Airfield and Highway Pavements: Efficient Pavements Supporting Transportation's Future

Accurate prediction of tensile strain at the bottom of hot-mix asphalt (HMA) is crucial for mechanistic pavement analysis. In this study, transverse tensile strain at the bottom of HMA was calculated using mechanistic analysis and compared to measured values from test sections exposed to accelerated pavement testing (APT). Three full-depth flexible pavement sections having 152, 254, and 420mm of HMA placed on 300mm of lime-stabilized subgrade were constructed and exposed to APT using the Advanced Transportation Loading ASsembly (ATLAS), housed at the University of Illinois at Urbana-Champaign. Transverse tensile strain histories at the bottom of HMA under various loading conditions (load, tire pressure, and speed) were measured through embedded strain gauges at the HMA-stabilized subgrade interface. Indirect tensile complex modulus tests for three HMA materials were conducted using an Instron Universal Test Machine (UTM). The elastic modulus of subgrade was backcalculated from FWD testing conducted on the test sections. The pavement responses of test sections were calculated using the NCHRP 1-37A Mechanistic-Empirical Pavement Design Guide (MEPDG) procedure as well as a finite element model. In general, the MEPDG approach underestimates the transverse and longitudinal strains when the pavement thickness is equal to or smaller than 254mm; the difference is more manifested at shallow depths below 152mm. Hence, the pavement thickness design based on MEPDG procedure could underestimate the pavement fatigue damage for thin pavements. Inaccurate calculation of the loading pulse period and the empirical conversion between loading period and frequency are among the assumptions that contribute significantly to the ill-prediction of pavement responses when current NCHRP 1-37A is used. A 3D finite element model, on the other hand, was developed in order to predict pavement response to tire loading. The model considers measured tire-pavement contact stresses, continuous moving-wheel loading, implicit dynamic analysis, and HMA viscoelastic characteristics. Difference between measured and predicted strains was found to be within 5%.

To study the mechanism of mitigating shear-induced rutting in semi-rigid based asphalt pavement using geotextile, a series of finite element simulations are carried out to evaluate the benefits of applying geotextile reinforcement. Finite element analysis is performed by ABAQUS with consideration of plastic behavior of asphalt concrete. Parametric study is also conducted to investigate the influence of geotextile properties and layout. Outer-directed transverse shoving in middle of AC layer, the major contributor for shear-induced rutting, can be effectively reduced by integrated geotextile there and such effect can be enhanced through using high elastic modulus geotextile or more layers of geotextile. However, geotextile laid at AC bottom makes no contribution to rutting mitigation. In addition, almost all common geotextile can fulfill the requirement on tensile strength.

Routine permitting of overloaded trucks and axles is a common practice within the U.S. These permits only require the filing of paperwork and the payment of a fee without any further infrastructure damage evaluation. As cited in the literature, the fees are based primarily on administrative fees rather than costs associated with more rapid deterioration of the highway infrastructure. This investigation evaluated the impact of routine permitting on flexible and rigid pavement deterioration using the Mechanistic-Empirical Pavement Design Guide (MEPDG). Life cycle cost analyses were also conducted to estimate increased pavement costs due to permitting of heavier loads. Similar trends were noted between both flexible and rigid pavement analyses. Namely, the predicted reduction in pavement life as a function of the volume of permitted axles can be modeled well as a negative exponential relationship. There was a corresponding exponential increase in life cycle cost from increases in permitted axle volume.

Different laboratory compactors and protocols are employed to simulate field compaction using a reduced representative asphalt mixture specimen. Studies show that the mixture density, air voids, and mechanical properties vary within the results of each compaction method and between different compaction protocols, which may yield to estimates that mislead the design and performance prediction of the asphalt pavement. X-ray Computed Tomography (X-ray CT), a non-destructive technique for generating three-dimensional (3D) imaging of the internal structure of opaque materials, has commonly been used to quantify the air void distribution of asphalt mixtures. However, aggregate location, orientation and aggregate-to-aggregate contact points have rarely been successfully quantified using the same technique mainly because of image noise and poor contrast between the coarser aggregates and the other phases of the asphalt mixture (i.e. the air voids and the blend of the finer fraction aggregates and the asphalt binder). To overcome these shortcomings, an advanced tool has been developed utilizing 3D X-Ray CT image processing and artificial neural networks (ANN) to perform image segmentation and identify the coarser aggregates even in poor contrast X-ray CT images. This paper presents the details of the ANN tool and its application in determining the approximate size and location of the coarse aggregates in asphalt specimens.

In recent years, recognition of the influence of environmental factors on pavement performance has greatly increased and many research studies have focused on this area. Although there is agreement on the significance of temperature and moisture impact on pavement performance, only limited field measured data is available to quantify its magnitude. Most available data is based on laboratory studies, such as the impact of temperature on asphalt mix stiffness. However, in reality pavements perform as one structure, and overall pavement performance is of more interest than the performance of individual layers. In this paper, field data collected from two New Jersey and California pavement sections is used to develop a probabilistic approach to address the daily changes in pavement stiffness and how these changes can be considered at the design stage. This data was collected as a part of field studies performed to quantify the impact of temperature and moisture on pavement performance. This probabilistic approach yielded distributions that were extremely similar for the New Jersey and California sections, despite the major differences in environmental zone, temperature range, and pavement structure between the sections.

Compared with an embedded programming language "FISH" within the Particle Flow Code (PFC), the user-written C++ code is an optional feature in the PFC. This optional feature is an advanced application and can improve simulation speeds. In this paper, the user-written C++ codes for two and three dimensional models were developed. The discrete element simulation of asphalt mixtures were conducted with user-written C++ codes along with FISH programs. The simulation results from the two methods were compared. It was found that the user-written C++ program can speed up discrete element simulation, where the speed ratios (C++/FISH) are from 2.34 to 4.95 and the averaged value is 3.74.

The fracture mechanism of reflective cracking in hot-mix asphalt (HMA) overlay was investigated using a three-dimensional finite element model utilizing the cohesive zone model. The effectiveness of interlayer systems to abate reflective cracking in overlays was evaluated. A fractured area due to potential reflective cracking was calculated at a region in which cohesive elements were inserted. A represent fracture area (RFA) is introduced as a weighted average value of degradation to calculate the fractured area. Utilizing global and local RFAs, the mechanism of reflective cracking is investigated for HMA overlay with interlayer systems. For various interlayer systems, this study found that different reflective cracking patterns occurred in terms of quantity and distribution. The sand mix interlayer reduces reflective cracking in leveling binder at the beginning; however, steel netting interlayer retards reflective cracking in wearing surface as well as leveling binder.

Current mechanistic-empirical rutting models relate permanent strains to resilient strains. However, the influence of layer thickness on the predicted rutting based on these resilient strains is in sharp disagreement with field observations. Thickness or depth correction factors are required to bring predictions into agreement with observations. Nonlinear elastoplastic finite element analyses of representative generic pavement structures are employed to provide qualitative and quantitative insights into this and related issues. Specific findings include: (a) horizontal stresses predicted by the elastoplastic analyses remain compressive at all times—i.e., the material at the bottom of the HMA layer is not in tension as predicted from multilayer elastic analyses but is yielding under triaxial confined compression conditions; (b) the residual strain variations with depth computed from the elastoplastic analyses are qualitatively similar to measurements from field pavements without resort to any empirical depth or thickness correction functions; and (c) the elastoplastic finite element analyses can directly predict surface heave outside the wheel path, which at best is included in mechanistic-empirical rutting models only through the field calibration factors. Concluding suggestions are included for a conceptual approach for enhancing mechanistic-empirical rutting prediction models.

Various highway vehicle axle/wheel arrangements adopted nowadays to accommodate increasing load levels impact flexible pavement response and performance in accordance with different multiple axle/wheel loading scenarios applied in low volume roads. This paper describes a recent three-dimensional (3D) finite element (FE) pavement modeling research effort focused on investigating effects of complex multiple axle/wheel loading scenarios on mechanistic analyses of critical pavement responses and their implications on low volume pavement designs. For this purpose, realistic nonlinear, stress dependent pavement geomaterial modulus models were employed in the base/subbase and subgrade layers of thinly surfaced asphalt pavements. The low volume road sections were next analyzed using a validated 3D FE structural analysis program. Comparisons made between the single wheel superposition and the full 3D loading results proved the need and importance of 3D FE nonlinear analyses of low volume flexible pavements to properly consider both the stress dependent geomaterial modulus behavior and the implications of multiple wheel loads and their interaction.

The research objective is to evaluate a new test procedure for determining the specific gravity and absorption of steel slag and crushed concrete, which are recycled and manufactured coarse aggregates, respectively. Steel slag and crushed concrete, unlike many coarse aggregates possess special physical characteristic such as many effective surface voids. It is hypothesized that the current AASHTO T 85 (24±4 hours) test method fails to adequately saturate these effective voids on the coarse aggregate surfaces. When the steel slag and crushed concrete were soaked for 36 and 48 hours, it underscored the fact that AASHTO T 85 underestimates the absorption capacity of special porous coarse aggregates. A new proposed vacuum saturation approach is thus utilized to suck the trapped air within the effective pores while replacing it with water. This method is expected to better determine the specific gravity and absorption of these special aggregates. The steel slag and crushed concrete were tested at 30 minutes of vacuum saturation under 30mm Hg pressure. Statistical analysis indicated that this proposed method was viable in determining the specific gravities and absorption of these aggregates. An extended research is ongoing to expand the scope of coarse aggregates in addition to testing at reduced saturation times to increase the efficiency of the proposed method.

There are approximately 10 aircraft overruns per year that occur within the United States. Overruns are more common during landing than during takeoff and more likely to occur in wet conditions. Aircraft overruns can result in passenger fatalities, injuries, and extensive aircraft damage. The majority of aircrafts involved in an overrun stop within 305 m (1000-ft.) of the runway threshold. To reduce overrun hazards, the Federal Aviation Administration (FAA) requires airports to have a 305 m (1000 ft) runway safety area beyond the design runway length. However, many airports are restricted from extending their runway because of either natural or man-made barriers. As an alternative to creating a 305 m (1000-ft) runway safety area through runway extension, the FAA allows for the installation of an engineered material arrestor system (EMAS). Arrestor systems are designed as passive systems to reduce aircraft stopping distance by inducing drag forces on aircraft landing gear. An EMAS is typically constructed using a low-density cementitious material. Previous work by the authors has studied the sensitivity of aircraft stopping distance to aircraft characteristics considering two types of arrestor bed materials: phenolic foam and low-density concrete. This article investigates a much larger suite of possible low-density concrete mixes. Three arrestor bed configurations along with twenty-six low-density concrete mixtures were studied to evaluate aircraft stopping distance behavior as a function of low-density concrete mixture. Two aircrafts were considered, B727 and B747. The aircrafts represent different landing gear configurations and weights. Stopping distance was determined for each low-density concrete material considering each aircraft with and without reverse thrust. Over four hundred stopping distance analyses were conducted during the study using the FAA ARRESTOR computer code. In this paper, plots are used to summarize the study results.

The Hot mix asphalt (HMA) can be characterized as a combination of three phases: air voids, coarse aggregate, and asphalt matrix (AM), which includes binder and fine aggregate. The coarse aggregate phase is stiffer than the matrix phase, and is elastic in nature. The matrix phase makes the HMA a visco-elastic material due to the time dependent strain response of the binder. The matrix phase is considerably weaker than the coarse aggregate phase, and more susceptible to moisture damage. This study focuses on the characterization of the mechanistic responses of the AM and the HMA mixtures under dry and moisture damaged conditions. The mixtures were made using limestone aggregates and two asphalt type: neat and hydrated lime-modified. The dynamic shear rheometer was utilized to determine fatigue damage at 25°C and complex shear modulus (G*) of AM mixtures for a range of temperatures and loading frequencies. An indirect tensile load test was conducted to characterize tensile strength, fatigue life, elastic and permanent deformation characteristics of HMA mixtures. The G*-master curve analysis revealed that the hydrated lime-modified AM significantly improves the visco-elastic response of the moisture damaged AM. The fatigue life of AM mixtures increased due to the increase in G* values as a result of hydrated lime addition. Moreover, the fatigue life and permanent deformation characteristics of the HMA improved due to decreases in the rates of accumulation of tensile and compressive plastic deformation, respectively. Finally, relationships were established between various HMA and AM mechanistic properties.

Fatigue cracking under repeated load is one of the primary factors to be considered for flexible pavement design. Dynamic modulus test appeared to be a promising simple performance test for linking fundamental material properties to fatigue cracking observed in the field. The dynamic modulus concept was introduced in the AASHTO mechanistic-empirical pavement design guide as one of the critical inputs for characterization of asphalt concrete mixture, and it is employed as a key parameter in most commonly used models to predict fatigue life of bituminous mixtures. This paper presents a laboratory experimental program to evaluate the dynamic modulus of Florida Superpave asphalt mixtures including granite and limestone materials. The dynamic modulus master curves were constructed using the time-temperature superposition principle. The results indicated that the master curves for same type of materials were similar in shape and close to each other. The Witczak prediction model was used to perform a comparison between the measured and predicted dynamic modulus. The comparison showed that the Witczak prediction model provided a good estimation and could be adopted for estimating the modulus characteristics of commonly used Florida asphalt mixtures.

Elastic modulus and Poisson's ratio are the main parameters in elastic analysis of pavements, and also used in viscoelastic and elasto-visco-plastic analysis. These are the main parameters in elastic analysis of pavements, and also used for viscoelastic and elasto-visco-plastic analysis. The values of these parameters for asphaltic mixtures are determined using empirical values, formulations or experiments specifically designed for their determination. This describes the determination of these parameters using uniaxial single and repeated creep recovery tests by measuring the radial and axial strain of specimen. The tests were carried out, over a range of test conditions, on two types of asphaltic mixtures used in the UK pavements, namely a 10 mm DBM and HRA30/10. The variation of the parameters with temperature, stress level and accumulated strain level has been studied for the mixtures. It is found that the elastic modulus of asphaltic mixtures decreases with increasing damage in the mixtures. A formulation is developed for prediction of the elastic modulus of the mixtures as a function of stress level, temperature and the accumulated damage in the mixture.

The Reclaimed Asphalt Pavement (RAP) can save money and save energy when recycling is done on the side. The use of RAP significantly reduced the usage of natural resources (i.e., aggregate and petroleum product), and assisted local governments to meet the global reducing disposal standard. In this study, a 15% RAP was used in Superpave mixtures and a mixture without RAP was used as the control mixture. Comprehensive laboratory tests such as dynamic modulus and rutting tests were conducted to evaluate the performance of the mixtures with RAP. The results show that the difference in E* for control and RAP mixture compacted at 7% air void is not significant. However, it was found that the additional 15% RAP decreased the rut depth significantly after 8000 cycles using the Asphalt Pavement Analyzer (APA). The dynamic modules of asphalt mixtures were used in the AASHTO Mechanistic-Empirical Pavement Design Guide (MEPDG) analysis for a given pavement structure as well. In the preliminary study, it was found that an additional 15% of RAP reduced the rut depth up to 13% over a 20-year period in MEPDG analysis.

Rising energy costs and increased environmental awareness have brought attention to the potential benefits of warm asphalt in the United States. Warm mix asphalt (WMA) is produced by incorporating additives into asphalt mixtures to allow production and placement of the mix when heated to temperatures well below the 150°C+ temperatures of conventional hot mix asphalt (HMA). Potential benefits such as reduced plant emissions, improved compaction in the field, extension of the paving season into colder weather, and reduced energy consumption at the plant may be realized with different applications. Trial installations of WMA, including two sections using the Sasobit WMA additive, have been investigated in Virginia. This study presents the results of laboratory testing to evaluate the performance of the mixtures used in the two trial sections. The evaluation included comparisons of volumetric properties, moisture susceptibility, rutting resistance, and fatigue performance between the HMA and WMA mixtures used in each section. Few differences were found. In addition, the findings indicated that the performance of HMA and WMA should be equal when proper construction methods are used.

As warm asphalt has been gaining increasing popularity in the recent years, there are still several characteristics about warm asphalt that are unknown. While several studies have been conducted to study the performance of warm asphalt mixtures, aging characteristics of warm asphalt binders are not known in great detail as the technology is relatively new, and there are no old pavements to study the aging behavior of warm asphalt. This paper presents the results of a study conducted to simulate the aging of warm asphalt binder in the laboratory by preparing asphalt mixtures containing two different binder sources and three different warm asphalt additives (Control, Asphamin® and Sasobit®). The mixtures were artificially aged in the oven, and the binders were extracted for testing. The binders extracted from freshly prepared samples were considered being short term aged binders and binders extracted from oven aged mixtures were considered being long term aged binders. Results of several tests (e.g., viscosity, high and low temperature properties, Gel Permeation Chromatography, etc.) are presented in this study. The results indicated that the binders extracted from the warm mix asphalt (WMA) had significantly lower aging index (ratio of the viscosity of extracted binders to original binders) compared to the binders extracted from control hot mix asphalt (HMA). It was also observed that the binders extracted from the WMA had aged significantly lower compared to binders extracted from control HMA. The results indicated that the warm asphalt additives did not have any significant effect on the fatigue cracking parameter (G*.sin δ) or the creep stiffness of the binders. However, Asphamin® significantly increased the m-value of the binders.

The hot mix asphalt (HMA) industry is commencing on a program to substantially decrease mix production temperatures. Reduced mix production and paving temperatures would decrease the energy required to make HMA, reduce emissions and odors from plants, and improve the working conditions at the plant and paving site. With regard to rubberized asphalt mixtures, they are produced and compacted at higher temperatures than conventional mixtures. If the technologies of warm mix asphalt are incorporated, it is expected to reduce the mixing and compaction temperatures of rubberized asphalt mixtures to those of conventional mixtures. This study was initiated to investigate the effect of compaction temperature on warm rubberized mixes. For this, two Superpave mix designs for two asphalt binders and one aggregate size (12.5mm) were conducted to determine the optimum asphalt contents (OAC). Warm rubberized mixes were produced using two of the available processes. A total of 96 specimens (4 mix types: control mix, rubberized mix, warm rubberized mix 1 and warm rubberized mix 2 * 4 compaction temperatures: 97, 116, 135, and 154°C * 6 repetitions) were fabricated using Superpave gyratory compactor. Volumetric properties of the specimens were evaluated. The results showed that the warm mix processes were effective to improve the volumetric properties of rubberized mixes at a certain range of compaction temperatures.

Cold in-place recycling (CIR) layer is normally covered by a wearing surface in order to protect it from water ingress and traffic abrasion while obtaining the required pavement structure and texture. Currently, various agencies have differing moisture content requirements prior to placement of the wearing surface based either on the total moisture content in the mixture or the increase in moisture content from the pavement prior to recycling. The industry standard for this curing time is 10 to 14 days or a maximum moisture content of 1.5 percent. The main objective of this research is to develop technically sound methods to identify minimum in-place CIR properties necessary to permit placement of the HMA overlay through the laboratory curing process. Indirect tensile strength and moisture content of CIR mixtures were measured from the specimens with two different curing procedures: uncovered and semi-covered. Based upon the limited test results, both the length of the curing time and the moisture content significantly affect the indirect tensile strength of the CIR mixtures. It should be noted that, given a similar moisture level, the longer curing period would produce the higher indirect tensile strength.

This paper presents an experimental study on investigating the properties of Alaskan asphalt binder modified with different percentages of gilsonite over a wide range of climatic conditions by addressing the performance grade (PG) of gilsonite-modified binders according to Superpave specifications. The base asphalt used in this study was the neat asphalt with PG 52-28, and 5 different percentages of gilsonite (0, 3%, 6%, 9%, and 12% of total binder content) were introduced. With the increase of gilsonite content from 0% to 12%, the PG high temperature increased from 52°C to 70°C. However, the PG low temperature also increased from –28°C to –22°C. The results indicated that the addition of gilsonite tends to improve the rutting resistance of asphalt binders, however, increases the tendency for fatigue cracking and low temperature cracking. Adding low content of gilsonite (i.e. 3% within the scope of this study), the modified binder presents improved rutting resistance without any compromise of resistance to low temperature cracking.

Conductive stone mastic asphalt (SMA) mixture is a kind of asphalt pavement material with excellent electrical performance, produced through adding conductive paste material to the mixture. It was produced by using graphite as conductive particle, and a kind of resistance test method of embedding showerhead electrode was designed in the present study. It was found that graphite can improve electrical performance of SMA mixture effectively. Fractal theory finds the reason why different graphite have various effect in improving electrical performance of mixture is their model parameters are diverse; electrical performance of conductive SMA mixture containing graphite is steady, and will not change with time; with the increase of graphite content, temperature sensitivity of conductive SMA decreases gradually and its linear V-I characteristic is more obvious; the present research shows: the conductive mechanism of conductive SMA is the result of combined action of conductive pathway, tunneling effect and field emission.

With the development of engineering construction and transport, the mileage of tunnels built by countries around the world have greatly increased. Asphalt Pavement has become the main form in the pavement of highways and bridges. Tunnel is a semi-closed space that when an accident and firing happen in it, gasoline and other flammable liquids flowdown and will burn quickly and wildly. The fire hazard seriously threaten the human and vehicles' security in tunnel, and cause great casualties and economic losses, which have occurred in many countries of the world. Because of the flammability of asphalt, the asphalt pavement appliances are severely limited in the tunnel project. However, the use of asphalt pavement in the tunnel can be promoted through the approach to flame-retarding treating and changing the material's property of combustion. Based on the flame-retarding system of ATH(aluminum hydroxide), this paper selected the suitable ATH, tested the flame-retarding performance of MH (magnesium hydroxide) and improved ATH flame-retardant properties by Zeolite powder, then designed a reasonable program about ATH flame-retardant technology. Based on researches on the flame-retarding performance of ATH & MH and the accelerating effect of zeolite powder through tested of limiting oxygen index and flash point, the optimum mixture ratio of compound flame-retarding asphalt can be presented. Results showed the limiting oxygen index of compound flame-retarding asphalt could climb to more than 29 percent, and the flash point came to about 420°C, the flame-retarding performance of asphalt was improved greatly. Its mechanism and theory also have been discussed and explored through DSC-TG analysis and SEM observation.

This paper discusses the mechanical modeling of the asphalt matrix (AM) and hot mix asphalt (HMA) mixtures for two types of aggregates and one asphalt grade. The AM gradation was extracted from the HMA gradation passing No. 8-sieve. Hydrated lime was used as a binder additive to investigate the improvement in mixture properties. A dynamic shear rheometer (DSR) was used to conduct frequency sweep and creep tests at various temperatures on AM specimens. An indirect tensile load test was conducted to determine the resilient modulus and the creep compliance of HMA mixtures. The master curves for complex shear moduli (G*) and creep compliance of AM were constructed using the data obtained at different temperatures from a DSR test. The G*-master curve data indicated improvements due to the hydrated lime addition for a range of frequencies, and were a function of aggregate type. The results showed that the generalized mechanical model (i.e., a combination of a Maxwel model and Kelvein models) can effectively characterize the creep response of both the AM and HMA mixtures. The study also focused on the application of a clustered distinct element two- dimensional (2-D) modeling (DEM) to predict the uniaxial compression modulus using a synthetic, heterogeneous microstructure reconstructed from scanned images of actual test specimens. The HMA 2-D microstructure was obtained by scanning HMA test specimens using a high-resolution scanner to obtain grayscale images. Bulk properties of the AM and aggregate structure were assigned and virtual compressive test simulations were conducted. The results indicated that the DEM simulation produced repeatable HMA moduli for a range of AM moduli, and can model the aggregate interactions, which represent some effects of the aggregate interlock in asphalt mixture. Furthermore, the micromechanical model using the DEM approach provides a reasonable physical portrayal of the force chains developed in the aggregate skeleton, which are known to be a critical aspect of HMA micromechanical modeling.

In this study, the accelerated loading equipment MMLS3, which applies scaled wheel load on a scaled pavement structure, has been used to investigate the effect of loading and temperature on the dynamic modulus (|E*|) of hot mix asphalt (HMA). Several HMA test slabs have been prepared in the laboratory by compacting mixes using vibratory roller compactor. The test slabs, instrumented with strain gauges and thermocouples, have been subjected to repeated wheel load using MMLS3 under controlled temperature condition. The strain and temperature data have been acquired continuously during loading with data acquisition system. The analysis of data indicated that strain signals are composed of several dominant frequencies. The constitutive equation of linear viscoelasticity in time domain was then transformed to frequency domain using the Fast Fourier Transform technique at steady state condition and the complex |E*| values have been determined continuously during the loading. The test results indicated that |E*| is significantly affected by the combined effect of loading and temperature. A general trend of reduction of |E*| values due to these factors has been observed in the study. A simple model has been proposed which can be used to determine |E*| under moving wheel load and varying temperature condition. A comparison of test result with the MEPDG model of dynamic modulus indicates that the MEPDG model represents the condition at the beginning of loading when the damage is minimal.

Since 2002, Washington Dulles International Airport has taken an aggressive approach to effectively managing its airfield pavement system. Each year, roughly one third of the total airfield pavement network is inspected based upon the FAA procedures, Advisory Circular 150/5380-6B, "Guidelines and Procedures for Maintenance of Airport Pavement," to develop the Pavement Condition Index (PCI). The PCI data is used for two purposes: first, to plan for in-house annual preventive and stop-gap maintenance requirements; and second, to define major rehabilitation projects. The airport has effectively used the process to develop successful, high-impact projects to rehabilitate the original airfield pavements that are 40 to 45 years old. During the process, each major project is defined into a constructible package, with cost and duration estimates developed for each. With all projects defined, they are prioritized and fit into the operational landscape and integrated with other airfield projects. This paper explains the project definition process and components and shows how PCI inspection data can be turned into a key tool for developing an airport's plan to maintain and improve its pavement infrastructure.

The Sarasota Manatee Airport Authority (SMAA) sponsored the Runway 14-32 Pavement Rehabilitation at the Sarasota Bradenton International Airport (SRQ) in Sarasota, Florida. Runway 14-32 is the primary runway at SRQ and serves commercial jet and general aviation traffic. Runway 14-32 is a 150-foot-wide asphalt runway, which was extended in 2002 to its present length of 9,500 feet, with published precision instrument approaches at both ends. This project consisted of a pavement rehabilitation of the center 7,000-foot section of Runway 14-32. The project consisted of milling two inches off of the existing runway pavement and overlaying the runway with two inches of new P-401 asphalt. Due to the continuous flight operations at SRQ, the project had a strictly enforced seven-hour construction window which consisted of three hours for paving before installing temporary pavement markings. Reopening the runway on time was critical to the Airport and for the Contractor to avoid financial penalties. This paper will present the construction coordination practices and schedule conducted during the fast-track pavement rehabilitation of Runway 14-32. The final construction was completed within the contract timeframe and below the contract amount.

The paper discusses the use of mechanistic-empirical analyses to predict the performance of the air-side asphalt concrete pavements at the New Doha International Airport. The materials and pavement layer geometry were designed in accordance with Federal Aviation Administration (FAA) requirements. To check the adequacy of the 75-blow Marshall mix design, moisture sensitivity and permanent deformation testing was conducted. For moisture sensitivity studies, both the AASHTO T-283 (Lottman) and AASHTO T-324 (Hamburg wheel tracking) tests were performed. While the AAHTO T-324 procedure can be used to evaluate the mix in a "wet" or "dry" state, it does not provide a realistic estimate of in situ rutting potential under actual traffic loading. Thus, to estimate the rutting performance of the materials in the pavement section subjected to the design traffic, data from the repeated load simple shear test at constant height (RSST-CH), AASHTO T-320, and mechanistic pavement analyses were utilized. Mixes at the design binder content, i.e., "optimum" and "optimum + 0.5%" were tested in repeated loading at 122°F (50°C). These test results were used in a rut depth estimation procedure developed during the WesTrack accelerated pavement test program conducted from 1995–2000. In this approach calculated stresses and strains within the multilayer elastic system and RSST-CH results are used to estimate rutting in the asphalt-bound layer for the anticipated traffic and site conditions, i.e., pavement temperatures. To accumulate permanent strains resulting from the anticipated aircraft mix, a time-hardening cumulative damage hypothesis was utilized. Results of these analyses suggest that the proposed mix design should provide adequate rutting resistance. However, the results also suggest that the production tolerance for binder content should be limited to ±0.25 percent. Using subgrade strain criteria suggested by Shell researchers, an estimate of rutting contributed by the unbound layers was also determined for the anticipated traffic and site conditions. Results of this analysis indicate that the overall pavement thickness is adequate. A brief description of the rut prediction methodology is included. RSST-CH results were compared to rutting criteria established for San Francisco International Airport subjected to stop-and-go movements of B747-400 aircraft. This comparison supports the conclusion reached from the mechanistic-empirical permanent deformation analyses for the asphalt bound layer.

In 1982 the Federal Aviation Administration, owners of Washington Dulles International Airport, undertook a Pavement Management program at the airport that included the Nondestructive Testing (NDT) of Runway 1L-19R. NDT analysis was obtained with the US Army Corps of Engineers' WES Vibrator and Falling Weight Deflectometer. The data was used to determine modulus of subgrade reaction, k, uniformity of the subgrade support, center and joint deflections and joint load transfer efficiency. Between 1982 and 2007, maintenance to the PCC runway pavement was limited to select panel replacement, joint sealing, crack repair and spall repair. In 2007, as part of a project to replace Runway 1L-19R, NDT tests were conducted on the runway to determine subgrade support values. This paper describes the results of this unique opportunity to compare NDT values taken on the same pavement 25 years apart, with similar equipment.

In 1961, the original construction of Runway 1L-19R was completed and the pavement remained idle for approximately one year until the opening of the Washington Dulles International Airport in 1962. The pavement was designed for a 25 year life and will have been in continuous use for nearly 50 years at the time when it is scheduled for reconstruction in 2009. This paper will examine the original design parameters and the history of loading (traffic growth) over the life of the pavement. It will also discuss the active pavement management system implemented by the Authority and the subsequent maintenance activities used to extend life of this pavement. Finally, the paper will discuss the pavement design associated with the upcoming reconstruction project as the Authority attempts to match the history of performance of the original pavement life.

In 1982 a Pavement Management program was undertaken on the airfield pavements at Washington Dulles International Airport to establish rate of pavement deterioration, predict remaining service life, formulate a pavement rehabilitation program and estimate rehabilitation cost. Based on three prediction models, two levels of pavement quality and the time phase for rehabilitation was predicted. The prediction models took into account the Pavement Condition Index (PCI), slab cracking and aircraft traffic. During the 25 years since the Pavement Management program, the airport has continued maintenance programs, including a several panel replacement programs and complete reconstruction of several airfield pavements. This paper describes the predictions methods and compares the time period predicted for reconstruction with the actual year the pavements were reconstructed.

Denver International Airport (DEN) has completed a comprehensive pavement evaluation of the entire airfield using the Geospatial Airfield Pavement Evaluation and Management System (GAPEMS). The comprehensive use of TabletPCs and GPS for distress mapping, photographic documentation, core sampling, structural evaluation, and mapping of legacy construction data has provided the pavement engineer with more data and a clearer big picture of the pavement condition. Traditional declining Pavement Condition Index (PCI) value was found to be ineffective as a means of forecasting remaining life for several reasons including the grouping of slabs unrelated to type of distress. The averaging of slabs in groups of 20 slabs for concrete is an inherent flaw in the PCI method when averaging slabs of highly variable distresses. A new pavement remaining life calculation method called the "FACS Method" was developed that used the acronym from four separate failure modes of concrete pavement: Fatigue, Alkali Silica Reaction (ASR), Cracking, and Spalling. Using geospatial mapping of all distresses and the additional data including geospatial photography, the team was able to develop a network forecast of remaining life based on each of the four failure modes by evaluating data at the individual slab level. This improved method of remaining life analysis was implemented at DEN and resulted in significant savings in the slab replacement program.

Skidding on wet pavements contributes to a substantial portion of highway crashes. The resistance to skidding however depends on the microtexture and macrotexture available on pavement surfaces. Several past studies have focused this aspect but with inadequate or inconsistent conclusions. The uniqueness of this study is that surface texture performance has been evaluated controlling the variability in aggregate mineralogy, environmental condition, construction and service. Portland cement concrete (PCC) specimens were prepared from a single mixture to evaluate the true effect of various surface textures on friction properties. Asphalt concrete (AC) surfaces with the same construction record were tested to examine the true effect of mix properties on surface texture and friction. Pavement surface texture was measured using the sand patch method and Automated Road Analyzer (ARAN) while the skid resistance was measured using the British Pendulum and skid trailer. Analysis has shown that a Mean Texture Depth (MTD) of about 1.8 mm is the optimum macrotexture for maximum surface friction on textured concrete surfaces. Exposed aggregate concrete may not be a preferred texture because of the benefit of sand microtexture is lost with washing out of surface mortar. AC surfaces with complex macrotexture have shown to perform differently from PCC surfaces with simple macrotexture pattern. The hypothesis that British Pendulum Number (BPN) is dependent only on surface microtexture and represents low speed friction has appeared to be invalid. The skid number-speed gradient is not something universal but varies from mix to mix. Several statistically significant models have also been developed correlating the skid resistance with the asphalt mix grading composition and surface macrotexture and with concrete surface macrotexture.

Pavement management can be considered to consist of network and project levels. Regardless of pavement management level, pavement condition data is an integral component and data quality can profoundly affect decision-making at all levels of pavement management. This paper therefore attempts to evaluate the quality of pavement roughness data (i.e. international roughness index or IRI) that is collected at project and network levels. IRI data quality collected at the project-level was found to be affected by the individual run, the wheel path, and the lane at which the profile is measured. IRI data quality collected during routine survey at the network level can be affected by the wheel path profile used to evaluate IRI. The variability of the IRI data was further quantified. Given the IRI collected from routine network-level surveys, a proposed relationship is developed to determine an IRI that is suitable for use in project-level pavement management applications.

As more and more utility installation and/or maintenance activities are located in highly congested urban roadways, frequent pavement utility cuts in such areas may cause more traffic disruption as well as deteriorate pavement life and quality. Utility owners normally need to obtain permits from public road authorities before commencing utility activities; however, public road authorities in Taiwan currently just issue permits without trying to coordinate and communicate with utility owners involved to schedule their utility-related activities in a more consecutive way. An information model based on the spatiotemporal objects database technique was proposed to help public road authorities identify the utility activities that might be combined together to avoid unnecessary pavement utility cuts. In the proposed model, constraints pertaining to pavement moratorium, utility clearance distance and traffic conditions were considered. The software architecture is discussed, followed by research conclusions.

This paper examines the characterization of a granular material lightly stabilized with slag-lime cementitious binder particularly utilizing the monotonic and cyclic load IDT testing method. An extensive laboratory investigation was carried out to determine the mechanical properties of the lightly stabilized granular material and to establish fatigue life relationships by IDT testing and typical results obtained from this ongoing research are presented in this paper. This study shows that the static stiffness modulus and dynamic stiffness modulus of the stabilized material increases with binder content and showed little change with moisture content variation around the optimum moisture content. Fatigue life relationships were established using two methods, namely the approach of determining the number of cycles for 50% reduction in the stiffness compared to the initial stiffness and the energy ratio method, and they both showed similar linear relationships. It is therefore concluded that cyclic load IDT testing can be used reliably to characterize lightly stabilized granular materials with slag-lime in terms of their strength, stiffness modulus and fatigue life relationships.

With the demands for environmental-benign technology for highway construction, recycling in-place pavement materials for reconstruction or rehabilitation has become an important re-construction alternative. For asphalt pavement reconstruction/rehabilitation, full-depth reclaimed (FDR) asphalt pavement materials is a viable option, which pulverizes the existing asphalt layer and/or base materials as a new base. In some occasions, to increase the support of base consisting of recycled pavement materials, additives, such as cement, emulsion, or self-cementing Class C fly ash, are added as a binder. Self cementing Class C fly ash is both economical and an environmentally-friendly approach which makes beneficial use of a coal combustion by-product. This paper addresses the performance evaluation of an asphalt pavement with Class C fly ash stabilized FDR asphalt pavement materials as the base. The performance was evaluated using distress survey, falling weight deflectometer (FWD), and mechanistic-empirical (M-E) design program, as a case study. It was found that within the three year after the construction, the modulus of Class C fly ash stabilized FDR base has continuously increased, as a result of continuing pozzolanic reactions. However, it was also found that in the sixth year after the construction, the modulus of base began to decline , when compared to the third year results. It is believed that freeze-thaw effects may have reduced the strength of the stabilized base course. A visual distress survey found that top-down cracking from the asphalt surface began to occur three years after the construction as the predominant distress, followed by thermal cracking and rutting. The verification of performance using M-E design program found that the M-E design program underpredicted the amount of top-down cracking and thermal cracking and did reasonably well for prediction of the rutting. It is believed that the stiff base could be a reason for the top-down cracking and that friction between the HMA layer and base contributed to the thermal cracking.

In recent times as good quality materials have become rarer, use of out-of-specification materials in structural parts of road pavement construction have been investigated. This is particularly attractive in developing countries where good quality materials may be prohibitively expensive. This paper describes an investigation into the use of cement stabilized fine to medium sand in the construction of roads undertaken entirely in Bangladesh. The laboratory results indicated that the unconfined compressive strength and constructibility of sand-cement mixes were acceptable for road pavement layers. The sand-cement material with 8 to 10% cement proved to be adequate for subbase layers for heavily trafficked roads. A pilot field trial showed the constructability of a pavement layer using fine to medium sand and 10% cement mix. The un-surfaced trial road only experienced a few minor cracks after six months of construction.

At existing airports, re-aligning and replacing taxiways is a common practice due to reconfigurations of the operational area or just normal wear and tear. For example, with the arrival of the new "Super-Jumbo Jet" aircrafts, such as the Airbus A380, our nation's taxiways will need widening and increased load capacity to accommodate the large aircrafts. It is common practice when removing and re-aligning taxiways to dispose of the material and replace it with new material, either asphalt or other base courses. The Port Authority wanted to try and reuse some of this material to develop sustainable design, and reduce material costs. Preliminary research in the Port Authority of NY & NJ Materials Laboratory investigated the possibilities of reusing existing asphalt pavement (RAP), lime-cement-fly ash base course (LCF) and blending it with Portland cement to create a sustainable base course. This research was successful and lead to the option of using either a new asphalt base or a blend of existing pavement and Portland cement in a contract to upgrade the taxiways at John F. Kennedy International Airport. The low bidder chose to use recycled pavement materials and blend it with cement on-site. This sustainable option not only proved to be economical but efficient as well. The on-site blending of Portland cement with the removed pavement material saved in travel time and reduced truck traffic on the surrounding infrastructure. This paper will discuss in detail the following topics related to sustainable base courses: 1. Preliminary laboratory results, 2. Sustainable base course mix design, 3. Batching and placement methods, 4. QC/QA procedures, 5. Test results.

Recycled asphalt pavements (RAP) and recycled concrete pavements (RCP) were evaluated for use as an unbound base/subbase material. The objective was to recommend procedures for performance-related testing and selection of recycled hot-mix asphalt (HMA) and Portland cement concrete (PCC) materials for use as aggregates in unbound pavement layers, singularly or in combination with other materials. Performance-related tests were conducted on RAP and RCP samples containing three constituent aggregate types (gravel, crushed limestone and granite) providing a range of performance from poor to excellent. The recycled materials were blended with a virgin aggregate known to provide good performance in unbound pavement layers. Requirements for test parameters for recycled materials were established to evaluate recycled materials' suitability for use in particular traffic and climatic conditions. The research results are implemented as a decision chart incorporating aggregate shear strength, stiffness, toughness, and frost susceptibility to provide a measure of the performance potential of a particular recycled aggregate.

Load wander in airport pavements is much wider than highway wander due to the varying paths of different aircraft gear configurations and applied wheel loading locations. Full scale pavement testing of aircraft loads at the FAA's National Airport Pavement Test Facility (NAPTF) indicates that wander can negate the stiffening in unbound granular layers, known as the shakedown effect, and make them prone to developing increased deformations on subsequent aircraft passes when compared to channelized highway traffic. As part of the research activities at the FAA's Center of Excellence for Airport Technology (CEAT) established at the University of Illinois, dynamic response data from airport pavement test sections were collected due to passing of each of the 6-wheel B777 type and the 4-wheel B747 type gears for various combinations of applied load magnitudes and loading sequences (application order and stress history effects), traffic directions, gear spacings, and wander positions and sequences. The field data analyzed showed that the permanent deformation during a complete wander cycle was negated due to aircraft wander, indicating recurring particle movements and rearrangements in the unbound pavement layers. Using the multi-depth deflectometer data and the concepts of base damage index and base curvature index from heavy weight deflectometer testing, the load wander was determined to cause high percentages of residual responses per wheel pass in the granular layers that were indicative of reduced strength and modulus properties for potentially higher damage accumulations during the initial stages of NAPTF test section trafficking to failure.

The Hartsfield-Jackson Atlanta International Airport opened a critical end-around taxiway in April 2007 to reduce operational delays for air and ground traffic. As part of the construction specifications, the Contractor was required to prepare three feet of soil subgrade by undercutting and recompacting in order to achieve a minimum design modulus of subgrade reaction (k-value) of 90 pci. A value engineering alternative was utilized to verify the capacity of in-situ soils using a portable, light weight deflectometer (LWD) and laboratory resilient modulus tests to model the pavement subgrade modulus. A validation of direct k-value (from LWD testing) was performed by comparing to the k-value obtained from resilient modulus testing. The final phase of the test program involved the computation of in-situ subgrade modulus from LWD for the remaining part of the Taxiway Victor to demonstrate the suitability of in-situ soils thus eliminating majority of the traditional subgrade preparation, as specified originally in project documents. The LWD offered an added advantage of fast turn-around results after the collection of field data. The paper provides a background of existing subgrade issues, the test program methodology and conclusions from this value-engineering approach.

The National Airport Pavement Test Facility (NAPTF) is located at the FAA William J. Hughes Technical Center, Atlantic City International Airport, New Jersey. It is used to generate full-scale pavement response and performance data for development and verification of airport pavement design criteria. During the Construction Cycle 5 — Test Strip, four flexible pavement test items were subjected to accelerated traffic tests using representative aircraft landing gear configurations. Pavements were constructed over two subgrades with similar CBR (approximately 3) but different soil types (silty clay and clay). Two test items (LFC1-N and LFC1-S) were designed to fail in approximately 100 passes (4-wheel gear and 55,000 lbs wheel load) and the pavement structure consisted of 2.5-inch P401 HMA surface, 8-inch P209 crushed stone base, and 16-inch P154 subbase. The other two test items (LFC2-N and LFC2-S) were designed to fail in approximately 2000 passes and the pavement structure consisted of 2.5-inch P401 HMA surface, 8-inch P209 crushed stone base, and 24-inch P154 subbase. The test items exhibited permanent deformations at the surface (evidenced by rut depths) of over 4 inches and upheaval at the sides of the ruts in excess of 1 inch. This paper presents the results from Heavy Weight Deflectometer (HWD) tests, trafficking tests (rut depth measurements) and posttraffic tests (trenching study). The trenching involved removal of the P-401 AC layer, the P-209 base, and the P-154 subbase layer to reveal the subgrade interface and subsequent subgrade layers below. Tests conducted on the pavement component layers included CBRs, in situ densities and moisture contents. Layer interface profile measurements from trench walls clearly show shear flow in the subgrade, with vertical movement of the subgrade material in the upheaval areas. This information will be used for developing thickness design procedures and load evaluation of airport pavements.

This research evaluated the use of recycled concrete aggregate (RCA) from airfield and highway pavements to enhance sustainability based on engineering, economic, and environmental criteria. The objective was to develop evaluation and construction guidelines by defining the minimum standards for RCA as unbound base. The research approach included contacts with industry representatives, technical assessments, site visits, and performance review of airfield pavements with unbound RCA layers. RCA can be used as unbound base material if produced from uncontaminated PCC. All virgin aggregate tests and their limits are applicable to RCA except the sulfate soundness test, which is waived for RCA due to the incompatibility of PCC components with the chemical reactants used in the test. RCA should not be used where there is a potential for sulfate exposure from subgrade soils, ground water, or other external sources. RCA from ASR-distressed PCC can be used considering site conditions. RCA is not a hazard to the environment. An economic analysis can be conducted by considering initial material and construction costs for both RCA and virgin aggregate.

The prediction of fatigue cracking in jointed concrete pavements has traditionally focused on transverse cracking initiating from the bottom of the slab and propagating both up and across the slab width. However, field surveys of several locations, particularly in the Western United States indicate that alternative fatigue cracking mechanisms, such as top-down and bottom-up longitudinal cracking, top-down transverse cracking, and corner cracking, exist in substantial quantity. To better understand these alternative cracking mechanisms and to account for such mechanisms in both the analysis and design of jointed concrete pavements, a mechanistic analysis software program named RadiCAL was developed. Mechanistic parameters such as built-in and cyclical curling, axle spacing effects, load transfer, etc. was utilized to predict the critical fatigue crack location using the method of linear fatigue damage accumulation. Several sites in California that have exhibited both traditional and alternative fatigue cracking mechanisms were examined using RadiCAL to validate the proposed mechanistic analysis principles for stress and fatigue damage development.

In traditional Design-Bid-Build projects, the engineering consultant generally has no financial incentive to minimize the construction cost as long as it stays within the client's budget. As a result, the design may be conservative, resulting in needless dollars being spent during construction. Design-Build projects require all participants involved to rethink their traditional roles on a project. The Owner no longer dictates the final design, but instead sets the design parameters, requiring the Design-Builder to determine the final design. Teamed with the contractor, the designer now has to look at the financial impacts of the design, considering material costs, procurement, subcontractor involvement, traffic and schedule. Therefore, the designer and contractor together can develop alternatives that meet the design requirements, while reducing costs. The contractor is being paid on a lump sum basis, so minimizing impacts to cost and schedule, while still meeting the design parameters, means more money in the Design Builder's pocket. The focus of this presentation is on a case study of the pavement design and construction for the I-5 Everett HOV Project located about 30 miles north of Seattle, Washington. The Design-Builder will present on the challenges of working as a Joint Venture between designers and contractors and the impact it had on the final product.

Composite pavement systems have shown good potential for becoming a cost-effective pavement alternative for new construction of high volume roads. This paper discusses the potential benefits that composite pavement structures (flexible layer over a rigid layer) have to offer during their long service lives, investigates the structural design approaches used nationally and internationally, and compares the theoretical performance of typical composite pavement systems. Typical structural packages obtained using various design methodologies are evaluated, and the mechanistic responses (stresses and strains) of typical composite pavements are contrasted with that of a comparable flexible pavement. Fatigue and rutting models are used to further study the behavior of the composite pavements present in terms of these distresses. The results suggest that composite pavement structures can provide a long-lasting and effective alternative for roadways carrying very heavy traffic.

Aircraft pavement thickness design remains tied to empirical relationships derived from full scale test data. With the introduction of the six wheel landing gears of the A380 and B777 the current failure criteria for the Australian developed pavement design program Aircraft Pavement Structural Design System (APSDS) were no longer valid. APSDS was recently recalibrated using a greater number of aircraft at different masses and a greater range of aircraft coverages than were used initially. The S77-1 pavement thicknesses against which the calibration was performed were generated using the replacement Alpha Factor values endorsed by the International Civil Aviation Organization (ICAO) in October 2007. Replacement values of the calibration constants have now been developed for the following three situations: 1. A single failure criterion over all subgrade California Bearing Ratios (CBRs) and wheel configurations. 2. A criterion for each value of CBR but combining all wheel configurations. 3. A criterion for each subgrade CBR and for each wheel configuration (1, 2, 4 and 6-wheel). The second scenario produced significant improvement in the agreement between S77-1 and APSDS pavement thicknesses when compared to that provided by the current calibration constants. By considering each aircraft wheel configuration separately, a more significant improvement was achieved. Combining all wheel configurations and subgrade CBRs into a single failure criterion provided the least improvement to the current APSDS calibration. The influence of subgrade CBR and aircraft wheel configuration were found to be significant and separate failure criteria should be adopted for each subgrade and each wheel configuration. This finding contrasts with the approach by the FAA in LEDFAA 1.3. LEDFAA 1.3 adopts a single failure criterion for all CBRs and all wheel configurations.

Cancún International Airport (CUN) located on the tip of the Yucatán peninsula in southeast Mexico is the second largest airport in Mexico. It served more than 11.3 million passengers in 2007 - the most international passengers in Latin America and Cancún is the biggest tourist destination in Mexico and the Caribbean. Aeropuertos del Sureste (ASUR) group has a concession contract for 9 airports in the southeast of Mexico and under their Master Development Agreement are committed to the construction of a second (parallel) runway at Cancún International Airport by the end of 2009 in order to meet the ever increasing demand for air services at this key worldwide tourist destination. This paper describes the key pavement geotechnical issues, design methods and construction materials and techniques utilized to engineer and build the embankment for the new 2800 metre (9200 foot) runway. The main design and construction issues covered include: discussion of the greenfield site featuring variable karst topography with the potential for extensive surface and hidden subterranean cavities; pavement design criteria including aircraft loading and minimum elevation for hurricane flooding; high water table and drainage by infiltration; design of runway and taxiway stabilized flexible pavements to FAA criteria including utilization of FAARFIELD methodologies; development of heavyweight proofrolling methods to confirm suitability of natural subgrade and identification of cavities; and, utilization of local materials and construction methods for construction of the subgrade embankment and pavement structure layers.

Rising and turbulent fuel costs have airlines challenged to meet the needs of future air travel. Recognizing this, aircraft designers/manufacturers have developed larger aircraft capable of flying greater distances, carrying more passengers and subsequently burning less fuel (per passenger). As the world's busiest airport, Hartsfield-Jackson Atlanta International Airport must be capable of evaluating each airlines needs to integrate new aircraft into their fleets, and the impact of doing so as it relates to operations and the structural performance of the airport's pavement network. The airport consists of over 42 million square feet of airside concrete pavement, ranging from 16 to 22 inches in concrete thickness. As part of the Pavement Management Program, a large historical database has been developed and maintained since 1984. Part of this database contains structural response data from falling/heavy weight deflection testing, as well as layer thickness data. This information is crucial for evaluating the impact of new aircraft added to the fleet. An evaluation of the structural impact on the existing pavement structures at the airport using the most recently collected (Summer-2007) structural response data is presented. Aircraft evaluated include the Boeing 787 and 777 as well as the Airbus A380, and results indicate areas which represent the highest risk of structural deterioration. Operational limitations are also examined, showing where pavement width, turning radius and gate capacity issues would limit the maneuverability of these aircraft.

Many airports in the United States and around the world list their runway pavement ratings according to the Federal Aviation Administration (FAA) system of Dual (D), Dual-Tandem (DT), and Double Dual-Tandem (DDT). This system has been in place for many years, and it has enabled airport authorities to determine allowable gross weights by a method that is easy to understand and use. In recent times, however, the development of larger widebody aircraft by the manufacturers has resulted in pavement loadings that cannot be adequately expressed by this type of rating, and so most ratings are now represented by the Aircraft Classification Number/Pavement Classification Number (ACN/PCN) system. Rather than develop new ratings for the 777 and other widebody aircraft, the FAA has gone ahead with a new design system, but left the current ratings in place. The ACN/PCN system will eventually take over as the rating of choice, but complete implementation appears to be far into the future, at least for U.S. airports. This has left the airport authority and many consultants with no guidance as how to evaluate an FAA-rated pavement which is traversed by aircraft such as the 777 or those with other unusual or non-standard gear configurations. The result is that many pavement loading analyses may be both inadequate and misunderstood. For example, the Boeing 777 has a 6-wheel gear, and it is not defined by the FAA system. Also, an Airbus A330 has a similar, but much larger wheel geometry than the standard FAA gear, and even though its pavement loading characteristics are superior to the FAA Dual-Tandem (DT), proper pavement loading credit may not be given. In the military sector, the C-17 has a six-wheel gear that is unlike any other arrangement. This paper proposes a method that adjusts the standard FAA rating to account for a variety of wheel sets such as those found in the larger widebody aircraft. Factors are developed that adjust the FAA rating for any widebody gear, including the 777. The method is easy to use, requiring only a use of a factor to arrive at an allowable gross weight. Pavement characteristics such as thickness, modulus, subgrade type and strength are not part of the standard FAA rating, and they are not required to utilize this method.

The upper level of the George Washington Bridge is a flexible, orthotropic steel deck. In the past, it has been difficult to obtain a significant service life from asphalt-wearing courses due to this deck design coupled with a high traffic volume. Lately, the asphalt-wearing course on the upper level has seen accelerated fatigue because all truck traffic is redirected to the upper level for security reasons. The primary modes of failure have been fatigue of the wearing course and loss of bond to the steel deck. In an attempt to increase the service life, The Port Authority of NY and NJ Materials Engineering Laboratory developed several asphalt mixture proportions with various polymer modifications. These asphalt mixtures were tested at the Rutgers Asphalt/Pavement Laboratory for fatigue and plastic deformation. Research and testing was also performed to improve the bond of the wearing course to the steel deck. This paper will present the mixture proportions tested, the results of the laboratory testing, the mixture that was chosen, and the experiences encountered during the installation of the asphalt-wearing course.

Proper construction of longitudinal joints in asphalt pavements significantly contributes to their longevity and reduces joint-related pavement distresses, such as surface raveling, joint cracking and opening. Despite the apparent importance of the joint, there is no single construction practice that is widely accepted in the US. Most states have their own approaches and requirements regarding the construction techniques and quality assurance (QA) activities associated with longitudinal joints. Recently, the Connecticut Department of Transportation and Federal Highway Administration sponsored a research study that investigated two types of longitudinal joints: traditional vertical butt joints and notched wedge joints. The data was collected from two re-surfacing projects in Connecticut that utilized both joint types. Each project was divided randomly into multiple sections and the density data was collected from each section. The density was measured at the joint location as well as on both sides of the joint immediately after compaction. Two methods were employed to determine the density. First, the in-place density was measured using the nuclear density gauge. Next, the cores were taken from the same locations to measure the density in the laboratory using the vacuum seal method. This paper presents the experimental setup and the construction details on both joint types. The collected data is statistically analyzed and factors influencing the final density for each project are discussed. Both density measurement methods are compared and the correction factor was established between the two methods using additional cores taken from the mat away from the joint.

Building successful pavements requires understanding the factors that contribute to making a pavement succeed. The first question to ask is what a successful pavement is. To answer this question and gather information from successful pavement sections, a two-year project was conducted by the Texas Transportation Institute (TTI) for the Texas Department of Transportation (TxDOT). Information about flexible pavements identified as superior performers has been collected and stored in a database with a user-friendly web-based interface. This database will be used to effectively learn from prior successes. Lessons learned in the past through experience will contribute to better understanding the factors that make a pavement succeed. The aim is to help practitioners improve technical specifications and testing techniques, which will in turn result in more consistent construction of premium pavements. This paper describes the methodology to identify a pavement as successful and briefly describes the Texas Successful Flexible Pavements Web Site.

This paper will discuss some interesting experiences working on airfields in Micronesia and Hawaii. None are unique but issues that are readily resolved in the continental United States become more difficult at airfields on remote islands. First Case study. The Palau International Airport runway, which had been overlain over 10 years earlier, was shedding aggregate at an alarming rate. To reduce the risk of FOD a heavy application of emulsion was applied. It performed satisfactorily for one year. The subsequent project proceeded well until the contractor unilaterally changed the surface lift aggregate gradation. After study, the surface was removed and replaced. Second Case study. At the Yap International Airport the PCC apron placed in 1999 had expanded by 2003 due to ASR. Forensic studies resulted in saving the cement treated base. The Pavement is being removed and replaced at this time. Third Case study. Grass grows fast all year in Micronesia. Constructing 3' wide concrete pads around signs and other equipment results in faster mowing without damage to the items. Fourth Case Study; Miscellaneous Conformance Issues. Some issues apply to several airfields but are often resolved on a case-by-case basis by the local FAA office. It would be desirable to have formal guidance from FAA Headquarters so that uniform standards are applied whenever possible. a) Fences on, or essentially on, the safety area and a penetration of FAR surfaces. b) Public roads outside the Runway safety area where the 5 meter (15 foot) requirements cannot be achieved. c) Applicable pavement design, geometric and use guides for service and security roads that must be on the runway safety area. d) Guidance for turnarounds at runway ends where no parallel taxiway can be provided. Fifth Case Study. Benefits of a Permanent Pavement Design. The reef runway at Honolulu International Airport is cited as an example.