make and use
this invention and are not to be interpreted as limiting in
scope.
[0041] While the devices, compositions, and methods have been
described with a certain degree of particularity, it is to be noted
that many modifications may be made in the details of the
construction and the arrangement of the elements and components
without departing from the spirit and scope of this disclosure. It
is understood that the devices, compositions, and methods are not
limited to the embodiments set forth herein for purposes of
exemplification.
[0042] In general, in a first aspect, the invention relates to a
method of applying a bituminous emulsion bonding layer and a thin
layer of cold-applied bituminous mixture to an existing surface by
destabilizing the bituminous emulsion bonding layer immediately
before applying the bituminous mixture. As noted above, it is
difficult to use a spray paver with cold-applied bituminous
mixtures because there is insufficient time for the bituminous
emulsion bonding layer to coalesce prior to application of the
cold-applied bituminous mixture, because the cold-applied
bituminous mixture must be applied thickly, and because the
cold-applied bituminous mixture has low lubricity, all of which
combine to produce slippage, tearing, shoving, and pushing. A
destabilizing agent, when appropriately applied to a bituminous
emulsion bonding layer, may sufficiently promote coalescence and
build adequate cohesive strength within the bonding layer to allow
for thinner application of cold-applied bituminous mixtures atop
the bonding layer when applied by a spray paver. The bituminous
mixture may have a resultant thickness of less than 4.5 cm,
preferably less than 3 cm, more preferably less than 2.5 cm, and
most preferably less than 1.5 cm. The type of destabilization agent
may be dependent on the properties of the emulsified bituminous
emulsion.
[0043] Examples of existing surfaces upon which the method may be
practiced include roads, streets, interstates, parking lots,
airport runways, airport taxiways, and the like. The existing
surfaces may be constructed of any material known in the art for
such types of surfaces, such as pavement, jointed Portland concrete
cement, and the like.
[0044] Bituminous emulsion bonding layers may be cationic, anionic,
zwitterionic, amphoteric, nonionic, and the like. Additionally, the
bonding layer may contain other additives suitable for use in
bitumen, such as polymers, cross-linking agents, vulcanization
agents, accelerators, extenders, fluixing agents, and the like. The
additives used for fabricating the bonding layer may be selected
based on the desired properties of the bonding layer. Suitable
polymers are described in U.S. Pat. No. 4,154,710 issued to
Maldonado et al. on May 15, 1979 and in U.S. Pat. No. 4,145,322
issued to Maldonado et al. on May 20, 1979, both of which are
hereby incorporated herein by reference.
[0045] The destabilization of a bituminous emulsion bonding layer
may be achieved in many ways, including but not limited to counter
ion attack, destabilization chemicals competing with the emulsion
surfactant system, pH change, temperature change, precipitation of
the surfactant system, the use of driers, chemical or physical
dehydration, HLB imbalance causing phase inversion, and the
like.
[0046] Cationic emulsions like CRS-2 are routinely stabilized with
a cationic surfactant like an amine. Cationic surfactants include
but are not limited to imids, amids, amidoamines, imidazolines, and
the like. These surfactants may be pH adjusted and/or salted with
an acid, including but not limited to hydrochloric acid, acetic
acid, phosphoric acid, and the like. These systems may owe their
ability to emulsify a bituminous material, in part or in whole, to
the pH adjustment or salting of the nitrogen group.
[0047] Anionic emulsions like RS-2P are routinely stabilized with
an anionic surfactant like salts of fatty acids. Anionic
emulsifiers include but are not limited to carboxylates, sulfates,
sulfonates, phosphates, and the like. These surfactants may be pH
adjusted and/or salted with an alkali, including but not limited to
sodium hydroxide, potassium hydroxide, and the like.
[0048] Zwitterionic or amphoteric surfactants exhibit both a
cationic and anionic functional group, and have the unique ability
to form either a cationic or anionic emulsion. Zwitterionic
surfactants include but are not limited to betaines, lecithin,
sultaines, and the like.
[0049] Nonionic emulsions are routinely stabilized with a nonionic
surfactant like ethoxylated nonylphenol. Anionic emulsifiers
include but are not limited to fatty alcohols, block co-polymers,
glycol ethers, and the like. These surfactants may be pH adjusted
with alkali or acid.
[0050] Pickering emulsions are a unique class of emulsions whereby
a solid creates a boundary between the oil phase (bitumen) and
water to stabilize the system.
[0051] A cationic emulsion may be destabilized by, but not limited
to, counter ion attack, pH change, the use of driers or dehydration
chemicals, and the like. Counter ion attack of a cationic
bituminous emulsion may be caused by applying an anionic surfactant
solution to the cationic emulsion. The concentration of the anionic
surfactant may be increased to accelerate the destabilization. A
non-limiting example comprises an anionic surfactant alkyl or aryl
sulfonate like dodecylbenzene sulfonate salt mixed in water to
create a destabilization solution. A sulfonate concentration of at
least about 0.05%, preferably at least about 0.2%, most preferably
at least about 1% by weight of the solution water is suitable to
destabilize a CRS-2P emulsion in an acceptable period of time.
Other types of anionic surfactants may achieve the same result. The
solution may be applied at a rate of 0.1% to 99% by weight of the
cationic emulsion. Alternately, changing the pH of a cationic
emulsion may cause destabilization. A non-limiting example
comprises an alkali mixed in water to create a destabilization
solution. Sodium hydroxide at a concentration of at least about
0.01%, preferably at least about 0.2%, most preferably at least
about 1% by weight of the solution water is suitable to destabilize
a CPS-2P emulsion in an acceptable period of time. Other types of
strong or weak alkali may achieve the same result. The solution may
be applied at a rate of 0.1% to 99% based on the weight of the
cationic emulsion. The destabilizing solution may be applied to the
bituminous emulsion bond layer within 15 seconds of the bond layer
being applied to a surface, more preferably within 10 seconds, most
preferably within 5 seconds.
[0052] An anionic emulsion may be destabilized by, but not limited
to, counter ion attack, precipitation, pH change, the use of driers
or dehydration chemicals, and the like. Counter ion attack of an
anionic cationic bituminous emulsion may be caused by applying a
cationic surfactant solution to the anionic emulsion. The
concentration of the cationic surfactant may be increased to
accelerate the destabilization. A non-limiting example comprises a
cationic surfactant fatty acid imidazoline mixed in water to create
a destabilization solution. A fatty acid imidazoline concentration
of at least about 0.05%, preferably at least about 0.2%, most
preferably at least about 1% by weight of the solution water is
suitable to destabilize a RS-2P emulsion in an acceptable period of
time. Other types of cationic surfactants may achieve the same
result. The solution may be applied at a rate of 0.1% to 99% by
weight of the anionic emulsion. Alternately, changing the pH of an
anionic emulsion may cause destabilization. A non-limiting example
comprises an acid mixed in water to create a destabilization
solution. Acetic acid at a concentration of at least about 0.01%,
preferably at least about 0.2%, most preferably at least about 1%
by weight of the solution water is suitable to destabilize a RS-2P
emulsion in an acceptable period of time. Other types of strong or
weak acids may achieve the same result. The solution may be applied
at a rate of 0.1% to 99% by weight of the anionic emulsion. Another
non-limiting example is the use of a divalent metal ion in a water
solution used to precipitate an anionic fatty acid salt that has
been used as a surfactant. An RS-2 emulsion emulsified with an
anionic fatty acid salt may be destabilized by a destabilization
solution containing at least about 0.01% Calcium Chloride by
weight, preferably at least about 0.10% Calcium Chloride, more
preferably at least about 0.25% Calcium Chloride, and most
preferably at least about 0.50% Calcium Chloride. The solution may
be applied at a rate of 0.1% to 99% by weight of the anionic
emulsion. The destabilizing solution may be applied to the
bituminous emulsion bond layer within 15 seconds of the bond layer
being applied to a surface, more preferably within 10 seconds, most
preferably within 5 seconds.
[0053] Those skilled in the art know that weak acids or bases would
require higher concentrations as compared to strong acids or bases.
Also, those skilled in the art know that, if quicker
destabilization is desired, higher concentrations of
destabilization agents, stronger destabilization agents, or higher
rates of destabilization solution will need to be applied, or
combinations of all three. Also, this is analogous to anionic and
cationic surfactants that have higher or lower ionic strength.
[0054] A universal solution to destabilizing most if not all
bituminous emulsion bonding layers is to sequester the water,
rendering the emulsion unstable. Sequestering agents include but
are not limited to silica gels, chalk, clay based desiccant,
Portland cement, fly ash, and the like. These destabilizing
materials may be applied to the bituminous emulsion immediately
before, during, or immediately after application of the bituminous
emulsion to the surface, as well as combinations of all three. A
non-limiting example is the application of a fine particle size
Bentonite clay powder at a rate of at least about 0.10%, preferably
at least about 0.25%, more preferably at least about 0.5%, and most
preferably at least about 1% by weight of the bituminous emulsion
bonding layer. The clay may be distributed into the emulsion as it
is sprayed onto the surface. The destabilizing material may be
applied to the bituminous emulsion bond layer within 15 seconds of
the bond layer being applied to a surface, more preferably within
10 seconds, most preferably within 5 seconds.
[0055] Destabilization component may be engineered into the
bituminous emulsion bonding layer. A surfactant that has a high
cloud point, high turbidity point, and/or high phase inversion
temperature (PIT) may be utilized as an internal mechanism for
destabilization. One non-limiting example is the use of a nonionic
surfactant that becomes insoluble in water under normal road
surface temperatures. Surfactants containing polyoxyethylene groups
are known in the art to have a distinct phase inversion temperature
(PIT). As the polyoxyethylene group increases in size, the PIT
increases. To build a destabilization technique into a bituminous
emulsion bonding layer, a nonionic surfactant with a suitably large
polyoxyethylene group may be chosen to produce the bituminous
emulsion. This emulsion may be stored at temperatures in excess of
the PIT. When the bituminous emulsion is applied, the lower
temperature of the road surface cools the emulsion quickly. Since
the PIT of the surfactant is chosen to be above the temperature of
the road surface, the surfactant destabilizes upon cooling, and the
bituminous emulsion becomes destabilized quickly upon
application.
[0056] Combinations of the foregoing may be sufficient to achieve
the destabilization of the bituminous emulsion bonding layer. As a
non-limiting example, an anionic bituminous emulsion utilizing a
sodium salt of a fatty acid could be used as a destabilizing agent
when applied to a cationic bituminous emulsion bonding layer like
CRS-2P. The anionic emulsion contains both free alkali and anionic
fatty acid salts, both of which would serve to destabilize the
CRS-2P.
[0057] Alternately, anionic SBR latex, which may be a dispersion of
a polymer in a potassium stearate, may be used as a destabilizing
agent for CRS-2P. Although the SBR latex contains polymer, it also
contains a potassium salt of a fatty acid and free alkali.
[0058] Although the destabilized bituminous emulsion bonding layer
is particularly useful when a cold-applied bituminous mixture is
applied by a spray paver, it is also useful when a warm-mix
bituminous mixture is utilized. Additionally, the use of a spray
paver is not necessary. The destabilization technique is equally
valid when the bituminous emulsion bonding layer is not drying or
coalescing sufficient quickly, regardless of application technique.
This is quite possible when the ambient environment is cold and/or
humid, thus slowing if not preventing drying and/or coalescence of
the bituminous emulsion bonding layer.
Example 1
[0059] A test trial was executed on the US 150 access road in
Deanville, Ill. The existing bituminous surface was milled to the
existing concrete surface. Two cold-applied bituminous mixtures
were produced using a CM-150 bituminous product and mixed in a pug
mill. One bituminous mixture used a 15 mm crushed limestone
aggregate and the second used a 9.5 mm crushed limestone aggregate.
The bituminous mixtures were independently brought to a spray paver
for application. A bituminous bonding layer was applied at about
1.17 L/m.sup.2 by the spray paver. The bituminous mixture followed
approximately one (1) second after the application of the emulsion.
The bituminous mixtures were successfully applied, but had to be
applied at about 100 kg/m.sup.2 or about 5.5 cm to 6 cm thick.
Example 2
[0060] Another test trial was conducted utilizing the
destabilization technique on Emke Road between Highway 94 and
Augusta Bottoms Road in Missouri. The bituminous emulsion bonding
layer was an RS-2P emulsion as per MoDOT specifications and was
applied between 1.08 L/m.sup.2 and 1.26 L/m.sup.2 by a spray paver.
The RS-2P was produced utilizing a surfactant system comprising
tall oil fatty acids salted with sodium hydroxide. A precipitation
method was chosen to destabilize the anionic emulsion. A
destabilizing agent was produced by mixing calcium chloride in
water to create a solution that was about 1.15% anhydrous Calcium
Chloride based on the weight of the total solution. This
destabilization solution was applied within 1 second of the RS-2P
to destabilize the anionic bituminous emulsion at a rate of
approximately 0.060 L of destabilization solution per liter of
bituminous emulsion or about 6.0% destabilization solution by
weight of the anionic emulsion. Two cold-applied bituminous
mixtures were produced by mixing a cationic emulsion CMS-150 with
aggregates as seen in Table 1. These mixtures were brought to a
spray paver for application on the road. The mixtures were applied
to the destabilized RS-2 within about one (1) second after the
bituminous emulsion application. Both mixtures were applied
successfully at about 35.4 kg/m.sup.2 to 45.0 kg/m.sup.2 or about
1.58 cm to 2.01 cm thick. The applications were successfully
applied without either mixture sliding on the destabilized
bituminous emulsion. Also, post-placement compaction with a rubber
tire roller did not experience sliding or pushing of the
mixtures.
TABLE-US-00001 TABLE 1 Aggregate Gradations Sieve Size Open-Graded
Gap-Graded 19 mm 100 100 12.5 mm 100 99.8 9.5 mm 95.5 97.6 4.75 mm
14.6 15.7 2.36 mm 2.6 4.6 1.18 mm 2.4 3.6 .6 mm 2.3 3.0 .3 mm 2.2
2.7 .15 mm 2.1 2.6 .075 mm 1.9 2.3 all in percent passing
[0061] From the above description, it is clear that the present
invention is well adapted to carry out the objects and to attain
the advantages mentioned herein, as well as those inherent in the
invention. While the devices, compositions, and methods have been
described for purposes of this disclosure, it will be understood
that other and further modifications, apart from those shown or
suggested herein, may be made which are accomplished within the
spirit and scope of the invention disclosed and claimed.
* * * * *