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Concrete Pavement Technology Update
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In This Update:
Doing It Fast, Doing It Right: Accelerated Construction Paves the Way
Pavement rehabilitation and reconstruction, major activities for all U.S. highway agencies, have a significant impact on agency resources and traffic disruptions because of extensive and extended lane closures. The traffic volumes on the primary highway system, especially in urban areas, have increased tremendously over the last 20 years, resulting in many instances in an earlier-than-expected need to rehabilitate and reconstruct highway pavements. Highway agencies continue to wrestle with the age-old problem: longer delays now and longer service life versus shorter delays now and shorter service life. In recent years, agencies have been investigating alternative strategies for pavement rehabilitation and reconstruction that allow for faster yet durable rehabilitation and reconstruction of pavements.
Accelerated construction, which minimizes construction impact on the driving public, is being implemented by many highway agencies that allow the use of concrete for rehabilitation and reconstruction of deteriorated pavements, both concrete and asphalt. Accelerated construction optimizes use of pavement design, available concrete materials, construction practices, and traffic management strategies to construct long-life concrete pavements. A key feature of accelerated construction is the recognition that pavement rehabilitation and reconstruction under traffic does not provide for longer lasting pavements and actually requires more extended lane closures with consequences on travel times and user and construction worker safety. Contractors typically prefer better management of the construction zones that include full road closure. As noted in a Federal Highway Administration (FHWA) report1 on full closures, “Contractors that are given full access to the road gain efficiencies that often reduce project duration and costs as well as improve the quality of the end product. These positive effects usually lead to more favorable public sentiment and potentially reduce both short- and long-term user costs.”
Full closures are being achieved using three strategies: nighttime, weekend, and extended closures. The selection of a specific strategy depends on several factors:
Several agencies have successfully utilized these strategies to accelerate rehabilition and reconstruction on high-volume highway pavements, including the following examples.
I-75, Georgia (Peach, Crawford, Bibb Counties). Three lanes in each direction of a 23.7-km (14.7-mi) section of I-75 were successfully rehabilitated during 2003. The project scope comprised removal and replacement of the outside lane with jointed concrete pavement 250 mm (10 in.) thick; full- and partial-depth patching in the middle lane; diamond grinding of all three lanes; and reconstruction of the outside shoulder.
The project was completed in 16 weeks. All major work was performed during the night. The specification required a minimum curing time of 4 hours before opening to traffic. Based on limited maturity testing, the concrete had a strength of 8.3 to 10.3 MPa (1,200 to 1,500 lbf/in2) at 4 hours. The mixture design was based on a strength of 17.2 MPa (2,500 lbf/in2) at 24 hours and 24.1 MPa (3,500 lbf/in2) at 3 days. The nightly work schedule is shown in Figure 1.
Figure 1. Nighttime work schedule on the I-75, Georgia, rehabilitation project.
I-5, James to Olive Pavement Rehabilitation, Seattle. The Washington State DOT has successfully carried out several weekend closure projects in the Seattle–Tacoma area along sections of heavily traveled I-5. This project was the first major rehabilitation of I-5 through downtown Seattle since its completion during the mid-1960s. The rehabilitation was planned to be conducted over four 55-hour weekends during April and May 2005. Two additional weekends were also available in case of inclement weather. Typically, lanes were closed at 10:00 p.m. on Fridays and reopened to traffic by 5:00 a.m. on Mondays. Project work included replacement of deteriorating asphalt over an unfinished portland cement concrete composite pavement section and removal and replacement of cracked concrete slab panels. In addition, two bridges were retrofitted with reinforced concrete approach slabs. A critical aspect of this project was construction noise impact. However, by optimizing use of demolition equipment, the project experienced only two noise complaints. Also, extensive public relations activities and traffic management strategies ensured that traffic backups around the work zones were kept at a low level. The concrete pavement rehabilitation included removal of the existing pavement, regrading the subgrade, placing a 75-mm-thick (3 in.) hot-mix asphalt base, and placing a 330-mm-thick (13 in.) jointed concrete pavement with dowel bars. Concrete was placed using both a slipform paver and hand placing operations. Concrete strength on the project was monitored using maturity meters. The opening-to-traffic strength on this project was 17.2 MPa (2,500 lbf/in2). Use of high-early-strength concrete allowed opening of the roadway on schedule for Monday morning traffic, with the last concrete placed being only 12 hours old.
I-75, Georgia (Cobb and Cherokee Counties). A section of asphalt pavement on I-75 northwest of Atlanta, carrying about 170,000 average daily traffic, is being reconstructed using 300-mm-thick (12 in.) jointed concrete pavement. Started in March 2007, the project involves 146 lane–km (91 lane–mi) of pavement. The paving portion of the project that requires lane closures is being constructed over 32 weekends and involves milling 300 mm (12 in.) of the existing asphalt pavement, leaving about 75 mm (3 in.) of the asphalt concrete in place and placing the 300-mm-thick (12 in.) jointed concrete pavement. The concrete strength requirement is 17.2 MPa (2,500 lbf/in2) at 24 hours for the concrete being placed during weekend lane closures. However, the specifications allow traffic on the pavement after 4 hours of curing, but the contractor’s schedule is based on a 12-hour curing period. Views of the project under construction are shown in Figure 2.
Figure 2. The I-75, Georgia, reconstruction of asphalt pavement using jointed concrete pavement during 32 weekend full closures.
Although extended full closures are the most challenging strategies to implement, many agencies view them as the most effective way to rehabilitate high-volume traffic corridors, even in urban areas. Recent examples include the I-57 corridor in Chicago and the Lodge Freeway in Detroit.
Lodge Freeway, Detroit. The Lodge Freeway (M-10) project is reconstructing or rehabilitating 23 km (14 mi) of pavement, repairing or replacing 50 bridges, upgrading utilities, and replacing freeway signs between Lahser Road in Southfield and Jefferson Avenue in Detroit. The $140-million project started in February 2007 and is expected to be completed in November 2007. Full closure is being implemented on this project so that the work can be completed in one season. Otherwise, according to the Michigan DOT, the work would take 2 or more years to complete, with only one lane open in each direction. In addition, according to the Michigan DOT, maintaining two lanes of traffic in each direction would have doubled the cost of the project.
The pavement-related work involves removal of the existing 1960s-built jointed reinforced concrete pavement, constructing the subbase and a 150-mm (6 in.) base, and placing a 250-mm-thick (10 in.) jointed concrete pavement. The contractor has full access to both directions of the roadway. The concrete pavement is being placed 7.3 m (24 ft) wide, and dowels are placed using a dowel bar inserter. Joints are spaced at 4.3 m (14 ft). The concrete mixture incorporates combined aggregate gradation, and the concrete is produced using a dual drum plant with a production capacity of about 459 m3 (600 yd3) per hour. Figure 3 shows construction views of the project.
Figure 3. Lodge Freeway, Detroit, reconstructed during an extended closure for placement of jointed concrete pavement.
As noted in this article, asphalt and concrete pavements in high-traffic areas can be effectively rehabilitated or reconstructed with long-lasting concrete pavements using accelerated construction techniques. Many U.S. highway agencies are successfully using these accelerated concrete pavement construction techniques to reduce construction costs, reduce lane closures, improve construction worker safety, and, importantly, reduce negative impacts on road users.
A conference on Optimizing Paving Concrete Mixtures and Accelerated Concrete Pavement Construction and Rehabilitation, sponsored by FHWA, will be held in Atlanta, November 7 to 9, 2007. A highlight of the conference will be two forums that will present case studies on accelerated concrete pavement rehabilitation / reconstruction using nighttime, weekend, and extended full closure strategies. The Georgia, Washington State, and Michigan projects will be discussed at the forums. For more details on the Atlanta conference, see page 12.
Article prepared by Shiraz Tayabji, email@example.com.
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