PPCP passes the test
In 2009, PPCP technology was really put to the test with projects in Delaware and Virginia. Both projects required that all reconstruction of the existing pavement be limited to overnight work windows to minimize disruptions to the traveling public. In Delaware, the contractor had to work between 7 p.m. to 5 a.m. each night to remove the existing 12-inch-thick concrete pavement, place a 4-inch pervious concrete base, install 8-inch precast panels, and post-tension them together so they could be opened to traffic each day. Just a few months later, a section of Interstate 66 in Northern Virginia that carries more than 180,000 vehicles per day was reconstructed using PPCP. As in Delaware, construction activities were limited to 9 p.m. to 5 a.m. each night to ensure the pavement was open to daytime traffic.
Both of these projects successfully demonstrated the viability of PPCP as a rapid reconstruction technique for deteriorated concrete pavement under the strictest time constraints. However, the success of these projects led to deployment on a much larger scale elsewhere.
California leads the way
After a successful PPCP demonstration project on Interstate 10 in 2004, the California Department of Transportation (Caltrans) appears to have embraced precast pavement technology. In 2011, Caltrans District 4 (Oakland-Bay Area) deployed PPCP on a large scale, for the rehabilitation of about 7.5 miles of Interstate 680 near Dublin.
The project consisted of spot reconstruction of isolated areas of three of the four lanes of I-680 in both the northbound and southbound directions for a total of about 5.5 lane-miles of precast pavement (PPCP and JPPS). Similar to the projects in Delaware and Virginia, all reconstruction activity was restricted to the hours of 8 p.m. to 5 a.m. This included removing the existing concrete pavement, placing a rapid-setting lean concrete base, and installing and post-tensioning the precast panels.
Precast supplier Con-Fab Corp. of Lathrop, Calif., proposed an innovative modification that further improved efficiency. Two-way pretensioned precast panels were oriented in the direction of traffic, allowing the contractor to install up to 36 feet of precast pavement with each panel. These two-way pretensioned panels were also used for isolated single-slab replacement portions of the project.
The success of the I-680 project has led to additional jobs in Northern California, including Interstate 80 east of Sacramento and Interstate 580 near Pleasanton/Livermore, comprising just more than 6.5 lane miles of precast pavement. Both are currently in construction.
Meanwhile in Southern California, where precast pavement was first introduced, PPCP has been specified for the reconstruction of a 9.2-mile section of Interstate 710. The project will utilize about 4300 precast panels for 36 lane-miles of new concrete pavement. When completed, it will be the largest PPCP project ever constructed in the U.S.
Additional projects totaling about nine additional lane-miles are currently planned for Interstate 5 truck lanes and Interstate 405.
California has also utilized a proprietary precast pavement system which uses reinforced panels and doweled joints to effectively replace existing jointed concrete pavement in-kind. This system has been successfully deployed on a large scale in New York and New Jersey, and for smaller projects in several other states.