Construction began on the two test pavement sections in mid-October 2001 and was completed in early December 2001. Shown here is the site in late November 2001, when the test sections were nearly complete. Central Illinois Tile Company (CIT) was the prime contractor for the test section construction.

The test pavements were built adjacent to the Advanced Transportation Research and Engineering Laboratory (ATREL), University of Illinois’ concrete and asphalt pavement research facilities in Rantoul, Illinois.

The two tracks (Pavement Lanes 1 – left and 2 - right) are each 500 feet long and 12 feet wide. In this photograph, the continuously reinforced concrete pavement is fully constructed and is curing.

A 4-inch-thick bituminous aggregate mixture (IDOT-approved N30 mix, PG64-22) was built by Champaign Asphalt, Inc. to serve as the base layer. The base layer is supported on a 6-inch-thick aggregate subbase (CA6, meeting IDOT specifications). A non-woven geotextile separates the gravel subbase from the subgrade, which consists of compacted native soil (AASHTO A-4 clay or silty clay).

Each track was divided into five segments (for a total of 10 segments) varying in length from 90 to 95 feet. The segment layout is shown in these two figures.

Each segment’s pavement design varies slightly so that various parameters (including percentage of reinforcing steel, pavement thickness, depth to top of reinforcing bars, and one- versus two-layers of reinforcing bars). Shown here is Section 7, consisting of #6 reinforcing bars spaced on 5.25-inch centers, for a total steel percentage of 0.80.

With the exception of Sections 4 and 5 (with 14-inch-thick pavement), all test sections are constructed 10-inches-thick in order to achieve failure under the accelerated loading program.

CRSI member Birmingham Steel Corporation of Bourbonnais, Illinois supplied the reinforcing bars for the program, while Toltec Steel Services/ABC Coating of Kankakee, Illinois supplied the epoxy coating and fabrication of the reinforcing steel. Approximately 35 tons of reinforcing bars were installed. All materials and labor were donated.

IDOT routinely uses ASTM A775 epoxy coating of reinforcing steel in its CRCP to protect against the potential damage from corrosion caused by deicing salts.

During construction, the longitudinal reinforcing bars are supported every four feet on #4 reinforcing bars in the transverse direction. The reinforcing bars are supported on plastic chairs.

Between segments there is a 15-foot-long splice section, in which staggered reinforcing bar splices are located. Splicing makes the reinforcing bars act continuously. Testing will be conducted over the un-spliced 80-foot-long section. The splices are a modified version of Lap Detail I of IDOT Standard 421001.

The pavement lanes are anchored at each end with lugs to restrain the pavement from moving and to anchor the longitudinal reinforcing bars. The lugs were built to provide equivalent anchorage to a 10-mile-long stretch of pavement.

The end lugs consist of two continuous beams across the pavement width, 4 feet deep each and 8 feet apart, connected by an 18-inch-thick reinforced concrete slab.

Sections 4 and 5 with pavement thickness of 14 inches contain two layers of reinforcing bars, one bar 3.5 inches and one bar 7 inches below the pavement surface, for a total steel percentage of 0.78.

The concrete mix was a Class PV with a maximum water-to-cement ratio of 0.42. Builder’s Supply of Champaign, Illinois supplied the ready-mixed concrete. A total of approximately 400 cubic yards was used to construct the two tracks.

Central Illinois Tile Company placed the concrete using side forms and hard scread placement. Standard practices for portland cement concrete consolidation, finishing, and curing were followed per IDOT extended-life concrete pavement specifications.

Sections 5 through 10 (Pavement Lane 2) were used to study the effects of uniformly spaced cracks. Regularly spaced cracks were induced every two to six feet on the pavement surface. The purpose of the cracks is to create a weakened plane to promote the regular development of cracks – at controlled locations – that would form naturally, but not necessarily uniformly, in CRCP. Cracks on Sections 8 and 9 (shown) were induced using a Soff-Cut saw at 1.5 inches deep.

Controlling the crack location and spacing eliminates one variable in the interrelationship between steel content, crack spacing, and crack width. Cracks on Sections 6 and 7 were induced by embedding a strip of plastic tape three inches deep in the fresh concrete, as shown here.

The 28-day concrete compressive strength tested in the range of 6,500-7,000 psi and the flexural strength at 700 psi. IDOT Technicians prepared the concrete test specimens.

In the future, this test section will be used to evaluate whether tining the concrete surface can eliminate problems with debonding of an asphalt overlay. Pavement Lane 1 has three different finished surfaces: transverse tined, longitudinal tined, and smooth. Pavement Lane 2 has a transversely tined surface over its entire length.

The completed test section reveals little of the sophisticated instrumentation encapsulated within it.