Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
8C H A P T E R 2 You do not have to be a civil engineer to know that there is something wrong with a section of pavement. Most of the time, you can see a problem. The most widely used indicator for airfield pavements is surface distress. Surface distress is any visible imperfection of the pavement that indicates a structural deficiency. To correct a pavement problem, you must first determine the distress type and then measure the pavement condition severity. Determine the Distress Type To determine the distress type, review the descriptions and pictures found in Appendices A (asphalt pavements) and B (concrete pavements). The entry for each distress type describes the appearance of the distress, possible root causes, and how it is measured. Table 3 lists distress types addressed in the online tool. Pavement Distress Guidelines and Resources Guidance for defining and quantifying airport pavement distresses specific to type and loca- tion of airports are found in the online tool and field guide developed for this project. Additional guidance and resources include: ⢠Airport Pavement Management Program (PMP) (FAA 2014), and ⢠ASTM D5340 (ASTM 2012). Pavement Distress Indicators As far as pavement maintenance is concerned, surface distress is the most critical indicator. Other pavement condition indicators can play a role. These are: ⢠Surface friction: The force that resists the sliding motion of a tire across the pavement surface. This is an essential aspect of aircraft safety during landing. ⢠Roughness: The ride quality or bumpiness. ⢠Foreign object debris (FOD): Any trash, debris from aircraft, loose and broken pavement material, animals or animal remains, and so forth that should not be present on an airfield pavement. ⢠Structural integrity: The ability of the pavement to bear a specific weight without being damaged. Checking for FOD should be done on a routine basis but should not be passed off as a distress survey. Routine skid, roughness, and structural measurements may not be necessary, if at all, for most GA airports. These can be contracted out on an as-needed basis. Airfield Pavement Distress
Airfield Pavement Distress 9 Pavement Condition Severity What Is the Pavement Condition Index? The Pavement Condition Index (PCI) is a score from 0 (failed) to 100 (good) that rates the ability of a pavement to perform its function effectively and safely. Engineers consolidate indi- vidual distress measurements (such as friction, roughness, FOD, and structural integrity) to calculate the PCI. For a runway, the condition indicators relate to the ability of aircraft to accel- erate or decelerate in a smooth manner and to the frictional capacity needed to stop the plane at landing. Over a given area of pavement, engineers record distress types and assign a unique deduct value based on severity and extent. All the deduct values are then analyzed to produce a corrected deduct value, which is subtracted from 100 to obtain the PCI. Table 4 shows the values in the rating scale, their descriptions, and the general pavement treat- ment that is recommended for each PCI. Asphalt Pavement Concrete Pavement Longitudinal cracking Transverse cracking Edge cracking Joint reflection cracking Block cracking Alligator or fatigue cracking Weathering Raveling Patching Roughness Corner breaks Longitudinal cracking Transverse cracking Joint seal damage Patching Settlement or faulting Shattered slab/intersecting cracks Spalling Table 3. Pavement distress types. PCI Rating Description Pavement Treatment 100 Good Only minor distresses Routine maintenance only 85 Satisfactory Low and medium distresses Preventative maintenance 70 Fair Some distresses are severe. Corrective maintenance and rehabilitation 55 Poor Severity of some of the distresses can cause operational problems. Rehabilitation or reconstruction 40 Very poor Severe distresses cause operational problems. Rehabilitation or reconstruction 25 Serious Many severe distresses cause operational restrictions. Immediate repairs and reconstruction 10 Failed Pavement deterioration prevents safe aircraft operations. Reconstruction 0 Source: Hajek et al. 2011. Table 4. PCI rating and recommended pavement treatment.
10 Pavement Maintenance Guidelines for General Aviation Airport Management Airport managers need to be familiar with the PCI and what the score means but do not need to know how to calculate it. The online tool created for this project calculates the PCI and the impacts of maintenance activities on the PCI for the user based on the inputs given. Measuring Distress Severity Understanding the severity of pavement distresses is crucial to determining the appropriate treat- ment for your airportâs pavement needs. At first, measuring the severity of particular pavement distresses can seem like a daunting task. In many cases, you can readily determine pavement distress severity when it comes to minimal conditions and severe conditions. Those in the middle are more challenging. Each pavement distress is unique when it comes to determining severity. Guidelines for iden- tifying distress severity have been developed by the U.S. Army Corps of Engineers for both asphalt and concrete pavements (U.S. Army Corps of Engineers 2009). These guidelines, which provide detailed definitions of each pavement distress and severity level, are included in Appen- dices A and B of this guidebook for easy reference. Pictures are included in the appendices to assist in the identification of both the distress type and severity level. Pavement Maintenance Treatments The types and uses of various pavement maintenance treatments are well-documented for both airport and highway applications. Table 5 lists the maintenance types used. Once the chosen treatment for each distress combination has been identified, the asphalt or concrete pavement treatment hierarchy table is consulted to determine whether a single treatment or multiple treatments should be performed. For example, if one combination suggested a fog seal and the other combination suggested an overlay, only the overlay would be performed. However, if the second combination suggested a crack seal, both would be performed. ACRP Synthesis of Airport Practice 22: Common Airport Pavement Maintenance Practices pro- vides a thorough catalog of most of these treatment options (Hajek et al. 2011). The catalog includes construction descriptions/illustrations, treatment selection criteria, typical service life/ costs, and additional resources. This same synthesis also includes data of the frequency of treat- ment application and the perceived performance of treatments. The online tool and its paper equivalent, the field guide, provide the user with recommended and acceptable treatment options. The online tool also provides a cost/benefit analysis. See Asphalt Treatments Concrete Treatments Do nothing Do nothing Crack seal/fill Crack/joint seal Rejuvenator Partial depth repair Fog/coal tar seal Full-depth repair (localized) Slurry/micro Cross-stitching/dowel-bar retrofit Chip/cape seal Slab stabilization/jacking/underseal AC overlay/mill + overlay Concrete/asphalt overlay Patch/reconstruct area Grinding/grooving Too severe (rehab/reconstruct) Too severe (rehab/reconstruct) Note: AC = asphalt concrete. Table 5. Pavement preservation, maintenance, and rehabilitation options.
Airfield Pavement Distress 11 Chapter 3: Airport Pavement Maintenance Recommendation Tool Usersâ Guide for guidance on how to use the online tool. Also see Chapter 4: How to Use the Field Guide. Treatment Decision Trees/Matrices Two common approaches described by the Federal Highway Administration to select a treat- ment are decision trees and decision matrices. The methods are essentially the same but organize and present the information in a different form. Hicks and Seeds suggest the following inputs to a decision tree/matrix: ⢠Pavement surface type, ⢠Facility type (classification/traffic level), ⢠At least one current condition index (distress and/or roughness), ⢠Specific distress information (any prominent distress), ⢠Geometrics (in case pavement widening or shoulder repair is necessary), and ⢠Environmental conditions (Hicks and Seeds 2000). For a thorough catalog of the most common treatment options and how they are accomplished, see ACRP Synthesis of Airport Practice 22: Common Airport Pavement Maintenance Practices (Hajek et al. 2011).
