Apparatus and method for transporting heated pavement repair materials

A portable apparatus is shown for transporting heated pavement repair materials. The apparatus has a heat chamber with an enclosed interior. A mixing chamber is contained within the enclosed interior of the heat chamber and has an inlet for receiving pavement repair materials and an outlet for discharging mixed and heated product. Either a dry radiant heat source or a liquid heat transfer source can be utilized to heat the mixing chamber. The apparatus is used to dispense a pavement repair material which is aggregate free, which does not require compaction and which is self-leveling.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates generally to truck and/or trailer mounted 
portable devices and methods for dispensing pavement repair materials. 
2. Description of the Prior Art 
In the past, as many as three vehicles were sometimes needed to repair 
openings and potholes in asphalt, concrete and other roadway surfaces. One 
vehicle provided an air compressor for use with various pneumatic repair 
tools which were used to dress the hole, crack or cavity to be filled. 
Another vehicle contained liquid asphalt tack material which would be 
sprayed into the dressed cavity, and a third vehicle would deliver asphalt 
mix material to the cavity. The asphalt would then be packed, compacted 
and leveled by hand to complete the repair. 
U.S. Pat. No. 4,196,827, issued Apr. 8, 1980, entitled "Portable Machine 
For Transporting Heated Asphalt Products For Use In Repairing Asphalt 
Pavement" shows a portable machine which was designed to incorporate all 
phases of the pavement repair into one mobile unit. The machine has a 
hopper for transporting asphalt mix, and a reservoir below the hopper 
having a heat source. The reservoir contained liquid asphalt tack 
material. The heat source is used to heat the liquid tack material, and 
the tack material is used to heat the asphalt mix in the hopper by heat 
transfer. Asphalt tack material is also dispensed from the tack material 
tank by means of spray equipment connected to a discharge valve on the 
rear of the truck. 
In spite of being less expensive to operate in terms of material and labor, 
the previously described device possessed several different disadvantages. 
Many of these disadvantages related to the type of repair material 
utilized and the fact that multi-component materials were required to do 
each job. Because multiple component materials were required for each 
patch job, the equipment used for transporting such components was 
complicated and often limited in versatility. For example, the liquid 
asphalt tank carried on the unit was suitable for road oils and cutbacks 
but was not well suited for use with asphaltic cements. Also, in the case 
of the device described in the '827 patent, the liquid asphalt tank was 
not suited for use with asphalt emulsions, because the volatile contents 
of the emulsions would be driven off and dry out the materials. 
U.S. Pat. No. 4,944,632, issued Jul. 31, 1990, and assigned to the assignee 
of the present invention showed a portable unit with a separate tack oil 
tank which was provided with its own heat source and which was designed to 
prevent phase separation of the tack oil materials. While this apparatus 
solved the problem of tack oil phase separation, it was still designed to 
be employed in a multi-component repair system. 
The present invention has as its object to provide a portable apparatus for 
dispensing a new type of pavement repair material which eliminates many of 
the shortcomings present in the prior art devices and methods. 
Another object is to provide an improved pavement repair process utilizing 
a class of repair material which eliminates the need for more complicated 
multi-component asphaltic repair materials, as well as the need for 
complicated tank, heating and valving arrangements. 
Another object of the invention is to provide a apparatus for use in such a 
method which is simple in design and economical to manufacture. 
SUMMARY OF THE INVENTION 
The portable apparatus of the invention is used to transport heated 
pavement repair materials for use in repairing roadways. The apparatus 
includes a heat chamber with an enclosed interior. A mixing chamber is 
contained within the enclosed interior of the heat chamber. The mixing 
chamber has an inlet for receiving pavement repair materials and an outlet 
for discharging mixed and heated product. Selectable and diverse heating 
sources are located within the heat chamber for heating the mixing 
chamber. The selectable and diverse heating sources include both a dry, 
radiant heat source and a liquid heat transfer source. 
Preferably, the dry, radiant heat source is at least one burner fired 
retort tube located in the heat chamber and at least partly surrounding 
the mixing chamber. The liquid heat transfer source can be a heat transfer 
oil located in the heat chamber and at least partly surrounding the mixing 
chamber, the heat transfer oil being heated by the heat transferred from 
the burner fired retort tube. 
In a preferred embodiment of the invention, the mixing chamber is generally 
cylindrically shaped and has a hydraulically powered mixing shaft 
centrally located therein. The hydraulically powered mixing shaft extends 
along a central horizontal axis of the mixing chamber and has a plurality 
of mixing paddle arms which extend outwardly from the shaft generally 
perpendicular thereto. Each paddle arm terminates in a paddle head which 
forms a V-shaped surface generally normal to the axis of the paddle arm. 
The choice of the heat source for heating the mixing chamber is made based 
upon the application temperature of the pavement repair material being 
utilized. The new type repair materials which are preferred for use in the 
present method have an application temperature in the range from about 150 
to 210.degree. C. Once heated and mixed, these materials can be dispensed 
from the mixing chamber through the outlet thereof without first applying 
a tack oil. The new materials also do not generally require mixing stone 
aggregate with an asphaltic binder in the mixing chamber. No compaction of 
the pavement repair material is generally necessary and the material is 
self-leveling. 
Additional objects, features and advantages will be apparent in the written 
description which follows.

DETAILED DESCRIPTION OF THE INVENTION 
Turning to FIG. 1, there is shown a portable device for transporting 
pavement repair materials of the invention designated generally as 11. The 
apparatus 11 includes a body 13 which is generally rectangular, as viewed 
in FIG. 1. The additional components of the apparatus 11 are mounted upon 
a skid 14 which is adapted to be mounted upon the bed of a truck, or upon 
a trailer which would be towed by a vehicle or other transport means. The 
truck or trailer would serve as a portable base for transporting the body 
13 and skid to a repair site for repairing a pothole in an asphalt or 
concrete pavement. A pair of running lights 16, 18 are mounted at the rear 
of the body 13. 
As best seen in FIGS. 1-3, the portable apparatus 11 includes a heat 
chamber 15 having an enclosed interior 17 and a fill port 90 for receiving 
a heat transfer oil. As best seen in FIG. 3, a layer of insulating 
material 19 generally surrounds the enclosed interior 17 with the 
exception of the area adjacent the fill port 90. The insulating material 
can be refractory, or any material commercially available for this 
intended purpose and capable of insulating for temperatures in the range 
of about 150-210 degrees C. 
A generally cylindrical mixing chamber 21 is supported in stationary 
fashion within the heat chamber 15 and has an inlet (27 in FIG. 3 and 5) 
or fill chute and an outlet which communicates with the discharge chute 23 
(FIG. 2) of the device. The main inlet 27 receives the new pavement repair 
feed stock, as will be more fully described. The mixing chamber thus has 
an inlet for receiving pavement repair materials and an outlet for 
discharging mixed and heated product. The mixing chamber exterior surface 
22 can be coated with a black paint or carbon black containing pigment to 
facilitate the absorption of heat. 
The mixing chamber 21 is shown in isolated fashion in FIG. 4. The 
stationary, generally cylindrically shaped chamber has a hydraulically 
powered mixing shaft 29 centrally located therein along a horizontal axis 
31. The hydraulically powered mixing shaft has a plurality of mixing 
paddle arms 33 (in this case 7 arms) which extend outwardly from the shaft 
29 generally perpendicular thereto and are generally equidistantly spaced 
along the shaft. Each paddle arm 33 terminates in a paddle head 35 which, 
as shown in FIG. 4, forms a V-shaped surface with sides 37, 39 generally 
normal to the axis 41 of the paddle arm 33. The mixing shaft is of the 
gear type and is driven through a gear reduction box 43 and hydraulic 
output shaft 91, the gear box having an approximately gear ratio of 5.29 
to 1.0. The torque rating capacity is approximately 3.189 foot/pounds. The 
hydraulic motor 93 used to drive the shaft is a 22 cubic inch, 6 gpm motor 
rated to operate at 2,000 psi. The hydraulic system is independently 
powdered by a 14 horsepower commercially available diesel engine 48 (FIG. 
1). 
A selectable and diverse heating source is located within the heat chamber 
15 for heating the mixing chamber. The selectable and diverse heating 
sources include both a dry, radiant source and a liquid heat transfer 
source. 
The dry, radiant heat source is preferably a burner fired retort tube 
located within the heat chamber 15 and at least partly surrounding the 
mixing chamber. In the embodiment of FIG. 3, a pair of burner fired retort 
tubes 45, 47 are located within the interior of the heat chamber 15. Each 
retort tube includes an inlet 46, 49 and an outlet 51, 53 which is routed 
to the vertical exhaust stacks 55, 57 mounted on the exterior of the 
apparatus. Each of the retort tubes 45, 47 is equipped with a commercially 
available 2,000,000 BTU retort tube propane, diesel or natural gas burner. 
The fuel source shown in FIGS. 1 and 2 comprises a plurality of propane 
bottles 52, 54, 56 mounted on the skid 14. The burners are 
thermostatically controlled and regulated at 10 psi. The ignition system 
for the burners is a 12 volt DC source with electronic igniters. The 
system can also be equipped with a shut-off system on loss of flame or 
excessively high temperatures. A metallic heat shield 50 is located below 
the retort tubes 45,47 and generally encloses the retort tubes within the 
heat chamber, focusing radiant heat in the direction of the mixing chamber 
21. 
In addition to the retort tube heaters, the apparatus also features a 220 
volt, 54.75 kw electric immersion heater 59. Electricity used to power the 
electric heater 59 is supplied from a 220 volt stationary electric outlet 
or by a 6,000 watt on board generator. Commercially available temperature 
gages (82, 84 in FIG. 7) are used to constantly monitor the temperature of 
the heat chamber and the mixer chamber. 
The liquid heat transfer source can be provided by optionally filling the 
enclosed interior 17 of the heat chamber thru fill port 18 with a heat 
transfer oil whereby the heat transfer oil is heated by heat transferred 
from the burner fired retort tubes 45, 47 and/or by the electric heater 
59. A circulating pump (62 in FIG. 2) of conventional design can be used 
to circulate the heat transfer oil within the enclosed interior of the 
heat chamber to prevent stratification of the oil within the chamber. 
Thus, depending upon the pavement repair material being mixed in the 
mixing chamber 21, an operator can elect to employ merely dry, radiant 
heat obtained from the retort tubes 45, 47 in an otherwise empty heat 
chamber interior, or the operator can at least partly fill the chamber 
with heat transfer oil and thereby utilize a liquid heat transfer source 
to heat the mixing chamber. 
The apparatus of the invention also utilizes a new class of pavement repair 
materials. These materials are commercially available as "ROADPATCH", 
"ROADFLEX" and "HOTCRETE" from Roadtechs, Inc., 2323 Commerce Center 
Drive, Rockville, Va. The commercial specifications for each product are 
described briefly below: 
ROADPATCH Materials Test Specifications 
Technical Data 
______________________________________ 
Color Black or concrete colored 
Form Solid 
Specific Gravity 2.0 
Application Temperature 
150-200 degrees 
Centigrade 
Maximum Safe Heating 
210 degrees Centigrade 
Temperature 
Surface Applications 
All concrete and asphalt 
surfaces 
Application Thickness 
75 mm plus 
Curing Time 10-60 min., depending on 
ambient air temp. 
Shelf Life Unlimited 
Packaging 3-ply silicon lined paper 
bags (50 lb.) 
Flash Point 250 degrees Centigrade 
______________________________________ 
ROADPATCH is a hot poured repair material with a 10-14% bitumen content 
containing polymers and grated fillers which produce an impermeable, 
voidless mass solid at ambient temperatures. The material is formulated to 
be utilized as a one repair material on both concrete and asphalt 
surfaces, including bridge decks. It is primarily intended to be utilized 
for asphalt repairs but can be utilized for concrete repairs as well. 
Surface preparation is minimal. Once the material has set up, it forms an 
impermeable seal to the adjacent material that is impervious to water and 
chemical intrusion. The material is self-leveling and requires no 
compaction to remain in place. The natural adhesive properties of the 
material ensure that it will adhere to the repair area without any type of 
preliminary tack coat for asphalt repairs. The material can be re-heated 
and applied with no adverse results and minimal cure time is required. 
ROADFLEX Material Testing Methods 
Technical Data 
______________________________________ 
Color Black or concrete colored 
Form Solid 
Specific Gravity 1.8 
Application Temperature 
150-200 degrees 
Centigrade 
Maximum Safe Heating 
210 degrees Centigrade 
Temperature 
Surface Applications 
All concrete and asphalt 
surfaces 
Application Thickness 
10 mm plus 
Curing Time 10-60 min., depending on 
ambient air temp. 
Shelf Life Unlimited 
Packaging 3-ply silicon lined paper 
bags (50 lb. capacity) 
Flash Point 250 degrees Centigrade 
______________________________________ 
ROADFLEX is a hot poured repair material with a 20-25% bitumen content 
containing polymers and grated fillers that produces an impermeable, 
voidless mass solid at ambient temperatures. It is formulated to be 
utilized as a one repair material on both concrete and asphalt surfaces, 
including bridge decks. The ROADFLEX material has the ability to be 
utilized over movement joints such as expansion joints in concrete, 
reflective cracking in concrete and asphalt, etc. 
HOTCRETE Material Testing Specifications 
Technical Data 
______________________________________ 
Color Gray (concrete colored) 
Form Powder until heated and 
applied 
Specific Gravity 2.0 
Application Temperature 
180-210 degrees 
Centigrade 
Maximum Safe Heating 
220 degrees Centigrade 
Temperature 
Surface Applications 
All concrete surfaces, 
including bridge decks 
Application Thickness 
8-10 mm plus 
Curing Time 10-20 min., depending on 
ambient air temp. 
Shelf Life Unlimited 
Packaging polypropylene bags (50 
lbs.) 
Flash Point 220 degrees Centigrade 
______________________________________ 
HOTCRETE is a hot poured polymer modified hydrocarbon resin binder with 
grated fillers. It produces an impermeable, voidless mass that is solid at 
ambient temperatures. It is formulated to be utilized as a one repair 
material on concrete surfaces, including bridge decks. It can be utilized 
over movement joints such as expansion joints in concrete. It is 
recommended that a concrete primer be utilized over the damaged area prior 
to applying HOTCRETE. The primer hinders the intrusion of water into the 
repair from below and enhances the adhesion properties of the material. 
These materials include an asphaltic binder, as did the prior art 
materials, but also include a synthetic, polymeric component. The pavement 
repair materials used in the method of the invention do not require a 
separate aggregate stone mixing step, do not require a compaction step, 
and are self-leveling. Yet, the materials are compatible with the asphalt 
or concrete pavements and stand up to demanding conditions of even heavily 
travelled interstate highways and city streets. 
In operation, the asphaltic/polymeric binder material selected for the 
intended application can be added directly to the mixing chamber of the 
device through the material-loading chute (27 in FIG. 2) at the top of the 
unit. The material is allowed to heat adequately with constant agitation, 
the intended application temperature being between about 150 to 210 
.degree. C., preferably about 165-195.degree. C. The temperature is 
controlled to ensure that the material is never heated above about 
210.degree. C. 
The pothole, crack, or other road surface imperfection is then prepared by 
cleaning the area of loose debris with a commercially available gas/air 
lance. A pavement breaker can be utilized to prepare the hole or remove 
any large debris. A pavement saw can also be utilized to shape the pothole 
if required. 
If the repair is to made in concrete, it is generally advisable to coat the 
application area with a suitable concrete primer. The concrete primer 
should have a minimum penetration into the concrete of 2-5 mm and have a 
rapid curing rate. Any primer can be utilized which is compatible with the 
pavement repair materials previously described. No primer is needed for 
asphalt repairs. 
The pavement repair material is then dispensed from the mixing chamber 
through the outlet chute into the repair area. For deep repairs, it may be 
necessary to "bulk out" the repair area by first placing a layer of clean, 
dry aggregate onto the application surface and then adding the pavement 
repair material. The "bulk out" process will increase the compressive 
loading capacity of the ultimate repair. 
The material can be smoothed with a smoothing/leveling iron to ensure 
adequate coverage into all crevices and cracks. The leveling irons are 
preferably stored in a heated storage compartment when not in use. No 
compaction equipment is necessary and the material is also self leveling 
after being initially smoothed. 
A dressing of 2 mm to 6 mm clean, dry and heated aggregate can be applied 
to the surface of the completed patch for enhanced traction if desired. 
The aggregate should be heated prior to application to the asphaltic 
binder material by utilizing a heated mixer drum. The aggregate drum can 
be heated with the gas/air lance utilized for preparing the application 
surface. Water can be applied to the surface of the repair material after 
it is in place to speed the curing time, if necessary. Water can be 
applied by means of a mist or spray applicator. 
For repairing longitudinal cracks in concrete or asphalt pavements, the 
cracks should generally first be milled out using a hydraulically powered 
cold planar. For example, a crack is typically milled to a depth of 3/4 
inch to 1 inch and shall be milled out a maximum of 4-6 inches on both 
sides of the crack itself. After the milling of the crack has been 
completed, the crack is cleaned using, for example the gas/air lance. The 
cleaned repair area should then be coated with a suitable primer, as 
previously described, for concrete surfaces. No primer is required for 
asphalt crack repairs. The pavement repair material which has been heated 
in the mixing chamber is then applied to the area, for example, by using a 
screed box. A finish application of 2-6 mm of heated, clean dry aggregate 
can be applied to the surface of the binder material if desired. 
An invention has been provided with several advantages. The apparatus of 
the invention provides a convenient means for heating a new class of 
roadway repair materials. The unique mixing chamber is heated by either a 
dry, radiant source or a liquid heat transfer source. A unique paddle 
arrangement on the mixing shaft provides enhanced mixing. The device is 
much simpler in design and more economical to manufacture than prior art 
devices of the same general type. The new pavement repair material which 
is dispensed by the apparatus does not require a separate aggregate stone 
mixing step, does not require compaction and is self-leveling. Old asphalt 
debris removed from the pothole work surface can be loaded back into the 
mixing chamber of the device, reheated and broken down so as to blend with 
the material being heated in the chamber. In this way, old asphalt 
materials from the work surface can be recycled and reused. 
While the invention has been shown in only one of its forms, it is not thus 
limited but is susceptible to various changes and modifications without 
departing from the spirit thereof.