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Pothole Patchers Demonstrated in Californiaby R. Clayton SlovenskyNothing can mess up an automobile wheel alignment and a motorist's disposition quite as quickly as a "good" pothole. Perhaps, we should say a big pothole because there's no such thing as a good pothole, and that's why state and local highway agencies throughout the county spend millions of dollars every year to fill and repair potholes.
And that's why, when the California Department of Transportation (Caltrans)
indicated an interest in observing a demonstration of pothole patching
technologies, particularly spray-injection techniques, as evaluated under
the Strategic Highway Research Program (SHRP) and when Caltrans offered
a real-world demonstration site, complete with traffic control, the California
Division Office of the Federal Highway Administration (FHWA) mounted a
full-scale blitz to secure commitments from the vendors, arrange a meeting
room near the site, send invitations, coordinate the support activities,
and co-host the event with Caltrans. The vendors responded well to the
challenge to "show off their wares" because this was an ideal opportunity
to provide a comparison among equipment and materials and to introduce
a new technology to prospective clients, representatives of highway agencies
who are always faced with "doing more with less" under the constant and
watchful eye of the traveling public.
The demonstration was observed by approximately 100 representatives of
cities, counties, ports, and airports throughout California and neighboring
states. Local television stations covered the event. The American River crossing on Interstate 5 near downtown Sacramento
was selected as the scene of the demonstration. The northbound #4 lane
on the bridge was ideal for demonstrating pothole patching technologies.
The asphalt concrete wearing surface was delaminating in the #3 and #4
(truck) lanes, primarily in the wheel paths, to the point where the quality
of ride was affected. The depth of the delaminated areas, approximately
3 centimeters, was a good test for spray-injection techniques, in which
an emulsion and aggregate mixture is sprayed on the surface to be repaired.
The test would be to confine the patching material within such a shallow
hole at those very high nozzle velocities. In addition, the site offered
the opportunity for a good comparison among the demonstrated patches and
of the demonstrated patches and traditional patching methods for delaminated
wearing surfaces, which tend to last only six months under traffic or,
under more severe conditions, one "wet" season. The scheduling of the
demonstration in October was optimum, coming just before Sacramento's
rainy season.
The demonstration also provided an opportunity to evaluate the equipment and materials for patching efficiency, durability, cost, and safety of the repair operation. While the bridge was ideal as a test site, it was not ideal for accommodating
a group of 100 observers. There was some concern that such a large group
would attract a lot of attention from passing motorists, leading to "rubber-necking"
that might slow the flow of traffic and possibly result in a crash. Therefore, the demonstration was continued on nearby Bannon Street, where there was plenty of distressed pavement, lots of room for the observers, and no problem with the traffic flow. The vendors arrived on Bannon Street and proceeded to make repairs to potholes and alligator-cracked asphalt pavement on adjoining segments of the street. The members of the group were permitted to observe at their own pace as each piece of equipment was demonstrated. The demonstration aptly showed the procedures and capabilities of each piece of equipment, as well as the speed and the effectiveness of the repairs. While the vendors and equipment technicians proceeded to patch distressed
pavement, the real business at hand was the interaction and exchange of
information. The vendors were also afforded use of a meeting room that
afternoon for any ongoing discussion with newly found business prospects.
The first patcher to arrive on Bannon Street was the Rosco RA-300. This unit is truck-mounted and completely self-contained. Rosco repairs the pavement in a four-step process of spray-injecting air, emulsion (CRS2), an emulsion-aggregate mixture, and finally, aggregate. The whole operation is controlled with a joystick from the comfort and safety of the cab. Aggregate size in the range of 0.6 centimeters to 1 centimeter is optimum with minimal dust. The RA-300 gets high marks for the speed and life of the repair, productivity, cost-effectiveness, and safety. Spray injection provides compaction of the patching material from the "bottom-up" in its delivery, and the patch is ready for immediate service. The RA-300 is produced by the Rosco Manufacturing Co. of Freeman, S.D. (The California Division Office has prepared a separate report on its observations of the RA-300 unit owned and operated by the Sacramento County Public Works Department. This report is available on request from the California Division.) The Duraco DuraPatcher also uses spray injection for the delivery of commercial hot mix, and it is also self-contained on a truck or trailer chassis. A heating unit keeps the mix hot for pothole patching and repairs, and the controls are operated from the delivery boom. Duraco Industries is located in Jackson, Miss. The trailer model was used for the demonstration. Spray-injection technology can be applied to alligator cracks as well as potholes. So, it works equally well for surface repairs, but its greatest flexibility is in pothole patching, where compaction is the end result of the process and not another operation requiring a separate piece of equipment. The ProPatch Pothole Patcher, manufactured by H.D. Industries of Jacksonville, Texas, was demonstrated on Bannon Street as well. This is a self-contained unit that features auger delivery of commercial hot mix. The unit comes with easy-on, easy-off (portable) excavating and compaction equipment for complete repairs. The ProPatch process is similar to traditional street repair operations, except that this one unit and its crew of two people can excavate distressed pavement, apply a hot-mix asphalt patch, and compact the patching material. The ProPatch eliminates the excavator and roller from the equipment train. Applied Polymerics and Road Techs demonstrated trailer equipment for both pavement grinding and delivery of RoadFlex patching material. RoadFlex is a patented material for patches on high-speed, high-volume roadways. It is a polymer blend that is delivered at 237 degrees Celsius (460 degrees Fahrenheit). It looks much like a slurry and provides a permanent patch when cooled. The delivery system is provided by the Viper, a trailer model used for this demonstration. Base rock may be used to supplement repair of a deep hole, and fine aggregate is applied for the wearing surface.
Based on the success of the Sacramento demonstration, Caltrans officials coordinated with the vendors to provide another demonstration the next day at Donner Summit on I-80. The Caltrans program manager also developed a video and presentation about the demonstrations. He showed the video and presentation to Caltrans district maintenance managers the following week. The agency has since entered into an equipment lease and training agreement with a manufacturer that will provide a statewide response team to pothole patching and other repairs while the purchase of the equipment is evaluated. These demonstrations proved that whether repairs are contemplated for potholes, alligator cracking, or raveled edges, any of these units offer a solution, even if it is only a stopgap until more permanent repairs can be scheduled. Spray-injection techniques were evaluated under the SHRP and remain the innovation for the future. The California Division brought vendors and interested public officials together to learn about equipment and materials available to resolve a serious problem for all highway agencies. The division recognizes (as reported in the September 1998 issue of Asphalt Contractor) that "preservation is the new pavement maintenance philosophy." The Surface Transportation Policy Project reported in November that there is a looming crisis in our deteriorating infrastructure, and a recent National Quality Initiative survey found that our customers, the driving public, are most interested in a smooth-riding pavement. We all understand the need to balance requirements and resources prudently, and we know that a reasoned response to a pothole problem can overcome serious problems, if not a crisis, in our ongoing pavement maintenance. That's why our efforts should be directed to these goals.
As a follow-up to this demonstration, Caltrans and FHWA produced videotape presentations. FHWA's California Division Office also has a library of videotapes, provided by vendors, about pothole-patching equipment. These videotapes and presentations are available for loan to any interested party or agency from Charlie Chen, construction and maintenance engineer, California Division, 980 9th St., Suite 400, Sacramento, CA 95814-2724, or via telephone (916) 498-5043, fax (916) 498-5008, or e-mail at Charles.Chen@fhwa.dot.gov. FHWA employees can also check the California Division Office site on the FHWA Intranet (http://fhwrc.fhwa.dot.gov/cadiv) for project information and a list of contacts. References
R. Clayton Slovensky is a senior transportation engineer in the California Division of FHWA. He serves six San Francisco Bay Area counties. Slovensky joined FHWA in 1977 and has served as an area engineer and a transportation engineer in the California Division and as a highway engineer at FHWA headquarters. His assignments have also included program review/product evaluation engineer for the California Division. He has a bachelor's degree in mathematics from Central Methodist College and a bachelor's degree in civil engineering from the University of Missouri at Rolla.
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