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Rapid Slab Repair and Replacement of Airfield Concrete Pavement (2021)

Chapter: Appendix A - Airport Case Examples

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Suggested Citation:"Appendix A - Airport Case Examples." National Academies of Sciences, Engineering, and Medicine. 2021. Rapid Slab Repair and Replacement of Airfield Concrete Pavement. Washington, DC: The National Academies Press. doi: 10.17226/26322.
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Suggested Citation:"Appendix A - Airport Case Examples." National Academies of Sciences, Engineering, and Medicine. 2021. Rapid Slab Repair and Replacement of Airfield Concrete Pavement. Washington, DC: The National Academies Press. doi: 10.17226/26322.
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Suggested Citation:"Appendix A - Airport Case Examples." National Academies of Sciences, Engineering, and Medicine. 2021. Rapid Slab Repair and Replacement of Airfield Concrete Pavement. Washington, DC: The National Academies Press. doi: 10.17226/26322.
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Suggested Citation:"Appendix A - Airport Case Examples." National Academies of Sciences, Engineering, and Medicine. 2021. Rapid Slab Repair and Replacement of Airfield Concrete Pavement. Washington, DC: The National Academies Press. doi: 10.17226/26322.
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Suggested Citation:"Appendix A - Airport Case Examples." National Academies of Sciences, Engineering, and Medicine. 2021. Rapid Slab Repair and Replacement of Airfield Concrete Pavement. Washington, DC: The National Academies Press. doi: 10.17226/26322.
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Suggested Citation:"Appendix A - Airport Case Examples." National Academies of Sciences, Engineering, and Medicine. 2021. Rapid Slab Repair and Replacement of Airfield Concrete Pavement. Washington, DC: The National Academies Press. doi: 10.17226/26322.
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Suggested Citation:"Appendix A - Airport Case Examples." National Academies of Sciences, Engineering, and Medicine. 2021. Rapid Slab Repair and Replacement of Airfield Concrete Pavement. Washington, DC: The National Academies Press. doi: 10.17226/26322.
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Suggested Citation:"Appendix A - Airport Case Examples." National Academies of Sciences, Engineering, and Medicine. 2021. Rapid Slab Repair and Replacement of Airfield Concrete Pavement. Washington, DC: The National Academies Press. doi: 10.17226/26322.
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Suggested Citation:"Appendix A - Airport Case Examples." National Academies of Sciences, Engineering, and Medicine. 2021. Rapid Slab Repair and Replacement of Airfield Concrete Pavement. Washington, DC: The National Academies Press. doi: 10.17226/26322.
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Suggested Citation:"Appendix A - Airport Case Examples." National Academies of Sciences, Engineering, and Medicine. 2021. Rapid Slab Repair and Replacement of Airfield Concrete Pavement. Washington, DC: The National Academies Press. doi: 10.17226/26322.
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Suggested Citation:"Appendix A - Airport Case Examples." National Academies of Sciences, Engineering, and Medicine. 2021. Rapid Slab Repair and Replacement of Airfield Concrete Pavement. Washington, DC: The National Academies Press. doi: 10.17226/26322.
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Suggested Citation:"Appendix A - Airport Case Examples." National Academies of Sciences, Engineering, and Medicine. 2021. Rapid Slab Repair and Replacement of Airfield Concrete Pavement. Washington, DC: The National Academies Press. doi: 10.17226/26322.
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Suggested Citation:"Appendix A - Airport Case Examples." National Academies of Sciences, Engineering, and Medicine. 2021. Rapid Slab Repair and Replacement of Airfield Concrete Pavement. Washington, DC: The National Academies Press. doi: 10.17226/26322.
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Suggested Citation:"Appendix A - Airport Case Examples." National Academies of Sciences, Engineering, and Medicine. 2021. Rapid Slab Repair and Replacement of Airfield Concrete Pavement. Washington, DC: The National Academies Press. doi: 10.17226/26322.
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Suggested Citation:"Appendix A - Airport Case Examples." National Academies of Sciences, Engineering, and Medicine. 2021. Rapid Slab Repair and Replacement of Airfield Concrete Pavement. Washington, DC: The National Academies Press. doi: 10.17226/26322.
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Suggested Citation:"Appendix A - Airport Case Examples." National Academies of Sciences, Engineering, and Medicine. 2021. Rapid Slab Repair and Replacement of Airfield Concrete Pavement. Washington, DC: The National Academies Press. doi: 10.17226/26322.
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Suggested Citation:"Appendix A - Airport Case Examples." National Academies of Sciences, Engineering, and Medicine. 2021. Rapid Slab Repair and Replacement of Airfield Concrete Pavement. Washington, DC: The National Academies Press. doi: 10.17226/26322.
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Suggested Citation:"Appendix A - Airport Case Examples." National Academies of Sciences, Engineering, and Medicine. 2021. Rapid Slab Repair and Replacement of Airfield Concrete Pavement. Washington, DC: The National Academies Press. doi: 10.17226/26322.
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Suggested Citation:"Appendix A - Airport Case Examples." National Academies of Sciences, Engineering, and Medicine. 2021. Rapid Slab Repair and Replacement of Airfield Concrete Pavement. Washington, DC: The National Academies Press. doi: 10.17226/26322.
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Suggested Citation:"Appendix A - Airport Case Examples." National Academies of Sciences, Engineering, and Medicine. 2021. Rapid Slab Repair and Replacement of Airfield Concrete Pavement. Washington, DC: The National Academies Press. doi: 10.17226/26322.
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Suggested Citation:"Appendix A - Airport Case Examples." National Academies of Sciences, Engineering, and Medicine. 2021. Rapid Slab Repair and Replacement of Airfield Concrete Pavement. Washington, DC: The National Academies Press. doi: 10.17226/26322.
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Suggested Citation:"Appendix A - Airport Case Examples." National Academies of Sciences, Engineering, and Medicine. 2021. Rapid Slab Repair and Replacement of Airfield Concrete Pavement. Washington, DC: The National Academies Press. doi: 10.17226/26322.
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Suggested Citation:"Appendix A - Airport Case Examples." National Academies of Sciences, Engineering, and Medicine. 2021. Rapid Slab Repair and Replacement of Airfield Concrete Pavement. Washington, DC: The National Academies Press. doi: 10.17226/26322.
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69   This appendix provides case examples of rapid slab repair and replacement (RSRR) practices and programs at several airports. In addition to completing the online surveys, airport engineer(s) or the airport’s consultant, or both, participated in a detailed interview; the information pre- sented here summarizes the information from the surveys and interviews. Table A-1 lists the airports that are featured in these case examples. The case examples are presented in order from west to east and according to FAA region and associated Long-Term Pavement Performance (LTPP) program climatic region (FHWA 2016). While these examples represent mainly large hub airports, most information presented can be applied to airports of any size. Each case example provides the following information: • Overview of the airport and general information about RSRR practice, • RSRR program highlights, • Challenges, and • Key takeaways. RSRR Practice at Seattle–Tacoma International Airport Overview Seattle–Tacoma International Airport (SEA) is a large hub airport located in Seattle, Washington. Nearly all aircraft-bearing pavements are concrete. SEA initiated an RSRR program around 1994, and it has evolved through trial and error, capitalizing on lessons learned from numerous projects. Table A-2 provides an overview of SEA’s RSRR practice. The airport does not monitor PDR performance. FDR performance is monitored as part of SEA’s annual pavement inspection program. Before SEA started its RSRR program, a typical service life for an FDR was 10 years. Since then, FDRs have lasted 15 to 20 years. Minimal to no cracking has been reported in recent PDRs. The airport identified quick setting time, which has a negative impact on concrete finishing, and low strength, which can lead to cracking, as key factors that can lead to poor performance. RSRR Program Highlights • Regardless of experience, the contractor is required to construct a mock-up panel off-site prior to starting work on the airfield. This provides the opportunity for the contractor’s crews to familiarize themselves with the behavior of the concrete mixture. SEA found that the behavior of VHES CSA cement concrete changes frequently, even during the same job. A P P E N D I X A Airport Case Examples

Airport FAA Region LTPP Climate Region Seattle–Tacoma International Northwest Mountain Wet, nonfreeze Vancouver International naa Wet, nonfreeze Los Angeles International Western Pacific Dry, nonfreeze McCarran International Western Pacific Dry, nonfreeze Phoenix Sky Harbor International Western Pacific Dry, nonfreeze John Glenn Columbus International Great Lakes Wet, freeze Hartsfield–Jackson Atlanta International Southern Wet, nonfreeze Louisville Muhammad Ali International Southern Wet, nonfreeze Raleigh–Durham International Southern Wet, nonfreeze Note: na = not applicable. aSimilar to Northwest Mountain. Table A-1. Airports with highlighted RSRR practice. Category Item Detail Airport information Airport location Seattle, Washington Owner Port of Seattle FAA classification Large hub FAA region Northwest Mountain LTPP climate region Wet, nonfreeze Number of runways Three parallel Planning Stakeholder communications FAA control tower and airport-operated ramp tower (for apron repairs) Airlines Airport operations and fire department Allowable closures All facilities: 6-hour night closure (11:00 p.m. to 5:00 a.m. typical) Aprons: Some exceptions for day closures with airline approval Funding Airport Emergency work Rarely done, as concrete pavements in aircraft movement areas are kept in good condition Project delivery Design–bid–build On-call contractors? No Design Designer Port of Seattle Design documents FDR: Plans and specifications Specification elements Liquidated damages for exceeding closure windows Requires backup equipment In-pavement lights Single light: Steel reinforcement around the light can Multiple lights: Steel reinforcement throughout slab Construction Construction PDR: Airport maintenance crews FDR: Contractors PDR materials Epoxy concrete (prepackaged) FDR materials Specialty cement (CSA) Material testing Port of Seattle personnel Inspection Port of Seattle personnel QC/QA elements Onsite inspectors Nuclear gauge to monitor sublayer compaction Concrete testing: Air content, flexural strength, and temperature Contingency planning Airport has its own precast slabs that can be temporarily installed Work is postponed if rain or fog is forecast Material acceptance PDR: None FDR: Flexural testing [550 psi at return to service, 650 psi at 28 days (acceptance)] Table A-2. Overview of RSRR practice at Seattle–Tacoma International Airport.

Airport Case Examples 71   • The contractor must start work on the least-critical areas of the airfield (i.e., apron and taxiway, then runway slabs). This allows the contractor to gain experience (or refamiliarize its crews) with working on the airfield and with accelerated construction, which slightly lowers the risk of an impact on airport operations if work extends past the return-to-service deadline. • The airport conducts a very good internal pavement inspection program. Sections of the airfield are inspected on an annual (rotating) basis. As a result, SEA can plan for slab repair and replacement activities well in advance. • A design–bid–build process with a change order option is used to deliver RSRR projects. Design is done in house, and each project includes a specific number of slabs for replacement. If the contractor is doing good work, SEA can add 25% additional quantities to the contractor’s work without needing the approval of the Port of Seattle Board. Additional work depends on slab location (i.e., runway, taxiway, apron) and whether additional planning or stakeholder coordination is needed. • SEA collaborates with a university. Researchers collect data on the CSA cement mixtures and provide feedback to enhance SEA’s RSRR program. • SEA permits concrete batch plants on-site for larger projects. Batch plants can produce a more uniform concrete mixture than mobile volumetric mixing trucks. Oftentimes, these batch plants are already on-site to produce FAA P-501 concrete mixture for conventional construction on the airfield. Challenges • Lack of technical knowledge, • Lack of skilled contractors and workforce, and • Very high cost of RSRR with VHES concrete (approximately four times greater than P-501 concrete). Key Takeaways • Conduct upfront and contingency planning (stated as one of the most important elements for RSRR project success). • Set realistic expectations when carrying out initial RSRR projects and plan for issues during construction. • Use VHES concrete only when necessary (i.e., very short closure windows). • Quick set time of VHES concrete can negatively affect concrete finishing, and low strength can lead to cracking; both are key factors that can lead to poor performance. • Select an experienced contractor (also important to RSRR project success). • Establish a backup plan (mainly for repairs in aircraft parking areas) in the event construction extends beyond the closure time frame. • Monitor the weather forecast and delay FDR if conditions (e.g., rain, fog, high wind) may potentially affect the construction schedule and quality. • Provide on-site inspectors and material testing. Material testing technicians must be trained or have experience preparing beam specimens with VHES concrete. RSRR (Cast-in-Place) Practice at Vancouver International Airport Overview Vancouver International Airport (YVR) is a large hub airport located in Vancouver, British Columbia, Canada. YVR is Canada’s second busiest airport and has two main (parallel) runways. Runway 8L-26R (north runway) is 9,940 feet and was originally built 1996, and Runway 8R-26L

72 Rapid Slab Repair and Replacement of Airfield Concrete Pavement (south runway) is 11,500 feet and originally constructed in 1953 (it currently has a partial asphalt concrete overlay). A third, crosswind runway, is 7,300 feet long. YVR initiated an RSRR project in 2010 to replace deteriorated slabs on the north runway. Eleven slabs, approximately 20 feet by 25 feet and 15 inches thick, were identified for replace- ment. Existing slabs contained in-pavement lighting that had to be maintained in the replace- ment slabs. The replacement slabs were reinforced to control potential cracking. Table A-3 provides an overview of this RSRR project. While formal condition monitoring has not been conducted, the replaced slabs have been performing satisfactorily for 10 years. RSRR Cast-in-Place Program Highlights Following are key features of YVR’s RSRR cast-in-place program: • The contractor was required to construct multiple mock-up panels off-site prior to starting a construction project on the airfield. This provided the opportunity for the contractor’s crews to familiarize themselves with the concrete mixture. For this project, the material was very stiff and required a lot of work for proper placement. The material supplier was part of the team to ensure proper placement. Category Item Detail Airport information Airport location Richmond, British Columbia, Canada Owner Vancouver Airport Authority FAA classification Large hub FAA region na (similar to Northwest Mountain) LTPP climate region Wet, nonfreeze Number of runways Two parallel and one crosswind Planning Stakeholder communications Air control tower Airlines Airport operations Allowable closures 59 hours Funding Airport Project delivery Design–bid–build Design Designer Consultant Design documents Plans and specifications Specification elements Liquidated damages for exceeding closure windows Requires backup equipment, backup batch plant, weather contingency plans, and so forth In-pavement lights Yes Construction Construction Contractor PDR materials Consultant FDR materials Proprietary, HES cement Contractor QC Testing firm Construction inspection Consultant and airport personnel QC/QA elements Onsite inspectors Concrete testing: Air content, slump, and flexural strength Contingency planning Redundant equipment; weather canopies Material acceptance Flexural testing (500 psi at 24 hours, 700 psi at 46 hours) Table A-3. Overview of a RSRR project at Vancouver International Airport.

Airport Case Examples 73   • Construction was planned during a time of year and over weekends with lower operations. Coordination with stakeholders is required to minimize disruption to airline operations. • A design–bid–build process was used. Traditional design in this case allowed time for thorough planning prior to bid and construction. Security access, haul route planning, tower coordination, and what-ifs (i.e., poor weather, material supply issues) were all planned out. • The supplier was included in the planning and construction processes. This helped ensure that a suitable material that met the allowable time restrictions for the FDRs was used. Challenges From the perspective of the engineer on this project, the biggest challenges were as follows: • Short allowable closure times because operations were severely restricted when one runway was closed, • Lack of a skilled workforce with experience in using accelerated setting materials, and • The high cost of RSRR with VHES concrete (approximately $50,000 per panel). Key Takeaways • Conduct upfront and contingency planning (stated as one of the most important elements for RSRR project success). Acquire security access and identify haul routes in advance due to the nature of material. • Require the selected contractor to conduct trials with the planned materials. At YVR, this has ensured complete understanding of methods and materials. Airport work only moved forward once all parties were comfortable with the process. • Require the contractor to prepare a contingency plan for inclement weather conditions. Once work started, it had to be completed (contractor had large canopies to cover work areas in case of rain). • Provide on-site inspectors and material testing. Material testing technicians must be trained or have experience preparing beam specimens with VHES concrete. Early trials helped all involved parties become more familiar with the material and construction methods. RSRR (Precast) Practice at Vancouver International Airport Overview YVR is a large hub airport located in Vancouver, British Columbia, Canada. It is Canada’s second busiest airport and has two main (parallel) runways: Runway 8L-26R (north runway) is 9,940 feet and was originally built 1996, and Runway 8R-26L (south runway) is 11,500 feet and originally constructed in 1953 (it currently has a partial asphalt concrete overlay). A third, cross- wind runway, is 7,300 feet long. As part of the planning process for an FDR project on the north runway, several design alternatives were assessed. Precast panel replacements were selected as the best alternative on the basis of the allowable 8-hour nightly closure window and life-cycle costs. The controlling factor in the decision was stakeholder needs to minimize runway shutdowns. This factor alone justified the additional cost of precast slabs as compared with the cast-in-place alternatives. However, the precast panel technology did not appear to have extensive history for typical large panel sizes (and weight) for airside pavements. Therefore, YVR conducted a pilot con- struction project in 2019 to confirm that the precast slabs would work as anticipated. Table A-4 provides an overview of YVR’s precast panel replacement pilot study.

74 Rapid Slab Repair and Replacement of Airfield Concrete Pavement For the pilot project, a preliminary design document and engineering drawings were developed to illustrate the engineering concepts. These were distributed as an expression of interest, and then a request for proposal was distributed to local contractors. While the precast panel system was not specified, all the submitting teams selected a proprietary panel design. The contractor selected for the project had experience using precast slabs during off-peak hours on a highway project. Taxiway V was selected for the pilot project, and 12 precast slabs were installed for the study. Conventional cast-in-place techniques were used to repair adjacent pavement. The first eight precast slabs were installed over a period of 4 weeks to refine the installation procedure. Replace- ment of the last four precast slabs was required to be completed during 8-hour closures to simulate work on the runway, although there was no impending need to reopen the taxiway at the end of the closure. The contractor was able to set up a precast facility next to the airport and mastered the logistics of fabricating the panels and moving them to the site for installation. Panels were 19.7 feet by 24.6 feet and 14.2 inches thick. The panels were designed as heavily reinforced ductile slabs because conventional design thicknesses would have been much thicker. With fabrication Category Item Detail Airport information Airport location Richmond, British Columbia Owner Vancouver Airport Authority FAA classification Large hub FAA region na (similar to Northwest Mountain) LTPP climate region Wet, nonfreeze Number of runways Two parallel, one crosswind Planning Stakeholder communications Air control tower Airlines Airport operations and security Allowable closures 8-hour night closure Funding Airport Project delivery Construction manager Design Designer Consultant/contractor/fabricator Design documents Plans and specifications Specification elements Liquidated damages for exceeding closure windows Requires backup equipment, weather contingency plan, and so forth In-pavement lights Yes, in some panels Construction Construction Established methods FDR materials Portland cement–based mixture Contractor QC Testing firm Construction inspection Consultant QC/QA elements Concrete testing: Air content, slump, flexural strength Contingency planning Redundant equipment, weather plan Material acceptance Flexural testing Table A-4. Overview of precast panel pilot study at Vancouver International Airport.

Airport Case Examples 75   adjacent to the airport, there were no challenges with transporting the panels from the adjacent site to the taxiway site. If fabricated off-site, the panels would have been difficult to transport on local roads, over bridges, and so forth. The contractor used a conventional large-aggregate mix with low shrinkage. The large aggregate was a concern in areas with a lot of reinforcement or corners. In the future, the contractor would try to have a smaller top-size mix approved for such instances. The pilot project established a variety of conditions for which unique precast slabs would need to be fabricated; for example, some of the panels included light cans and some did not, and some panels were surrounded by cast-in-place panels and some were adjacent to other precast slabs. These conditions required different reinforcement and load-transfer details. RSRR Program Highlights YVR does not have an established RSRR program using precast slabs. This pilot project provided information for additional precast RSRR work at the airport. Challenges From the perspective of the consulting engineer, the biggest challenges to carrying out the precast panel pilot project at YVR were as follows: • There were challenges with the cement-treated base. In some cases, it was high, and part of the base needed to be removed prior to panel installation. The contractor used different techniques to trim the base in high areas, including a small milling machine and excavation equipment, depending on the geometry of the repair. The presence of a lot of base irregulari- ties and associated requirements for base repair would likely eliminate the feasibility of using precast slabs, especially during a short construction window. There were also cases where the cement-treated base was bonded to the existing concrete pavement. The contractor used the lift-out method, and when pieces were bonded, they could break the bond during removal with a dynamic load. • Five of the precast slab repairs included light cans. Two-piece cans with the upper portion cast in the precast panel were used. One issue with removal and replacement was that the new upper section could not be bolted with the lower section in the cement-treated base. The location of the inset can (in the new slab) was the one that could be controlled, but the lower section could not be connected to the upper section Therefore, tight placement tolerances were required. • Wind/weather restrictions could come into play for the types of cranes used to lift the panels. This could affect the ability to complete work within an 8-hour shift for a runway. Weather scenarios might require more equipment and different types of equipment during a limited construction window. Key Takeaways • Check grades and slab thickness for precast projects. • Fabricate precast slabs on or near the site to eliminate problems with moving large slabs over public roadways. • Require previous experience with installation of precast panels; there are many important details that cannot be overlooked. For example, the contractor must be prepared to trim or repair the base material (after panel removal) to accommodate the panel thickness. • Perform sawing of existing pavement in advance of the 8-hour closure so that the closure begins with lift-out rather than sawing. For the pilot project, sawing around the perimeter

76 Rapid Slab Repair and Replacement of Airfield Concrete Pavement needed to be done on a rail to make sure it was precise enough for the replacement panels and the light can locations. Sawing information was then shown on the shop drawings. To facilitate panel construction, the precision sawing of the perimeter was done several shifts in advance of the actual installation. The internal saw cuts for lift-out were also done in advance. • Conduct deflection testing on in-place precast slabs after completion of the project work to evaluate load transfer, corner support, and presence of voids or other defects. These results are compared with those obtained from the cast-in-place approach. Overall, the pilot project illustrated the feasibility of using precast slabs while also illustrating that it is more expensive than conventional, cast-in-place FDR. In this case, the necessity to minimize runway closure times for future repair work made the additional cost acceptable. RSRR Practice at Los Angeles International Airport Overview Los Angeles International Airport (LAX) is a large hub airport located in Los Angeles, California. LAX initiated an RSRR program between 1999 and 2000 that used a VHES mix to repair taxiway pavement between runways. Everything within the runway safety area was constructed with a mixture that achieved a 4-hour flexural strength of 350 psi. LAX does not perform individual slab repairs but has carried out many accelerated construction repairs under tight time constraints. Table A-5 provides an overview of LAX’s RSRR practice. Category Item Detail Airport information Airport location Los Angeles, California Owner Los Angeles World Airports FAA classification Large hub FAA region Western Pacific LTPP climate region Dry, nonfreeze Number of runways Four parallel Planning Stakeholder communications Air control tower Airlines Airport operations and security Allowable closures Runways have 6- to 7-hour night closures Taxiways and aprons may have longer closures, depending on location Longer (weekend) closures can be planned with stakeholder coordination Funding Federal Project delivery Design–bid–build Design Design documents Plans and specifications Specification elements Liquidated damages for exceeding closure windows Requires backup equipment, weather contingency plan Construction Construction Contractor FDR materials Portland cement–based HES QC/QA elements Concrete testing: Air content, slump, and flexural strength Contingency planning Redundant equipment Material acceptance Flexural testing (350 psi at 4 hours) Table A-5. Overview of RSRR practice at Los Angeles International Airport.

Airport Case Examples 77   In general, LAX’s rapid slab repairs have experienced shorter service lives than conventional FDR, primarily due to shrinkage-induced map cracking and surface scaling. Map cracking was related to challenges getting the material to cure properly without cracking. In the airport’s experience, the performance of the material being used was highly dependent on temperature. Cooler nighttime temperatures had a large impact on the initial set of the concrete and led to more map cracking. Approximately 40 repaired slabs were subsequently replaced because of the map cracking. Most of the slabs from the project have been removed over the years because of reconstruction of the adjacent runway. RSRR Program Highlights • The contractor is required to construct test sections in noncritical areas (such as aprons) prior to starting construction on a critical area of the airfield. This provides the opportunity for the contractor’s crews to familiarize themselves with the behavior of the concrete mixture. It also allows all the parties involved to become comfortable with the overall accelerated con- struction process prior to moving into a critical area. • A design–bid–build process is used to deliver RSRR projects. The design process allows working through security access, establishing the haul route, coordinating with the tower, and planning for potential contingencies. Working through the anticipated process and identifying all contingencies during the design stage reduces the likelihood of changes during construc- tion that can cause increases in costs and potentially lead to delays. A few years ago, LAX employed a City of Los Angeles ordinance allowing the use of a com- petitive contractor selection process that considers the quality of the team and its experience. This has been included on one project and is being considered for use on future projects. As part of the request for proposal process, LAX requires proposers to submit experience, references, and key personnel (e.g., construction manager, concrete superintendent, quality control manager, safety manager, scheduler, lead engineer). LAX also requires proposed bidders to identify antici- pated project challenges and proposed solutions. A hard bid is also required, but the pricing information is sealed and not opened in the initial proposal evaluation. After the responses are ranked, key contractor personnel participate in an interview and are scored on the basis of their responses. The overall scoring includes 50 points for experience and personnel and 50 points based on costs. The cost scoring includes the low bidder receiving 50 points, while the remaining proposers receive scores lower than 50 points. Liquidated damages are enforced for the removal of any key personnel after contract award. Challenges From the perspective of the airport engineer, the biggest challenges included • Access to the site and working among heavy aircraft operations, • Contractor experience with expedited methods and materials, and • Closure coordination with stakeholders. Key Takeaways • Engage stakeholders early. As part of the work coordination, send notices in a timely manner and submit Form FAA 7460-1 for federally funded projects. It is also essential to involve the FAA Airports District Office early on, as part of the planning process. • Develop a preliminary phasing plan and work through it with internal operations and the air traffic control tower. Conduct regular meetings with the FAA control tower and terminal radar approach control facilities as well as airline representatives. Plan for monthly meetings, which may become more frequent as the work nears or is underway.

78 Rapid Slab Repair and Replacement of Airfield Concrete Pavement • Plan site access and potential complications when work is being conducted amid active operations. One of the biggest challenges at LAX is getting material to the site, and while the airport does have dedicated construction gates, there is also a vehicle inspection process that must be administered, which requires an additional 5 to 10 minutes. Planning must also consider and coordinate access locations through the airfield and work with airport opera- tions and the air traffic control tower to make sure the materials can get to the job site within specified time limits. These challenges can lead to increased costs (e.g., planning, coordina- tion, extra security, and flaggers). As part of the process, alternative access routes should be considered. For example, a longer service road drive may be faster than waiting to cross busy taxiways. • Construct a test strip prior to work in critical areas. LAX typically uses parking ramps as test strips. Test strips are not constructed in critical areas, so they provide an opportunity for the contractor to gain familiarity with the materials and the process before it enters the critical areas. Once in critical areas, the construction team has a rough timeline and milestones that must be hit by certain times within the duration of the closure. • Consider overall project constructability during the planning and design phase. The project may call for a change in design to create subsurface layers that can be placed more rapidly. For example, substituting granular or asphalt materials for econocrete may make the project more constructible in a short closure window. RSRR Practice at McCarran International Airport Overview McCarran International Airport (LAS) is a large hub airport located in Las Vegas, Nevada. While LAS does not have a formalized RSRR program, it has more than 20 years of experience with RSRR and has developed a very detailed approach to planning, engineering, and construc- tion oversight that yields well-performing PDR and FDR. PDR is performed more regularly than FDR. The traffic levels and airport configuration allow construction timing to dictate the closure time rather than the opposite. This unique combination allows most PDRs and FDRs to be constructed with conventional materials in lieu of early-strength materials. Table A-6 provides an overview of LAS’s RSRR practice. Overall, LAS is satisfied with the performance of its PDRs and FDRs. PDRs last several years, with performance dependent on location relative to traffic. If not properly constructed, PDRs are easily damaged or dislodged during runway rubber removal operations. Factors that negatively affect performance include placing PDRs in hot weather, poor surface preparation, use of concrete mixtures that do not meet the coarseness and workability factors described in FAA’s P-501 specification, and lack of construction oversight. RSRR Program Highlights • The airport conducts weekly inspections to identify locations requiring PDR and FDR. Work is scheduled for the following week. Any future larger-scale work is discussed with FAA on a weekly basis. This approach minimizes surprises and allows work and closures to be planned and scheduled well in advance, which results in better-quality PDRs and FDRs. • Construction time required for proper PDR and FDR installation almost always governs the closure time. This approach results in longer service life and works for LAS because it has several aircraft traffic configurations that permit longer closures on runways and taxiways. • Temporary PDRs are done to address emergency repair needs in critical aircraft traffic areas (e.g., runways, taxiways). These repairs are performed during short closures and replaced with permanent repairs when aircraft traffic configuration permits longer closure times

Airport Case Examples 79   necessary for proper construction. Weekly meetings provide opportunity for stakeholder input on upcoming closures. • Permanent PDRs and FDRs are constructed at the opportune time. Factors that are used to determine construction timing include periods with lower aircraft traffic and favorable weather conditions for construction (i.e., not during hot summer months when longer takeoff distances are required). • For nonemergency work, detailed presentations are provided to stakeholders (e.g., control tower, airlines, tenants) during the planning stage. This includes information on the planned closures, work areas, haul routes, site visits, and so forth. Stakeholders have an opportunity to provide input regarding impacts on their operations. • Closures for permanent PDRs and FDRs are planned well in advance. This allows proper time to coordinate work with stakeholders and the use of more conventional construction techniques and materials. • LAS has an established procedure when design plans are not prepared. This procedure includes – Use of applicable design details from previous projects; – A preconstruction safety briefing with the engineer, contractor, and airport operations; – Exhibits showing project site and barricade locations; and – Full escort from the airport operations group during construction. • The cause of failure is investigated prior to determining permanent treatment. This infor- mation helps LAS improve its RSRR practice and may result in an FDR rather than PDR to avoid returning for subsequent repairs. Category Item Detail Airport information Airport Location Las Vegas, Nevada Owner Clark County FAA classification Large hub FAA region Western Pacific LTPP climate region Dry, nonfreeze Number of runways Two sets parallel, open V configuration Planning Stakeholder communication Air control tower Airport operations Traffic management unit Airlines and tenants Allowable closures PDR and FDR: Construction time governs closure time Funding Airport Project delivery Design–bid–build Change order to existing contract Solicit quotes from local contractors Design Design documents Plans and specifications Typical details from past projects Specification elements Project-specific QC/QA requirements Liquidated damages Construction Construction PDR: Airport maintenance crews or contractors FDR: Contractors with concrete experience on the airfield PDR materials Prepackaged: Cementitious and noncementitious FDR materials Portland-cement based, HES QC/QA elements Concrete testing: Unit weight and compressive strength Contingency planning Preconstruction meeting Backup construction dates included in planning Table A-6. Overview of RSRR practice at McCarran International Airport.

80 Rapid Slab Repair and Replacement of Airfield Concrete Pavement • Suppliers of PDR material are required to provide regular training to airport maintenance personnel. This ensures crews are knowledgeable about specific material handling and installation requirements. • Concrete mixtures used for FDRs are required to meet P-501 specifications for coarseness and workability factors. This has led to a significant reduction in spalling distress. • Construction oversight and attention to details result in better-quality PDRs and FDRs. Examples include performing work during optimal weather (on the basis of material type), thorough cleaning of the repair area, and monitoring of material conditions (e.g., discarding material that starts to set before installation). Challenges From the perspective of the airport, the biggest challenges to carrying out successful RSRR projects at LAS include planning closures to avoid peak aircraft traffic times and less optimal seasons. Summer temperatures can be very high in Las Vegas, which complicates PDR and runway closures (large aircraft operations need to use the longest runway). Key Takeaways • Conduct weekly pavement inspections and meetings with FAA to coordinate RSRR work. Engage with other stakeholders (e.g., airlines, tenants) once the work locations are identified and the initial planning is completed. • Use detailed meetings, presentations, visual exhibits, and site visits to engage stakeholders and plan RSRR work on the airfield. • Schedule work during periods with lower aircraft operations and when climatic conditions are more favorable to construction. This permits longer closure times (sometimes more than a week) to properly construct PDRs and FDRs. • Use caution when considering PDR materials that require blending three or more components. There is increased risk of improper mixing of these materials during construction. Also, these products tend to produce a fixed volume of material per batch, which may be more than is needed for the planned PDRs or may set before the batch is fully used. • Install PDR material higher than the surrounding concrete and then grind flush once it sets to create a level surface. This approach results in a better-performing PDR. • Store and install PDR materials per the manufacturer’s recommendations. (This is very important!) Only mix the amount needed for the repairs and discard any material that starts to set. Do not install PDRs when pavement surface temperatures are very high or when the temperature differential between the pavement and PDR material is great. Store materials in a cool place; consider using chilled water to reduce pavement surface temperatures. • At LAS, the minimum size of FDRs in noncritical areas (e.g., apron or outside aircraft main gear paths) is one-half of a slab. Only full-slab replacement is used in critical areas that are expected to experience aircraft loading. • LAS uses conventional concrete paving mixtures for FDR but includes a relatively high total cementitious content (compressive strength requirement of 6,000 psi at 28 days) and a retarding admixture. Compressive strength tests provide more consistent results than tests of flexural strength, and the FDR can be returned to service once a compressive strength of between 4,000 and 4,500 psi is achieved (typically 2 to 3 days). • Design and construct PDRs and FDRs for long-term performance. FDRs that have been completed since LAS began adhering to the coarseness and workability factors described in FAA’s P-501 specification and using 45-degree beveled joint edges have exhibited much better performance (minimal to no spalling) than those constructed in the past. • Emphasize attention to detail during construction to improve service life. This includes adequate construction oversight, attention to concrete mixture proportioning, and accep- tance testing.

Airport Case Examples 81   • Provide airport maintenance personnel with annual training from suppliers of PDR repair material, including a site visit and demonstrations on handling and installing materials. • Select a contractor that has good experience with early-strength materials and working in the airfield environment. RSRR Practice at Phoenix Sky Harbor International Airport Overview Phoenix Sky Harbor International Airport (PHX) is a large hub airport located in Phoenix, Arizona. The airport has concrete pavements for runways, all main taxiways but one, and most aprons. PHX has been performing RSRR for many years but recently began to formalize the process by documenting practice and preparing standard procedures. PHX’s maintenance crews can perform PDRs (and some FDRs) and the airport has engineering, laboratory testing, and construction inspection support from the City of Phoenix. Table A-7 provides an overview of PHX’s RSRR practice. The airport does not have a formalized process for monitoring specific PDR and FDR perfor- mance. In general, PDRs last between 9 months and 3 years, depending on the repair conditions (i.e., size, depth, condition during placement). The airport does not have concerns related to FDR performance, as these repairs typically perform well until they are replaced during the next large construction project (FAA funded). RSRR Program Highlights Following are highlights of some of the key features of PHX’s RSRR program: • PDR work is performed almost daily at the airport. Airport maintenance crews use a single product (noncementitious material) for all repairs. This helps the crews understand how to mix, handle, and install the repair material as well as how the material behaves during different climatic conditions. • Advance coordination is crucial to the success of RSRR work. Airport operations plays a key role in coordinating work and is involved during all planning stages. • Airport operations handles safety and phasing if design plans are not prepared. This is done as part of the preconstruction meeting and includes site access requirements, badging, haul route planning, and so forth. • The City of Phoenix (airport owner) provides design and construction support. This includes preparation of design plans and specifications, construction inspection, and material testing. The city designers determine whether repair or replacement of sublayers is necessary during FDR. • The City of Phoenix materials group provides technical input to the airport. This includes recommendations on material selection, specifically, selection of HES concrete mixtures. The group is aware of available (and city-approved) mixtures at local concrete plants. Challenges Following are the biggest challenges to carrying out successful RSRR projects: • Material selection, as a result of constantly evolving concrete mixtures using different con- stituent materials (e.g., fly ash, admixtures); • Lack of a process for reviewing and considering new types of proprietary repair materials; • Lack of technical knowledge within the maintenance group; • Poor long-term performance of PDR repairs;

82 Rapid Slab Repair and Replacement of Airfield Concrete Pavement • Difficulty of closing runways at a large hub airport with only three runways; • Need for mobilizing maintenance crews, which are not on-site, before nighttime emergency PDR can be started; • Need for determining the location and extent of damage and for identifying the preferred repair method and material for nonemergency PDR; and • Estimating concrete strength gain: PHX experimented with concrete maturity meter testing but discontinued its use because of cost concerns. Category Item Detail Airport information Airport location Phoenix, Arizona Owner City of Phoenix FAA classification Large hub FAA region Western Pacific LTPP climate region Dry, nonfreeze Number of runways Three parallel Planning Stakeholder communications Emergency PDR only: Airport operations coordinates closures Nonemergency (nonmovement area): Airport operations coordinates closures Nonemergency (movement area): City of Phoenix project manager or a consultant handles stakeholder coordination (airlines, airport, and so forth) Allowable closures Runways: 8-hour night closure (typically 10:00 p.m. to 6:00 a.m.) Taxiways: Nighttime closure preferred Aprons: Nighttime closure preferred; weekend closure possible Funding Airport: PDR and FDR (two panels or fewer) FAA: FDR (more than two panels) Emergency work PDR only Project delivery Job-order contract for large projects On-call contract for smaller, noncritical PDR and FDR On-call contractors? Yes (job-order contract) Design Designer City of Phoenix Design documents FDR: Plans and specifications In-pavement lights Steel reinforcement around the light can Form FAA 7460-1 Only submitted if work affects FAA systems or is FAA funded Construction Construction PDR: Airport maintenance crews FDR: contractors, airport crews starting to do some FDR PDR materials Noncementitious repair material FDR materials Portland cement–based concrete with accelerators, sometimes specialty cement Material testing City of Phoenix personnel Construction inspection City of Phoenix personnel QC/QA elements City of Phoenix standard procedures Contingency planning Airport crews can back up contractors if necessary, as they have experience and on-site equipment Common to have multiple concrete contractors doing work at the airport Material acceptance PDR: None FDR (movement area): Compressive strength (4,000 psi at return to service) FDR (nonmovement area): No testing, requires 72-hour cure time Table A-7. Overview of RSRR practice at Phoenix Sky Harbor International Airport.

Airport Case Examples 83   Key Takeaways • Upfront planning is one of the most important elements for RSRR project success. • Establish standard operating procedures for emergency PDRs, to include criteria for repair, and provide guidance on material selection based on repair depth, type of repair, and conditions. (PHX is working on this task. Similar procedures are being developed for nonemergency repair work.) • Confirm existing conditions prior to slab removal. Concrete core samples can be taken for FDR to confirm concrete thickness and to understand the condition of sublayers (i.e., deteriorated or intact). • Update as-constructed records when PDRs and FDRs are performed. This can be useful in tracking performance. • Increase technical knowledge. PHX maintenance believes additional technical knowledge will help lead to the installation of longer-lasting PDRs and ensure the life of FDRs. This includes examples of other airport practices, case examples of projects, and even a national database that highlights what other airports do. • Obtain local input. If available, technical input from a local agency (i.e., local city, county, state) can provide much-needed technical support related to the construction aspect of RSRR. RSRR Practice at John Glenn Columbus International Airport Overview John Glenn Columbus International Airport (CMH) is a medium hub airport located in Columbus, Ohio. The airport has two parallel runways (Runway 10R-28L at 10,114 feet and Runway 10L-28R at 8,000 feet) with multiple parallel taxiways. CMH’s PDRs are primarily performed by airport maintenance personnel. Table A-8 provides an overview of CMH’s RSRR practice. For rapid PDRs, CMH uses a proprietary, two-part polyurethane repair material on the basis of experience working with a local contractor. CMH has been using the material for several years, and it has worked well; the airport says the material is like other proprietary materials but seems to be more forgiving when the repair surface is being prepared under constrained time frames. The material is self-leveling, which helps with finishing, and can be extended with sand for deeper patch areas. Since the material sets very rapidly, crews can patch a spall and return the pavement to operation within 30 minutes. The airport has tried other materials but experi- enced some failures related to shrinkage. The airport operations department decides whether an emergency repair is needed (i.e., whether the area needs to be repaired in less than 8 hours) or whether the repair can be performed in a nonemergency manner. However, the same material is used for both. The maintenance personnel carry out planned (nonemergency) repairs as well as emergencies that arise. RSRR Program Highlights • CMH uses site-specific material. The airport has performed PDR for many years using different materials, repair details, and methods. The current patching material is not the most expensive material available, but airport personnel find it to be more forgiving in terms of preparation and ease of use, and it performs as well as the more expensive materials for the conditions at CMH. PDRs set quickly, allowing the facility to return to service in as little as 30 minutes, if needed. CMH has been using the material for 3 to 4 years and has had very few patches fail during this time.

84 Rapid Slab Repair and Replacement of Airfield Concrete Pavement • CMH ensures that adequate resources are available. The airport has maintenance personnel available 20 hours per day, with personnel on-call for the 4 hours without active employees. CMH can also draw personnel from Rickenbacker International Airport (part of the Columbus Regional Airport Authority’s oversite), if needed. Creating a maintenance plan in the spring allows CMH to ensure adequate patching supplies are available. Challenges From the perspective of the maintenance personnel, the biggest challenges to carrying out successful PDR projects are as follows: • Minimizing operational disruption: Although CMH has two parallel runways, one runway is longer than the other, and the airport works with the air carriers to do as much work as possible during daylight hours. The work on the longer runway can typically be performed from 8:00 a.m. to about 11:00 a.m. or noon, because a greater number of cargo operations are at night. Parallel taxiways and connectors typically allow alternate routes to maintain aircraft movements when work is required in areas of taxiways. • Lack of maintenance personnel with FDR expertise: Airport staff do not perform larger repairs (slab replacement). Also, the material used for PDR is too costly to use for large FDRs. Category Item Detail Airport information Airport location Columbus, Ohio Owner Columbus Regional Airport Authority FAA classification Medium hub FAA region Great Lakes LTPP climate region Wet, freeze Number of runways Two parallel Planning Stakeholder communications Airport operations Weekly notices to airmen (NOTAMs) (routine PDR projects) Air traffic control tower and tenants (large PDR projects) Allowable closures Variable, depending on facility and extent Funding Airport Emergency work PDR Project delivery No information provided On-call contractors? No information provided Design Designer No information provided Design documents No information provided Specification elements Preparation and placement per manufacturer guidelines Construction Construction PDR: Airport personnel FDR: Contractors PDR materials Proprietary two-part polyurethane repair material FDR materials No information provided Material testing No information provided Construction inspection No information provided QC/QA elements No information provided Contingency planning Weather monitoring, alternate operation routes Material acceptance No information provided Table A-8. Overview of RSRR practice at John Glenn Columbus International Airport.

Airport Case Examples 85   However, maintenance crews have temporarily patched slabs needing replacement with this material. Contractors are then brought in to perform the FDR. Ongoing work has generally meant contractors are already on-site and available to be called on to place large repairs. Key Takeaways • Find the best material for airport conditions and needs. While CMH has tried more expensive proprietary materials for PDR, it is currently having success with a lower-cost proprietary material that maintenance personnel have found to be more forgiving for rapid repair. The material is easy to mix and place and sets quickly, which allows the facility to return to service in as little as 30 minutes. • Take a proactive approach to internal maintenance work by conducting annual PDR assess- ments to plan work quantities. RSRR Practice at Hartsfield–Jackson Atlanta International Airport Overview Hartsfield–Jackson Atlanta International Airport (ATL) is a large hub airport located in Atlanta, Georgia. ATL has built an effective and successful RSRR program over many years. PDR is the primary work performed, but FDRs are also periodically installed. Over the years, ATL has successfully used a portland cement–based mix. Repair details have been refined to help ensure success within limited closure times. Table A-9 provides an overview of ATL’s RSRR practice. Category Item Detail Airport information Airport location Atlanta, Georgia Owner City of Atlanta, Department of Aviation FAA classification Large hub FAA region Southern LTPP climate region Wet, nonfreeze Number of runways Five parallel Planning Stakeholder communications Air control tower Airlines Airport operations and security Allowable closures PDR: 6- to 7-hour night closure FDR: 72-hour weekend closure Funding Airport Project delivery Design–bid–build Design Designer Consultant Design documents Plans and specifications Specification elements Liquidated damages for exceeding closure windows Requires backup equipment and weather contingency plan Construction Construction Prequalified contractors PDR and FDR materials Portland cement–based, HES, some earlier trials of proprietary rapid- set materials QC/QA elements Concrete testing: Air content, slump, flexural strength, and maturity Contingency planning Redundant equipment, weather plan Table A-9. Overview of RSRR practice at Hartsfield–Jackson Atlanta International Airport.

86 Rapid Slab Repair and Replacement of Airfield Concrete Pavement RSRRs at ATL are often performed on pavements that are nearing planned major rehabilita- tion; therefore, a complete record of repair performance is not maintained. However, the PDRs generally last at least 5 years. Failures that have occurred are often the result of poor construc- tion practices, such as materials placed when the ambient temperatures are too high or excessive paste has worked to the surface. ATL does monitor repair work through its 3-year pavement management updates. RSRR Program Highlights • Building on past experiences helps ATL ensure success. RSRR has been performed for many years at ATL with different materials, repair details, and methods. As a result, there is a knowledge base of what can and cannot be accomplished. Current materials and details have proven successful. While ATL has tried proprietary materials in the past, it is currently having success with a portland cement–based material (high cement content). ATL also has a reinforced PDR detail that has proven successful. The detail includes a horizontal reinforcing steel mat that is anchored to the adjacent sound concrete by tie bars. This repair detail has given ATL an effective means of addressing slab spalling. • The design–bid–build process is used to deliver RSRR projects. During the design process, extensive coordination with stakeholders is conducted to identify closure times and access routes. • A dedicated gate is provided for construction. The contractor covers the cost of additional security personnel. • The batch plant is located directly outside of the gate to shorten haul times. Haul routes are planned with input from the airport operations group and air traffic control tower. The haul routes are driven prior to the work to make sure materials can get to the job site within the time constraints. Challenges From the perspective of the consulting engineer, the biggest challenges at ATL include the following: • Very heavy airport operations that necessitate a significant effort to coordinate closures and haul routes and • Lack of contractor experience with expedited methods and materials. Key Takeaways • Develop airport-specific material specifications and PDR details that work. • Plan site access and movement across the airfield well in advance. ATL dedicates a construc- tion gate for this work, and the contractor provides additional security personnel for the gate as part of the contract. • Schedule work during periods with historically better weather. ATL generally tries to have this work performed from September through November on the basis of historical weather trends. Weather days are built into the construction schedule, particularly if construction occurs during other times of the year. • Select contractors that have good experience with early-strength materials and working in a congested airfield environment. At ATL, test areas are used to ensure the contractor is familiar with the materials.

Airport Case Examples 87   RSRR Practice at Louisville Muhammad Ali International Airport Overview Louisville Muhammad Ali International Airport (SDF) is a small hub airport located in Louisville, Kentucky. SDF’s airside pavements are primarily concrete. There are three concrete runways, two of which are parallel and one a crosswind. Runway 17R-35L is the longest of the three, at 11,890 feet long, and Runway 17L-35R is 8,580 feet long. In addition to commercial and Air National Guard operations, the airport serves as a United Parcel Service Worldport. With the heavy volume of cargo operations, maintaining operational pavement is essential. FDR needs are determined by regular visual inspection. Cracking and spalling are major drivers triggering the need for slab replacement, and FDRs are identified and grouped into the next rehabilitation project. Table A-10 provides an overview of SDF’s RSRR practice. Replacement of the large slabs (25 by 25 feet by 17 inches thick) on Runway 17R-35L started in 2009 and is conducted at least annually (in some years there have been two projects). When the airport started these projects, there were some pretty bad conditions, including shattered slabs. SDF also experienced the “zipper effect,” in which a cracked slab, if left unrepaired, would affect Category Item Detail Airport information Airport location Louisville, Kentucky Owner Louisville Regional Airport Authority FAA classification Small hub FAA region Southern LTPP climate region Wet, nonfreeze Number of runways Two parallel, one crosswind Planning Stakeholder communications Air control tower Airlines Airport operations and security Allowable closures 56.5-hour (weekend) closure for runways Funding FAA and entitlements Project delivery Design–bid–build Design Designer Consultant Design documents Plans and specifications Specification elements Liquidated damages for exceeding closure windows Requires backup equipment, weather contingency plan, and so forth In-pavement lights Some slabs Construction Construction Prequalified contractors FDR materials Portland cement–based, conventional and MES Contractor QC Testing firm Construction inspection Consultant QC/QA elements Concrete testing: Air content, slump, flexural strength, and maturity Contingency planning Redundant equipment, weather plan Material acceptance Flexural strength and thickness Table A-10. Overview of RSRR practice at Louisville Muhammad Ali International Airport.

88 Rapid Slab Repair and Replacement of Airfield Concrete Pavement adjacent slabs within a short time. The airport considered alternatives, including cross-stitching, but has primarily performed FDRs. FDR work is done with a portland cement–based MES mixture, but only where early strength gain is needed, which is primarily on the runway or in critical areas such as intersections where cargo carriers need access. In SDF’s experience, the MES achieves 550 psi compressive strength in 30 hours. However, the mix is difficult to work with (“sticky”) and is very volatile. For example, during the summer, mixes arrive at or near 90°F, which is close to a temperature at which the mix will flash set. During placement, several technicians are on-site for mix acceptance testing. When trucks arrive on-site, they have about 20 minutes for placement, with a total period of typically 60 minutes from time of batching to time of placement. On the taxiways, which allow 14-day closures, the use of MES is not required, and 550 psi is achieved in 7 days with a standard portland cement–based concrete mix. FDR projects are generally carried out during short closure windows, as there is little availability for long-term closures because of significant cargo operations. A typical schedule includes a 7.5-hour Friday closure for preparation (sawing), followed by the primary runway closure from Saturday to Monday afternoon. Taxiway slab repairs are performed under longer closures. Contracts for rapid repairs include liquidated damages, which vary in amount, depending on the location of the repair: $500 per day for areas with minimal impact, $1,000 per day for taxiways, and $5,000 per hour or portion thereof for runways. RSRR Program Highlights • Building on past experiences has helped SDF refine its program. Achieving the required strength was a big concern during the first year of the airport’s FDR program. However, the project specifications did not have an upper limit on strength, and during that first year, the concrete gained strength too rapidly and developed microcracking. For the next year’s FDR contract, SDF implemented an upper strength limit (1,200 psi at 28 days), which improved results. While contractors first resisted this upper limit, it has since become standard proce- dure, and local suppliers have learned how to use their additives to achieve the requirements. ATL has also changed how it handles light cans. Initially, the contractor had the option of putting in light cans during FDR or using a two-stage process in which the contractor would come back the next week to perform coring and replacement. Use of the two-stage process resulted in cracking, and, consequently, that process is no longer allowed. • The design team uses contingency planning to manage risk during construction. In case of the need for an emergency reopening, temporary precast slabs are constructed that can be placed in the FDRs. • Each project includes substantial stakeholder coordination. Early project meetings involve coordination with a variety of stakeholders, from the escorts to the material testing to the go/no-go meeting with airlines. A preconstruction meeting is held with contractors, producers, truckers, and others. This meeting gets everyone to agree on the means and methods asso- ciated with the production and placement of the materials. Weekly go/no-go meetings are conducted with the cargo carrier, which has access to excellent weather-forecasting tools; even if conditions look good on Friday and Saturday, scheduled construction is usually called off if there is a chance of rain on Sunday. A daily pour agreement meeting is also con- ducted. The operations department is responsible for communication and coordination with the commercial and cargo airlines. The contractor is always included, and the companies that do these projects have experience with coordination. SDF operations puts out barricades and sends out a notice to airmen (NOTAM) showing barricade locations.

Airport Case Examples 89   Challenges From the perspective of the consulting engineer, the biggest challenges at SDF are as follows: • Closure decisions based on cargo carrier input, • Significant coordination of closures and haul routes, and • Need for contractors and materials suppliers familiar with VHES concrete. Key Takeaways • Protect the surrounding slabs during saw cutting. SDF has used a steel plate along the adjacent slab as one method of preventing oversawing. Because friction during removal can cause spalling in the adjacent remaining pavement, a piece of laminate is placed in the saw cut to reduce friction. A sawing pattern is used in which a cut is made 1 foot in from the joint to facilitate removal and minimize the risk of damage to adjacent pavement. Sawing near cracks is avoided (the pattern being adjusted on each slab) to minimize the risk of FOD between closures. Finally, interior cuts are angled so that pieces can be more easily lifted out. Sawing is typically performed in a shorter closure (1 to 2 days) prior to removal. On one occasion, sawing was allowed a week in advance, and the ensuing traffic significantly damaged the saw cut slab. • Remove saw slurry to keep the facility in service. SDF has turned to both maintenance and ARFF personnel to help clean up. These departments can mobilize equipment that the contractor cannot when there is an urgent need. • Conduct green sawing at the proper time to control cracking. There have also been past issues with the ability to saw in a straight line, which can cause thousands of dollars of rework. RSRR Practice at Raleigh–Durham International Airport Overview Raleigh–Durham International Airport (RDU) is a medium hub airport located in Morrisville, North Carolina. RDU has three runways: two parallel runways and a crosswind. Runway 5L-23R is a 10,000-foot concrete facility that serves as RDU’s primary runway. Runway 5R-23L is 7,500 feet and is currently overlaid with asphalt. Runway 5L-23R was originally constructed in 1986 as a jointed concrete pavement, and much of the original pavement is still in place. However, alkali–silica reaction began appearing around 2002 and has caused ongoing deterioration and the need for repairs. Some patching and joint sealing were performed in 2003 and 2004, and those patches have performed relatively well. However, after a few wet winters, deterioration on the runway accelerated. As a result, the airport undertook a multiyear pavement repair project beginning in 2019. During 2019, the airport replaced 117 slabs (25 by 25 feet by 16 inches thick) between the spring and fall during day-long runway closures. While it was planning to do the same in 2020, it instead had a 40-day COVID-19-related closure and was able to replace another 108 slabs. Table A-11 provides an overview of RDU’s RSRR practice. For this project, the contractor fabricated some precast slabs for emergency use. The airport viewed these as a last resort and did not want the contractor to feel it could depend on them. The precast slabs were not needed, as no disruptions occurred, although the contractor had to demonstrate that it could place the precast slabs by practicing on an apron. The contract for the 2019 project incorporated liquidated damages of $100 per minute. This was intended to focus attention on the need for immediate opening at the specified time rather

90 Rapid Slab Repair and Replacement of Airfield Concrete Pavement than in larger increments of quarter or full hours past the opening time. Damages were capped at $36,000 to allay contractor concerns and increase the number that bid on the project. In the end, the runway repair work was bundled with an apron project to ensure contractors would bid on the work. RSRR Program Highlights • RDU utilizes pavement management to track deterioration and identify repair needs. RDU has been monitoring and mapping distresses and collecting PCI and deflection data, which it has incorporated in computer-aided drafting software maps to track conditions and make decisions. RDU determined the pavement was losing about 4 PCI points per year, which is a high rate for the airport. It also observed an increasing rate of full-depth cracking in recent years, and the 23R end of the runway seemed to have saturated subgrade, which was associ- ated with poorer performance than the 5L end. • It can be beneficial to have a construction manager at risk onboard (for a large-scale RSRR project) to answer questions during planning. An experienced construction manager can make decisions about RSRR materials, accepting or rejecting concrete loads, weather condi- tions, and project coordination, among other things. The importance of effective communica- tion cannot be overemphasized. Category Item Detail Airport information Airport location Morrisville, North Carolina Owner Raleigh–Durham Airport Authority FAA classification Medium hub FAA region Southern LTPP climate region Wet, nonfreeze Number of runways Two parallel, one crosswind Planning Stakeholder communications Air control tower Airlines Airport operations and security Allowable closures 18- to 22-hour closures for runways Funding Airport Project delivery Design–bid–build, construction manager at-risk Design Designer Consultant Design documents Plans and specifications Specification elements Liquidated damages for exceeding closure windows Requires backup equipment, weather contingency plan, and so forth In-pavement lights Some slabs Construction Construction Prequalified contractors FDR materials Portland cement–based, HES; some earlier trials of proprietary rapid-set materials Contractor QC Testing firm Construction inspection Consultant QC/QA elements Concrete testing: Air content, slump, flexural strength, and maturity Contingency planning Redundant equipment, weather plan Material acceptance Flexural strength and thickness Table A-11. Overview of RSRR practice at Raleigh–Durham International Airport.

Airport Case Examples 91   Challenges • Coordination of airline operations: Coordinating closures is a significant effort. The team obtained airline input early and offered either one extended closure or multiple daily closures to complete the work. The airlines chose the daily closures (on the basis of accommodating flight schedules) and were engaged stakeholders from the beginning. Personnel also kept stakeholders informed with monthly meetings. The determination of the allowable closure time frame is a balance between construction efficiency and operational efficiency. • Dealing with in-pavement lights in FDR projects: The lights are hard to replace within the 18- to 22-hour closure. RDU’s solution is to keep the lights in place by coring or saw cutting around them, chipping concrete off the cans, and then placing new concrete around the existing cans. It was also planned to have no more than three lights out at a time. This process worked well for slabs with light cans, and no lights were out during the repairs. Additional cans were available on-site in case they were needed for replacement. Key Takeaways • Develop repair material specifications that meet, but do not significantly exceed, strength- gain requirements. The concrete mix (developed by contractor) was specific to this project, but RDU had previously used similar materials. It wanted to avoid ASTM C150 Type III cement due to concerns about early cracking. The contractor needed to be convinced time constraints could be met with the use of a mix with a cement content of less than 800 pounds per square yard, which was achieved. The contractor did a lot of on-site practice under a range of simulated real-world conditions to gain confidence it could meet project requirements. The process of finding a concrete mix that would work took 3 to 4 months. The airport anticipates 8 to 10 years of performance before total reconstruction but has no reason to believe the FDRs could not last much longer. None of the 2019 slabs has failed; there were also no failures among the 2020 slabs, but the work was not performed with the same closure constraints. • Perform sawing the night before beginning the project; use wood shims in the cracks to keep the slabs from moving and causing spalls that create FOD. • Use maturity meters to better target break times for determining the time for opening to traffic. • Postpone work if poor weather is forecast. Include a line item in the contract to cover the situ- ation in which a contractor mobilizes but then cannot not perform the work.

Next: Appendix B - Examples of Rapid Slab Repair and Replacement Projects »
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Proper maintenance and repair of concrete airfield pavements is critical to the longevity of these pavements and their ability to safely support airport operations over their design life. However, these activities can be costly and operationally disruptive.

The TRB Airport Cooperative Research Program's ACRP Research Report 234: Rapid Slab Repair and Replacement of Airfield Concrete Pavement is designed to assist airport personnel and engineering consultants in selecting and executing rapid slab repair and replacement (RSRR) projects and to provide relevant information for airport maintenance personnel performing RSRR work.

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