Dowel Bar Retrofit and Pavement Rehabilitation

Winner of a 2010 ACEC-IL Merit Award

The Lake County Division of Transportation served as the lead agency for the Buffalo Grove Road Dowel Bar Retrofit and Pavement Rehabilitation project. The project involved resurfacing, patching, and adding a southbound through lane along Buffalo Grove Road between IL Route 83 and Deerfield Parkway (approximately 3,000 ft or 0.57 mi). It carries approximately 16,500 vehicles per day and is anticipated to carry 20,000 or more by the year 2020 while providing a continuous, north-south thoroughfare, implementing goals for traffic safety, roadway and intersection capacity, pedestrian safety, and an improved longitudinally textured, smooth pavement.

The existing pavement of Buffalo Grove Road consists of 10 inches of concrete pavement over 4 inches of granular sub-base material. It was constructed in 1984 and additional work on sections of the pavement was conducted in 1988, 1996, and 2006. At this time, it was uncertain if the concrete pavement had doweled joints or other reinforcing steel. The joint spacing for a majority of the pavement appeared to be approximately 40'. Over the years, the slabs developed mid-span cracks with some joint spalling and noticeable faulting of mid-span cracks.

The County partnered with Civiltech Engineering, Inc. in 2008 to evaluate impacts associated with the proposed lane widening and to investigate, design, and implement a concrete pavement rehabilitation plan utilizing available industry practices and techniques to manage the rate of concrete deterioration and to increase its service life.

It was decided that the project would be a good candidate for a dowel bar retrofit, or load transfer restoration, which is primarily used on roadways that receive heavily channeled loadings (highways). The transverse joints or cracks that would benefit from improved load transfer were identified by the engineers during the design process and constructed on joints or cracks that had greater than 1/10 inch of faulting or differential deflection of 1/20 inch or more. Slots were cut across each joint or crack that was to receive a dowel bar retrofit with three dowels to be spaced 12 inches apart within the wheel paths. Slots were cut so the dowels are allowed to rest parallel to the pavement surface and centerline, and at mid-depth of the slab. A properly performed dowel bar retrofit, with a mix comparable to the existing pavement, results in repair area that is hardly noticeable to drivers.

A diamond grinding pavement restoration technique was then used to restore the surface of the existing concrete pavement. Diamond grinding was used in conjunction with other Concrete Pavement Rehabilitation (CPR) techniques, such as full-depth repair, dowel bar retrofit (load transfer restoration), and spot curb and gutter repairs to restore structural integrity to the existing concrete pavement. Although this type of construction technique has been performed successfully throughout other midwestern states, both the American Concrete Pavement Association and International Grooving and Grinding Association have praised the Buffalo Grove Road project as the first of its kind in Illinois to incorporate a Dowel Bar Retrofit construction technique in conjunction with a Diamond Grinding pavement rehabilitation.

Civiltech determined that by implementing a Dowel Bar Retrofit pavement preservation technique instead of traditional concrete patching, in combination with a diamond grinding pavement plan, the County’s goal of a service life extension for a minimum of 8 to 10 years was realistic and could meet public expectations. The public does not like that an agency rehabilitates the same section of roadway at four-, six- or eight-year cycles with an HMA overlay-inlay. By implementing these techniques, the County’s goal can be realized at a fraction of the reconstruction cost, “a new road ride at used road prices.”