California has taken a long time to embrace continuously reinforced concrete pavement (CRCP) technology. But since 2010 the California Department of Transportation (Caltrans) has built nearly 800,000 cubic yards (over 2,000,000 square yards), not counting design-build projects, on 17 major projects in 6 districts. From I-5 near the Oregon border to Calexico near the Mexico border, CRCP has been used on interstates to routes on city streets.
The state highway department built its first experimental pavement in 1949 as a 1-mile long, 2-lane westbound section on U.S. Route 40, (The Lincoln Highway) near the town of Fairfield. It consisted of 8-inch-thick pavement with equal sections of 0.52% and 0.60% longitudinal steel. Today, that test project serves as the two inner lanes of westbound I-80; the two outer lanes of the roadway were built with the conventional Caltrans standard JPCP in the 1970s. The test project experienced one punchout within first 20 years. Recent inspections indicated that no further failures were observed in the pavement. Lane 2 received a diamond grind in the 1990s and I-80 pavement was completely overlaid with asphalt in both directions through the Fairfield area in 2010, when the roadway shoulders were incorporated for the addition of HOV lanes.
California next constructed its second CRCP experimental section in 1971 as part of a larger test of various concrete pavement structures. The CRCP was 8.5-inches thick with three trials of longitudinal reinforcing types. Subsequent LTPP distress surveys until 2000, nearly 30 years after construction, showed: signs of 1 low-severity and 1 medium severity Y-crack in outer edge, no punchouts, inner edge with no failures whatsoever along the LTPP section’s 500-foot length. It too was overlaid with asphalt, in the mid-2000s, when the entire roadway in both directions through Fairfield was restriped to allow HOV lanes on the inside shoulders.
The recognition by Caltrans of the incredible performance of the 60+ year old I-80 section and the 35+ year old I-5 section, along with the successful use around the U.S., has led the Agency to adopt CRCP in its specifications, standard drawings, design catalog and highway design manual starting in the mid 2000s. In recent presentations, Caltrans has pointed out their interest in CRCP: smoothness, low maintenance costs, no transverse joints, thinner slab thickness relative to unreinforced concrete pavement, lower Life Cycle Cost (despite higher initial cost), and a higher capacity for truck loading and traffic volumes.
As many of the state’s pavements are nearing the end of their service life or requiring widening, Caltrans has begun focusing on sustainable pavement they have defined as pavement that is long lasting, minimizes environmental impacts, is easy to maintain and manage, as well as focusing on its ultimate goal: to optimize current and future costs. Caltrans issued a Department Directive that decisions are to be based on life cycle costs and that LCCA is required on all but preventive maintenance projects. To implement this directive, the pavement group adopted RealCost software in 2007, developed a manual for LCCA with data needed to run RealCost, finally developing a newer version for its use, and started documenting life cycle costs in project reports.
The CRCP structure being used in California consists of:
- Layer 1: 10- to 12-inch-thick CRCP, depending on climate and subgrade, with 0.70% longitudinal steel with 4”cover; 28-day concrete flexural strength of at least 675 psi; CTE below 6 in/in/deg F Well cured and paved during low to moderate ambient temperatures.
- Layer 2: 4-inch-thick non-erodible cement treated or asphalt treated base; CTB modulus at least 2 million psi; ATB with at least 10% binder content by volume. Surface that can provide adequate friction.
- Layer 3: 6-inch-thick granular base with low fines; well compacted with adequate drainage to keep base from pumping.
- Layer 4: existing subgrade, treated as required.
Over the last five years Caltrans has been selecting CRCP for new highways and truck lane replacements, for overlays on projects in high truck traffic areas, in remote locations (where maintenance is difficult), and where long term consistency is important.
Samples of current projects using CRCP include:
Interstate 80 Emigrant Pass
Interstate 80 Emigrant Pass: A 2-mile-long, northbound section with climbing and a 0.6-mile-long section between 2 bridges was built with 14-inch CRCP in 2011. This was part of a larger reconstruction project. The extra thickness is to allow for future grinding that will be required due to the use of tire chains. Epoxy coating of the reinforcing bars was used for additional protection against the use of deicing chemicals.
CA Route 99
CA Route 99, the transportation backbone of the San Joaquin Valley, is being updated with CRCP, including Caltrans’ first design-build contract. The Annual Daily Traffic (ADT) for Route 99 ranges from a current level of 42,000 vehicles near I-5 in Kern County to over 100,000 vehicles at the north end. The projected traffic volume in 2025 is from 84,000 to 260,000 vehicles. Truck traffic accounts for anywhere from 19 to 27 percent, compared to the statewide average of about 9 percent. So far CRCP has been part of 6 projects built in Kern County, Modesto, Merced, Fresno, and Bakersfield.
Presidio Parkway (SR-101)
Presidio Parkway (SR-101), San Francisco: CRCP is currently being constructed as the mainline pavement in two major phases — Phase I delivered through traditional design-bid-build method, Phase II delivered through public-private partnership. Designers followed the Caltrans Highway Design Manual to select a 9-inch CRCP, with a 3-inch hot-mix asphalt or 4-inch lean concrete base, and a 7-inch aggregate subbase. This minimum maintenance pavement will avoid the need to acquire work permits from the U.S. Park Service.
Interstate 5: To date there have been six CRCP projects on I-5, including two large highway reconstruction projects through Stockton. The Stockton projects contain thru-lanes and HOV lanes.
SR-20/SR-70, Marysville, near Sacramento: 0.90-foot CRCP was used to rebuild the roadway that serves as the state route through the town of Marysville. The project is designed as an urban street with curbs and gutters and decorative patterns at the crosswalks, but it handles lots of truck traffic due to logging in the Sierras.
Imperial Valley Projects
Imperial Valley projects: CRCP was used on US-78/111, Brawley Bypass, a standard Caltrans project, for both repairing sections of JPCP on Phase I and for all of Phase II. Currently, SR-7 in Calexico is being built with 0.90-foot CRCP and soon three sections will be let on I-8 through Imperial County.