Note: Descriptions are shown in the official language in which they were submitted.
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PFSI-2 1 ,855
IN THE UNITED STATES PATENT AND TRADEMARK OF~ICE
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COMPOSITION AND METHOD FOR SEALING POTHOLES ~ - -
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BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to the repair of potholes in asphaltic pavement or
concrete roadways, and more particularly, to a compositi~n and method for
effectively sealing the bottom and sides of potholes when they are patched.
5 2. Description of Related Art
Potholes are often created when water that has seeped or otherwise
penetrated beneath the surface of a roadway softens the underlying base. When
the roadway is subjected to vehicular traf~lc, the pressure exerted on the roadway
due to the weight of the vehicles is transferred to the softened suppor~ layer.
10 Because the subsurface water permeating the base is incompressible, it is forced
upward through cracks in the roadway as the support layer compresses, and the
hydraulic pressure thus created ~urther erodes the pavement or concrete, leadingto localized structural failure and collapse.
With conventional pothole patching compositions and methods, patching
15 material is packed into the pothole. Depending upon the type and quality of the
patching material used, however, further water seepage and ~he hydraulic
pressure associated with repeated compression cycles due to vehicular traffic are ~ -
likely to either erode the patching material or erode the edges of the former
pothole around the patching material. In either case, the pothole typically
20 reappears at the same location some time afterward, and is often larger than
befiore. Tn many instances potholes are patched repeatedly over a period of years
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until the roadway is so degraded that resurfacing, repaving or reconstruction isrequired.
Prior art compositions~ methods and devices said to be useful for repairing
pavement and potholes are disclosed, for example, in United St~tes Patent Nos.
3,891,585; 3,919,148; 3,930,100; 4,069,182; 4,113,401; 4,744,693; ~,781,490;
and 5,092,706.
Patent Nos. 3,891,585; 3,930,100; 4,069,182 and 4,113,401 generally
relate to elastomeric pavement repair compositions that are formulated using
paving grade asphalt, commercially processed reclaimed rubber (including tire orinnertube rubber) and aggre~ate. The use of asphalt-con~aining rubber in such
high percentages and temperatures as to cause jelling in the formation of a
completely elastic mixture when heated, is said to be unique in its ~ormulation
and its application for pavement repairs.
IJ.S. 3,919,148 discloses an elastomeric pavement patch material prepared
from a hot asphalt-rubberjelly composition that is mixed with a predetermined
amount of a compatible solvent to form an elastomeric material having a
predetermined viscosity. The addition of the solvent lowers the viscosity of thecomposition and permits its application with existing equipment. The material
can be applied, worked on and covered with chips for up to an hour after its
application. When the material begins to set up, it sets up at a very rapid rate,
which is independent of the evaporation of the solvent. The reclaimed rubber
used in the invention can be prepared from reclaimed tires, tire scrap, innertube
scrap, retread scrap, tire peel, tire carcass and other rubber scrap.
U.S. 4,781,490 discloses a pothole repair method in which an aqueous
2S solution of a water soluble acid s~lt of an amine compound is applied to the
pothole area prior to filling it with an asphaltic concrete patch.
IJ.S. 5,092,706 discloses heating and drying a pothole (liquid spray
followed by hot air blower or gas flame burner); spraying a composite tack
(which can include polymeric mixtures but must include a lossy microwave
material) into the pothole at a thickness of approximately 1/16 inch; filling the
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pothole with asphalt patch material and thereafter microwaving the patch to ~ -
produce a strong interface bond.
Flame spray technology, used in the method of the inven~ion, is previously
known within the industrial coating art but ~o applicant's knowledge has not
S previously been used for the application disclosed herein.
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SUMMARY OF THE INVl~NTION
According to the present invention, a composition and method are
disclosed for repairing potholes through the use of flame spray technology, and
more particularly, through the use of flame sprayed thermoplastic coatings to seal
5 the interior and surrounding edges of potholes prior to patching the potholes with
conventional materials. Applicant has discovered that by sealing the interior and
adjacent surfaces of a pothole with a layer of flame sprayed thermoplastic
material prior to refilling the pothole with a patching material, a seal is produced
that prevents or significantly impedes the inward migration of moisture through
the affected area and also the erosion that occurs when subsurface moisture is
forced toward the surface under pressure due to vehicular traffic on a roadway.
According to one embodiment of the invention, potholes are first cleaned
to remove chunks of debris, dried to remove excess moisture, and then sealed
with a flame sprayed coating of a thermoplastic resin such as, for example, an
ethylene ac;d copolymer like ethylene methacrylic acid ~EMAA) copolymer,
preferably having a melt index in the range of ~rom about 10 to about 500.
According to another embodiment of the invention, particles of ground rubber
from recycled tires are mixed with the sealing material prîor to flame spraying.The thermoplastic resin is preferably flame sprayed into the pothole to
form a continuous sealing layer having a thickness ranging from about 30 to
about 40 mils, which desirably serves as a pliable but moisture impervious
membrane within and immediately surrounding the pothole.
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13RIEF DESCRIPTION QF THE DRAWINGS
The apparatus of the invention is ~urther described and explained in
relation to the following figures of the drawings wherein:
FIG. 1 is a simplified cross-sectional elevation view of a pothole in a
5 paved roadway;
FIG. 2 is an enlarged cross-sectional detail view of the pothole of FIG. 1
after it has been cleaned and sealed with a flame sprayed layer in accordance with
the method of the invention and before the patching material is added; and . :~
FIG. 3 is a simplified cross-sectional elevation view of the pothole of FIG.
1 after the pothole is sealed and patched in accordance with the method of the
invention.
Like reference numerals are used to indicate like parts in all figures of the
drawings.
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~ESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to FIG. 1, paved roadway 10 is depicted as having concrete
layer 12 disposed over subsurface soil layer 14. Potho]e 16 defined by interior
walls 18 has formed in paved roadway 10, and extends downward]y through
S concrete layer 12 into subsurface soil layer 14. Broken chunks 20 of pavement
are shown in the bottom portion of pothole 16. It shou]d be understood that
whi]e paved roadway 10 is depicted as a simple two layer construction ~or eaise of
illustration, the invention is likewise applicable to potholes in other pavementconstruction that may include a plurality of subsurface layers, different pavingmaterials, steel reinforcing bars, or the like. Thus, for example, the composition
and method of the invention are likewise suitable for repairing potholes in asphalt
pavement. Similarly, whi]e roadways are the most common location in which
potholes occur, it will be apparent upon reading this disclosure that the
composition and method of the invention are likewise applicable to potholes in
other paved surfaces such as airport runways or the like.
According to the method of the invention, loose debris such as broken
chunks 20 shown in PIG. 1 are desirably removed from pothole 16, and any
standing water is also removed by any suitable conventional means. Once any
standing water has been removed from pothole 16, interior walls 18 are desirablyfurther dried by use of the flame from a flame spray gun prior to starting the
flow of thermoplastic powder as disclosed, ~or example, in U.S. Patents Nos.
4,632,309 or 4,934,595, which are incorporated by reference herein. ~ ;
Referring to FIGS. 2 and 3, once pothole 16 is free of loose debris and
excess moisture, it is preferably sealed by flame spraying a thermoplastic resincoating over interior walls 18 and the edges of the pavement surface surroundingthe pothole. The thermoplastic resin is preferably supplied to the flame spray
gun in a finely divided particulate form, most preferably entrained in a flow of
air. Preferred thermoplastic resins for use in the method of the invention
comprise a major portion of an olefinic copolymer containin~g a carboxyl group
and having a very low viscosity ae the melting point. ParticlJlarly pre~erred
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thermoplastic resins for use in the invention are ethylene acid copolymers having
a melt index ranging from about 10 to about 500, most preferably ethylene
methacrylic acid (EMAA) copolymer. The thermoplastic resin is preferably
flame sprayed into pothole 16 and over the surrounding edges 28 to a thickness
5 ranging from about 30 to 40 mils, although it will be appreciated that the
thickness of sealing layer 22 can vary according to factors such as the polymer
used, the texture and type(s) of material present in interior walls 18, the type of
patching material to be utilized, and the like. Applicant has discovered that a
flame sprayed coating of a polymer such as EMAA provides a seal within pothole
16 that is substantially impervious to the further migration of water through the
pothole.
In addition to the preferred thermoplastic polymer, it will be appreciated
by those of ordinary skill in the art that minor effective amounts of other
materials utilized in mixing or compounding flame sprayable thermoplastic resinscan also be included within the scope of the present invention. A particularl~
preferred EMAA copolymer suitable for use in the method of the invention is
commercially available from Plastic Flamecoat Systems, Inc. under the tradename
PFS-113. EMAA copolymer is preferred for use in the method of the invention
because of its excellent adhesion in addition to its function as a moisture barrier.
According to one preferred embodiment of the invention, visible in FIG.
3, particles 26 of recycled tire rubber can optionally be mixed into the
thermoplastic powder that is flarne sprayed into pothole 16. The use of recycledtire rubber is not required, but in the preferTed composition of the invention,
serves the two-fold purpose of reducing the needed quantity of the more
expensive thermoplastic resin while simultaneously providing a beneficial end use
for recycled tires.
Sealing layer 22 cools quickly when applied to the interior of pothole 16,
and according to the method of the invention, a conventional pothole patching
material 24 such as an asphalt-aggregate mixture is then placed and compacted
into pothole 16 over seaiing layer 22. (In FIG. 3 only a portion of pothole
patching material 24 is shown for ease of illustration.)
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Pothole repairs made in accordance with the method of the invention
demonstrate significantly improved service life and resistance to washout,
enlargement or further structural collapse.
Other alterations and modifications of the invention will likewise become
5 apparent to those of ordinary skill in the art upon reading the present disclosure,
and it is intended that the scope of the invention disclosed herein be limited only
by the broadest interpretation of the appended claims to which the inventor is
legally entitled.
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