CPR Saves Oklahoma Freeway
A survey of the Oklahoma City section of I-44 proved to the Oklahoma Department of Transportation (ODOT) that it was in desperate need of repair. Their solution: concrete pavement restoration (CPR).
ODOT discovered the section of I-44 between I-40 and I-35 suffered from severe panel damage and faulted pavement. The survey results revealed transverse joint faulting from 1/4 to 3/8 inch with isolated 1/2 - to 5/8 -inch faults, and longitudinal joint faulting from 1/4 to 3/4 inch.
Due to the road’s high level of traffic —between 125,000 and 135,000 vehicles per day—ODOT needed a solution that was fast and long lasting, with as little traffic disruption as possible. Rather than beginning a costly remove-and replace project, ODOT chose CPR as a cost-effective method that extends concrete’s life.
Lane repairs in both directions, as well as auxiliary and ramp lanes, began in 2004, with CPR used on all parts of the project. The method involved several elements, depending on an area’s level of damage. Severely damaged panels were removed and replaced with new concrete, but many existing portions were rehabilitated.
To restore structural support to existing concrete, voids that had formed under slabs at joints, cracks, and edges were filled. Dowel bar retrofit—which involved cutting and cleaning slots across joints or cracks, placing dowel bars, then backfilling the slots with cement—linked slabs together to evenly distribute the load. All joints were sealed to limit water or corrosive chemicals from entering and damaging concrete and dowel bars. Finally, diamond grinding was used on the concrete surfaces to provide a smooth, quiet, and skid-resistant driving surface.
Because CPR repairs are applied only to areas that specifically need them, traffic disruption was kept to a minimum during the five-phase project. To save additional costs and keep the freeway open as much as possible, most of the work was conducted at night. “In the past decade, many dowel bar retrofit and diamond grinding projects have been completed in the Oklahoma City metro area,” says Tom Hubbard, resident engineer for ODOT. “In each case, user costs were minimized by performing the work during nighttime hours.”
Working around the temporary nighttime lane closures created some additional challenges, however, especially when new concrete needed to be placed. Careful planning was used to complete the necessary steps while accommodating the temporary nighttime closures. Safety of both workers and travelers was another major concern. During the last phase of the project, two of the four lanes remained open, and fast, heavy traffic continued during construction. Activity briefings each evening helped keep safety a priority on the jobsite. Despite the challenges and dangers, the renovations were completed this summer. “The cost-effective nature and minimized user costs are key in the success of pavement restoration,” says Hubbard of the $11.3 million project. ODOT expects the CPR repairs to extend the service life of the concrete another 15 years.
PSU’s New Parking Garage
When the Pennsylvania State University (PSU) planned its new parking garage for the Milton S. Hershey Medical Center in Hershey, Pa., it needed a building that was durable, attractive, and low-maintenance. The school administration turned to Walker Parking Consultants, Elgin, Ill., who determined that precast concrete was the best option for the project.
The company decided that a precast pre-topped concrete double-tee system was a durable and cost-effective choice. With an adaptable drainage profile and a good bumper guard, this system offered the university a versatile and long-lasting concrete garage.
In-plant manufacturing of the precast concrete components for the six-level, 412,000-square-foot garage helped lead to a shorter construction schedule. Weather was not a factor in production, and components were made while the foundation was constructed. Production sequencing ensured the concrete parts were durable and consistent. Additionally, high-level, in-plant quality control guaranteed the concrete had a uniform finish.
When the foundation was complete, the precast components were installed. The north, west, and east elevations of the parking garage used precast concrete spandrel panels and shear walls.
To give PSU the option of expanding the four-bay garage in the future, the south elevation was constructed with a precast concrete wall load bearing system, plus a foundation that could support another load bearing wall if necessary. The wall design included removable wall panels on the end bays, plus window-like wall openings covered with black vinyl galvanized wire frame material to allow fresh air to enter the structure.
The stair and elevator tower also used precast concrete. Walker used cantilevered precast components to give the unit an airy, open feel and increase garage users’ sense of security when inside the structure.
Although double tees gave the structure a built-in aesthetic component, special finishes were used on the precast concrete. Most of the building had a light sandblast finish, while a heavier sandblast finish was used in the recessed areas and along the bases of the shear walls.
The result was a 1308-stall parking garage that was both durable and attractive. Walker anticipates that repairs to the precast concrete for cracks or deterioration will be minimal, which will help to keep the university’s maintenance costs down in the future.