Utah Demonstration Project: Precast Concrete Pavement System on I-215
Project Overview and Lessons Learned
This demonstration project consisted of rehabilitating a 4-mi section of concrete pavement on southbound I-215 in Salt Lake County, UT. The limits of the project are Milepost 22.78 to Milepost 26.94. This section of I-215 is next to Salt Lake City International Airport and is used by both truck and commuter drivers. The section is predominantly three lanes per direction and typically serves about 68,000 vehicles per day (vpd), or about 34,000 vpd in the southbound (SB) direction. To reduce the impact of construction, UDOT wanted to use accelerated pavement construction (APC) technologies.
The primary purpose of the project was to rehabilitate the existing concrete pavement. Deficiencies included the following:
- The existing concrete pavement was constructed in 1976 and was well beyond its 20- to 30-year design life.
- Pavement repairs had not been made since original construction.
- The existing concrete pavement showed signs of surface polishing and cracking.
- The skid resistance of the pavement needed to be improved.
- About 1,500 square yards of the pavement required full-depth replacement.
- The IRI pavement rating suggested that the pavement was in fair condition.
- Joints had debris and missing materials that contributed to cracking.
This section of road required full-depth panel repairs and introduced local designers and contractors to the use of APC. Central to the APC approach on this project was use of a PCPS consisting of precast concrete panels leveled with urethane grout and dowel bars retrofitted across the joints to enhance load transfer.
HfL Performance Goals
Safety, construction congestion, quality, and user satisfaction data were collected before, during, and after construction to demonstrate that innovations can be an integral part of a project while simultaneously meeting the HfL performance goals in these areas.
- Work zone safety during construction—No incidents occurred during the construction period, including the closure period, which met the HfL goal of achieving a work zone crash rate equal to or less than the preconstruction rate.
- Worker safety during construction—No workers were injured on the project, so the contractor achieved a score of 0 on OSHA Form 300, meeting the HfL goal of less than 4.0.
- Facility safety after construction—The effect of the pavement improvements on the HfL goal of 20 percent reduction in fatalities and injuries in 3-year crash rates compared to preconstruction rates is yet to be determined.
- Construction Congestion
- Faster construction—The APC approach shortened construction-related lane closures from 7 to 10 days, which could have affect large numbers of vehicles during daytime peak hours, to 7- to 10-hour overnight closures with minimal impact on traffic, meeting the HfL goal of a 50 percent reduction in the time traffic is impacted compared to traditional construction methods.
- Trip time—Although no actual travel time studies were conducted, a review of spot speeds each night at several sensor locations verified that the project had little, if any, impact on traffic, meeting the HfL goal of no more than a 10 percent increase in trip time compared to the average preconstruction conditions.
- Queue length during construction—No traffic backups occurred, so the project met the HfL goal of less than a 1.5-mi queue length in a urban areas.
- Smoothness—IRI was reduced from 150 in/mi before construction to 130 in/mi after construction. Motorists will notice a somewhat smoother ride, but the road remains rough and does not meet the HfL goal for IRI of 48 in/mi.
- Noise—SI data showed a noticeable noise decrease of 7.7 dB(A). The SI value dropped from 108.1 dB(A) before construction to 100.4 dB(A) after rehabilitation, which does not meet the HfL requirement of 96.0 dB(A) or less.
Through this project, UDOT gained valuable insights into using innovative techniques and materials—both those that were successful and those that need improvement in future project deliveries. The following are some of the lessons learned:
- A solid, well-compacted base is needed to control displacement when the panel load is transferred to the leveling bolt plates. Using a thinner layer of material and denser materials with high fine content is recommended. Proper base work must be performed and subgrade disturbance should be minimized for a successful installation.
- Use wide leveling plates for better weight distribution of the leveling bolts.
- Both urethane and cement grout flow and cover voids extremely well. Urethane sets in 20 minutes, which allows for opening the road sooner. However, because it sets so fast, it has the potential to lift the panel before the injection is completed and can cause uneven load bearing. Cement grout sets in 1 to 3 hours and shows no signs of setting up between injections or lifting the panel, but injections and slow setting time may delay opening the road.
- Setting and spacing of panels are critical. An exact layout or jig should be used for panel placement spacing, or a concrete saw should be onsite for field modifications.
- Longitudinal joints need to be saw cut because of the jagged edges.
- Over-width cutting of the existing roadway creates the need for some type of forming or control to avoid waste of grout or urethane and the need for repairing the overcut.
- Curvature of the roadway cannot be ignored. The curvature should be cast into the panels or saw cut for proper fit.
- Panels are not perfect and vary to some degree. Tighter tolerances may need to be specified during prefabrication.
- Work in multiple lanes can be done simultaneously and can proceed from multiple directions.
- A hot-mix asphalt (HMA) plug is used at the end of the work area to allow for opening to traffic the next day. To minimize delay times before opening to traffic, the HMA mix should be prepared and ready to use ahead of time.
- The scheduling sequence of subcontractors and suppliers is critical for the timely completion of the project.
UDOT gained valuable insights into PCPS use and the improvements needed to make this process a more viable tool. UDOT evaluated PCPS with a goal to minimize traffic impacts by performing concrete curing offsite to improve the cure environment, construction zone safety, and overall construction time, all of which were achieved on this project. The ride quality of the rehabilitated panels did not meet the HfL performance goals.