Airfield Pavements: Challenges and New Technologies

The volume of air traffic continues to grow, resulting in an increasing number of aircraft movements. To cope with such growth it is necessary to make optimal use of all available runways, taxiways and aprons. An optimum utilization of such resources also means that maintenance has to be structured into a planned approach making it a prerequisite to have insight knowledge of the performance of the pavements, asphalt as well as concrete. By carrying out the right maintenance at the right time, the airport will reduce the overall need for maintenance, which in turn will produce economic benefits. The pressure on the availability of at least three runways at all times due to environmental reasons, noise, does mean that no unforeseen maintenance can be allowed and that the condition of these pavements has to be forecasted based on reliable performance indicators and performance models. This situation made Amsterdam Airport Schiphol decide to start already in 1994 with a systematic approach of maintaining the condition of all pavements. This pavement management methodology is based on the MicroPAVER Pavement Management System using the pavement condition index (PCI) surveys as a rating procedure. As pavement condition surveys only show visually detectable distresses, other condition measurements are used to enhance this system. The pavement condition is periodically evaluated using various condition measurements such as non-destructive deflection testing, roughness, skid resistance, Ground Penetrating Radar (GPR) and core-borings. This method of maintaining pavements is called Structured Management. The system used at Schiphol Airport shows clearly how managers, maintenance engineers and field-level personnel can take advantage of the information made available in a structured process.

In June 2001, the rapid replacement of three rigid airfield pavement panels was conducted at Washington Dulles International Airport, Washington, DC (IAD). The project involved the demonstration of a new technique for full-depth, overnight concrete panel replacement on an active taxilane and an active taxiway that allows for full reopening of the pavement to normal traffic each morning. The technique consists of excavation and removal of damaged panels and their replacement with precast concrete panels. This is followed by the controlled injection of an expanding high density polyurethane (HDP) polymer mixture under the panels which underseals and accurately lifts the panel to the required elevation. The rigid high density polyurethane forms a stable bearing surface for the precast replacement panels. The pavement may be open to traffic at this point, non-corroding composite inserts are subsequently installed to tie the panels together and establish load transfer capability at the newly formed joints. This same technology has been applied successfully during the past three years for the Colorado DOT, CalTrans (California Department of Transportation) and the Transit Authority in Seattle, Washington for the overnight replacement of highway pavement and pavement in large municipal parking areas. Washington Dulles International Airport was the first airport to use this technique and evaluate precast panel repair. Based on this and the experience gained in this demonstration, it may be concluded that this technique is viable for the rapid rigid pavement replacement under circumstances where an airport cannot tolerate traffic disruption during its normal operating schedule.

This paper discusses the development of a fuzzy logic-based system of airport pavement condition rating and maintenance-needs assessment, and its application as part of an airport pavement system in Singapore. The airport authority had found that its previous pavement condition rating system of classifying pavement distresses into three different severity levels was unsatisfactory for effective pavement maintenance, because each severity level covered too wide a range in terms of extent and density of the distress concerned. The new fuzzy logic-based procedure no longer relies on discrete classification rules, but relates the distress conditions directly to maintenance needs. The concepts of fuzzy logic enable additional information on each assessment to be contained in the form of membership functions. The maintenance management software consists of a fuzzy logic-based micro-computer algorithm that analyzes the pavement condition survey data and computes a maintenance-needs level for each pavement distress. It also serves as a useful training tool for new maintenance crew members.

Utilizing historical full-scale airfield pavement test data (that has been collected from the 1940's to the mid-1970's), and updating the historical record with test-to-failure data from the FAA National Airport Pavement Test Program, the pavement life cycle relationship to aircraft loading as indexed by landing gear type (dual, dual tandem, tri-tandem, etc.) has been investigated. The resulting collection of pavement failure data was analyzed for applicability to the existing S-77-1 methodology (using what is commonly referred to as the CBR equation). The investigation and analysis establishes that the CBR equation retains its usefulness for predicting pavement thickness requirements and pavement life for airfield pavements. It is concluded that the unique solution of the CBR equation at the 10,000 coverage level for four precisely defined subgrade support conditions (as defined by ICAO ACN guidelines) continues to be well suited to the use for which it was intended. A parallel study of the FAA test results via multi-layer elastic system solutions is included, which renders a similar conclusion.

A new runway complex of approximately 300,000 S.Y. of concrete pavement was designed using a three-way mix of 50% cement, 25% fly ash and 25% blast furnace slag as the cementitious material for the concrete pavement. The design was based on 650 psi flexural strength. The fly ash specified is Class "C" or Class "F" fly ash (ASTMC-618) and the blast furnace slag was specified as ASTMC-989, Grade 120. This runway was designed for Boeing 747's, Antonov 124's and other heavy cargo aircraft. Trial batch runs of the concrete mix indicate remarkable strength gains in 90 days. Flexural strengths of 800 psi were obtained in 90 days, due, in part, the use of 50% pozzolanic materials. The concrete trial batch runs were made using crushed granite rock with a maximum Los Angeles abrasion of 30 maximum. This $100 million project includes storm drainage and sanitary sewer system and airfield electrical work.

This new North Parallel Runway complex costs approximately $300 million, including land acquisition of 1,500 acres costing approximately $100 million. This runway 8L-26R is 5000 feet north of the existing Runway 8R-26L in order to facilitate simultaneous landings on both runways. This runway will be 9000 feet long by 150 feet wide with 35-foot wide shoulders on each side. This runway will have an ILS category III on both ends.

The National Airport Pavement Test Facility (NAPTF) was constructed to generate full-scale testing data to support the investigation of the performance of airport pavements subjected to complex gear loading configurations of new generation aircraft (NGA). The objectives of the NAPTF traffic/performance test program were to explore gear configuration/load and wander effects on pavement responses and performance as a function of number of load applications (N). Two gear configurations, a six-wheel tridem landing gear (B777) in one lane and a four-wheel dual-tandem landing gear (B747) in the other lane were tested simultaneously. Transverse surface profile (TSP) measurements and straightedge rut depth measurements were made at regular intervals to monitor the development of rut depth (RD). Using these measurements, a rutting study of the NAPTF flexible test sections was conducted. Statistical tests were performed to consider any difference in mean rut depths between B777 trafficking and B747 trafficking. The rut data were analyzed using the most common surface rutting models (the power model and the third-order polynomial model) and the models were compared. The results showed that the maximum surface rut at the termination of test trafficking is higher for conventional-base flexible test items than for stabilized-base flexible test items. From an engineering standpoint, the mean rut depths accumulated under B777 loading and B747 loading were similar. The number of passes required by the B777 and B747 gears in order to reach a 25.4-mm (1-inch) rut depth was similar. The power model was statistically significant at the 99% probability level for all of the sections. The third-order polynomial rutting model is a good curve-fitting model, but its engineering significance is questionable. The rutting rate (RD/N) exhibits a linear relation with the number of load repetitions on a log-log scale.

Rutting of flexible pavement is a load-induced phenomenon. It is caused by a combination of densification and shear deformation of any layer of the pavement structure. Severe rutting was observed on the Taxiway A at the Sacramento International Airport. The Runway 16R-34L and associated taxiways at the airport were originally constructed in 1965–66 and were placed in operation in 1967. The entire airfield received a strengthening overlay in 1979 and a second strengthening overlay in 1995. The pavement structure consists of 10 inches of asphalt concrete, 12 inches of crushed gravel base course and 12 inches of subbase. Taxiway A north of Taxiway Y exhibited severe rutting in excess of 2.5 inches. This section of taxiway is exposed to slow moving aircraft and is built on a low strength subgrade soil with a CBR of about 3. This section was exposed to high water table prior to drainage improvements in the early 1990's. There was no pavement subdrain system installed at this site. A visual pavement condition survey in 1992 indicated severe rutting in the same section of the Taxiway A. This section was rehabilitated by milling the existing pavement to a depth of about two inches and resurfacing with four inches of asphalt concrete. The 1993–94 rehabilitation work did not perform well, and the rutting recurred. The recurrence of very severe rutting observed in 2002 indicated that the rutting may have been caused by a combination of many factors, and milling and resurfacing will not correct the problem.

During the first series of traffic tests, two flexible pavement test items on medium-strength subgrade (MFC & MFS) exhibited severe rutting, with upheaval outside the traffic lanes, and asphalt surface (AC) cracking in the wander path. Four trenches were opened perpendicular to the centerline of the test items to conduct posttraffic investigation into the failure mechanism of the pavement structure. 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 CBR's, in situ densities and moisture contents, and dynamic cone penetrometer tests. Elevation profiles of the interfaces show clear evidence of shear flow in the subgrade, with vertical movement of the subgrade material in the upheaval areas.

Measurements of permanent deformations are presented from traffic tests on a stabilized base flexible pavement test item at the Federal Aviation Administration's (FAA) National Airport Pavement Test Facility (NAPTF). The tests were run with four- and six-wheel gear configurations at wheel loads of 20.4 tonnes (45,000 pounds) and over a total wander width of 3.66 m (12 ft). The test item was trafficked to structural failure with permanent deformations at the surface evidenced by rut depths of over 100 mm (4 inches) and upheaval at the sides of the ruts in excess of 25 mm (1 inch). The permanent deformations were measured with three different systems: a 3.66-m (12-ft) straightedge, a rolling inclinometer, and multidepth deflectometers (MDDs). The straightedge results are reported as maximum rut depth at prescribed repetition intervals. The profiler results are reported as transverse profiles at prescribed repetition intervals. And the MDD results are reported as time histories of structure displacements at the surface, in the asphalt layers, and in the aggregate layer. The net accumulated unrecovered (permanent) deformation in the pavement structure over a complete wander cycle is shown to be a small fraction of the range of the unrecovered deformations occurring during the wander cycle over individual back and forth load applications. That is, the sum of the upward and downward unrecovered displacements almost cancel, leaving the structure in approximately the same configuration at the end of a wander cycle as at the start. The unrecovered displacements are about the same magnitude as the recovered (elastic) displacements, with the relative magnitudes depending on the transverse position of the load relative to the transverse position of the measurement. As the pavement test item deteriorated, all three measurement systems showed increased magnitude of the unrecovered displacements. The MDDs also showed increased magnitude of the recovered displacements as the test item deteriorated.

After 10 years of service, the condition of two innovative PCC pavements, designed with a reduced number of joints, is reported. A third pavement, a conventional PCC pavement, was constructed at the same time. The performance of the two innovative pavements is compared to the performance of the conventional PCC pavement.

The Airbus A-380 aircraft is expected to begin operating at United States (U.S.) airports in 2006. Proposed Federal Aviation Administration (FAA) geometric standards require 60 meter (200 feet) runway widths for this aircraft. Since most commercial airports in the U.S. have 45 meter (150 feet) runway widths, runways that will accommodate the A-380 may require widening prior to initiation of service. This can result in expensive and operationally disruptive pavement construction at many of the nation's busiest international airports. Federal Express, one of the major carriers at the Memphis International Airport (MEM), intends to purchase A-380 aircraft for use in Memphis, beginning in 2008. Although pavement strength is not an issue for the concrete runway pavements, since the three parallel north-south runways are 45 meters (150 feet) wide, the runways may require widening to 60 meters (200 feet) prior to initiation of A-380 service. However, the runways do have 11 meters (35 feet) asphalt shoulders, 7.5 meters (25 feet) of which may be considered as operational pavement if it could be demonstrated that the shoulder pavements can withstand A-380 excursions. While this would require relocating the runway edge lights and re-stripping, the costs and operational disruptions would be far less than new construction for widening. Conversely, if the pavements are not structurally sufficient, options for economical and less disruptive strengthening could be explored. This paper discusses the analytical approach that was undertaken to evaluate the suitability of the runway shoulders for use as operational pavement at the runway edges. Analytical elements included nondestructive testing (NDT), combined with layered elastic and conventional structural analyses. NDT was conducted with a Heavy Falling Weight Deflectometer (HWD) to evaluate in-situ pavement layer and subgrade strength and generate inputs for the structural analyses. Layered elastic analyses used the cumulative damage factor (CDF) approach contained in FAA's LEDFAA program and a new FAA pavement design program, COMFAA, was used for conventional design analysis. The conventional and mechanistic design computations were supplemented by recent full scale testing data from FAA's National Airport Pavement Test Facility (NAPTF).

Vancouver International Airport (YVR) is Canada's second busiest airport, with some 15.5 million passengers and 274,400 aircraft movements in 2001. It is also the second largest international passenger gateway on the west coast of North America. It is a premier gateway to Asia and has been involved in an aggressive program of terminal and airside expansion since 1992. As part of its next major international terminal expansion, which will ultimately include six new Code F gates, YVR required a new remote apron which would act as an aircraft staging area to feed the terminal incorporating three deicing pads for Code E and Code F aircraft, remote cargo loading and refueling capabilities. The West Apron Expansion project combines 74,500m² (802,000 S.F.) of rigid and flexible pavement structures, an extensive subsurface stormwater and deicing fluid collection system, low-visibility inset lighting for CAT III conditions and high-mast floodlighting to provide unobstructed parking and power-in/power-out maneuvering for Code E and F aircraft. This paper describes the West Apron Expansion project as an engineering and construction case study. The major pavement design elements included: geometry for Code F aircraft maneuvering; staged preloading of the site to induce long-term settlement on the weak (CBR 2) river delta deposits where YVR is founded; rigid pavement structures for the main parking and taxi lanes; rigid pavement panel sizes to suit gear tracks of the new large aircraft and adjustments for over 230 inset lights; grading and drainage plan suitable for apron parking and rapid removal of deicing fluids; and, flexible pavement structures with hot mix asphaltic concrete surfaces and cement-stabilized base courses for smaller remote aircraft loading. The main construction issues included multi-stage preloading to minimize imported subbase, seven construction stages to minimize operational impact on adjacent pavements, quality control management by the contractor and rigid pavement construction using fixed form paving without internal vibrators. The construction encompassed six main contracts completed over a two-year period ending in early 2002.

Current PCC airfield pavement design methods generally select PCC joint spacing distance based on slab thickness. This paper explores the relationship between slab size (joint spacing) and pavement performance as measured by Pavement Condition Index (PCI). Various parameters known to affect pavement performance were investigated for their effect on the pavement performance-slab size relationship.

An 11 inch thick Portland Cement Concrete (PCC) test strip was constructed on an existing econocrete subbase, at the NAPTF, to investigate the effects of slab size, mix design, and curing procedures on shrinkage and curling of the PCC slabs. Two slab sizes: (4.5 by 4.5 meter (15 by 15 feet) and 6 by 6 meters (20 by 20 feet) were used on the test strip. The econocrete subbase had previously been constructed on a granular lower subbase over a low strength subgrade (4–5 CBR). A three-part optimized concrete mix was placed on half of the test strip, and the original two-part mix design was used on the other half. Both mixes complied with the FAA P-501 specification. Special attention was given to the curing stage. In addition to watering, the effect of thermal blankets was investigated. After the curling studies were completed the slabs were trafficked to failure.

Most concrete airfield pavement design procedures are based on developing sufficient slab thicknesses to resist fatigue cracking, that is, structural cracking caused by repeated load applications at stress levels less than the ultimate static strength of the concrete. At the heart of these design procedures is a concrete fatigue model, which relates slab stress conditions (expressed in terms of a stress-to-strength ratio) to the allowable number of load repetitions to a pre-defined "failure" level. Although a variety of fatigue models are available for use in concrete airfield pavement design, each provides different results, largely because of the differences in the way that they were developed. As a result, one fatigue model can not be simply substituted for another in a given design procedure. This paper presents a summary of the characteristics of some of the common fatigue models used in concrete airfield pavement design. The background and basis for the development of each model are described, highlighting some of the assumptions and limitations inherent in their development. The focus of the discussion is on the development and basis of the fatigue models themselves, and not on the development and basis of the design procedure in which they may be a part. Such information is of value to pavement design practitioners in both developing effective new concrete airfield pavement designs and in conducting meaningful mechanistic "checks" of pavement designs.

During a two-week period in October – November 2002, a rapid panel replacement of six panels of rigid airfield pavement was performed at Washington Dulles International Airport, Washington, DC (IAD). The work was performed during the night on active taxilanes and taxiways. The durations of the closures were 15.5, 9.5 and 8.5 hours on each of three replacement nights, showing a steep learning curve is involved. However the project demonstrated the process is viable for use in rapid pavement replacement projects using only nightly closures, enabling immediate reopening of the pavement to aircraft service loads. A special grading machine was used to create an accurate bearing surface in a compacted layer of granular subgrade material. The grading and precasting processes can produce planar surfaces or warped, fully three-dimensional surfaces. This project required warping. Panels were uniform in thickness but deviated from a true plane by as much as 40 mm (1–9/16 in.) vertically. Panels were placed within 6 mm (1/4 in.) on the vertical axis and had a 6 mm (1/4 in.) maximum placement deviation laterally. The new panels are expected to have a minimum service life of five years. Though the precast panels are likely to survive longer, surrounding original pavement is expected to continue to deteriorate, requiring replacement after five years. Although the project at IAD involved a total of six panels replaced two at a time, the technique can be applied to smaller scale projects or expanded over several months to replace hundreds or thousands of panels. With the technology's history on highways plus the success of the IAD project, the rapid panel replacement process shows promise for important new applications such as reconstruction of taxiways using only night closures, or replacement of a critical access Taxiway over a weekend.

Four methods can be used to determine the required thickness of rigid airfield pavement to support the expected traffic. Each method, except Layered Elastic Design Federal Aviation Administration (LEDFAA), models the pavement as a rigid slab supported by a dense liquid foundation (commonly referred to as a Westergaard foundation). However, each method incorporates different assumptions about the load that induces maximum stress and material fatigue. The difference in assumptions results in a divergence of the answers generated by each method. Equivalent pavement thickness designs should not be expected from the different design methods.

Nondestructive structural evaluation of existing airfield pavements by deflection testing is used to assess the load carrying capacity and strengthening design for future aircraft operations. The current backcalculation programs analyze the deflection data and calculate in situ Young's modulus values based on linear elastic structural response analysis for static loading. Advanced three dimensional-finite element dynamic analysis is used in this study to simulate airfield pavements subjected to nondestructive test load pulses. This study validates the in situ modulus values of a thick and strong airfield pavement section backcalculated from static analysis. The effect of different shape and time duration of the load pulses on dynamic response analysis is investigated. The results of the three dimensional-finite element dynamic analysis agree reasonably well with the results of the two dimensional-finite element dynamic analysis for this thick and strong pavement section.

Asphalt pavements have a long history of outstanding performance in airfield applications. One of the first modern airport projects in the country was Washington National Airport. Upon its completion in 1940, more than one million square yards hot-mix asphalt (HMA) pavements had been constructed to meet the bright future of commercial aviation. Much has changed in both the asphalt and airfield pavement industries over the last 63 years. Larger and more powerful aircraft have changed how we design pavement structures and mixes. Enhanced production, laydown, and quality control technology has led to increased quality and higher production capability on airfield paving projects. Finally, with the advent of Superpave, we now have a mix design system that is capable of developing improved HMA mixes for airfield projects. During this long period of success with asphalt pavements, the Asphalt Institute has assisted the Federal Aviation Administration (FAA), Corps of Engineers, the US military departments and other agencies in developing best practices for the design and construction of HMA pavements. The Asphalt Institute continues to work in partnership with the airport community as it transitions to the Superpave system. This paper discusses the status of the transition and offers a description of the Superpave mix design system for airfields. Specifically, we address the differences between airport and highway pavements, current HMA specifications for airfields, and a strategy for implementing the new Superpave binder and mix design system, and finally, a brief look at some cases where Superpave has been successfully adopted.

Properties of asphalt binder are some of the contributing factors that affect the performance and life expectancy of hot mix asphalt (HMA). Analysis of test data of laboratory aged binder and recovered in-place binder helps to create selection criteria of proper type and grade of binder for future projects. In this study, HMA binder properties from laboratory-aged specimens were compared to those extracted from field specimens. The properties are absolute viscosity, penetration, bending beam rheometer creep stiffness, bending beam rheometer m-value and direct tension failure strain. The data for the study were collected from the project files of Clark County Public Works, Las Vegas, NV. The comparisons based on a statistical analysis show that (1) there is no difference between the field and laboratory specimens for absolute viscosity (2) there is a significant difference between the field and laboratory specimens for penetration (3) the comparison of other three properties is inconclusive. Significant differences between laboratory penetration test results and the inconclusive evidence in the results of BBR creep stiffness and BBR m value tests between the in-place and laboratory-aged samples show that laboratory tests may not reflect the changes in asphalt binder during its performance life.

This paper focuses on predicting rutting performances of airport pavement granular layers from laboratory testing. Typical field stress states occurring in the granular layers of the Federal Aviation Administration's (FAA's) National Airport Pavement Test Facility (NAPTF) flexible pavement sections were realistically assessed from finite element analyses. The granular specimen tested was the FAA's P209 base course material, a crushed aggregate, also used in the NAPTF test sections. Using an innovative repeated load triaxial testing device with the capability to apply multidirectional stress pulsing on laboratory specimens, permanent deformation accumulation was studied for various applied stress levels, stress ratios, and stress loading paths. The test results indicated that an increase in the applied stress levels/ratios, or a decrease in the confinement, mainly resulted in a higher rate of permanent deformation accumulation. Such high stress levels/ratios and the rotating nature of applied principal stresses under a moving aircraft wheel are the primary factors that contribute to significant rutting in airport pavement granular layers. Models were developed from the test results to predict the accumulation of permanent deformation.

Nondestructive testing (NDT) is an important tool in the design, management, maintenance, and rehabilitation of airport pavements. An NDT device known as the Rolling Dynamic Deflectometer (RDD) was developed at the University of Texas at Austin to evaluate the structural condition of both flexible and rigid pavements. The RDD is a large truck with a servo-hydraulic vibrator that applies static and dynamic loads to the pavement through two specially designed loading rollers and measures deflections using an array of rolling sensors. Compared to other commonly used nondestructive testing devices that perform testing at discrete locations, the RDD measures continuous deflection profiles, efficiently and robustly. Among the many uses, continuous deflection profiles represent an excellent means of: (1) identifying locations where further discrete type testing should be performed, and (2) relating the relative character of the discrete test sites to the overall pavement system. The RDD has been used to test pavements at the Dallas-Fort Worth International, Hartsfield Atlanta International, Seattle-Tacoma International, Portland International, Meacham International, and Greenville Municipal Airports. Results from the Meacham International and Greenville Municipal Airports are presented in this paper. At Meacham International, a Jointed Concrete Pavement (JCP) was tested with both the RDD and a Falling Weight Deflectometer (FWD). At Greenville Municipal, a JCP with an asphalt overlay was tested. Analysis methods using the collected data are discussed. These analysis methods include statistical descriptors, location of "unique" pavement features, and the comparison of deflections at joints and mid-slab regions.

Several recent accidents involving aircraft punching through pavements prompted the Navy to address this problem. Initially, a successful void detection survey was completed at a Naval Air Station (NAS) where several voids were generated by leakage of large underground drainpipes. Various methods were used such as internal video taping of the pipes, heavy weight deflectometer (HWD) testing, ground penetrating radar (GPR), and dynamic cone penetrometer (DCP) testing. A state-of-the-art review was also completed to assess all existing technology applicable to void detection under pavements. However, the optimum technology determined (visual inspection, HWD, and DCP) still presented limitations in terms of availability and speed of data acquisition, requiring prioritization of the work. A risk analysis was then completed, establishing work prioritization within each airfield and providing a prioritization of all U.S. Navy and Marine Corps airfield pavements. An Interim Policy and Technical Guidance (IP&TG) was issued on 23 March 2000 to establish the developed void detection methodology. The void detection methodology has been successfully used at several airfields and Naval stations, detecting voids or loose layers, and providing repair recommendations.

Alkali silica reaction (ASR) mitigation techniques from various states in the United States, and from various countries and international organizations, were assessed and summarized. A set of recommended mitigation procedures was developed, which requires not only the use of low alkali cement, but replacement of part of it by Class F fly ash (or Class N pozzolan) (25% to 40% by weight), or ground granulated blast furnace slag (GGBFS) Grade 100 or 120 (40% to 50% by weight), or a combination of both. The Class F fly ash (or Class N pozzolan) should also have a maximum of 1.5% available alkali, a maximum 6% loss on ignition, and a maximum of 8% CaO (lime). Some recent applications following these guidelines are presented. In addition to mitigating ASR, these recommendations are expected to: (1) reduce concrete costs, (2) enhance the durability of concrete, (3) increase fly ash and GGBFS recycling, and (4) support the 1997 Kyoto protocol by significantly reducing CO₂ production. If 25% of all cement were to be replaced (in addition to current replacements), total yearly savings to the United States economy could be in excess of $1 billion.

Hot weather pavement rutting and moisture induced damage have become problematic on several taxiways and aprons that are subject to slow moving and standing aircraft loads at Logan International Airport in Boston, MA. The Massachusetts Port Authority is evaluating the performance of seven mix designs that are presently in service by the testing of field cores at the Worcester Polytechnic Institute (WPI). Three mixes were tested for rutting and moisture susceptibility: a Trinidad Lake Asphalt (TLA)/latex modified P-401, a PG 64-28 P-401, and Densiphalt, a semi-flexible pavement. Four mixes were selected for more extensive testing: a PG 76-28 modified P-401, a reclaimed asphalt pavement (RAP)/latex modified P-401, a latex modified stone matrix asphalt (SMA), and a Rosphalt 50 modified P-401. Laboratory studies included use of loaded wheel track tests for determination and comparison of rutting and moisture induced damage at 60°C (140°F); determination of resilient modulus with the universal testing machine (UTM); determination of volumetric properties; and determination of the high temperature PG rating of the binders. Results indicate that significant improvement in rutting resistance can be achieved by providing a higher performance grade asphalt, a modified binder, or coarser gradation. The modification of mix designs comes with an increased cost of production. Not surprisingly, the two most expensive mixes, Densiphalt and Rosphalt 50, tested very well; they may be most cost effective in locally troublesome areas. Based on Massport's field experience, Densiphalt, and probably Rosphalt 50, must be installed on a very stable subbase. These mixes may thus be best suited as the wearing course of new construction as opposed to an overlay or inlay of existing pavements. The TLA mix shows good rut resistance in the laboratory, but is prone to cracking and susceptibility to moisture after four to five years of service. The PG 64-28 P-401 also proved to be susceptible to moisture. Both mixes are no longer used at Logan Airport. The RAP mix has performed very well in the field through two summers and tested well in the laboratory. The PG 76-28 and SMA mixes have shown slight indications of rutting in the field. These last three mixes are the least costly to produce and should be studied further. It is recommended that long-term field performance of these mixes be evaluated, and that accelerated loading and testing of these mixes be conducted. Using the results of this program, proper specifications and quality control tests can be developed for assuring design and construction of economical and stable mixes.

The feasibility of using stress wave technique, a nondestructive testing technique, to monitor and predict the strength and modulus development of Portland cement concrete was investigated. The measured quantity of this technique is the dynamic modulus of elasticity. The dynamic modulus can then be related to the strength parameters and static modulus obtained from conventional testing on the molded specimens or drilled cores. In this investigation, the laboratory tests on molded concrete specimens and cores were carried out with the simplified free-free resonant column method and the field or in-place tests on concrete elements were conducted with a hand-held device called the Portable Seismic Pavement Analyzer. In all instances, the maturity of the concrete as a function of curing time and temperature (time-temperature factor) was measured. A database, containing results from about 1000 specimens made from low, medium and high-strength concrete mixes, has been developed. Preliminary relationships between the dynamic modulus and the strength and static modulus parameters are proposed in the basis of the type of coarse aggregate. Unlike a strength-maturity relationship that is usually very specific to a particular mix under a particular curing condition, a dynamic modulus-based relationship is mainly affected by the nature of the coarse aggregate and, to a lesser extent, by other parameters such as curing condition, admixture, and water-cement ratio. The technique used in this study has shown to be a rapid, simple and very economic means for estimating the strength and modulus development of concrete and determining the time required to open a repaired or newly constructed concrete pavement to traffic.

Within the FAA Integrated Airport System airfield infrastructure and the U.S. Defense Department airfield inventory, there are more than 83 million square meters (100 million square yards) of heavy load concrete airfield pavements greater than 33 cm (13 inches) in thickness and more than 35 years old. These pavements will need major rehabilitation within the next 10 years. Traditionally, concrete pavement restoration (CPR) procedures (including techniques such as sub-sealing, full-depth patching, partial-depth patching, load transfer reconstruction, diamond grinding, and joint sealing) have been employed to maintain these pavements in a fair to good condition. These CPR procedures are becoming less effective today as the present pavement condition ratings are reaching a critical point where major rehabilitation is required. Rubblizing concrete pavement is becoming the paramount concrete pavement rehabilitating technique adopted by state highway agencies for heavy load highway pavements (Armaghani, 1999). From 1994 – 2002, states in the northeast, south and Midwest United States have rubblized Portland Cement Concrete Pavement (PCCP) and placed Hot Mix Asphalt (HMA, primarily Superpave) overlay over more than 41 million square meters (50 million square yards) of highways. Most experience with the proven rubblization technique has been with concrete pavements of thickness between 20–30cm (8–12 inches). However, new concepts have been employed to successfully rubblize up to 66cm (26 inches) of heavy load concrete airfield pavement at two military airfields. Information acquired during construction of these projects provided criteria for development of prototype Rubblization equipment for heavy load concrete airfield pavement in the 66cm (26 inches) range. This paper presents the concepts associated with the process of Rubblization, equipment development, in-service performance and specification criteria for rubblizing heavy load concrete pavements. Discussion is placed on rubblization process; characteristics of state-of-the-practice equipment; project performance at Wright-Patterson Air Force Base, OH, and Selfridge Air National Guard Base, MI; and specifications for rubblizing heavy load concrete pavement.

A new approach for estimating the lengths of transitional ramps to be constructed during runway rehabilitation work is presented. The lengths of the ramps are estimated as a function of the asphalt concrete overlay thickness and the longitudinal slopes of the runway exactly at the areas where the ramps should be constructed. This investigation was carried out during the rehabilitation work of the Runway 15/33 of "Jorge Chávez" International Airport, in Lima, Peru. The pilots' opinions, the ICAO — International Civil Aviation Organization standard, the Boeing approach for runway roughness evaluation as well as the author's "rms — root mean square" criterion, were the basis for the development of this approach. This paper presents curves for estimating the ramp lengths for runway longitudinal slopes of 0%, 0.1%, 0.3%, 0.5%, 0.7%, 1%, 1.2% and 1.5% and overlay thickness up to 100 mm. The approach was specifically validated for a 60 mm overlay thickness, based on the systematic collection of pilots' opinion, after many takeoffs and landings.

The use of precast concrete (PC) to rehabilitate pavement is gaining interest as roadways and taxiways become more congested and the amount time of provided to rehabilitate pavements has been reduced greatly. PC is believed to provide a durable pavement, which can be constructed during reduced work periods. Congested airports, that move passengers by day, and cargo by night, are good candidates for PC pavement. The Port Authority of NY and NJ, which operates John F. Kennedy International (JFK), LaGuardia (LGA), and Newark Liberty International (EWR) airports is familiar with tight time constraints for construction of pavement rehabilitation projects. In a continuing effort to identify a durable pavement that can be constructed within the allowable closure period, The Port Authority of NY and NJ installed a PC pavement test on Taxiway D-D at LaGuardia Airport during September of 2002. The PC pavement test was installed over an existing asphalt concrete (flexible) pavement. Two systems were developed and constructed. One system (System B) consisted of 30.5 m (100 feet) by 15.25 m (50 feet) area of 406 mm (16 inch) thick conventionally reinforced precast concrete. The other system (System A) consisted of 30.5 m (100 feet) by 15.25 m (50 feet) area of 304 mm (12 inch) thick pre-tensioned PC. All panels in both systems were sized at 3.8 m (12.5 feet) by 7.6 m (25 feet). Dowels were used for load transfer. This paper describes the design and the experience gained from the construction of the PC pavement tests.

A continued emphasis in the aviation community is to minimize critical runway closure associated with maintenance or construction activities. Reducing or eliminating closure time for work within the intersection of the two primary runways at William P. Hobby Airport, Houston, Texas, is a major priority due to Southwest Airline hub activities and more than 250,000 operations per year. This paper reviews the lessons learned from a high-early-strength Portland Cement Concrete pavement design mix which led to a reduced life span of the runway intersection primarily as a result of deteriorating effects associated with secondary ettringite crystal formation. Additional lessons learned from the design of the subsequent and successful repair program are also documented, including the use of existing and proposed pavement elevation modeling along the centerline and outside landing gear track in order to improve aircraft ride smoothness. A well thought out, coordinated construction-phasing plan using an industry-standard, Federal Aviation Administration P-501 compliant mix design led to a successful reconstruction of the damaged intersection. This paper reviews the steps taken to demolish and reconstruct the critical runway intersection and the alternative analysis undertaken during the design process.

Memphis International Airport, the largest cargo airport in the world, is uniquely constrained in available construction time and allowable impact to aircraft operations. Most airports are able to plan construction around aircraft operations, particularly at night, to minimize impact. However, due to FedEx Express day and night operations plus day and evening hub operations by Northwest Airlines, Memphis-Shelby County Airport Authority (herein identified as the Airport) does not have significantly large time segments for construction and must often develop creative, fast-track methods to meet requirements. This article describes planning, design and project management methods used during Reconstruction of Runway 18R-36L, a CAT IIIb facility, under an imposed 9-month time constraint. The project scope was such that the normal construction time would have been 18 to 24 months. Reconstruction, in this case, means complete removal of the existing facility to subgrade, reprocessing the subgrade, excavation and replacement of entire deep drainage system much of which was over 6 meters (20 feet) deep, replacement of two water mains, replacement of sanitary sewer main, complete reconstruction of NAVAIDS power and control systems, and expansion of the facility to allow operation as a 61-meter (200-foot) wide runway capable of handling Group 6 aircraft, including the A-380 airbus. Planning and Design categories are often treated as one topic, and Project Management as another, but for this project separate treatment is useful to more clearly define the owner's involvement with, and ultimate control of, the project.

Aviano Air Base in Aviano, Italy required repair and replacement of the concrete ends of the runway. The 23 end required complete demolition, replacement, and grooving, while the 05 end received minor concrete replacement, rubber and paint removal, new joint sealant, and grooving. Beginning on September 18, 2002 and ending on October 25, 2002, 3,600 m³ of concrete was demolished and replaced with concrete exceeding the required 7-day strength of 4.4 MPa, along with replacement of 9300 m of joint sealant and 13,900 m² of concrete grooving. The Naval Facilities Engineering Command (NAVFAC) Atlantic Division utilized their Emergency Construction Capabilities, Worldwide (CONCAP) contract with Kellogg Brown & Root (KBR) to deliver a quality product on time. Heavy rainfall and thicker concrete were two conditions that threatened to delay the project, but several time-expedient methods were employed to minimize potential delays and to phase the work efficiently. Aviano Air Base is an Italian base but is home to the 16th U.S. Air Force's 31st Air Expeditionary Wing, home to both the 510^th and 555^th Fighter Squadrons. The Base is in the midst of a five-year, $530 Million Air Force and NATO funded construction program. It is the largest construction program ever undertaken by the U.S. Air Force and NATO. Aviano Air Base, supported by its NATO member forces and United States Air Force squadrons, are critical to U.S. Air Force Europe's Air Expeditionary Operations. The aircraft there are the closest to the Eastern European Theater and Western Asia. During Operation Allied Force, the 31st Air Expeditionary Wing at Aviano flew nearly 9,000 combat sorties and accumulated almost 40,000 hours of combat service over the skies of Kosovo, Serbia, and throughout the Balkan region in support of NATO operations. They are currently actively involved in real world operations so getting the runway operational was essential. With the 40-day runway closure resulting in two Fighter Squadrons and 800 military personnel being temporary deployed at a cost of $1,000,000 each day, the project had to be completed in an extremely accelerated manner to bring the F-16V home.

A study was recently completed to develop the "Best Practices Manual for Airport Portland Cement Concrete Pavement Construction" that can be used by all segments of the airport construction industry to construct cost-effective, long-lasting PCC airport pavements. The manual presents construction and inspection practices that are accepted by the industry as practices that produce quality concrete pavements and lead to long-term pavement performance. The manual is not a construction specification guide nor does it provide detailed instructions on conducting specific construction-related activities. Items covered in the manual include pre-construction activities, grade preparation, base and subbase construction, concrete mixture design and concrete plant issues, concrete placement, joint sawing and sealing, and quality control/quality assurance requirements. Implementation of best practices for construction of airport concrete pavements may have cost implications and these costs may vary from region to region because of availability of local materials. Therefore, airport owners, design engineers, and contractors need to work together to achieve a proper balance between total project cost and expected pavement performance.

Design for the apron pavement at Chicago's O'Hare International Airport began in the 1950's with construction starting in the late 50's. Construction continued for many years through the late 50's and into the 1960's. In fact, it is still being done today with the airport's continued growth. With time, the pavement has aged while it has also been required to handle larger and greater numbers of aircraft. Maintenance and updating of the pavement areas have been continuously needed since original construction. In the early 1990's, the City of Chicago decided it was time to replace the apron pavement in preparation for the new millennium. An ambitious design plan was presented that would replace the pavement around Terminals 2 and 3. With the start of this new construction in 1999, any ambitious time tables or phasing plans were immediately laid waste. Restrictions were put on the amount of interruption to the airline operations and the amount of pavement area to be reconstructed at one time. Proposed work areas were often not adjacent to recently reconstructed areas, effectively making this project a large number of individual projects wedged together. Additional conditions that had to be considered during each phase included such items as variable pavement and base thicknesses, unexpected subgrade conditions, and unexpected utilities. Throughout the project, flexibility has been a key. A close working arrangement with the City of Chicago, the designer, and the contractors has been one of the beneficial features to making this replacement work a success over the years.