The Boyertown project began at the asphalt plant where a special hardening modifier was added to a DOT-approved wearing surface. It was then thoroughly integrated into the primary mix to achieve a consistent blend.
The on-site process began on a bright day in 1995 with preliminary preparation consisting of sweeping the existing street to eliminate any loose debris such as dirt, leaves, or twigs. Once completed, a tack coat was then applied. This step ensures quality adhesion of the new product to the existing material.
The next step was the application of a leveling course. This step provided for recrowning and eliminating any voids that may have been present in the existing surface, thus providing a consistent surface to work on. Consistent depth and compaction eliminates unnecessary labor and provides the required base for clear print definition.
After application of the leveling course, the wearing course was installed. ID-2 wearing was used with a modifier added and the necessary 1.5-in. compaction depth was maintained. To achieve a quality print, it was important to have 90% of the rolling/compaction process complete before imprinting began.
With a wide variety of imprinting templates available, a pattern was selected prior to the date of installation. There are different sizes and shapes for different areas. For this project, a standard brick pattern was chosen. The basic template is 6 ft 6 in. x 12 ft wide. These templates have been designed in such a way that they are easily overlapped to achieve the desired width. The template is constructed of specially woven wire rope, which is cut and welded in various patterns. Impressions are created after the templates are pressed into the asphalt during final compaction rolling. The template is then removed and positioned on the next section of surface to be imprinted until the job is complete.
As with any project, having the right tools for the job reduces the potential for errors and delay. The added asphalt modifier permitted early accessibility to the material but reduced the amount of available end working time. The required time frames were met comfortably by using a series of standard wackers, a smaller three- to five-ton roller, and a large vibrating reversible plate. Use of the larger Dynapac reversible plate was essential. The Dynapac unit itself weighs about 11,000 lb and it applies 13,000 lb per sq in. This combination achieved the DOT-approved compaction factor of 92% in minimum time. Standard wacker plates were used to set the templates. To achieve consistent depth of print, the roller and the large vibrating Dynapac wacker plate were used to follow up at a slow speed. Removing the templates was simple with the use of a mild soapy solution.
All the steps in the process were happening simultaneously, as the project moved along. Initial material was continually laid out in front, with the rolling/compaction process following in-line. The printing stage worked forward third in line. Masking techniques were used to protect the integrity of the product. For those hard to print areas, special hand printing tools were used. The same installation techniques were used to install an intersection radius. When the second pass was required, the templates were interlocked and correct alignment was achieved.
A series of seven or eight templates were used simultaneously, in this manner. Using a paver equipped with a joint matcher was extremely helpful. The matcher rides on the in-place surface and assured a perfect match every time.
Approximately 60 to 70 ft of paving was completed before stopping to evaluate and catch up on hand finishing. For corners or curves, there are several template patterns available. A soldier course can be very effective in this application. Hand printing tools can also be used. For this project, a combination of hand tools and templates were used. Continued integrity of pattern was ensured after the corner or curve surface was installed. This process was labor intensive, but the cost remained dramatically less than hand-laid brick.
As crews placed the initial wearing course, luting was done as usual. It was then followed up with a broom process. This ensured a tight pinched joint as the process progressed.
In July 1994, Dayton, Ohio, became the first city in the country to use the printing process on a decrepit brick residential street, preserving the historic charm of the neighborhood. In 1922, the residential street was originally constructed of brick placed on a concrete base. Almost 75 years later the street was showing its age. The concrete had disintegrated, the sub-base was heavily water damaged, winter temperatures had taken their toll and the speed limit was reduced to 15 mph in response to the poor ride quality.
The city of Dayton is committed to retaining and preserving its many historic neighborhoods, while remaining within its allotted budget. The city planning department's Urban Design Guidelines require that street repair must restore the original surface material. In this case, unless an alternative could be found, the repair would involve removing the brick, replacing the concrete base, and re-laying the brick. This labor-intensive process would have been expensive, and would require closing the street for an extended period of time.
Butler Asphalt of Vandalia, Ohio, presented a cost-effective solution using the StreetPrint system. The Urban Design Guidelines were relaxed by the city board and approval of the system was granted. Butler Asphalt began the work in July 1994 and completed the full repair in less than one month.
