RGG United Contractor Inc. (RGG) completed a major terminal gate repaving project at Phoenix Sky Harbor International Airport three months ahead of schedule, using reversible metal paving forms that were designed to accommodate different concrete depths.
The project was part of a $15.4 million contract to repave areas where Southwest Airlines aircraft taxi to and from the gates at Terminal 4, the airport’s busiest terminal. At the time of the award, FAA Administrator Michael Huerta highlighted the importance of the project by pointing out that deteriorating pavement can produce debris that damages aircraft and engines.
The contract included removal and replacement of approximately 94,000 sq yd of 18-in. to 22.5-in. concrete pavement, totaling 51,500 cu yd of concrete. According to Civil Engineer and Operations Manager John Kliethermes, of RGG, the job was finished three months ahead of schedule, despite severe rain and flooding in the Phoenix area.
Flexibility in forms
For the project, RGG selected steel paving forms. At the outset, Kliethermes cautioned the manufacturer that the forms had better be straight, as forms purchased earlier from another source proved to be under-designed and failed the requirements for rigidity and straightness in the field. He was pleased with the quality and accuracy of the new forms, saying, “We insisted that the forms be held within a 1⁄16-in. tolerance, and they were.”
The contractor ordered 160 paving forms in two different sizes, totaling more than 1,600 linear ft. All are 10 ft in length, made of 1⁄4-in. steel, and designed so they can be used for two different pavement depths. Some of the forms can be used for either 18-in. or 22.5-in. pavement, while others can be used for either 18 in. or 16 in. depths. This cost-effective feature provided greater flexibility for use on this and future jobs.
Prior to the concrete work, the original pavement was removed by Banicki Construction of Tempe, Ariz., under a joint venture with RGG. The concrete was broken with an excavator-mounted hydraulic impact breaker. The resulting material then was crushed to provide a base for the new pavement. Kliethermes said the original base was old fill material that did not meet current FAA specifications. The crushed concrete met FAA Standard P-219 for Recycled Concrete Aggregate Base Course. By recycling the old pavement, the environmental impact of the project also was reduced substantially.
Kliethermes said that a majority of the concrete on this job was 18 in. thick, with sections thickened to 22.5 in. where load transfer dowels were not used. He explained that the Southwest Airlines fleet is composed entirely of Boeing 737 models, which constitute Group 5 design and require a pavement thickness of 18 in.
The concrete mix was designed to lower the potential for alkali-silica reactivity (ASR) while still achieving 650-psi flexural strength. Kliethermes reported that the concrete contained 30% fly ash due to the highest potentially reactive aggregates in the nation being from the Salt River near Phoenix. He said most other sites are closer to 10-15% fly ash by comparison.
The forms all incorporate angled stake pockets that allowed them to be staked in either direction. Gusset-style end connections facilitated bolting the forms together securely. Although the forms were made with a 2-in. top tread to allow a paver to ride along the top if desired, the paver used on this project was equipped with rubber-tired wheels that straddle the forms, as well as a wire guide system and an internal concrete vibration system.
Transit mixing trucks delivered concrete to the arranged form area from an on-site batch plant, primarily at night to aid cure time and minimize disruption to airport operations.
The forms’ bolted end connections minimized joint misalignment and enabled RGG to speed up the job. Kliethermes said they also welded eye-bolts to the forms so they could move 40-60 ft lengths as a single unit with a large tracked excavator. When lifting and moving the joined forms, stiffeners were added to stabilize the joints. This approach eliminated the need to realign the forms each time and also improved quality by minimizing the possibility of joint misalignment that could have caused stress points in the concrete.
Concrete for most airport projects of this type is slip-formed, typically in 20-ft-wide lanes. RGG United demonstrated that it could do the job just as quickly by pouring fewer but wider lanes using the forms and conventional paving equipment. In addition, the equipment required for this approach was smaller than that used for slip-forming and had less impact on airport traffic.
Forms were set in 40-ft-wide lanes, with the paver traveling outside the forms in the adjacent lanes. Transit mixers delivered concrete from an on-site batch plant to both sides of the area within the forms. Alternate lanes were poured first, with the remaining lanes poured after the first sections had cured. On one of the largest pours, the contractor completed more than 700 linear ft of a 40-ft-wide lane in a single evening. According to Kliethermes, this amounted to about 120 truckloads of concrete. Most concrete placement and finishing operations were done at night when temperatures were cooler for better working conditions and proper concrete curing as well as minimal impact on airport operations.
In addition to the forms, a heavy-duty truss screed was used for the project. Kliethermes said it was used mainly for backup on this project: “If our paver broke down and we still needed to finish a 40-ft-wide lane, the screed was ready as our contingency plan, but will be used on future jobs as well.”
The vibratory screed incorporated a direct-drive system that required no extra belts or pulleys, as well as reversible “double life” finishing tubes that last twice as long as conventional angle blades.
More on the horizon
Based on the quality and speed of its work, RGG recently received two new contracts to replace pavement at additional gates in the airport. Kliethermes pointed out that most airport paving contracts awarded by the FAA are through competitive bidding on a design-build basis. In this case, his company was awarded the two contracts based on their proven qualifications. In addition to the capabilities RGG demonstrated and the quality it delivered on the recently completed job, the company already had the necessary equipment and an on-site batch plant, which helped ensure that the work would be completed faster and with minimal disruption.
The new projects include removal and replacement of approximately 35,000 sq yd of pavement on the west side of the same terminal to make way for Sky Harbor’s brand new Terminal 3, with work already underway, and a larger project to remove and replace about 186,000 sq yd of pavement on the north side of Terminal 4 for American Airlines. Work on this contract began in August 2015 and will extend through 2019. R&B