Cheer of the Unknown

July 19, 2002

For a relatively small town like Sheridan, Wyo., whitetopping an arterial street with over 17,000 sq yd of concrete during the height of the tourist season is no small undertaking. Finishing the project two weeks ahead of schedule and almost 20% under budget is no small accomplishment, either.

For a relatively small town like Sheridan, Wyo., whitetopping an arterial street with over 17,000 sq yd of concrete during the height of the tourist season is no small undertaking. Finishing the project two weeks ahead of schedule and almost 20% under budget is no small accomplishment, either.

This is the brief story of a project that with a lot of unknowns turned out to become a quadruple-award-winning project. The project received honors from the American Concrete Pavement Association, the Colorado/Wyoming Chapter of the American Concrete Pavement Association, the Concrete Association of Wyoming and the Wyoming Engineering Society. To this date it is still the largest concrete whitetopping project in the state. 

Whitetopping is a concrete street resurfacing method by which approximately 3-4 in. of high-strength, fiber-reinforced concrete is applied directly on top of an existing (usually distressed) asphalt road, street or intersection. Important to the success of this overlay method is rotomilling, or cleaning of the surface, prior to placing concrete and sawcutting longitudinal and transverse control joints at intervals of 3-4 ft (i.e., 3-in. overlay, 3-ft spacing) after the concrete is placed.

Two years ago, a whitetopped intersection—complete with colored and textured concrete crosswalks—was donated by the local Mullinax Concrete Service Co. to the city of Sheridan, Wyo., to test the viability of whitetopping as a resurfacing option.

Following that introduction, Sheridan was convinced that this was in fact a good option for resurfacing—not only intersections, but also a major street like Loucks Street in its entirety. Such a project had not previously been undertaken in Sheridan or anywhere else in Wyoming. This seemingly small leap of faith ended up setting a great example for other communities in the state, proving that whitetopping is a very viable and cost-effective solution for long-term street maintenance. 

Start big

The project, which cost just under $450,000, entailed whitetopping just over 4,000 ft of Loucks Street, a major arterial street in Sheridan that provides access to much of the city and sole access to a number of residents that live west of town. The top width of Loucks Street varies from 37-49 ft. At the time of construction the project was the largest of its kind in the state and the sixth largest nationwide.   

The whitetopping design section consisted of a variable 3-3.5-in., 4,800-psi concrete overlay. A 3-ft-wide, 8-in. full-depth replacement transition was constructed on each side of the street to connect to the existing gutter. This transition also provided additional strength adjacent to parking areas and intersections.

Control joints were sawcut at a spacing of 3 in. in the transverse direction and 3-3.5 in. longitudinally. At the two ends of the project and at each bridge end, 30-in. full-depth transition sections were utilized to meet the existing grade.

Because there was no guarantee that the existing asphalt was uniformly thick everywhere, the design team was concerned that preparing the street with the rotomiller could mill through the asphalt in certain areas, thus requiring a partial reconstruction, which would add costly delays and change orders to the project.

It was therefore determined to rotomill as little as feasibly possible. With the donated use of Sheridan’s small Bobcat rotomill, a simple 1-ft “taper” was rotomilled adjacent to the 3-ft transition area on the edges of the street to allow the most gradual slope connecting to the existing curb and gutter. The milling taper also minimized the increase in crown that was a result of the overlay.

Due to extremely high temperatures, two different concrete mixes were utilized, both with polypropylene fibers added for durability. The first mix, used at the beginning of the project where connecting traffic was heaviest, was designed to cure as quickly as possible so that the roadway could be open to traffic within 48 hours. The second mix, with fly ash (coal slag), was designed to cure slower and was used in areas with less connecting traffic and on days with temperatures near 100?F. Its slower cure time gave the construction crew a little more time to sawcut the total of 18 miles of control joints that were required.

Rosy neighbors

There was high daily public attention and interest in the project. The mayor and other city officials visited the construction site every day and continually talked to residents who were affected by the street construction. Contrary to what was expected, several residents along the road were glad to have the street closed to traffic and enjoyed taking part in the construction progress.  

Halfway through the project, the city of Sheridan came up with the idea of including a colored crosswalk for pedestrian safety. Because the project was ahead of both schedule and budget, the construction team quickly figured out how to incorporate this feature. It now clearly adds to the overall beauty of the project, and also ties the street nicely together with the previously donated crosswalk located at the east end of this project. This type of flexibility and incorporating ideas on-the-go was typical of the overall effort on the project and definitely added to the fun of the work. 

Cutting constant care

At the time of construction, whitetopping would have been approximately 28% cheaper than a total reconstruction with asphalt, the only other feasible option for resurfacing Loucks Street. In addition, it took only four weeks of paving to complete the project, versus what would have been at least a six-week paving period for asphalt reconstruction.

“For the past 25 years Sheridan’s Loucks Street has been a problem. It seemed to need attention every single year and was costing the city a lot of money. For the first time, I think we have found a solution that works. It has surpassed my expectations already,” said Sheridan Mayor Jim Wilson.

Whitetopping also provides a very low maintenance street and an extended service life. This project provides ample evidence that whitetopping is not only a fast and very cost-effective resurfacing option, but it also reduces manpower and equipment demands. Ready mix trucks, a vibrating screed, a couple of saws and eight workers was all that was needed to complete this project. Compelling simplicity in an often complicated world.

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