Abstracts: 2020-2021


Evaluating the use of microencapsulated PCMs to melt ice and snow in hot mix asphalt

Daniela Betancourt-Jimenez, Miguel Montoya, John Haddock, and Carlos J. Martinez

Ice formation and snow accumulation are responsible for flight delays and cancellations in airports around the world, increasing their operation costs by millions of dollars. The use of phase change materials (PCMs) to melt ice and snow on pavements has been briefly studied in the past and even when proven successful, this technology is far from being implemented in real life. The present article looks to expand the work done on this field by adding microencapsulated PCMs to asphalt pavements and comparing their snow melting capabilities to conventional asphalt. The microencapsulated PCMs used in this study demonstrated to exhibit high latent heats of crystallization (130 J/g) and to be thermally stable well above asphalt mixing and compacting temperatures (up to 350 °C). A PCM-containing and a reference specimen were then prepared by adding 20 vol.% and 0 vol.% microencapsulated PCMs, respectively, and thermal cycling and snow melting experiments were conducted inside an environmental chamber. The former experiments confirmed that heat is released in the PCM-containing specimen when it is cooled down below the melting temperature of the PCM, allowing its temperature to remain above that of the reference for a total of 20 hours.  The latter showed that the PCM-containing specimen is capable of completely melting approximately 1 inch of man-made snow 24 hours faster than the reference. It is then concluded that microencapsulated PCMs can effectively be used for snow and potentially ice melting applications in asphalt pavements.


Air Traffic Flow Models for Varying Airspace Structures: A Look at the Impact of Aircraft Heading Ranges

Christopher Cummings

Advanced air mobility (AAM) promises to enable faster travel times and ease roadway congestion through use of smaller configuration aircraft at a high density. The proposed densities of operations will pose challenges to the air traffic management system and airspace, and therefore has been the focus of recent research. Several papers have developed macroscopic air traffic flow models for unstructured airspace. This work extends those air traffic flow models to other types of airspace with aircraft heading restrictions, specifically geo-vectored and tube airspace. Theoretical models to describe air traffic flows in these types of airspace are developed and validated through the use of simulation. The results show that in high-density airspace a higher degree of structure reduces the conflict rate between aircraft, protecting vehicle speeds and throughput. The models in this paper further researchers’ understanding of air traffic flow, and the insights offered are useful to AAM operators and planners who make decisions about how to structure airspace and manage traffic flow within these structures.


Pavement Performance Trends and Distress Analytics for Airfield 1 Pavements in Various Climatic Regions

 Ebenezer Duah

Differences in climatic conditions, aircraft traffic, and maintenance practices drive airfield pavements to perform differently. Through the Federal Aviation Administration’s (FAA’s) PAVEAIR online database and the National Oceanic and Atmospheric Administration’s (NOAA’s) online public platform, historical pavement condition and climate data from nearly 200 airfields in the dry freeze (DF), dry no-freeze (DNF), wet freeze (WF), and wet no-freeze (WNF) climatic regions were collected to evaluate pavement performance and distress trends. This paper presents the results of a two-part analysis. First, overall pavement performance trends were evaluated using the pavement condition index (PCI) by fitting a linear regression and cluster analysis. Then, historical distresses data were analyzed for various pavement families in the different climatic regions. Families were assigned with respect to climate, pavement structure (conventional asphalt or asphalt overlays), and branch type (apron, taxiway, and runway).  The regression results showed that pavements in the WF region have the highest rate of deterioration, followed by the pavements in the DNF region. In terms of branch type, in three of four climatic regions, aprons have the fastest rate of deterioration, followed by taxiways and runways, respectively. The distress analytics revealed that cracking type of distresses were the most common in all the regions regardless of the pavement family.

The results showed that climatic data alone were not adequate to characterize airfield pavement behavior due to the heterogenous character of pavement condition datasets. An accurate pavement and distress prediction modeling effort should at least include additional information on the structure and traffic level.


Potential Use of Waste Plastics in Flexible Airfield Pavements: High-Density 1 Polyethylene (HDPE) Impact on Asphalt Binder and Mix

Javier J. García Mainieri and Imad L. Al-Qadi

Flexible airport pavements often require polymer modified asphalt binder in the asphalt concrete (AC) mixes. Styrene–butadiene–styrene (SBS) modifiers are commonly used. Their application could be prohibitive occasionally due to availability and cost. Therefore, alternatives to SBS may be warranted, including the use of waste plastics. Most plastics are not recycled but rather landfilled or incinerated, which are high-cost operations and cause significant impact on the environment. The construction cost difference between Polymer-modified asphalt binder (PMAB) AC and HDPE-waste-modified AC may be justified only if the potential pavement performance is similar. The objective of this study was to evaluate the possibility of using an HDPE granulated waste as an asphalt binder modifier for airfield pavements.  To achieve that, an asphalt binder base was modified, to obtain a desired Superpave performance grading (PG) and compared to a commonly used SBS-modified asphalt binder (control) in three categories: asphalt binder performance, binder–aggregate adhesive compatibility, and AC-mixture performance. Although waste-HDPE-modified asphalt binder, evaluated in this study, improved high-temperature characteristics of asphalt binder, which is related to rutting susceptibility, it is not comparable to potential SBS-modified control binder performance. This conclusion was verified during the mix assessment stage.


Life-Cycle Approach to Healthy Airport Terminal Buildings: Spatial-Temporal Analysis of Mitigation Strategies for Addressing the Pollutants that Affect Climate Change and Human Health

Fiona Greer, Arpad Horvath, and Jasenka Rakas

The potential environmental and human health impacts associated with constructing and operating terminal buildings is explored for commercial airports in the United States. Research objectives are to quantify: (1) baseline and mitigated greenhouse gas (GHG) and criteria air pollutant (CAP) emissions; (2) operational costs; and (3) climate change damages from terminal building construction and materials, operational energy consumption, water consumption and wastewater generation, and solid waste generation. An Excel-based decision-support tool, Airport Terminal Environmental Support Tool (ATEST), has been created to allow stakeholders to conduct preliminary assessments of current baseline and potential mitigated impacts. Emissions are quantified using a life-cycle approach that accounts for cradle-to-grave effects. Climate change and human health indicators are characterized using EPA’s Tool for Reduction and Assessment of Chemical Impact (TRACI) factors. ATEST is applied to multiple case study airports— Reno/Tahoe International (RNO), Pittsburgh International (PIT), Newark Liberty International (EWR), Seattle-Tacoma International (SEA), San Francisco International (SFO), and Hartsfield-Jackson Atlanta International (ATL)—to demonstrate its scalability and capability to assess varying spatial factors. Across all airports, electricity mix and construction are significant in determining GHG and CAP emissions, respectively. A sensitivity analysis of GHG emissions for the SFO case study reveals that the electricity mix, amount of electricity consumed within the terminal, terminal gross area, and amount of compostables in the solid waste stream have the most impact on increasing annual GHG emissions. ATEST represents a crucial first step in helping stakeholders to make decisions that will lead to healthier, more sustainable airport terminals.


Airport Pavement Stiffness Monitoring and Assessment of Mechanical Stabilization using Bender Element Field Sensor

Mingu Kang, Issam I. A. Qamhia, Erol Tutumluer, Navneet Garg, and Wilfredo Villafane

The bender element (BE) field sensor is a newly developed embedded pavement instrumentation that measures shear wave velocity to estimate constructed layer moduli of unbound aggregate bases and subbases. This paper presents findings related to monitoring stiffness characteristics of airport pavement base courses instrumented with BE field sensors and tested under full-scale accelerated pavement testing during Construction Cycle 9 (CC9) of the National Airport Pavement Test Facility (NAPTF) by the U.S. Federal Aviation Administration (FAA). The CC9 aggregate base courses were constructed following FAA’s P-209 specification for a geosynthetic experiment using a biaxial geogrid installed at the bottom of the 8-in. (203-mm) thick base in the north test section, while the control pavement in the south test section was built without a geogrid. Two BE field sensors were installed in the north and south test sections approximately 1 in. (25 mm) above the base–subbase interface. Multiple stages of aircraft gear loads, including static dual-gear, dynamic slow-roll (moving wheel), and dynamic proof-roll, were applied to the test sections. BE field sensor data collected throughout multiple loading stages were used to investigate the stiffness characteristics of the pavement base. These preliminary tests conducted at the NAPTF CC9 experiment revealed the effects of static and dynamic aircraft gear loads on the stiffness of the aggregate base layer and how confinement influenced the moduli of the geogrid-stabilized base. Further, previously observed anti-shakedown effects caused by vehicle load wander could be quantified through changing base course modulus and deformation behavior from the BE field sensor data analysis.


Impact of Airspace Restrictions on Urban Air Mobility Airport Shuttle Service Route Feasibility

Mark T. Kotwicz Herniczek and Brian J. German

Initial urban air mobility (UAM) operations are anticipated to include airport shuttle services between airport terminals and city centers. UAM airport shuttle operations have the potential to improve the customer experience and provide airports with new revenue streams but risk interfering with current airport operations. In this paper, we develop a discrete, heuristics-based optimization framework to explore the impact of airspace constraints and the placement of vertiports in the airport terminal area on the feasibility of UAM shuttle operations. The framework is applied to the terminal areas of Hartsfield-Jackson Atlanta International Airport (ATL), Dallas Fort Worth International Airport (DFW), and Los Angeles International Airport (LAX). Small-scale UAM operations are found to be feasible at all three airports with current terminal-area procedures, particularly if UAM aircraft are classified as helicopters. Scaled-up operations are found to be most feasible at ATL because of the possibility of segregating UAM aircraft from commercial traffic, whereas scaled-up operations at LAX and DFW are expected to require the adoption of new technologies, procedures, and regulations.


Ultrafine Particle Ground-Level Impacts During Aircraft Approach and Climb-out Operations at a Major Cargo Hub 

Maryssa Loehr and Jay Turner

Ultrafine particles (UFP) contribute to adverse health outcomes such as asthma, obstructive pulmonary disease, cardiovascular disease, and lung cancer. Recent research draws attention to elevated ambient UFP number concentrations near airports. In this study, high time-resolution UFP measurements were conducted along public roads near Mohammad Ali International Airport (SDF; Louisville, KY) which is a commercial passenger airport and a major air cargo hub. Short-duration (∼3 h) measurements with two instrumented vehicles were designed and executed to capitalize on the distinct features of the air cargo hub including periods of high flight activity (and either all landings or all take-offs) at night and early morning when the atmospheric mixing layer depth is shallow. We present preliminary measurements for quantifying individual aircraft contributions and showcase the complexities involved in interpreting these data. For example, during periods with high arrivals frequency, UFP plumes from multiple aircraft on approach are superposed and it is challenging to apportion impacts to individual aircraft. Ground-level impacts for individual aircraft on climb-out are difficult to discern because the planes rapidly ascend above the atmospheric mixed layer height and take different flight paths soon after take-off. Elevated UFP concentrations are observed downwind of the airport, in some cases admixed with approach/climb-out emissions. Although from these data UFP concentrations are difficult to associate with specific aircraft characteristics, UFP concentrations are elevated downwind of the airport. These impacts decrease with increasing distance from the airport yet are clearly discernible at least 3 km downwind.


ACRP Student Paper: Developing a New Decision-Making Tool for Selecting Rapid Repair Cementitious Material (RRCM) for Concrete Airfield Pavement

Lamiya Noor and Jason H. Ideker

According to the Federal Aviation Administration (FAA), timely repair and restoration of airfield pavements will reduce reconstruction costs by four to five-fold. Selecting an appropriate repair material will not only reduce the frequency of repair activities but also minimize the overall cost significantly. The current decision matrix in the Airport Pavement Maintenance Recommendation Tool directs the user to choose a repair technique, but it does not include any guidance on rapid repairs, such as which material should be selected for timely construction activities (to minimize traffic delay) or the estimated long-term performance of the selected material. In this study, a new decision-making tool based on TOPSIS-MCDM (The Technique for Order of Preference by Similarity to Ideal Solution- Multi-Criteria Decision Making) had been developed for airport agencies for rapid repair cementitious material (RRCM) selection with a boundary condition of opening to traffic in less than 8 hours. The criteria of the decision-making tool were developed from survey responses of FAA classified eleven (11) primary commercial service airports (large, medium, and small hubs). Prequalification testing, long-term performance, local material availability, and user cost were identified as the main criteria influencing the decision-making process of the airport agencies. The sub-criteria of the decision-making tool were developed from the survey responses combined with the existing guidelines/standards for RRCM(s) application.  This developed tool has a potential of large-scale multilevel RRCM selection implementation and can help aviation policy makers to choose appropriate RRCM(s)- cost effective and durable- for concrete airfield pavement.


Analysis of Ultra Low-cost Carriers and Airport Choice 

 Drew Taplin and Michael Kuby

Recently the domestic aviation industry has been influenced by rapidly growing ultra low-cost carriers (ULCCs). Existing literature, however, is limited for North American ULCCs, often lumping them together with mainstream low-cost carriers. The pattern of markets served by ULCCs is incongruous with models of other airlines, requiring further research to examine causal factors. This paper seeks to establish conclusions surrounding market factors used for ULCC service decisions.

The relationship between ULCC operations and airport choice factors was analyzed using three methods: a collection of 2019 flight data to establish existing conditions, two regression analyses to evaluate airport market variables, and three case studies examining distinct scenarios through interviews with airport managers. Enplanement data was assembled for every domestic airport offering scheduled service in 2019. Variable data were collected for every Part 139 airport in the U.S. The first regression analysis estimated a OLS regression model to analyze enplanements. The second model estimated a binary logistic equation for ULCC service. Case studies for Bellingham, Waco, and Lincoln were selected using compelling airport factors and relevant ULCC experience.

Maps of enplanements and market share revealed concentrations of ULCC operations on the East Coast. Each regression analysis showed a strong relationship between population and quantities of ULCC operations. Tourism was only significantly related to enplanements. Distance and competition variables were significantly associated to ULCC presence. Case studies revealed the importance of airport fees in ULCC preferences. Further research may shed light on this complex and ever-changing subset of the domestic commercial aviation industry.


Impact of Climate Change on Asphalt Pavement Temperature and Failure Potential of Airport Pavements 

Pengyu Xie and Hao Wang

The existing airport infrastructure system is designed based on historical climate conditions. This study aims to evaluate the impact of climate change on asphalt pavement temperature and failure potential in the airfield. Thermo-mechanical models were developed to predict pavement temperature and analyze critical pavement responses under moving aircraft loading. The effect of pavement temperature on multi-axial stress states and near-surface failure potential was investigated under current and future climate scenarios. The impact of warming temperature on pavement life was investigated by airfield pavement design software (FAARFIELD) considering representative temperature and loading frequency in asphalt pavement. According to the results, air temperature would increase around 2℃ in the future 40 years because of climate change. The pavement temperature will also increase due to climate change but pavement surface (8℃) shows higher temperature increase than bottom (4℃). Meanwhile, the warming temperature increases the shear failure potential at pavement near-surface. The critical near-surface failure potential would increase 12% to 13.5% if the pavement temperature increases 6℃. Thicker asphalt layer is more susceptive to the increase of temperature and has more potential of near-surface shear failure. 15 The analysis of pavement damage using FAARFIELD shows that the pavement life reduces by 16 30% under climate change scenario in 15-inch asphalt layer but barely changed in 10-inch overlay. This might be because the 10-inch structure is damaged too soon to see the noticeable impact of climate change. Thus, the adaptation strategies of climate change are highly recommended to be considered in the future design of airfield flexible pavement.


Developing a Cost-Effective Assessment Method for Noise Impacts at Non-Towered Airports: A Case Study at Purdue University 

Chuyang Yang and John H Mott 

Aircraft noise is considered as one of the environmental impacts that most adversely affects airport development. Aircraft noise estimation tools such as the Aviation Environmental Design Tool (AEDT) are widely used by airports to mitigate local concerns for airport development. Aircraft operations and fleet mix information play important roles in aircraft performance modeling for noise prediction. However, such information is difficult to obtain at almost 85% of the 3,348 National Plan of Integrated Airport Systems (NPIAS) airports, which lack full-time air traffic control facilities and personnel. Given the increasing percentage of equipped automatic dependent surveillance-broadcast (ADS-B) aircraft in the U.S. national airspace, this paper presents a cost-effective noise estimation approach for non-towered general aviation (GA) airports. Instead of deploying physical sound meters or relying on the local air traffic control facilities, the authors collected aircraft positional data and fleet mix information based on ADS-B broadcasts. Advanced aircraft performance model parameters are constructed using four-dimensional aircraft position and a kinematic point-mass model. Aircraft-specific noise levels are interpolated based on the EUROCONTROL Aircraft Noise and Performance (ANP) database. To obtain the final noise level, two adjustments are applied to the interpolated noise values. The test results show the proposed approach can help non-towered airports predict the noise impact on any selected locations near the airport cost-effectively. Recommendations and opportunities for future investigation are also included.