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North Dakota Demonstration Project: Whitetopping on U.S. 2 West of Rugby
Project Overview and Lessons Learned
U.S. 2 between Rugby and Berwick, ND, is a four-lane divided highway that serves as a vital interregional east-west route linking the northern portion of the State. In the westbound direction, the original hot-mix asphalt (HMA) pavement surface was in increasingly poor condition because traffic and harsh seasonal weather caused distresses to increase beyond the budget of normal maintenance efforts. Rutting, fatigue cracking, and severe transverse and longitudinal cracking made this section of U.S. 2 not only rough, but also unsafe for the traveling public.
Whitetopping offered NDDOT a cost-effective rehabilitation alternative to restore ride quality in the westbound lanes while leaving the existing deteriorated HMA pavement in place as a sublayer. Bonding between the original pavement and the new 7-inch (in) thick portland cement concrete (PCC) whitetopping optimizes the material properties and eliminates the need for dowel bars and tie bars that would be required in conventional concrete pavement. Not using steel reduces the initial project cost, increases construction speed, and simplifies any future repairs.
The U.S. 2 divided highway alignment presented a perfect opportunity to use full lane closure by shifting traffic onto the two open eastbound lanes, removing traffic from the work zone and enhancing worker and public safety during paving operations.
HfL Performance Goals
Safety, construction congestion, quality, and user satisfaction data were collected before, during, and after construction to demonstrate that whitetopping and total lane closure can be used to achieve the HfL performance goals in these areas.
The benefits and costs of this innovative project were compared with those of a similar resurfacing project with a more traditional delivery method. The result of a life cycle cost analysis indicates that NDDOT's approach is similar in cost over the life of the pavement to conventional overlay methods. The actual savings were realized by minimizing the number of construction days, saving $32,927 in user delay costs during construction.
With this project, NDDOT achieved a better understanding of the whitetopping method. Until now, whitetopping was not considered for major highway rehabilitation largely because of lack of local experience. This was the first major whitetopping project in North Dakota, and it was successful in demonstrating the constructability of whitetopping and enlightening designers and contractors alike on the viability of this innovative rehabilitation method.
The contractor on this project was able to use the milled HMA pavement as a stable haul road to supply fresh concrete to the paver. This is not always the case on whitetopping or any overlay project in which the original pavement is severely distressed and milling reduces the structural capacity of the pavement. NDDOT had originally specified that no traffic be permitted on the milled HMA pavement, but allowed the contractor access after no damage by haul trucks was observed.
During the first few days of paving, the contractor was extra diligent in timing sawcutting operations because of the possibility of shrinkage stress from large temperature swings during the late-season paving schedule. Some relief cuts were made to prevent uncontrolled cracking early in the paving schedule until curing rates were fully understood. After the first few days of paving, the contractor was more comfortable with the operation and was able to increase production. Also, the lack of steel reinforcing made production more efficient by eliminating the time required to set dowel baskets, as traditional concrete paving methods require.
The North Dakota whitetopping project on U.S. 2 exemplifies the Highways for LIFE principles. Paving construction time was cut by 36 percent compared with traditional paving operations, while a high level of safety was maintained for workers and the traveling public. Crashes are expected to be lower over the project's service life because of design features and a durable pavement surface. The whitetopping and full lane closure innovations were major contributing factors in reducing the overall project cost. The postconstruction smoothness level, while not meeting the HfL goal, is a vast improvement over the smoothness level of the original pavement. The noise level after construction also does not meet the target value, but is within the range for similar textured pavements. Overall, the end users of the new roadway are very satisfied with the finished product.