Airfield and Highway Pavements 2021: Airfield Pavement Technology

Since the privatization of the major Australian airports in the 1990s, there has been no centralized body for the definition of Australian aircraft pavement design practice. Consequently, there is now no clearly defined practice followed in Australia for aircraft pavements, including the design and detailing of rigid pavements. This research defines Australian rigid aircraft pavement design and detailing practice by surveying 17 designs completed over 20 years. Subgrade preparation, testing, and proving as well as sub-base layer materials and thicknesses were considered, as were the basis of thickness calculation, concrete strength assumed in design and required during construction, as well as the size of slabs, joint types, and joint details. The findings provide a reference for rigid aircraft pavement designers, as well as providing a basis against which future research can be contextualized. It is recommended that a nationally consistent design and detailing practice be reestablished in the future.

The new runway at Sunshine Coast Airport (Queensland, Australia) was assigned a pavement strength rating based on aircraft traffic and pavement material design assumptions. This research revisited the runway strength rating, using both deterministic and stochastic approaches, using as-constructed data extracted from the construction quality assurance records. Four key pavement properties were considered: asphalt thickness, asphalt modulus, crushed rock base thickness, and subgrade bearing strength. Thousands of measured or calculated values of these properties were analyzed and used in a Monte Carlo simulation to generate 10,000 statistically appropriate strength rating values, which were then compared to the design-based and post-construction deterministic strength ratings. It was concluded that the pavement was constructed much stronger than intended by the design, with the design-based strength rating exceeded by 98.6% of the simulated strength rating values. Other airports may follow the same process to undertake post-construction strength assessment of any new pavement structures.

There are 711 registered airports in Australia. Of these, 480 have sealed runways. Based on categorization of these airports and analysis of the pavement areas, strength, and subgrade conditions, the replacement value and maintenance costs of Australian aircraft pavements were estimated. The value was estimated to be $5.8 billion and the annualized maintenance liability was estimated to be $255 million. The regional and remote airports, which generally fail to generate revenues that exceed their operating costs, require $135M per annum to maintain pavement assets across 443 airports. The Commonwealth and State governments should provide a long-term commitment to funding this maintenance liability and should establish a program to support the delivery of the diverse aircraft pavement maintenance required across the regional and rural airport network in Australia.

Runway 4R-22L at John F. Kennedy International Airport (JFK) is an asphalt concrete (AC) runway that received a major rehabilitation in the spring of 2017. The rehabilitation of the runway included 4 in. of milling below finished grade, placement of in-pavement lighting systems, and installation of a centerline light can drainage system. The installation of the in-pavement lighting systems required 140 kerf cuts which partially penetrated into the underlying Portland cement concrete (PCC) layer. The kerf cuts were backfilled with PCC and the entire runway received an AC overlay. During a heat wave in July 2017, four locations on the runway exhibited pavement upheaval. The upheavals, described by staff as 6 in. high bumps, caused the closure of Runway 4R-22L. Emergency repairs consisting of milling off the AC overlay and patching the pavement were performed at the four upheaval locations and the runway was reopened. An investigation ensued and it was concluded that the upheavals were all in a location where a kerf cut was performed. Following the emergency repairs, surface profile measurements were made during 2017 to investigate whether upheavals had occurred at any other locations unidentifiable by visual observation and runway profiles were measured using a lightweight profilometer (LWP) device. In order to assure that the repairs made in 2017 had mitigated the risk of additional upheaval, the Port Authority of New York and New Jersey (Authority) monitored the surface condition of Runway 4R-22L from June to September 2018 on a weekly basis. The analysis of surface profile measurements conducted by LWP and mobile LiDAR equipment and the comparison between the two in assessing surface irregularities on the runway pavement are presented in this paper.

There would be significant benefits in construction, maintenance, and service life of airfield pavement if concrete slabs were constructed overnight and in sizes of 40 ft or more, while being capable of handling wide-body aircraft. We investigated using belitic calcium sulfoaluminate (BCSA) cement concrete instead of portland cement concrete for this purpose. Seattle Tacoma International Airport (SEA) has a 25-year successful history of using BCSA for rapid airfield construction. A test slab of 11.3 m × 12.2 m × 0.5 m (37.5 ft × 40 ft × 18 in.) thick was placed at SEA on November 1, 2019. This report describes the placement, instrumentation, and an analysis of slab behavior in terms of shrinkage and curling, as measured using embedded strain gauges. Preliminary data show exceptionally low strains even for such a large slab. This unusual behavior is probably due to the unique chemistry of BCSA, which involves early strength gain caused by water-retaining ettringite, followed by the minimal shrinkage associated with belite content. Analysis of the data collected over a year shows that this unique chemistry would support improving construction protocols and slab design allowing overnight replacement of four contiguous, regular-sized portland cement concrete slabs with a single BCSA slab on an active taxiway.

The Australian Government Department of Defence (Defence) is the largest airfield owner in Australia. The 28 sealed airfields cater for a range of aircraft types and operate in different environmental conditions ranging from temperate to tropical climates. In 2009, the National Aircraft Pavement Maintenance (NAPM) Program was established to inspect, design, and implement maintenance of aircraft pavements across the network supporting the projection of airpower. The content of the paper includes details of the pavement condition inspection and assessment process including use of a simplified condition rating system; various pavement distress types; pavement maintenance and repair techniques adopted; the development of the annual planned routine minor maintenance program; and the ten-year capital expenditure (CAPEX) maintenance plan. The paper also provides a historical perspective of the NAPM Program between 2009 and 2020 and demonstrates the benefits of a “simple, pragmatic, and cost-effective” pavement asset management program for a complex network of airfields and operating conditions. It also provides an overview of some of the benefits and improvements of the NAPM Program.

The project of rigid pavements in airport aprons is a complex process considering several factors, spanning from the critical aircraft that is expected to park in the stand to the subgrade bearing strength. However, issues occurring during the construction phase or overloading of the pavement are likely to reduce the service life with respect to the design expectations. This work presents outcomes from a still on-going non-destructive monitoring activity carried out from 2008 over three park stands located in APRON 700 in Fiumicino Airport of Rome, Italy. In particular, the three stands were subjected over the years to different loadings that produced various rate of damage of the concrete slabs. The area was surveyed, at different time intervals, by visual inspection of the cracking (i.e., calculation of the pavement condition index), heavy weight deflectometer (HWD) testing, and ground penetrating radar. By comparing the outcomes from NDTs with the visual evolution of the damages over the area, it was possible to stress out the evolution pattern of the decays and to determine a reliable domain of service life by means of damaging versus time prediction curves.

Airfield pavements are one of the most important airport assets. Among them, fundamental function is the ability to provide sufficient load-carrying capacity of the expected traffic, which helps to ensure the uninterrupted operation of airport facilities. However, several airfield pavements often face the challenge of either serving aircraft types that have not been considered during the initial pavement design, or aircraft, although considered during the design, but exhibiting more operations than the ones foreseen. In these cases, the current airfield pavement overloading ICAO guidance is usually implemented. With this in mind, the present paper aims to make an interpretation of the current practical overloading criterion, through the implementation of recent Federal Aviation Administration (FAA) airfield pavement evaluation techniques. The analysis indicated that there may be a significant impact on pavement damage due to overloading, which must be considered when overloading practices are implemented.

The Tucson Airport Authority (TAA) has developed an Airfield Safety Enhancement Program for Tucson International Airport (TUS) which includes the design of a new parallel Runway 12R/30L with new parallel and connector taxiways. Considering the vast scope for new pavement construction and ultimate cost implications, the development of an appropriate life-cycle cost analysis (LCCA) is a critical tool to evaluate and select viable pavement design alternatives. Following the Federal Aviation Administration guidelines, the LCCA was customized for project-specific conditions to closely represent the anticipated maintenance and rehabilitation measures across the 40-year analysis period. Utilizing the LCCA results, alternatives that involve a combination of flexible and rigid pavement systems are being designed for the project based on future pavement use, typical maintenance practices, and performance history of pavements at TUS. This customized and practical design approach provides a significant benefit to the airport and government agency when providing funding for the recommended pavement section.

The performance of cement treated permeable base (CTPB) material under full-scale aircraft traffic is investigated on two dedicated pavement sections during construction cycle 9 (CC9) at the Federal Aviation Administration’s (FAA) National Airport Pavement Test Facility (NAPTF). Laboratory and field characterization of the CTPB material was performed during the construction stage. In addition to testing for compressive and flexural strength, measuring resilient modulus on 28-day cured CTPB cylindrical specimens was experimented as part of the laboratory characterization. Although producing specimens of flat and smooth end surfaces was one of the major challenges in measuring reliable vertical deformations, stress-dependency of CTPB material was captured in the resilient modulus test results. The light weight deflectometer (LWD) was identified as a feasible field alternative for the characterization test on the finished CTPB surface. The CTPB modulus measured in the laboratory was approximately 1.8–2.6 times the field modulus derived from LWD testing. This paper discusses laboratory and field characterization results and provides an overall evaluation of CTPB material properties and anticipated performance under full-scale traffic. The implications of test results for future CTPB material FAA specifications are also addressed.

A “Smart” Runway initiative was conducted by the U.S. Army Engineer Research and Development Center (ERDC) to install and monitor pavement response instrumentation in an operational airfield pavement. This paper describes construction activities and instrumentation installation techniques for the project. A flexible airfield pavement located at Hill Air Force Base (AFB), Utah, was selected due to its wide range of environmental conditions and relevant military aircraft traffic. During a runway pavement rehabilitation project in 2019, a segment of the runway was reconstructed to facilitate embedment of instrumentation. Dynamic pavement response instruments included 30 earth pressure cells, 20 asphalt strain gauges, 4 multi-depth deflectometers, and 4 laser distance sensors. Long-term performance sensors included five bender elements, five smart rocks, and one frost depth sensor. Ambient condition monitoring included six soil moisture-temperature sensors, six thermocouples for asphalt temperature with depth, two staring radiometers for pavement surface temperature, and a co-located weather station.

The Federal Highway Administration (FHWA) has recently introduced a new reactivity index (RI) to predict alkali–silica reaction (ASR). This novel chemical reactivity index can be used to develop two different types of screening tests to evaluate aggregates alone or job mix designs. The objective of the study presented in this paper was to explore the applicability of the new RI for ASR screening in aggregates used in the construction of airport facilities. The alkali–silica reactivity of the aggregates selected in this study varied from nonreactive to slowly reactive based on their historic field records. The ASR susceptibility of these aggregates was determined using two different testing protocols based on the RI. The first protocol, known as the Turner-Fairbank ASR susceptibility test (T-FAST), was used to determine the alkali–silica reactivity of the aggregates alone. The second protocol, also based on the RI, was applied to determine the ASR susceptibility of the job mix designs. The results of these two new ASR screening protocols were compared against those obtained using the Advisory Circular 150/5370-10H Item P-501, and ultimately with the historical field performance of the aggregates. The new RI accurately identified a slow reactive aggregate that triggered ASR deterioration in the concrete pavement and other structures in Denver International Airport (DEN) after 25 years of service life.

The Federal Aviation Administration (FAA) is currently developing a model of reflection cracking for the thickness design of hot-mix asphalt (HMA) overlays on existing airfield concrete pavements, for eventual implementation in the standard FAA thickness design program FAARFIELD. To date, the FAA has performed six phases of full-scale tests under controlled loading conditions, using an indoor test rig at the National Airport Pavement Test Facility (NAPTF) that mimics the overlay response to temperature cycles. In addition, the FAA is monitoring a set of outdoor overlay test pavements subjected to natural climate cycles and simulated aircraft loads. In parallel with these full-scale tests, the FAA conducted advanced laboratory characterization of the fracture properties of HMA overlay materials under repeated loads. This paper presents laboratory test results for the HMA overlay specimens extracted from full-scale test pavements. Tests included the disk-shaped compact tension (DCT) test in monotonic mode, the Texas Overlay Test (OT), and non-standard tests of both notched and unnotched specimens using the Texas OT apparatus. The DCT results showed a decrease in fracture energy when the specimen temperature fell below freezing. Overlay tests on notched specimens revealed high sensitivities of fatigue strength, fracture energy, and crack propagation rate to ligament length. On unnotched specimens, fracture energy and strain energy were able to capture the effect of displacement rate on the crack growth. At 0°C, the critical energy release rate (J_c) was determined, and below this threshold, the mixture may start to lose the fracture resistance capacity.

The study of airfield rigid pavement is an arduous task, for they are subjected to a combination of two superimposed phenomena: slow slab deformations and associated stress due to thermal variations and mechanical traffic loading. The French Civil Aviation Technical Center (STAC) has developed a two-step approach which takes into account both components. First, a thermal final element (FE) simulation allows calculating, from temperature field within the slab, the slab deformation and associated contact conditions with the sublayer, as well as the stress field within the slab. A dynamic mechanical modeling is then applied to the deformed slab, considering associated contact conditions. This paper focuses on the thermal FE simulation. Numerical results are presented and compared with field data from the STAC’s instrumented test facility (Bonneuil, France) which include temperature probes within the concrete slabs as well as vertical and horizontal displacement sensors which enable to continuously record the slabs corners and mid-edges vertical displacements and the joints expansion/contraction as a function of the mean slab temperature and vertical thermal gradient throughout the slab.

The use of manual inspections to evaluate Pavement Condition Index (PCI) on airfield pavements is typically time-consuming and represents a logistical challenge in busy airports. Recently developed 3D laser scanner systems can detect cracks in the pavement, reduce fieldwork time, and increase safety. There is some commercially available software that use a semi-automated approach by using 3D laser data, which have been successfully implemented. However, these programs also present limitations such as wandering of testing vehicles during data collection or insufficient overlap or gaps between multiples passes. These programs also cannot incorporate point cloud data from multiple passes, which is very important for the detection of surface geometry distresses, such as rutting, bumps (blister), or depressions. This paper proposes using an alternative semi-automated approach to overcome these limitations. In the proposed method, PCI is calculated using engineering judgment, right of way images, and 3D laser scanner data. The method also resolves some of the shortcomings found on commercially available programs. The new proposed software, Distress Inspector (DI), has been used in many airports to determine PCI, and its results are comparable with PCI values from standard manual inspections.

Highway departments and airports perform regular pavement condition inspections in order to record pavement distress data, which are important inputs into pavement management systems (PMS). Increasingly pavement condition data are captured using high-speed 3D lasers and high-accuracy blended inertial positioning systems. This enables fast, accurate, and objective pavement assessment. Recent advances in 3D scanning and GNSS positioning data integration now permit these routine pavement inspections to deliver much more value; effectively creating a “3D Digital Twin” of roads and runway surfaces. These 3D Digital Twins can provide a much richer data set to the asset manager while reducing closure time, data collection costs, and staff exposure. 3D Digital Twins can be directly imported into road design software applications and used to generate volumetric estimates, preliminary, and final designs. Outputs of 3D design software can then be sent to laser tracking total stations in order to control 3D pavers and milling machines such that better-designed surfaces are now possible. This paper and presentation present details of the capture technology, key workflow steps, and finally point density and accuracy compared to traditional.

Climate change impacts, especially in terms of rising temperatures and changes in precipitation patterns, have been widely noted in several regions in Canada during the past two decades. Such remarkable changes raise concerns about pavement serviceability, since both temperature and excess precipitation can ultimately affect the pavement materials properties. This paper focuses on two major factors, namely temperature and moisture level fluctuations. An increase in the maximum temperature can decrease asphalt concrete stiffness making the pavement more prone to rutting, shoving, and premature age hardening. On the other hand, high levels of saturation in the granular layers and subgrade can lead to pavement degradation through a reduction in the resilient modulus of these layers, increasing the rate of permanent deformations. However, accounting for realistic environmental factors in airport pavement design could be a challenge since most of the existing design methods do not systematically consider moisture and temperature variation during the service life of airfield pavements. Therefore, this paper proposes a methodology on how to efficiently account for temperature and moisture fluctuation by quantifying their effects on the performance of flexible airport pavements. To this end, the damage occurred over discrete short periods of time is estimated, considering the corresponding temperature and modulus at each stage. The cumulative damage is then calculated and compared with that of conventional design methods. The findings of this research indicate that it is crucial for airport pavement designers to consider realistic climatic factors to account for climate change implications in their airfield pavement design practices.