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COMMON AIRPORT PAVEMENT MAINTENANCE PRACTICES SUMMARY Every airport operator is faced with the need to maintain airside pavements in good order for safe and efficient aircraft operation using the available budget. This synthesis describes how airports of all sizes currently practice pavement maintenance. Decision making for maintenance and rehabilitation (M&R) of airport pavements typ- ically consists of two stages of sequential decisions. The first stage involves identifying and prioritizing future pavement preservation needs, treatments, and projects, consider- ing the needs and priorities of all airport pavements together. The objective of this stage is to decide at a given time which pavement sections are prioritized to receive M&R treat- ments. The second stage consists of determining, using site-specific engineering consid- erations, what type(s) of M&R treatment is to be carried out on the previously selected sections. Although both stages are described in the synthesis, the emphasis was placed on the first stage, identifying and prioritizing future pavement preservation needs. The main challenge facing airport authorities is not which M&R treatment to use, but how to justify that M&R treatments are necessary, using a judicious and objective process, and to obtain funding for their implementation. In other words, the first priority is to select the right pavement sections for treatment. The synthesis describes pavement preservation practices and treatments for asphalt con- crete (AC) and portland cement concrete (PCC) pavements. Pavement preservation treat- ments for surface-treated and aggregate-surfaced pavements are not included. The technol- ogy of pavement preservation treatments is summarized in the Catalog of Airport Pavement Preservation Treatments in Appendix B. The Catalog contains a description of 24 common pavement preservation treatments for AC and PCC airport pavements The synthesis addresses both M&R treatments because these two treatment types overlap, have a common goal, and work together to provide a cost-efficient pavement preservation program. Special attention was paid to describing the role of preventive maintenance in pave- ment preservation. Preventive maintenance is carried out to prevent premature pavement deterioration. Routine pavement maintenance that does not substantially improve the pave- ment surface is not included in the synthesis. The main sources of information were an extensive literature review and a survey of air- port pavement professionals representing individual airports or small groups of airports serv- ing one small geographical area. The survey was a four-page questionnaire and is included in Appendix A. The survey focused on the use and operation of airport pavement management systems (APMSs), evaluation of pavement conditions, procedures used to select M&R treat- ments, use of preventive maintenance, identification of pavement preservation needs, fund- ing sources, and the usage and field performance of common airport pavement preservation treatments. Survey responses were obtained from 50 pavement maintenance professionals, an 80% response rate for airports with daily aircraft operations ranging from a few to several thousand flights.

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2 The role of an APMS is to support the technical, engineering, and management activities of airport personnel responsible for providing pavement infrastructure for safe and efficient oper- ation of aircraft. The pavement management process provides systematic and objective proce- dures for maintaining the inventory of pavement infrastructure, monitoring pavement perfor- mance, selecting the right treatment for the right pavement at the right time, planning and budgeting of pavement preservation activities, and evaluating the cost-effectiveness of past pavement preservation actions. Based on the survey, more than 80% of airports have a func- tional APMS or are in the process of developing one. Approximately 30% of respondents rated their APMS as excellent and essential, and about 34% rated their system as functional but in need of improvement. The rest of the respondents were generally satisfied with their system. The inventory of pavement infrastructure is the basic building block of an APMS. Because pavements deteriorate with time, the inventory includes the past and the current condition of pavements and the anticipated future pavement conditions. The predominant pavement per- formance modeling technique for airport pavements uses a set of characteristic pavement per- formance curves developed for groups (or "families") of similar pavement sections. Pavement condition evaluation includes the review of pavement surface distresses, roughness, friction, presence of foreign debris, and the evaluation of pavement surface deflections. With the excep- tions of a few small airports, all airports surveyed carry out periodic pavement condition evaluation of runways using the Pavement Condition Index, with the average frequency of 3.4 years. Additional pavement evaluation cycles are utilized for timely selection and imple- mentation of preventive maintenance treatments. The pavement evaluation results are used to assess trends in the overall condition (the health) of the pavement network, document the fund- ing needs and the benefits of the APMS, identify major causes of pavement deterioration, and determine the performance of specific pavement structures and M&R treatments. For purposes of the survey, 38 separate M&R treatments were identified; 19 for AC pave- ments and 19 for PCC pavements, and airport officials were asked to provide information on the use and performance of these 38 treatments. For AC pavements, the most frequently used treat- ment was crack sealing using hot-poured bituminous sealant, which was used by 90% of all air- port agencies that had such pavements on at least one facility. The next four most frequently used treatments were pothole patching with hot mix, hot-mix overlay, milling and overlay, and pot- hole patching with cold mix. For PCC pavements, the most frequently used treatments were full- depth slab repairs and replacement using PCC or AC materials, joint resealing using silicone sealants, and shallow patching repairs using AC material. Based on the survey results, the aver- age performance of the 19 M&R treatments for AC pavements was considered to be slightly bet- ter than the average performance for the 19 M&R treatments for PCC pavements. Pavement preservation needs depend on the level of service the airport pavements are expected to provide. For the same pavement structure, a higher level of service results in higher M&R costs. The levels of service that can be used to guide the needs for M&R treat- ments include target or desirable level of service, minimum acceptable level of service, and minimum safety-related level of service. Trigger values can be used to provide guidance on timing for M&R treatments. The identification of needs is discussed for two time horizons: short-term planning for the time horizon of about 5 years or less, and long-term planning for the time horizon exceeding 5 years. Approximately 56% of respondents systematically iden- tify pavement sections that would benefit from pavement maintenance. Prioritization of M&R projects is typically based on priority levels that are related to the levels of service used to identify pavement preservation needs. Prioritization can be based on a single characteristic, such as the Pavement Condition Index, or on a composite indicator that combines several characteristics. Budgeting takes into account not only pavement preservation needs but also other airfield needs affecting airport pavements, such as projects involving safety and functional improve-

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3 ments, underground utilities, and in-pavement lighting. Budgetary issues involve financial considerations related to the available funding and the time when the funding is available and operational considerations that include the impact on airport operations and safety during construction. Based on the survey, all airport agencies that have an APMS use a software application to facilitate the identification of needs, prioritization, and budgeting. About 53% of survey respondents reported using MicroPAVER, 13% used other commercial software, and 34% used in-house software. With a few exceptions, all airport authorities surveyed already operate or are developing an APMS. The average age of the existing systems at the time of this survey was 9 years. The reported challenge for most of the agencies is not to develop an APMS, but to sustain and enhance its operation. Approximately 27% of airports that have an APMS characterized their systems as operational, but in need of improvement. The attributes that contribute to the suc- cessful operation and sustainability of an APMS include long-term commitment and support from decision makers, data integrity and timeliness, periodic reporting of results, meeting user needs through ongoing improvements, and a provision for training and succession planning. In addition to ongoing system enhancements, a structured comprehensive review and enhancement of the APMS operations can be done using gap analysis and benchmarking.