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EXECUTIVE SUMMARY The need for the new device was initiated based on the practical request of the Nebraska Department of Roads (NDOR) for a tool to be developed that efficiently prepares pavement cracks and joints for sealing. NDOR was particularly interested in the tool’s ability to remove de-icing chemical buildup that forms on the crack and prevents sealant adhesion. Flexible and rigid pavement joints and cracks are sealed or filled to mitigate further damage caused by the infiltration of water and the buildup of foreign debris. “Materials and procedures for sealing and filling cracks in asphalt surfaced pavement” (FHWA-RD-99-147) recommends crack sealing for 5 to 19 mm (1). However, the traditional procedures for preparing roadway joints and cracks for sealing/filling— which include air blasting, sanding, routing, and hot air blasting—are largely ineffective, labor intensive, or dangerous. The most viable solution found was a combination of preparation methods that included air blasting and abrasive wire brushing. The simple and innovative design of this tool is an air powered rotary wire brushing system with onboard air nozzles that blow out the pavement crack behind the wire brush. The device is illustrated in Figure 1. Incorporating a pneumatically powered rotary motor allows for a seamless connection between existing maintenance vehicles’ air compressor systems, which reduces the need for further retrofit costs and eliminates the need to haul flammable liquids. FIGURE 1: Crack Cleaning Device Concept and Product. Throughout development a number of hypotheses were tested and there were several issues to overcome. The first of which was discovering the most effective rotary brush type to be used for crack preparation. After testing a number of brush types and thicknesses it was found that a ¼” twisted wire brush performs best. An adequate guide wheel assembly was also machined for the device in two different forms which included a height-adjustable mechanism and a free moving spring system that enables the operator to plunge into cracks when desired. Additionally, issues regarding the shape and size of the device’s shaft had to be overcome. Originally, it was thought that a straight shaft design would allow for more freedom of motion, giving the user the ability to stand erect while using the device. It was discovered that most operators wished to stand over the device and use leverage to work the device into the pavement cracks. For that reason, an ergonomically curved shaft or wand was machined and fitted to the device. 4
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In addition to a number of innovative design concepts, a number of field and laboratory tests have been conducted. While the entire device is a product based on the feedback of actual pavement maintenance crews, many of the details were processed in the manufacturing lab. The first concept to be tested in the lab was the device’s ability to generate heat by the frictional force of the wire rotary wheel, which would warm the pavement crack to an acceptable level to receive sealant on cold days. The test results showed that generating heat is not a time-efficient process since it requires multiple passes to generate desirable levels of heat. In addition, the effectiveness of the onboard air blasting nozzles was investigated. The device was fitted with two nozzles, one that shot directly into the cleaned crack, and one that fanned on the surface of the crack to disperse debris away from the pavement crack. Perhaps the most important laboratory test was identifying the device’s efficiency in removing de-icing chemical residue from pavement cracks. The residue was simulated using aerosol paint and visually inspected and rated on a percent cleaned basis. The device preformed this task efficiently. The crack cleaning device has been tested a number of times by actual industry roads maintenance personnel at NDOR and the City of Omaha in Nebraska. From such testing, its high potential for significantly improving the current crack/joint sealing practices was recognized (Figure 2). A continuous improvement process according to industry feedback, including the nation’s largest roadway maintenance equipment/material supplier CRAFCO Inc., proved to be an invaluable method of creating such a practical device. It was the group of operators who tested the device and motivated improvements like a guide wheel assembly, nozzle design, and shaft design. Overall, the operators were very receptive to the concept and impressed with the performance of the crack cleaning device. Business development is currently ongoing. The roads maintenance group in the City of Omaha has recently requested their own adoption of the device and is currently testing the device at with crack and pothole cleaning and repair projects. As of today, the ruggedness of the device is proved by the City of Omaha’s daily use of device for a total of about 30 hours. Since a wire brush can be simply replaced with a router bit or a rotary masonry cutting blade, the device can rout cracks and cut a pothole area in conjunction with a jackhammer before placing a new patch. Through the long term field use by the City of Omaha, the practicality and versatility will be further proven. NUtech Ventures, a nonprofit corporation dedicated to linking FIGURE 2: Test by a local roads companies, entrepreneurs and investors with the University of Nebraska- maintenance crew. Lincoln researchers who are driven to develop commercial products or services based on their pioneering research, is currently working with the research team in order to solidify a viable course of action for commercialization. This plan includes either (1) establishing a start-up company at the Scott Technology Center, a small business incubator that partners directly with the University of Nebraska; or (2) licensing the technology to a road maintenance company such as CRAFCO Inc., Lab Manufacturing, Asphalt Sealcoating Direct or others. Utilizing the developed device for crack and joint preparation will undoubtedly lead to an increase in overall quality of pavement maintenance. This improved quality will promote an increase of the useful life of pavements, and postpone the allocation of valuable tax revenue towards the rehabilitation or new construction of existing roadways. 5