The traffic on California’s Highway 23, a major roadway in Ventura County, has grown from an average of 87,000 vehicles daily in 1995 to about 99,000 vehicles per day. A steady population growth and an increase in jobs in the county has led to the increase, which is expected to rise even more.
The answer to the traffic problem is a $65 million highway improvement project. The project widens the highway from four lanes to six with one lane and shoulder added in each direction from Los Angeles Avenue in Moorpark to Highway 101 in Thousand Oaks. California Department of Transportation (Caltrans) officials say the expansion will help handle a projected 35 percent increase in traffic over the next 25 years.
Security Paving Company, in Sun Valley, California, was in charge of slipforming the new lanes. Security Paving needed a new machine for the project. They ultimately decided on a GOMACO four-track GP-4000 slipform paver with an In-The-Pan Dowel Bar Inserter (IDBI).
“We are responsible for paving 18 miles (29 km), nine miles (14.5 km) in each direction, on Highway 23,” Mike Mattivi, Vice President of Security Paving, said. “We used our GOMACO 9500 to trim the grade. Then we brought in our GOMACO GT-6300 for our base. We had six inches (152 mm) of lean concrete base underneath our Portland Cement Concrete (PCC). Then we followed that with our GP-4000 with the IDBI.”
Project restraints created some tight working conditions for the GP-4000. A barrier wall was placed along the edge of the existing roadway to separate workers from live traffic. Sometimes, there was only a 22 inch (559 mm) wide ledge, between the edge of the existing roadway and the barrier wall, for the paver’s tracks to run.
“Before starting the project, I was very concerned,” Mattivi said. “We had never worked with this paver before or an IDBI, and we were working in such a small area with very little room for the tracks. After the first or second day of paving though, it was just full speed ahead. There were no problems.”
GOMACO engineered six foot (1.8 m) leg extensions for the right and left rear legs and the right front leg to help with the clearance issue. Each leg on the four-track GP-4000 has manual pivoting mount arms which allow the legs to pivot 19.5 inches (495 mm) to the inside or outside of the straight ahead position. The pivoting feature allowed Security to place the legs in the optimum locations for their tight-clearance requirements.
The new lane had to match the profile of the existing highway. Security operated their GP-4000 locked to grade on the right side of the paver. Stringline on the left side of the paver controlled steering and grade. A standard California PCC mix design, with an average slump of 1.5 inches (38 mm), was used on the project. It was produced by Security’s on-site batch plant. Up to 15 trucks, each carrying a 10 cubic yard (7.6 m3) load, dumped directly on grade and kept the paver supplied with concrete.
The new lanes are 23.6 feet (7.2 m) wide and 11 inches (279 mm) thick. A front-mounted bar inserter on the GP-4000 was inserting a #6 deformed tie bar, 29.5 inches (750 mm) long, every 28 inches (710 mm) for the longitudinal joint. The IDBI’s computer manages the timing and the spacing of these bars for accurate placement, including skipping the insertion point where the transverse joint is located.
The IDBI on the GP-4000 inserted 18 inch (460 mm) long, 1.5 inch (38 mm) diameter bars, spaced 12 inches (305 mm) apart, every 23.6 feet (7.2 m) for the transverse joint. The first bar was offset five inches (127 mm) from the edge of the slab.
The IDBI’s computer control manages all of the systems and presents the information on an easy to understand display. The computer controls the timing and operations of the IDBI functions, including sending the bar-loading trolley, positioning the IDBI in standby, and activating the IDBI system for bar insertion.
Production averaged approximately 2000 cubic yards (1529 m3) per eight hour shift.
The IDBI produced a quality pavement with bar insertion accuracy. After the first day’s pour, Caltrans wanted to test bar placement. They drilled 26 test cores to check placement and all the bars were within tolerance. None were found to be deficient in either depth or position.
“I was worried about using the IDBI, because we had heard they could be temperamental,” Mattivi explained. “It couldn’t have gone any better for us. It’s been a real eye opener for us, and as far as we’re concerned, it’s the only way to get the job done. The IDBI has saved us a lot of money, as far as inserting dowels versus men working the dowel baskets. We are just thrilled with it.”