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4 There are 382 primary airports and 2,950 non-primary airports in the United Statesâ NPIAS, including 530 Part 139 airports. Taken together it is estimated that there are approximately 460 million square yards of paved airfield surfaces at NPIAS airports. The pavement infrastruc- ture at many of these airports is at least several decades old, and pavement conditions vary considerably. The FAA has a goal of maintaining 93 percent of the NPIAS airport runway pave- ments in excellent, good, or fair condition, and as of 2016 this value is reported as 97.7 percent (FAA 2016, U.S. DOT Bureau of Transportation Statistics 2017). Keeping airport pavements in a state of good repair is critical to the safety of the traveling public and does not occur by chance. The process of managing these pavements involves making appropriate decisions about their maintenance, preservation, rehabilitation, and reconstruction in an environment constrained by limited funding and time. Good pavement condition data, coupled with the proper analysis of those data, help airports make these decisions in a timely and economical manner. Beyond pavement management, pavement condition data are measured and reported to meet many different needs. This chapter explores the use of such data to achieve the following: â¢ Meet FAA requirements; â¢ Determine the timing, type, and cost of pavement maintenance and repair; â¢ Identify candidates for pavement preservation; â¢ Determine the need to improve pavement surface characteristics; â¢ Report on the structural capacity of pavements; â¢ Report on pavement performance, performance over time, the rate of change, and predicted future performance; and â¢ Prepare multi-year capital improvement programs (CIPs) and communicate needs to various stakeholders. FAA Guidance on Pavement Condition The FAA has several requirements and recommendations regarding pavement condi- tion. Related to managing a safe operating environment for aircraft, Advisory Circular (AC) 150/5200-18C, Airport Safety Self Inspection, calls out four components of a safety self-inspection program; the pavement component of each inspection is outlined and described as follows: â¢ Regularly Scheduled Inspections: As a minimum, a daily inspection before flight operations begin should check for pavement lips (edge drop-off); determine if there are any cracks wide enough to cause direction control problems; determine if there are any holes that could cause directional problems (5 inches diameter and greater than 3 inches deep); look for pavement conditions that could cause foreign objects; check for vegetation growth that would impede C H A P T E R 2 Importance of Pavement Condition Data in Managing Pavements
Importance of Pavement Condition Data in Managing Pavements 5 drainage; and monitor and report cracks, holes, variations, and vegetation that can cause loss of aircraft directional control or pavement damage, including contributing to ponding water. â¢ Continuous Surveillance Inspections: These inspections occur when inspection personnel are in the air operations area (AOA) and focus on foreign object debris (FOD) removal. â¢ Periodic Condition Inspection: This inspection is a regularly scheduled check of safety. Applied to pavements it includes checking for rubber buildup, polishing, and other factors affecting safety. The frequency could be weekly, monthly, or quarterly, depending upon the activity and the facility. â¢ Special Inspections: After weather events or a complaint by users, the pavement should be checked for ponding, edge damming, or other conditions affecting safe aircraft operation. The FAA also requires more detailed pavement inspections, which cover a broader range of conditions than the safety inspection and provide data that are used for other purposes. These requirements are tied to the Airport Improvement Program (AIP) where an agency must agree to obligations in order to accept funding. One of these obligations is the requirement that air- field pavements be maintained at a safe level. AC 150/5380-7B, Airport Pavement Management Program (PMP), states that at federally obligated airports âtrained personnel must perform a detailed inspection of airfield pavements at least once a year,â but âif a history of recorded deterioration in the form of a Pavement Condition Index (PCI) survey as set forth in ASTM D5340, Standard Test Method for Airport Pavement Condition Index Surveys is available, the frequency of inspections may be extended to 3 years.â Considering all of these regulations together, airports are required either to carry out an annual pavement condition survey, with little guidance offered on what constitutes an accept- able survey, or complete a PCI survey, which is described in great detail in the ASTM standard and elsewhere. Because an annual survey can be costly and disruptive, most airports opt to meet their PMP requirements with a PCI survey carried out at least every 3 years. Surface friction is another measure of pavement condition addressed by FAA require- ments. FAAâs AC 150/5320-12C, Measurement, Construction, and Maintenance of Skid Resistant Airport Pavement Surfaces, provides FAAâs guidance on surface friction measurement. Although, 150/5320-12D, Measurement and Maintenance of Skid-Resistant Airport Pavement Surfaces, which is currently available in draft form, will soon replace the existing standard. This AC also addresses pavement grooving dimensions. Additional relevant references on surface friction measurement include ASTM E-274, Standard Test Method for Skid Resistance of Paved Surfaces Using a Full-Scale Tire, and Inter- national Civil Aviation Organization (ICAO) Cir 329 AN/191, Runway Surface Condition Assessment, Measurement and Reporting (DRAFT). It is important to note that friction, surface texture, and pavement markings are monitored apart from pavement management, and when these reach unacceptable levels, appropriate corrective measures are triggered that are not pavement maintenance and rehabilitation (M&R). Identify Pavement Maintenance Needs Triggering the application of various pavement treatments, or even determining that no treat- ment is currently necessary, is an important use of pavement condition data. One category of pavement treatments is pavement maintenance, and identifying pavement maintenance needs is important from both a safety perspective and as a component of the pavement management process. The FAAâs AC 150/5380-6C, Guidelines and Procedures for Maintenance of Airport Pave- ments, notes that: Early detection and repair of pavement defects is the most important preventive maintenance proce- dure. Failure to perform routine maintenance during the early stages of deterioration will eventually result in serious pavement distresses that require extensive repairs that will be costly in terms of dollars and closure
6 Guidelines for Collecting, Applying, and Maintaining Pavement Condition Data at Airports time. The cause of pavement distresses must first be determined so an airport can select a repair method that not only corrects the present damage, but will also prevent or retard its progression. This AC describes the components of a drainage inspection, friction evaluation, and non- destructive testing (as described in AC 150/5370-11, Use of Nondestructive Testing Devices in the Evaluation of Airport Pavement) and introduces the concept of a pavement management program, which is discussed later in this chapter. While pavement management programs, friction, and nondestructive testing are all introduced in FAAâs AC 150/5380-6C, they are discussed in greater detail in their own ACs. Identifying, rating, and determining the quantity of pavement distress is a core component of pavement evaluation. In AC 150/5380-6C, distresses are identified according to the pave- ment type: flexible pavement distresses are categorized as cracking distresses, disintegration, distortion, and loss of skid resistance, while rigid pavement distresses include cracking, joint seal damage, disintegration, distortion, and loss of skid resistance. The value of the pavement maintenance inspection can be summarized as follows (AC 150/5380-6C): Maintenance inspections reveal at an early stage where a problem exists and provide warning and sufficient time to perform corrective action. Postponement of minor maintenance may evolve into ma- jor pavement repairs. Visible evidence of excessive stress and/or environmental distress in pavement systems may include cracks, holes, depressions, and other types of pavement distresses. The formation of distresses in airport pavements may severely affect the structural integrity, ride quality, and safety of airport pavements. To alleviate the effects of distresses and to improve the airport pavement service- ability, airports should adopt an effective and timely inspection and maintenance program and adequate repair procedures. An additional value of these inspections is found in the links that are established between the distresses identified for each of the pavement types and appropriate maintenance treat- ments. While no specific pavement condition evaluation process is identified, it is sug- gested that additional guidance is found in the FAAâs AC on PMPs, which discusses the PCI procedure. For pavement maintenance purposes in particular, tracking individual distresses provides more value than an index or a general rating such as good, fair, or poor. For example, patching and crack sealing are common maintenance activities, and when using pavement condition data to patch or seal cracks, it is useful to know the quantity of the distresses requiring those specific maintenance actions. If the PCI procedure is used to evaluate pavement conditions, crack seal- ing of flexible pavements might be associated with medium-severity longitudinal and transverse (L&T) cracking, and patching on rigid pavements might be associated with medium- and high- severity joint and corner spalls. Knowing the linear feet (LF) of cracking and the number of spalls facilitates planning the proper maintenance activities. A useful enhancement, in many instances, is to use a distress map such as that shown in Figure 1 to show not only the distress type and severity but also the location of distresses. If distresses are mapped initially, it is a simple effort to associate the distress type/severity combination with the proper maintenance or repair technique. However, accurate maps of maintenance needs are developed from a 100 percent survey and not from the sampling survey that is often performed for strategic or tactical planning purposes. Identify Candidate Pavements for Preservation AC 150/5380-7B describes pavement preservation as the practice of addressing pavements while they are still in good condition. This is illustrated in the curves of pavement condition over time in Figure 2, where preservation treatments triggers are shown while the pavement is still
Importance of Pavement Condition Data in Managing Pavements 7 performing well and where multiple applications of preservation may precede the first rehabili- tation treatment. While the FAA does not appear to have a formal definition of âgood,â âfair,â and âpoor,â one approach it uses to apply descriptive terms to PCI ranges is shown in Figure 3 (see the General Ratings column). ASTM D5340 (2012) presents a similar graphic in which PCI ranges are associated with the following generic categories of pavement actions: â¢ PCI from 100 to 70 â Preservation â¢ PCI from 70 to 40 â Rehabilitation â¢ PCI from 40 to 0 â Reconstruction Pavement preservation is increasingly being recognized as a valued strategy to help to manage a pavement network in a cost-effective manner. There are several different types of pavement condition data that help to identify suitable candidates for pavement preservation. An over- all pavement condition rating is often used to categorize pavement performance and as a link to recommended strategies. Figure 3 illustrates this concept, where the PCI for a pavement is Â© 2018 Applied Pavement Technology Figure 1. Display of rigid pavement distresses by slab.
8 Guidelines for Collecting, Applying, and Maintaining Pavement Condition Data at Airports assigned a qualitative rating and categories of probable treatments are indicated. Preservation is identified as an appropriate strategy for airport pavements with a PCI of 70 or greater. Individual distresses are also used to trigger pavement preservation, either alone or in com- bination with an overall rating such as the PCI. Table 6-1 in AC 150/5380-6C can be used to match âproblemsâ (i.e., individual distresses) with appropriate preservation treatments based on the probable cause of the condition. Table 1 suggests appropriate preservation strategies for distresses in both flexible and rigid pavement surfaces. If the presence of a distress or distresses indicates a pavement will benefit from preservation, additional inventory information in the PMP can be used to develop costs for that activity. In using condition data to identify candidates for pavement preservation, it can also be impor- tant to confirm that the pavement does not have a structural deficiency that has not yet appeared as a pavement distress. That is, a pavement may have a PCI greater than 70 and not exhibit Original Pavement Pavement Preservation (i.e., Surface Treatment) Rehabilitation Trigger Rehabilitation/ Reconstruction Trigger Age of Pavement P av em en t C on di tio n Optimal Timing (Rehabilitation Trigger) Figure 2. Relative timing of pavement preservation and pavement rehabilitation based on pavement condition (AC 150/5380-7B). 100 85 70 55 40 25 0 10 PCI General Rating Treatment Strategy Preservation Rehabilitation Reconstruction Good Satisfactory Fair Poor Very Poor Serious Failed Figure 3. Relationship between PCI values, pavement ratings, and treatment strategies (based on AC 150/5380-7B).
Importance of Pavement Condition Data in Managing Pavements 9 distresses indicative of a structural deficiency, but still be a poor candidate for pavement preser- vation because of insufficient long-term structural capacity. This can be evaluated by determin- ing the structural capacity of the pavement with FWD testing. Similarly, a pavement may have a PCI less of than 70 and no identified structural problems and therefore be a good candidate for pavement preservation. The structural capacity of most airfield pavements is determined using a heavy FWD, sometimes referred to as a heavy weight deflectometer (HWD), because of its ability to simulate the gear loads of large aircraft using those pavements. All references in this document to FWD may be interpreted as meaning either an FWD or an HWD, whichever is appropriate. Report on Pavement Performance, Performance Over Time, and the Rate of Change The FAAâs requirements for pavement management programs and the associated require- ments for collecting pavement condition data were previously introduced. The PMP serves multiple purposes, as described by the FAA AC 150/5380-7B: . . . a consistent, objective, and systematic procedure for establishing facility policies, setting priorities and schedules, allocating resources, and budgeting for pavement maintenance and rehabilitation. It can also quantify information and provide specific recommendations for actions required to maintain a pavement network at an acceptable level of service while minimizing the cost of maintenance and rehabilitation. A PMP not only evaluates the present condition of a pavement, but also predicts its future condition through the use of pavement condition indicators. By projecting the rate of deterioration, a life-cycle cost analysis can be made for various alternatives to determine the optimal time to apply the best M&R alternative and avoid higher M&R costs in the future. Pavement condition data are a key part of an effective PMP and the following PMP compo- nents specifically relate to pavement condition: â¢ A systematic means for collecting and storing information regarding existing pavement structure and pavement condition, â¢ An objective and repeatable system for evaluating pavement condition, â¢ Procedures for predicting future pavement condition, â¢ Procedures for interpreting past conditions and modeling future pavement conditions, â¢ Ability to predict and subsequently evaluate the effect on pavement condition of maintenance and repair work, and â¢ Capability of analyzing various budgets to determine the impact on pavement condition of individual sections and of the pavement network as a whole. Flexible Pavement Rigid Pavement Distress Preservation Treatment Distress Preservation Treatment Weathering/oxidation Surface treatment Joint sealant damage Reseal Cracking Seal/reseal Cracking Seal/reseal Surface irregularities Grinding, milling Joint spalling Partial-depth repair Loss of skid resistance Surface treatment Loss of skid resistance Diamond grinding Poor drainage Grade shoulders (if turf), clean drainage features Poor drainage Grade shoulders (if turf), clean drainage features Table 1. Preservation strategies appropriate for pavement distresses (modified from AC 150/5380-6C).
10 Guidelines for Collecting, Applying, and Maintaining Pavement Condition Data at Airports Current conditions are frequently reported in either tabular or graphical form to communi- cate the findings from a pavement condition survey. Table 2 is a tabular presentation of PCI data from a network-level survey, while Figure 4 shows conditions plotted on a map of an airportâs pavement facilities. The map is a particularly useful way to communicate both the pavement rating and the relative conditions of one pavement to another. While any measure of pavement condition may be reported in this manner, the use of the PCI is standard practice throughout the U.S. airport community. The foundation of the PCI rating is the identification and measurement of the type, severity, and extent of observed dis- tresses for flexible- and rigid-surfaced pavements. The resulting measurements are aggregated into a single numeric value on a scale of 0 to 100 to represent a pavementâs performance, but additional analysis of the distresses can indicate the probable factors contributing to pavement deterioration (considering the link between distress type and cause), the likelihood of FOD, and the structural performance of the pavement. The value of reporting current pavement conditions lies in the ability to use that information to make informed decisions about the current need for pavement maintenance and rehabilita- tion. When pavement condition information is reported over time, the data can be used to model or predict future conditions. Figure 5 illustrates the plotting of pavement conditions over time, as well as the best-fit model generated from those data (shown as the green line). Using either a plot of condition over time or the associated equation of the best-fit model, the results can be used to predict when a pavement will deteriorate to the point where rehabilitation or some other intervention is necessary. It should be noted that the distresses incorporated in the PCI do not cover all of the factors that might trigger a pavement treatment, as the PCI does not include friction, ride quality, or structural response. The use of a consistent pavement condition measurement procedure, such as the PCI, over multiple cycles also allows a rate of change in condition to be determined. A small annual drop in PCI is expected in a pavement that is in good condition, while a larger annual change suggests that the pavement is entering a phase in which intervention may be needed. For example, in Figure 6 the âcalculated model dataâ curve is representative of a performance model with a steep initial drop in PCI followed by a period of stabilization and then subsequent decline. Given a model with these characteristics, intervention could be planned during the stabilization period to extend the life of the pavement. Branch ID Section ID Pavement Type Area, ft2 PCI A01PB 10 Asphalt 45,000 55 AFUELPB 10 Concrete 2,000 98 RW826PB 10 Asphalt 399,750 71 TH01PB 10 Asphalt 22,559 74 20 Asphalt 21,760 69 30 Concrete 30,180 93 40 Concrete 765 88 TWA1PB 10 Asphalt 65,925 67 TWA2PB 10 Asphalt 16,320 65 TWA3PB 10 Asphalt 14,185 63 TWB1PB 10 Asphalt 7,710 72 TWFUELPB 10 Asphalt 17,815 66 Table 2. Tabular presentation of PCI data.
Figure 4. Graphical presentation of PCI data (PCI value is shown in parentheses).
12 Guidelines for Collecting, Applying, and Maintaining Pavement Condition Data at Airports Prepare Multi-Year CIPs and Communicate Needs When pavement condition data are generated, analyzed, and stored as part of a PMP, the information needed to develop multi-year CIPs is available. In contrast with a maintenance or preservation plan, which is typically linked to actions required in a given year or at most a year away, a CIP is a planning tool in which the projections of future pavement conditions are used to indicate when a capital project such as a structural overlay or reconstruction will be needed. Bundled costs can be associated with different strategies to develop budgets associated with each year included in the multi-year plan. The PCI and the models that predict future conditions are the starting point for generating multi-year CIPs. This information can be combined in many different ways to communicate dif- ferent options to decision makers, and even to those without an extensive technical background in pavement condition data. The PCI and predicted future PCI may also be used to compare current conditions and projected needs to previously generated CIPs and anticipated projects. At the same time, it is recognized that other factors impact capital programs, including existing Airport Master Plans and capacity and operational constraints. Calculated Model Data High Calculated Model Data ModelData BadData Calculated Model Data Low Figure 5. Example plot of flexible pavement condition versus age. Calculated Model Data High Calculated Model Data ModelData BadData Calculated Model Data Low Figure 6. Example plot of asphalt overlay of concrete pavement condition versus age, showing comparatively rapid initial decline in performance.
Importance of Pavement Condition Data in Managing Pavements 13 A CIP may start with a table of capital projects that are triggered in future years and the associ- ated costs, as shown in Table 3. With PCI-based models, a wide range of alternate scenarios can be analyzed, such as the following: â¢ No budget: predicted conditions in 5 years if capital projects are not constructed. â¢ Fixed-budget option: predicted condition in 5 years if the capital budget is fixed at a given amount. â¢ Maintain current PCI: required budget over the next 5 years to maintain the network PCI at current levels. â¢ Achieve target PCI: required budget over the next 5 years to increase the network PCI to a target level. â¢ Eliminate backlog: required budget to fully address the backlog of capital needs over a given time period. â¢ Unlimited budget: funding required to address all capital needs. The project costs used for planning and programming at this level are usually treatment costs with some, but not all, of the ancillary costs (such as engineering, permitting, planning, design, construction oversight, and mobilization) added. Because these numbers are primar- ily used for planning purposes, an important consideration is to use a consistent approach in reporting these. Summary Condition data are integral to the process of managing airport pavements. Condition data represent the performance of a pavement at a given time, and condition data over time are used to model future performance. Both the current condition and projected future condition may be considered in determining whether maintenance, preservation, rehabilitation, or reconstruction Year Branch ID Section ID Area, ft2 PCI Before Capital Project Cost 2018 OR1331 01 200,000 56 $289,000 02 200,000 50 $289,000 RW1331 02 193,200 76 $295,000 03 6,540 58 $10,000 06 14,800 59 $21,000 2018 Total $904,000 2019 TWM 01 78,850 37 $2,850,000 02 103,100 44 $3,722,000 2019 Total $6,572,000 2020 OR1836 01 199,600 48 $587,000 02 201,000 50 $591,000 RW1331 09 99,200 43 $292,000 RW1836 03 250,100 55 $735,000 04 420,600 54 $1,237,000 2020 Total $3,442,000 2018â2020 Total $10,918,000 Table 3. Example capital project list.
14 Guidelines for Collecting, Applying, and Maintaining Pavement Condition Data at Airports is appropriate for a given pavement section. The projection of pavement condition multiple years into the future is used to develop realistic and logical CIPs. The presentation of condition data in graphs, tables, and maps helps to communicate important pavement concepts to all types of stakeholders. Through relevant ACs, the FAA provides guidance on collecting pavement condition data but has very few unequivocal requirements. One requirement the FAA does impose is the use of a PMP for those airports receiving federal funds for pavement work. However, there is some latitude on the pavement condition data that are entered into that PMP. Airports are indirectly encouraged to use the ASTM D5340 PCI procedure by allowing such inspections to be done on a 3-year cycle; otherwise, an annual evaluation must be performed. Where safety is concerned, several different types of pavement inspections are specified, but no single method of conduct- ing such inspections is required. There is an emphasis on the frequency of such inspections to monitor and ensure that there are safe conditions for operating aircraft. There is general guidance linking pavement condition ratings to categories of treatment actions, such as maintenance, preservation, rehabilitation, and reconstruction. However, put- ting together a CIP is much more complex and must consider not only pavement conditions, but treatment costs, available funding, logical project groupings, and other factors.