2021

Christopher Senseney, University of Colorado, Boulder
Peter Smith, Precast Pavement Technology LLC
Mark Snyder, Pavement Engineering and Research Consultants (PERC), LLC

In 2019, Vancouver International Airport conducted a precast concrete panel replacement pilot project on Taxiway Victor to establish whether precast concrete was a viable option for a planned runway repair project. This was the first major use of precast airfield pavement in North America in nearly 20 years. Twelve panels measuring 6 m x 7.5 m x 360 mm thick and weighing up to 43 metric tons each were installed to demonstrate the viability of in-situ concrete panel replacement in 8-hour night work windows. The panels were designed as heavily reinforced “ductile slabs;” conventional pavement design procedures would have required much greater slab thickness and removal/replacement of base material, which would have greatly slowed panel replacements. Load transfer was provided by 38-mm diameter galvanized steel dowels, which were spaced nonuniformly along each panel edge. The use of bottom slots presented a clean surface with minimal potential for FOD. Five of the panels included embedded airfield light cans, which required great placement precision to ensure their proper alignment and function. Seven of the panels were nonplanar, requiring a special first-of-its-kind warped casting bed that was large enough to produce nonplanar airfield-sized panels to the specified fabrication tolerances. Many valuable lessons were learned during this pilot project, which confirmed that long-life jointed precast concrete pavement repairs could be successfully constructed in 8-hour overnight work windows on an active airfield using large repair panels and doweled joints, while adhering to strict panel to panel elevation tolerances.

Zehui Zhu (zehuiz2@illinois.edu), University of Illinois, Urbana-Champaign
Imad Al-Qadi, University of Illinois, Urbana-Champaign

Approximately 90% of airport runways, taxiways, and aprons in the United States are paved with asphalt concrete (AC). Considering the substantial development in the commercial aircraft industry and changes in pavement construction materials, the semi-performance-based AC mix design method adopted by the Federal Aviation Administration requires improvement to meet current and future operation needs. This paper proposes a climate-based balanced mix design approach, which balances potential AC rutting and long-term cracking based on climatic conditions. Performance indices used in the proposed framework include long-term flexibility index, total rut depth, stripping inflection point to evaluate AC moisture susceptibility, and secant modulus to assess AC stiffness. Four dense-graded airport AC mixtures at two geographic locations were tested. The proposed framework appears to be effective in screening mixes that may have potentially poor long-term performance, which will help build durable pavements that satisfy current and future airport operation needs.

Greg White, University of the Sunshine Coast

Asphalt resurfacing of airport pavements typically uses local aggregate sources, but the bituminous binder is often transported long distances to remote airport sites before being incorporated into asphalt production.  To produce asphalt with suitable mechanical properties, the bituminous binder is usually modified with elastomeric or plastomeric polymers and it is well established that polymer modified binders can segregate and degrade during heated transportation or during reheating on-site.  The type of polymer, the source of the base bitumen and the transportation arrangements are all expected to influence the magnitude of the change in measured binder properties, but the expected change during typical transportation arrangements is not well understood.  This research analysed production and on-site binder properties measured during nine airport resurfacing projects, aiming to improve the prediction of the magnitude of binder property migration and the factors that affect it.  It was concluded that elastomeric binders are more susceptible to change than plastomeric binders, and that cold transportation in bitutainers, before reheating on-site, was associated with the greatest changes in binder properties.  Tolerances were developed for the allowable difference between production and on-site property values, with wider tolerances required for elastomeric binders due to the greater changes associated with that polymer type.

Jamie Clark, University of Illinois, Urbana-Champaign
David Lange, University of Illinois

Engineered Material Arresting System (EMAS) is a cellular concrete material currently used as passive aircraft arresting systems at airports around the United States and abroad. Its cellular structure crushes upon impact helping to absorb energy and create drag resistance. Energy absorbed during crushing is defined by the load-deformation response curve, in which a plateau is indicative of crushing behavior at a near-constant load. At the microstructural level, the energy absorbed from crushing is a combination of elastic buckling, plastic yield, and brittle fracture of the cellular microstructure. Therefore, optimization of the cellular structure (e.g., bubble size and distribution) is paramount to the overall performance of these systems. This study makes use of microstructural investigations, quasi-static indentation, and drop weight testing to investigate the performance of cellular concrete with varied microstructures. The results show that while density (air content) has traditionally been considered the main predictor of overall performance, the nature of the cellular structure, owing to the use of different foaming agents, can be a useful design tool. Thus, adding another important consideration in the design of impact-resistant infrastructure. Given this finding, a new set of design guidelines are presented in this paper. The goal of this work is to inform better design of impact-resistant infrastructure by identifying cellular concrete microstructures which lead to optimal energy absorption in low-velocity impact events, such as aircraft overruns.

Xiaowei Shi, University of South Florida
Zhiwei Chen, University of South Florida
Xiaopeng Li (xiaopengli@usf.edu), University of South Florida

Baggage transport plays a crucial role in airport operation. Rapid and on-time baggage transport guarantees the normal operation and improve the level of service of an airport. Modular autonomous vehicles (MAV) are an emerging transportation technology that allows vehicles to adjust their capacity flexibly by assembling or dissembling identical detachable units. This innovative technology offers us a new perspective to solve the baggage transport problem for airports since it is promising in reducing the relevant operational costs and baggage delay time. To investigate this possibility, this paper proposes an operational design and a corresponding MAV scheduling model to optimize the baggage transport. The objective of the optimization model is to minimize the MAV operating cost while transporting the baggage from the terminal to the aircrafts without any delay. To solve the proposed problem efficiently, a fast construction heuristic (CH) is proposed based on the theoretical analysis of the feasible solution. A series of case studies at the Tampa International Airport are conducted to evaluate the performance of the proposed operational design and the CH algorithm. The results indicate that the proposed operational design can effectively reduce the baggage transporting cost, and the computational time of solutions obtained by the CH algorithm is much faster than that of the Gurobi solver without much loss of the optimality of the solutions. Results from this study can provide important managerial and operational insights into baggage transport for airport operators.

Yuanyuan Liu, Chang'an University
Longjia Chu, Chang'an University
T. Fwa (ceefwatf@nus.edu.sg), Chang'an University

Prevention of aircraft skidding is the governing consideration in the design and safety maintenance management of rapid exit taxiways (RET) of a runway. One critical input parameter in the design and safety analysis is the available RET pavement skid resistance in wet weather. Unfortunately, currently due to the lack of suitable analytical and physical measurement tool, the real skid resistance value cannot be easily determined. In practice, standard geometric designs based on aircraft type and speed are adopted in the design. A shortcoming of this practice is that the safety margin against skidding or the risk of skidding is unknown. This study presents an analytical procedure to determine the skidding risk of an arriving aircraft exiting a runway via a RET. The key aspect of the procedure is the determination of the wet-weather pavement skid resistance value under the influence of the following factors: properties of pavement surface material, RET geometry, aircraft load and speed, aircraft tire properties, and thickness of water film on pavement surface. It involves the application of a finite element simulation model to solve the dynamic interaction among tire, water and pavement. The development and validation of the model are described. Numerical examples are presented to illustrate the analysis involved in the determination of skidding risk of a commercial passenger airplane negotiating a RET. The examples serve to show how various influencing factors affect pavement skid resistance and the risk of skidding. The benefit of pavement grooving in reducing skidding risk is also demonstrated.

Jeremiah Stache, U.S. Army Engineer Research and Development Center

Runway roughness poses significant risks to aircraft and aircraft personnel. Roughness irregularities can be found in both civilian and military airfields – from rutting to bomb-damaged repairs. Various methods exist for determining roughness criteria, such as discrete surface deviation evaluation and dynamic response models. While validated dynamic response models such as TAXI-G were used extensively in the HAVE BOUNCE program from the 1970s up to the late 1990s, modern military aircraft have not undergone the same formal analysis. This paper presents the mathematical formulation and validation of the WESTAX dynamic response model. The computer program is capable of simulating the response of different critical aircraft components while trafficking over idealized runway profiles. Validation results show that the numerical model is capable of closely matching field data over single and double bump events. Findings suggest that the WESTAX dynamic response model is a capable candidate for establishing aircraft roughness limits.

Danial Mirzaiyanrajeh, University of New Hampshire
Eshan Dave, University of New Hampshire
Jo Sias, University of New Hampshire
Navneet Garg, Federal Aviation Administration (FAA)

Reliable prediction of asphalt mixtures cracking performance is a critical element to investigate airfield pavements’ service life. This research used three types of warm mix asphalt (WMA), along with a mix of WMA and reclaimed asphalt pavement (RAP), to assess cracking performance of WMA and RAP mixtures for airfield pavements and to explore performance-based airfield asphalt mix specifications. Fundamental properties of these mixtures were investigated through advanced performance-based laboratory testing methods such as complex modulus, semi-circular bend (SCB), and direct tension cyclic fatigue (DTCF) tests. Laboratory measured properties were utilized as inputs in advance performance prediction software (i.e., FAARFIELD and FlexPAVE) to evaluate mixture performance during the design period. Based on the results of complex modulus and SCB tests, it was found that organic additive and RAP tend to increase mixture susceptibility to fracture. In contrast, chemical and hybrid additives showed statistically similar fracture properties as compared to control mixture. According to the results of the DTCF test, all fatigue indices ranked asphalt mixtures in different ways, which emphasizes the importance of using performance prediction programs to investigate mixture fatigue performance as opposed to use of laboratory measurements index properties as a standalone parameter. The results of FAARFIELD software demonstrated that utilization of WMA and RAP would increase the fatigue damage in the pavement except for the chemical WMA additive. Moreover, based on the results of FlexPAVE, it was concluded that chemical and organic additives improve mixture fatigue performance. While hybrid additive and RAP seemed to worsen the fatigue properties.

Navneet Garg, Federal Aviation Administration (FAA)
Hasan Kazmee, Applied Research Associates Inc
Lia Ricalde, Applied Research Associates Inc

Warm mix asphalt (WMA) technologies allow the production and placement of asphalt concrete materials at a lower temperature than the traditional hot mix asphalt (HMA). These materials simultaneously reduce the production fuel costs, increase the hauling distance, lengthen the paving season, are eco-friendly, and ensure safer working conditions. Airport authorities can use such materials for construction applications to minimize the downtime and user-delay costs. However, the existing Federal Aviation Administration (FAA) construction specifications does not provide guidance on the implementation of such technologies, specially under the influence of aircraft high tire pressure. To this end, the FAA National Airport Pavement and Materials Research Center (NAPMRC) conducted an accelerated pavement testing as part of Test Cycle – 1 (TC-1) to study application potential of WMA (using chemical additive) on airport pavements. TC-1 results showed WMA performance was comparable to P-401 HMA performance in rutting. TC-2 study investigated the rutting performances of chemical, organic and hybrid additive based warm mixes alongside an FAA specification P-401 HMA counterpart. Four different test lanes were constructed accordingly in the outdoor area of NAPMRC, each encompassing three different test sections. Using the sixth generation airport heavy vehicle simulator (HVS-A), sections on the north side of the test lanes were trafficked with a 61.3 kips (272.7 kN) moving wheel load at a controlled temperature of 120°F (48.9°C). The chemical additive based warm mix appeared to exhibit comparable performance to the hot mix asphalt. Laboratory characterization effort also seemed to corroborate the rutting observations from traffic tests.

Jesse Doyle, U.S. Army Corps of Engineers (USACE)
Jennifer Jefcoat, U.S. Army Corps of Engineers (USACE)
Margarita Ordaz, U.S. Army Corps of Engineers (USACE)
Craig Rutland, Air Force Civil Engineer Center

Surface deterioration of concrete pavements requires maintenance. Highway and airfield pavements exhibit many of the same maintenance issues, but airfields have several additional unique requirements. Among them are petroleum contamination on aircraft parking areas, and high sensitivity to the potential for failed concrete or maintenance materials to damage aircraft. To address these issues, commercially available surface-applied treatment products were assessed for use on concrete pavements with particular focus on the special requirements of airfields. Fourteen products encompassing numerous chemistries were evaluated in a full-scale field experiment. Specific objectives of this study were to investigate materials for: field application issues; adhesion to concrete (for both clean and oil contaminated concrete); ability to seal cracks; behavior under aircraft traffic loads including surface friction; and durability over time with exposure to environmental conditions. Test strips of each material were applied to deteriorated concrete slabs. Half of the concrete was intentionally contaminated with oil while the other half was left clean. Simulated aircraft traffic was applied during which periodic visual observations and surface friction measurements were made. Two years after material application, a final visual assessment was made. Many of the products performed well on clean concrete, however oil contaminated concrete detrimentally affected many of them. Of the fourteen products evaluated, two of the epoxy based materials emerged as the clearly best performing.

Gael Le Bris (gael.lebris@gmail.com), WSP
Loup-Giang Nguyen, WSP

The assessment of runway length requirements for runway planning and design purpose relies on the data charts released by aircraft manufacturers through aircraft characteristics for airport planning publications. The industry practice and the standards of the U.S. Federal Aviation Administration (FAA) recommend performing runway length requirement determination for the most demanding aircraft – also known as design or critical aircraft – based on these charts. The main trends driving the long-term evolution of the overall runway length requirements are global warming due to climate change and the continued improvement of aircraft performances. They have opposed effects, and the research findings suggest that the technological driver might actually be stronger than the human-induced temperature increase at most aviation facilities. Airports with a high Mean Daily Maximum Temperature (MDMT) and forecasting a significant change in temperatures may still observe an increase in the runway length requirements. Locally, the introduction of larger aircraft to address the growth of the air travel demand and the development of new direct air services – especially new international routes served with wide-body aircraft – will still require aircraft- and route-specific studies that will justify short- and medium-term runway extensions. Therefore, the equations provided on the evolution of takeoff field length requirements should be used for high-level planning decision-making only, preferably at airports where future design aircraft are expected to remain within the same category of service.

April Clemmensen, Rutgers University, New Brunswick
Hao Wang (hwang.cee@rutgers.edu), Rutgers University

This study aims to develop discrete-time Markov chains models for airport pavement performance prediction based on Pavement Condition Index (PCI). The FAA PAVEAIR database that consolidates pavement condition and age data from over 2000 airports in the US. The transition probabilities developed from pavement ages and respective PCI values for flexible and rigid pavements on runway, taxiway, apron. The probability of remaining in good condition decreases for all pavements over time, although at different rates depending on the pavement type and branch. The probability of remaining in fair condition was more stable over time for flexible pavements. Furthermore, the historical data was used to analyze the uncertainty of the PCI probability transitions using mean and standard deviation of pavement conditions and ages, and margins of error for each of the transition probabilities. Finally, the relationship between rigid and flexible pavement PCI and Foreign Object Damage (FOD) Potential data was assessed. The results reveal a strong linear relationship between two indices for flexible pavements, but more variations for rigid pavements.

Limon Barua, University of Illinois, Chicago
Bo Zou, University of Illinois, Chicago

Maintenance and Rehabilitation (M&R) of airport pavement assets involves considerable financial resources. As such, even modest improvement in M&R action planning could lead to non-trivial savings. The state-of-the-practice for planning M&R actions mostly relies on condition thresholds and prioritization rules, while the state-of-the-art often requires unduly assumptions, and the computational challenge can present an important issue when characterizing pavement conditions and M&C actions involves large dimensions. This study proposes a machine learning (ML) approach that integrates pavement condition prediction using supervised ML with M&R action planning empowered by reinforcement learning (RL). The Q-learning method is used to train the RL model. The use of the integrated model is demonstrated using real-world data from the Chicago O’Hare International Airport. The results show the effectiveness of the proposed approach and potential to reduce M&R cost compared to the existing practice.

Jianming Ling, Tongji University
Liang Ren, Tongji University
Jianhua Gao, Tongji University
Li Man, Tongji University
Yu Tian, Tongji University

Rutting is a typical distress of hot-mix asphalt (HMA) overlay in airfield composite pavement (ACM). An approach that can provides comprehensive and reliable evaluation about ACM rutting characteristics is needed. I n this study, A finite element method (FEM) was developed based on the parameters derived from laboratory and field tests, considering the influential factors: temperatures, dynamic load factors, and pavement structural conditions. The full-scale accelerated pavement testing (APT) was conducted to verify the accuracy of FEM. The tests results revealed a coefficient of deviation that was within 15%, indicating that the FEM exhibited satisfactory accuracy. Additionally, the typical rutting profile shows a non-uniform W-shaped deformation. Especially, temperature variations, driving status and interface bonding conditions influence pavement rutting characteristic significantly, reflected in the significant increase of deformation levels and the changed rutting profile. Aircraft braking and turning will cause a large horizontal displacement on the pavement surface, which may result in severe slippage cracking of asphalt layer. Moreover, all the load levels and overlay thickness have great and steady impacts on pavement rutting deformation. The rutting depth presents a power-function relationship with temperatures and load cycles, and a linear relationship with tire pressures and overlay thickness. The uplift coefficients are stable between 0.26-0.29 with the variation of above factor levels.