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.
