High-performance concrete is integral to massive airside paving project at Louis Armstrong New Orleans International Airport’s new North Terminal.
By Robert Doubleday and Steve Salzer
Louis Armstrong New Orleans International Airport achieved great success during the last several years as it continued to grow and improve travel to and from the Greater New Orleans region. In 2016, the airport experienced a 21 percent growth in nonstop destinations and surpassed 11 million passengers served. In 2017, the airport set yet another record, with more than 12 million passengers handled.
In 2016, the airport began building a new world-class terminal complex to replace its current terminal and support continued progress and projected growth in passenger and cargo volumes. The Hunt-Gibbs-Boh-Metro Joint Venture team is serving as the Construction Manager at Risk (CMAR) for this $1.029 billion new terminal project, which is scheduled to be completed in May 2019.
The 972,000-square-foot terminal will feature three concourses with 35 gates, a consolidated checkpoint, seamless connections between concourses, parking garages, and surface parking lots. It will also include a new high-performance concrete apron surrounding the concourses where aircraft are parked, refueled, or boarded, as well as the extension of two taxiways connecting the new terminal to the airport’s existing runway system.
As with any large-scale project, planning, coordination, production, and various technical issues created challenges that required a tremendous level of collaboration among industry professionals to deliver a high-performance airfield pavement for this new world-class airport.
Building a strong foundation
The new terminal is being developed on reclaimed swamp lands typical in southern Louisiana, with nearly 100 feet of organic soils. To build on these challenging Louisiana subsurface conditions, significant ground improvement was necessary before placement of the concrete pavement could begin.
As a first step, the subgrade below the paved areas was surcharged with 2.5 million tons of sand and 3,200 miles of wick drains. It took almost a year of night deliveries to haul in all the infill; the 4-foot-deep layer of sand was left in place for nine months to progress settlement.
To provide a suitable subbase foundation, the subgrade was stabilized with an in-situ cement soil solidification treatment. For this application, the Ste. Genevieve Plant of Holcim (a member of the LafargeHolcim family of companies) supplied more than 16,000 tons of portland I/II cement, which was homogenized with the soil and firmly compacted.
As the final step in creating a solid base under the surface concrete pavement, a 7-inch-deep layer of econocrete (lean concrete) was placed on top of the soil-cement-treated subbase. In compliance with Federal Aviation Administration (FAA) P-306 specifications, the quality-control laboratories of Lafarge (also a member of the LafargeHolcim family of companies) designed and received approval for two econocrete mixes containing a blend of portland I/II cement, p-gravel, sand, and fly ash to achieve stringent performance criteria.
Optimizing the pavement mix
Vital to the success of any high-performance paving project is the concrete mixture. For New Orleans’ new airport terminal, this required a strong collaborative effort between Boh Bros. Construction Co. and Lafarge in developing a high-quality airside concrete pavement.
The pavement mix design was guided by FAA P-501 specifications, with a flexural strength of 650 psi at 28 days. Slump was specified at 0.75 (plus or minus 0.25) inches and air content at 5.5 (plus or minus 1.2) percent. Field testing of the high-performance mix included a 1,000-foot section of the pavement.
For the project, materials and processes needed to meet stringent quality standards. To make the best decisions on mix ingredients, the team conducted an extensive evaluation of various aggregates, cementitious blends, and admixtures to determine what materials would work best together in achieving the targeted performance characteristics specified for the concrete.
Upon successful completion of exhaustive testing and performance assessments, a concrete mix design containing a 45 to 55 percent blend of Type I/II portland cement and NewCem slag cement was selected for the project. This high slag cement content in the mix produces denser concrete with higher compressive and flexural strengths, reduced permeability against chlorides, increased resistance to alkali-silica reaction, and excellent finishing qualities. It also achieves a high early strength of 500 psi, which allowed the paving crews to work off of the concrete three to four days after it was placed.
Consistency, quality, and attainment of specified target performance were greatly enhanced by using a combined aggregate gradation approach for meeting mix specifications. Aggregates used included a #57 course aggregate, a native sand from the Lafarge Honey Island site, a concrete sand with a very controlled gradation and fineness modulus, and an intermediate aggregate to bridge the gap between the course and fine aggregates.
Reproportioning the blend ratio of these aggregates in every batch allowed the team to reproduce a near-identical mix with very little variability. “This would drive strengths higher, reduce water demand, allow the absolute minimum cement content dictated by the specification and greatly exceed the average required 28-day strength,” said BJ Eckholdt, quality control manager at Lafarge.
Quality control at the forefront
To ensure a high degree of consistency, reliability, and quality control, the project team mobilized two concrete batch plants at the jobsite, each producing an average of 150 cubic yards of concrete per hour. Gradation tests were run every day, and Lafarge’s quality-control laboratories adjusted aggregate proportions in the mix to achieve a consistent coarseness and workability factor for optimal paving performance. “The aggregate quality was excellent, and we well surpassed the required strength using the prescribed cementitious material content,” Eckholdt said.
The quantity of concrete produced was based on detailed day-to-day planning. Typical daily production was 1,800 to 2,000 cubic yards for dump trucks during the night and 400 to 600 cubic yards for mixer trucks during the day. For the entire paving project, Lafarge produced more than 165,000 cubic yards of concrete for airfield paving requirements. Jobsite quality-assurance plans included multiple tests on the first batch from each plant, including slump, air, unit weights, and temperature. Flexural strength was tested every 200 cubic yards.
The large-scale paving project also required a significant degree of inventory planning and logistics to meet production demand. LafargeHolcim kept its Lafarge slag cement processing facility and Holcim portland cement manufacturing plant open for supplying cementitious materials whenever they were needed, which was important because jobsite central mix operations were working around the clock.
Paving gets underway
Work on the apron and taxiways started in late January 2018, and Boh Bros. and Lafarge attacked the job from the very beginning. Slipform paving was performed in 10-hour increments at night, and the team’s execution had to be flawless in order to overcome the challenges of keeping work crews going, replenishing material inventories, and coordinating trucks to transport concrete from the batch plants to the front of the pavers. Ongoing communication kept the team aware of what needed to be done and when, enabling workers to run the operation like a well-oiled machine.
A new state-of-the-art G&Z S600 slipform paver purchased specifically for the project greatly enhanced jobsite maneuverability, as it could go into a counter-rotate mode and spin 360 degrees inside its own tracks. This feature allowed the operator to get off of a lane, make a quick U-turn and start paving again within five minutes. An advanced Leica control system allowed for precision grade control.
According to Tim Lewellen, Boh Bros.’ paving project manager, paving widths at the airport site measured 18 feet, 9 inches, even though the machine is capable of paving as wide as 30 feet. “The paver put out a very well closed surface, the edge slump was negligible, the edge corner was 90 degrees, and there was very little additional work on the pavement after it came out the back end of the paver,” he said.
Contractors drilled holes and inserted load-transfer dowels every 18.75 feet on the 17-inch and 18-inch slabs, and every 9.375 feet on the 9-inch slabs. Test sections of pavement were cored every 15 feet to ensure that the aggregate was evenly distributed below the surface.
Total pavement installed in the airside operations area encompasses more than 76 acres, the bulk of which was performed during a three-month period. This includes 277,000 square yards of 17-inch pavement and 26,100 square yards of 9-inch pavement for the apron, 46,150 square yards of pavement for the taxiways, and 14,250 square yards for the ground support equipment road.
Broad and lasting benefits
The new world-class terminal at Louis Armstrong New Orleans International Airport will offer broad and lasting benefits to the New Orleans air transportation system, its economy, and the lives of those who live and work in the region. From the beginning, the new terminal was designed with flexibility to allow the airport to adapt as quickly as needed to support future growth in domestic and international flights. The construction project is currently more than 85 percent complete. When the new terminal opens in 2019, the current terminal will close.
Robert Doubleday (firstname.lastname@example.org) is operations manager and Steve Salzer (email@example.com) is sales manager at Lafarge, a member of the LafargeHolcim family of companies (www.lafargeholcim.us). They can be reached at 504-834-3341.