Jan 2016-Maxwell Pavement Eval.pdf

AIRFIELD

PAVEMENT

EVALUATION

January 2016

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TYNDALL AIR FORCE BASE, FLORIDA 32403-5323

AFCEC-APE-895

Maxwell AFB, Alabama

ICAO: KMXF

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EXECUTIVE SUMMARY

Based on the current eight-year structural evaluation cycle for most Air Force airfield assets, eight members from the Air Force Civil Engineer Center (AFCEC) conducted the field portion of an airfield pavement evaluation at Maxwell AFB, Alabama, during the period 22 June to 1 July 2015.

The objective of this evaluation was to determine the structural capacity, pavement surface condition of the airfield pavements, and friction characteristics of the runways at Maxwell AFB, Alabama. This report summarizes the analysis of the data collected in order to identify the most important observations, common themes, areas of concern, and maintenance and repair (M&R) recommendations for Maxwell AFB airfield pavements. The data in the appendices may be used by various entities, including personnel within different areas of airfield operations, base civil engineering, and higher headquarters and staff agencies in order to assist in operations, pavement management and maintenance, and project programming and funding.

A separate reference file located at the AFCEC Airfield Evaluation Community of Practice describes the background information and testing procedures used to determine the airfield characteristics (link on page 17). The appendices to this report present the test results for each section of the evaluation in visual maps and various tables. The reference file also discusses the procedures used to analyze the collected data to determine the structural capacity and surface condition of the individual pavement sections. Allowable gross loads (AGL), Pavement Classification Numbers (PCN), Pavement Condition Index (PCI) data, and the Engineering Assessment (EA) are presented for each pavement section.

Conclusions

1. Structural Capability: Most airfield pavements are capable of supporting current mission requirements. There is only one section (T19A) on Taxiway Alpha with AGL limitations based on the C-130H primary mission aircraft. Overall, the runway and taxiway networks are in GOOD condition and suffer from few load-related distresses. The “Using the Structural Results” section of the reference file provides general examples of how to use the AGL tables to answer specific questions. These techniques will help airfield managers and base leadership make informed decisions on pavement use and overload scenarios to preserve pavement life while balancing mission requirements. The standard PCNs published in National Geospatial-Intelligence Agency (NGA) references for U.S. Air Force airfields are based on the most restrictive primary runway section (full width over 1,000 feet at the ends and the 75-foot-wide keel section for the entire length of the runway) and maximum-weight C-17 aircraft at 50,000 passes. For the Maxwell AFB primary runway and paved assault strip, the recommended PCNs for publication are:

Runway 15/33: 66 R/B/W/T

Assault Runway 009/189: 56 R/B/W/T

2. Surface Condition: The overall surface condition of the airfield pavements at Maxwell AFB ranged from GOOD to SERIOUS, with the majority of pavements by area in GOOD condition.

Most pavements will only require routine M&R to sustain the condition. However, the pavements that rated FAIR or worse are due for more major M&R and, in some cases, a new design and complete reconstruction may be required. Of the 56 sections surveyed (not including shoulders), 30 are portland cement concrete (PCC), 25 are asphalt concrete (AC), and one is double bituminous surface treatment (DBST).

a. Concrete Distresses: The primary distresses observed on the PCC pavements included joint seal damage, faulting, and small patches.

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b. Asphalt Concrete Distresses: The primary distresses observed on the AC pavements included low- and medium-severity weathering, block cracking, and longitudinal and transverse cracks.

Recommendations

1. Asphalt Concrete Sections

a. Reconstruct Taxiway A section T19A to provide long-term structural support for mission aircraft (C-130H).

b. Accomplish a mill and overlay project on Runway 15/33 sections R05A1, R04C1, and R09C.

c. Accomplish a selective crack-sealing project on Assault Runway 009/189 (R02A), including the turn-around taxiway (T06A).

d. Program a mill and overlay project for section T06A in FY17. Particular attention should be paid to correcting slope deficiencies between the Assault Runway and Runway 15/33 to restore positive drainage.

e. Apply an asphalt surface treatment to the shoulder sections of Runway 15/33 and shoulders of Assault Runway 009/189.

2. Portland Cement Concrete Sections

a. If not already programmed, schedule a project to provide M&R of global crack and joint sealant on all PCC pavement sections identified with medium- and high-severity longitudinal/transverse cracking or joint sealant damage. This will slow deterioration of the PCC pavement and reduce spalling. See the extrapolated distress report in Appendix F to identify concrete pavements with Distress Code 63 or 65 at high or medium severity. Focus efforts on Runway 15/33, Assault Runway 009/189, the Maintenance Hangar Access Apron, the West Apron, Taxiway Alpha, and the North Apron.

b. Continue replacing slabs as necessary and sealing cracks on various pavement sections, focusing funds on Runway 15/33 (R03A1) and the West Apron (A05B).

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TABLE OF CONTENTS

EXECUTIVE SUMMARY .................................................................................................. I TABLE OF CONTENTS ................................................................................................. III LIST OF FIGURES .......................................................................................................... V

INTRODUCTION

BACKGROUND INFORMATION

CONCLUSIONS AND RECOMMENDATIONS

DISTRIBUTION

APPENDICES

APPENDIX A—AIRFIELD MAPS A-1

APPENDIX B—REAL PROPERTY INFORMATION B-1

APPENDIX C—PCI COMPARISON AND DETERIORATION C-1

APPENDIX D—PHYSICAL PROPERTY DATA D-1

APPENDIX E—WORK HISTORY REPORT E-1

APPENDIX F—PCI RESULTS F-1

APPENDIX G—FOD POTENTIAL RATING G-1

APPENDIX H—STRUCTURAL EVALUATION RESULTS H-1

APPENDIX I—FRICTION TEST RESULTS I-1

APPENDIX J—ENGINEERING ASSESSMENT SUMMARY TABLE J-1

APPENDIX K—PROBABILITY OF FAILURE DATA K-1

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LIST OF FIGURES

FIGURE 1—ANNUAL TEMPERATURE SUMMARY, MAXWELL AFB, AL

FIGURE 2—AVERAGE ANNUAL CLIMATE DATA, MAXWELL AFB, AL

FIGURE 3—PONDING ON RUNWAY 15/33 (R04C2)

FIGURE 4—PONDING NEAR SECTION T06A

FIGURE 5—ANALYSIS OF TOTAL AIRFIELD SURFACE CONDITION

FIGURE 6—ANALYSIS OF RUNWAY AND OVERRUN SURFACE CONDITION

FIGURE 7—ANALYSIS OF TAXIWAY SURFACE CONDITION

FIGURE 8—ANALYSIS OF APRON SURFACE CONDITION

FIGURE 9—OVERRUN, ALZ RUNWAY 009/189 (O02C)

FIGURE 10—OVERVIEW RUNWAY 15/33 (R06A1)

FIGURE 11—DAMAGE JOINT SEALANT (R06A1)

FIGURE 12—JOINT SEAL DAMAGE (R03A)

FIGURE 13— FAULTING OF PCC SLABS (R03A)

FIGURE 14— BLOCK CRACKING/ WEATHERING (R09C)

FIGURE 15— WEATHERING/ LONGITUDINAL CRACKING (R02A)

FIGURE 16—JOINT SPALLING AND JOINT SEAL DAMAGE

FIGURE 17—OVERVIEW, TAXIWAY ALPHA (T04A)

FIGURE 18—OVERVIEW RUNWAY 009/189 TURN AROUND (T11A), BLOCK CRACKING

FIGURE 19—JOINT SEAL DAMAGE (T03A)

FIGURE 20—JOINT SEAL DAMAGE AND FAULTING (T03A)

FIGURE 21—OVERVIEW NORTH APRON (A04B)

FIGURE 22—MEDIUM SEVERITY PATCHING ON NORTH APRON (A04B)

FIGURE 23— LOW SEVERITY PATCHING ON WEST APRON (A05B)

FIGURE 24—SHRINKAGE CRACKING, WEST APRON (T29B, A05B)

FIGURE 25— SHATTERED SLABS, AERO CLUB APRON (A10C)

FIGURE 26— MEDIUM SEVERITY TRANSVERSE CRACKING, AERO CLUB APRON (A10C))

FIGURE 27—BRANCH-LEVEL WEIGHTED AVERAGE PCI BY AREA

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INTRODUCTION

Authority

Based on the eight-year structural evaluation cycle for Air Force airfields, eight members from the Asset Visibility Division of the Air Force Civil Engineer Center (AFCEC) Operations Directorate conducted the field portion of an airfield pavement evaluation at Maxwell AFB during the period of 22 June to 1 July 2015.

Description of Appendices

The detailed appendices report the information gathered during the evaluation. Table 1 provides a description of each appendix.

Table 1—Description of Appendices

Appendix Description

A Airfield Maps: Graphically depicts the different pavement facilities, branches, section designations, rank, surface condition of the airfield, the overall Engineering Assessment (EA) ratings, and core test locations.

B Real Property Information: Includes facility information and branch-level designations.

C PCI Deterioration Rate Table: Historical deterioration by pavement section.

D Summary of Physical Property Data: Tabulates the physical properties data of each evaluated pavement section. Section area, material types, layer thickness, and engineering properties are included.

E Construction History: Provides a brief summary of the construction and maintenance activities on each section.

F Section Condition Report and Extrapolated Distresses: Provides the PCI rating and the distresses recorded for each section.

G FOD Potential Rating: Provides the FOD Potential Rating (as related to the FOD Index or PCI of FOD-producing distresses) used as part of the EA.

H

Pavement Classification Number (PCN) Table: Lists PCNs, a standardized method of reporting pavement strength, for each section.

Allowable Gross Loads (AGLs): Lists the allowable loads for every section at four pass intensity levels for each aircraft group.

Aircraft Classification Number (ACN) Charts: Provides ACN charts for the 14 standard aircraft groups, plus some additional aircraft.

Related Data: Includes aircraft group indices, gross weight limits for each aircraft group, and pass intensity levels.

Structural Index Report: Lists the structural index for the EA by section.

I

Friction Results: Includes the texture table (surface type, rubber buildup, and outflow meter times for assessing macro-texture), average friction ratings at 40 and 60 mph for every 500-foot section of each runway, CFME readings (graphical representation) for each runway, and the friction index table as part of the EA.

J Engineering Assessment Summary Table: Presents EA ratings by section for each of the four categories (PCI, Structural Index, FOD Potential Rating, and Friction Index).

K

Probability of Failure (PoF): Uses a method outlined in the AFCEC business rules to determine a score for project prioritization along with the Consequence of Failure (CoF).

Project Development: Provides list of projects recommended by AFCEC engineers after assessing all of the data collected during the evaluation.

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BACKGROUND INFORMATION

Location

Maxwell AFB is located in the northwest corner of Montgomery, Alabama, in the Alabama River Valley. The base is bounded by the Alabama River along the northeast. The valley consists of broad, flat, well-drained areas that include both farmland and wooded areas.

The airfield at Maxwell AFB (ICAO: KMXF) is located at an elevation of 171 feet above mean sea level.

Construction History

There have been several recent and ongoing airfield projects since the last structural evaluation in November 2006 and PCI in December 2010. A detailed list by section for all airfield pavements can be found in Appendix E, with a summary below of recent projects completed and programmed.

Recently Completed Projects:

Repair Asphalt Runway 15/33 – 2012

Repair Assault Strip 009/189 – 2012

Mill and Overlay Overrun, Runway 15/33 and 009/189 – 2013

Mill and Overlay Taxiways A, B, C, D, and E – 2014

Programmed Projects:

Replace Sections Runway 15/33 – FY16, PNQS157400, PNQS167500, PNQS172593 ($17M)

Replace Concrete Pads North End Assault Zone – FY16, PNQS137001 ($40K)

Soil Conditions

A soil map of the Montgomery area from the United States Department of Agriculture (USDA), Natural Resource Conservation Service (NRCS) website for Montgomery County, Alabama, shows the predominant subgrade surface soils in the vicinity of Maxwell AFB to be a number of clays (CL), silts (ML), and sands (SC) in the Unified Soil Classification System (USCS). Although very little published data is presented for the airfield area, the most dominant subgrade soil in the vicinity of the airfield is Roanoke Silt Loam. The airfield is constructed in an alluvial valley that contains varying layers of low-plasticity clay (CL), low-plasticity silt (ML), and clayey silts (SC). Both visual field classifications and formal laboratory classifications of subgrade soils were consistent with predominant clay soil subgrades within the pavement structures. Due to the proximity to the river and alluvial deposition of the subgrade soils, high soil moisture contents and low in-place compaction values have been reported during previous evaluations. In general, these subgrade soils are not well suited for supporting pavements as these subgrade soils are known to have moisture sensitivity issues, including strength loss. The pavement structure has performed relatively well, however, despite its age. This is likely the result of comparatively light aircraft traffic loading. Macadam PCC layers were found under many pavement sections before reaching the clay or silt subgrade. Results of laboratory testing are included in the Summary of Physical Properties in Appendix D for all soil layers encountered beneath the pavement to formally classify these soils using the USCS symbol. For more

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http://websoilsurvey.sc.egov.usda.gov/App/WebSoilSurvey.aspx.

Climate

Maxwell AFB lies in the Alabama River Valley. The climate during most of the year is influenced by the Bermuda High which brings warm, humid maritime air masses from the Gulf of Mexico, located approximately 140 miles to the south. High temperatures in the summer months of May through September are routinely above 90 °F. Temperatures below freezing are not common throughout the year. The average annual precipitation is approximately 47 inches, with July and December being the wettest months. Figures 1 and 2 give temperature and average annual rainfall summaries; more detailed engineering weather data (EWD) can be obtained from the 14th Weather Squadron website at https://www.climate.af.mil/. The area averages 17 freeze-thaw cycles per year and the design freezing index at Maxwell AFB is 34 degree-days.

The average depth of frost penetration is a maximum of 9 to 20 inches. The frost depth of 20 inches is not significant enough to provide freezing temperatures in any frost-susceptible materials due to relatively thick pavement layers. Therefore, thaw-weakened AGLs were not produced for this evaluation.

Figure 1—Annual Temperature Summary, Maxwell AFB, AL

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Figure 2—Average Annual Climate Data, Maxwell AFB, AL

Frost Evaluation

Local climate and conditions are such that the potential for freezing and subsequent thaw-weakening of the subgrade need not be addressed and analyzed. The climate history at Maxwell AFB indicates an average of only 17 freeze-thaw cycles annually. For frost susceptibility to be a concern, three conditions must be present: (1) the presence of frost-susceptible soils, (2) the existence of a discernable water source, and (3) freezing temperatures such that the frost line reaches saturated and frost-susceptible soils. If frost-driven distresses are encountered at an airfield, particular attention should be paid to using the thaw-weakened AGLs and PCNs during the spring thaw for the location. At Maxwell AFB, several sections exhibited signs of potentially expansive soil-related distresses, including faulting among PCC slabs, structural distresses (longitudinal/transverse cracking) in non-trafficked areas, and accelerated distress conditions. These pavement distresses are likely the result of expansive soil interactions with local variations in moisture conditions versus the effects of frost.

Depth of Freeze: The ModBerg program developed by the U.S. Army Corps of Engineers Cold Regions Research and Engineering Laboratory indicates that the design air freezing index for Maxwell AFB is 34 °F-Days. Using a Modified Berggren analysis, the design depth of frost penetration under pavements is approximately 9 to 20 inches, depending on pavement thickness and soil type.

Frost Susceptibility: Soil samples collected during this evaluation and from previous evaluations indicated that the base course materials were primarily poorly graded gravels with silt mixtures (GP-GM) or clayey sands (SC). These types of soil generally have a low susceptibility to freeze-thaw action. Subgrade soils were primarily low-plasticity clays (CL) or low-plastic silts (ML). These types of soils generally have a moderate susceptibility to freeze-thaw action.

Water: Soils under the pavements were saturated in some areas. The water table at Maxwell AFB is relatively shallow and has been reported at depths between 20 and 23 feet below the ground surface. Subsurface drainage problems have been previously reported, but

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Figure 3—Ponding on Runway 15/33 (R04C2)

Figure 4—Ponding Near Section T06A

The need to conduct a frost evaluation has been consistently ruled out during previous structural evaluations conducted at Maxwell AFB dating back to 1980. As such, the effects of freezing, and subsequent thaw weakening of the subgrade, were not considered in the production of PCNs and AGLs as part of this evaluation.

Aircraft Traffic

Aircraft stationed at Maxwell AFB include C-130H aircraft assigned to the 908th Airlift Wing. Various transient aircraft use the airfield, including fighter and cargo aircraft.

Previous Evaluations

Several structural and surface condition pavement evaluations have previously been performed at Maxwell AFB, dating back to 1980 for the first structural evaluation and the first airfield PCI in 2000. The field work for the last PCI evaluation was accomplished in December of 2010.

The previous reports listed below provided reference data for various parts of the evaluation, mainly in terms of past construction history, soil classifications, and previous conditions that may have changed due to new construction. All referenced reports can be found at the AFCEC SharePoint site link: Pavement Evaluation Reports (https://tyndall.eim.acc.af.mil/apps/afcec/Pavement%20Reports/default.aspx)

“Airfield Pavement Evaluation, Maxwell Air Force Base, Alabama,” HQ Air Force Engineering and Services Center (AFESC), Tyndall AFB, Florida, September 1980

“Airfield Pavement Evaluation, Maxwell Air Force Base, Alabama,” Air Force Civil Engineering Center Support Agency (AFCESA), Tyndall AFB, Florida, October 1998

“Airfield Pavement Evaluation, Maxwell Air Force Base, Alabama,” Air Force Civil Engineer Support Agency (AFCESA), Tyndall AFB, Florida, March 2008

“Airfield Pavement Condition Index Survey Report, Maxwell Air Force Base, Alabama,” Applied Research Associates, Inc., December 2010

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Pavement Condition – Maxwell AFB Pavements

A pavement condition survey was conducted as part of this airfield pavement evaluation to establish the condition ratings for airfield pavement sections and to identify the types of distresses observed on the airfield. The following pages discuss the findings of the visual survey, along with other aspects of the pavement such as structural and friction observations.

All references to pavement condition in the following text use the standard (not simplified) pavement condition ratings defined in ASTM D5340, Standard Test Method for Airport Pavement Condition Index Surveys, and are described further in the reference file.

Overall Airfield

The surface condition observed on the Maxwell AFB airfield pavements is generally GOOD, as shown in Figure 5. The condition has improved since the December 2010 PCI due to an aggressive mill and overlay maintenance program on the asphalt sections of the airfield network, including projects on both runways (including their overruns) and Taxiways Alpha, Bravo, Charlie, Delta, and Echo. Approximately 91 percent of the 5.67 million total square feet of pavement sections by area are in GOOD or SATISFACTORY condition, and 6 percent are in FAIR condition. Only two sections were rated as POOR (O01C) or SERIOUS (A10C). Perhaps more importantly, 81 percent of the runway and overrun sections by weighted area are in GOOD or SATISFACTORY condition.

Figure 5—Analysis of Total Airfield Surface Condition

Figure 6—Analysis of Runway and Overrun Surface

Condition

Figure 7—Analysis of Taxiway Surface Condition

Figure 8—Analysis of Apron Surface Condition

P er ce n t A re a

P er ce n t A re a

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As the overwhelming majority of pavements at Maxwell AFB are in GOOD condition, the only routine maintenance actions that should be required in the near term are to correct low-and medium-severity distresses. Maintenance practices as simple as re-sealing joints and cracks and patching concrete pavements or applying an asphalt surface seal to AC pavements can increase some section PCIs to the next higher category. Preserving pavements in this condition and averting future major M&R projects minimizes operational downtime, extends the overall pavement service life, and requires much less capital expense.

A rating of FAIR generally indicates that pavements are in transition from a state of high-quality surface condition to low-quality condition. FAIR pavements require timely M&R funds to improve the surface condition at a less-expensive long-term cost versus complete reconstruction. Pavements rated POOR or below on the PCI scale generally require major M&R or possibly reconstruction, depending on several factors such as pavement purpose, use, traffic frequency and loads, and the integrity of underlying base and subbase foundation layers of the pavement structure. Base personnel have already programmed projects to complete repairs on all sections rated as FAIR. Section O01C is currently rated as POOR; however, no corrective action is recommended. Only one section on the entire Maxwell AFB airfield rated SERIOUS (Section A10C), the Aero Club Apron. Load reductions were made on the AGL tables in Appendix H for this section.

Appendix F includes a summary of the findings of the pavement surface condition survey, including the condition rating and the types and severity levels of observed pavement distresses. The full seven-category rating scale and visual map of conditions is provided in Appendix A. Refer to UFC 3-260-16FA, Airfield Pavement Condition Survey Procedures, and ASTM D5340 for descriptions and definitions of the types and severity levels of the distresses listed in this section of the report or the extrapolated distresses for each section found in Appendix F.

The following paragraphs describe in more detail the observed surface condition of the airfield pavements, broken down at the branch level of runways, taxiways, and aprons.

Runways The main runway at Maxwell AFB is 8,016 feet long by 150 feet wide; the assault landing zone is 3,000 feet long by 60 feet wide. The main runway, along with the ALZ surfaces and associated overruns, make up approximately 33 percent of the airfield network area. The runways and overruns consist of 23 pavement sections (including seven overrun sections), 18 of which are a part of the main runway. Overall, several project efforts on Runway 15/33 have resulted in a significant PCI increase for this branch since the December 2010 survey and approximately 81 percent of the sections by weighted area are in GOOD or SATISFACTORY condition. However, the majority of the AC keel sections on Runway 15/33 are currently rated FAIR. The current overrun of ALZ 009/189 is 1,000 feet in length, with the nearest 300 feet to the ALZ composed of newly placed AC (Figure 9); the remaining 700 feet of the overrun is constructed of DBST. This portion of the overrun is currently rated in POOR condition due to significant raveling of the aggregate surface. Despite the deterioration of the surface on this portion of the overrun, no repair is currently recommended. Per ETL 09-6, only 300 feet of the overrun is required for C-130 operations and it is highly unlikely that this portion of the overrun will ever receive aircraft traffic.

Runway 15/33 is structurally sound, with no AGL limitations for assigned mission aircraft.

Figure 10 shows an overview of the north end of Runway 15/33. The PCC sections of Runway 15/33 are all rated in GOOD condition; however, the joint sealant in most of these sections is generally damaged. For example, in Section R06A1, the compression sealant does not adequately prevent incompressible material from becoming deposited in the joints, which have begun to spall and produce FOD (Figure 11). The silicone joint sealant in Section R03A1 is in considerably worse shape, and is non-existent in some areas (Figure 12). Maintaining good sealant is paramount to prevent moisture infiltration from the surface into the underlying base

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A recent mill and overlay project on the AC sections outside of the runway keel has increased the rating of these pavement sections from FAIR to GOOD. Unfortunately, environmental distresses such as weathering and block cracking have degraded the condition of the AC keel sections of the runway from GOOD to FAIR. In some cases, the cracks have become wide enough for vegetation to appear (Figure 18).

There are also no AGL limitations for assigned mission aircraft on the Assault Strip Runway 009/189. Similar to the main runway, the ALZ is composed of both AC and PCC sections. The primary distresses observed on the AC sections were weathering and longitudinal/transverse cracking, all of which are progressing from low to medium severity (Figure 15). Joint and corner spalling is prevalent in the PCC section (R01A) and is likely exacerbated by the relatively poor condition of the joint sealant in this section (Figure 16).

The lowest-rated runway or overrun sections were the DBST overrun section on ALZ 009/189, section O01C. Besides this overrun section, sections R04C1, R05A1, and R09C on Runway 15/33 rate FAIR. These sections are weathered, with low-severity block cracking beginning to degrade to medium severity. The taxiway lighting and markings on Runway 15/33 have been moved in to decrease the operational width of the runway from 300 to 150 feet. Joint sealant is in poor or non-existent condition in the PCC shoulder sections; the AC shoulder pavements are weathered and experiencing high-severity block cracking. A project should be programmed to replace joint sealant as well as route and seal cracks on the shoulder areas to prevent moisture from infiltrating through the pavement and becoming trapped in the base and subgrade. Maintain the AC surfaces outside of the 150 feet wide markings with sprayed asphalt surface treatments in order to seal cracks and slow the rate of FOD generation.

Figure 9—Overrun, ALZ Runway 009/189 (O02C)

Figure 10—Overview Runway 15/33 (R06A1)

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Figure 11—Damaged Joint Sealant (R06A1)

Figure 12—Joint Seal Damage (R03A)

Figure 13— Faulting of PCC Slabs (R03A)

Figure 14— Block Cracking/ Weathering (R09C)

Figure 15— Weathering/ Longitudinal Cracking (R02A)

Figure 16—Joint Spalling and Joint Seal Damage

The primary 8,016-foot runway and 3,000-foot ALZ Runway both consist of non-grooved PCC and weathered AC surfaces. Despite relatively high coefficient of friction (mu) values obtained during continuous friction measurement equipment (CFME) testing, outflow meter times obtained were generally in excess of 5 seconds. This indicates relatively marginal bulk water drainage characteristics; nearly 56 percent of the measured transverse slopes measured on Runway 15/33 were equal to or greater than the 1.0 percent minimum required by UFC 3- 260-01. As noted previously, ponding is a common occurrence on both runways during and after rain events. Therefore, there is a FAIR potential (moderate risk) for the runway pavement to contribute to a hydroplaning incident on both Runway 15/33 and ALZ Runway 009/189.

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The heaviest rubber buildup observed was Medium to Light (see the scale in Appendix I, page I-9 for a description). Currently Maxwell AFB performs rubber removal annually using a detergent process, which was last accomplished in July 2014.

Taxiways Of the entire pavement area, the open taxiways account for approximately 22 percent of the total airfield and include 17 surveyed sections. The PCI breakout by area is fairly uniform in this branch, with 94 percent of taxiway pavement sections by area rated either GOOD or SATISFACTORY and the remaining 6 percent rating FAIR. This is largely due to an extensive series of mill and overlay projects completed in December 2014 to correct pavement surface deficiencies on the AC portions of Taxiways Alpha, Bravo, Charlie, Delta, and Echo. Figure 17 depicts an example of this recently completed work.

With the exception of a single section (T19A) the taxiway network is capable of supporting mission-assigned aircraft (C-130H) with no AGL limitations. Although this section recently received a structural overlay, the new surface course overlays a relative thin layer of macadam pavement and buried AC. In order to remove AGL limitations in the future, a full-depth repair project should be programmed. The section will likely perform satisfactorily for many years and the current surface should remain until serious distresses develop.

Section T06A is the sole taxiway section rated FAIR; it provides access to the ALZ runway from the main runway. The primary distresses on this section are block cracking and weathering (Figure 18—Overview Runway 009/189 Turn Around (T11A), Block Cracking). A mill and overlay project should be programmed to repair this section. Any resurfacing project should pay particular attention to correcting slope deficiencies in this area and mitigate current ponding issues.

The majority of Taxiway Alpha is composed of PCC pavements; the predominant distresses in these sections are joint seal damage, small and large patching, and faulting.

Figure 19 and Figure 20 illustrate the typical high severity of damage to the joint sealant on Taxiway Alpha. The current condition of the joint sealant does not provide adequate protection against moisture intrusion into the base material and subsequently into the highly expansive subgrade. As a result, considerable faulting is present throughout these sections (Figure 19).

Correcting joint sealant deficiencies is imperative to maintaining the structural life of these pavement sections and should be conducted as soon as practical via a programmed contract effort and/or an in-house phased maintenance effort.

Figure 17—Overview, Taxiway Alpha (T04A)

Figure 18—Overview Runway 009/189 Turn

Around (T11A), Block Cracking

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Figure 19—Joint Seal Damage (T03A)

Figure 20—Joint Seal Damage and Faulting (T03A)

Aprons The apron branch makes up the largest percentage of the airfield pavement area at approximately 45 percent, yet only includes seven sections. The PCI distribution is captured in Figure 8 and shows 99 percent rated in GOOD or SATISFACTORY condition. The apron sections are represented primarily by three large sections that make up the interconnected parking aprons of the North (Transient) Apron and the West (C-130) Apron. Additional smaller aprons include a hangar access apron along the east side of the airfield and an engine run-up apron off of Taxiway Alpha. As with the PCC taxiway sections, the overall apron branch pavement suffers primarily from medium- and high-severity joint seal damage and the PCI would increase with an extensive joint and crack re-seal project.

The large interconnected apron sections rate GOOD (West Apron) and SATISFACTORY (North Apron). Figure 21 shows an overview of the North Apron, which suffered from higher severity distresses including joint and corner spalling as well as linear cracking and patching (Figure 24). The predominant distresses on the West Apron consist of large and small patching, as well as low- and medium-severity corner spalling (Figure 23). A thin surface treatment has previously been applied to sections of the North and West Aprons, presumably to mitigate additional growth of shrinkage cracks present on the surface. This treatment (which gives the finished concrete an odd yellow color) is beginning to degrade, and shrinkage cracks are noticeably beginning to migrate and grow (Figure 24). Although not an immediate structural concern, a reapplication of the initial surface treatment could be performed to prevent additional pavement surface damage. It should be noted that no shattered slabs were encountered on either of these aprons, indicating that the pavement is structurally capable to support mission-assigned aircraft.

Figure 25 and Figure 26 are taken on the Aero Club Apron that rates SERIOUS overall due to low- and medium-severity linear cracking and low- and medium-severity shattered slabs.

This apron is primarily used by small-frame Civil Air Patrol and Aero Club aircraft. Despite the extensive damage in this section, there are no AGL restrictions for Group 1 aircraft. No major M&R project is recommended for this section (A10C) at this time, primarily due to pavement use.

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Figure 21—Overview North Apron (A04B)

Figure 22—Medium Severity Patching on North Apron (A04B)

Figure 23— Low Severity Patching on West Apron (A05B)

Figure 24—Shrinkage Cracking, West Apron (T29B, A05B)

Figure 25—Shattered Slabs, Aero Club Apron (A10C)

Figure 26—Medium Severity Transverse Cracking, Aero Club Apron (A10C)

Network Summary Overall, the airfield pavements have been well maintained and have had several reconstruction projects completed in recent years. Since the March 2010 PCI inspection, these efforts have increased the overall area weighted PCI of the airfield network from an 82 to a 91.

From these results, it is evident that airfield management and civil engineers are appropriately managing the pavement. An accelerated joint and crack sealant maintenance program on the PCC runway, taxiway, and apron sections would further enhance the overall PCI rating of the

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From a network perspective, the airfield is structurally capable of carrying primary mission aircraft and some heavier load group transient aircraft. A general lack of load-related distresses was observed during the PCI survey; weight limitations for the various sections can be found in the AGL tables in Appendix H. The average area-weighted PCI by branch level shown in Figure 27 clearly indicates that the airfield is in excellent condition overall. The Apron sections are in the most need of M&R; however, a large percentage of the available parking area is currently not required for mission operations.

Figure 27—Branch-level Weighted Average PCI by Area

85 93 92 97

APRON OVERRUN RUNWAY TAXIWAY

W e ig h te d A ve ra ge

C o n d it io n

Branch Use

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CONCLUSIONS AND RECOMMENDATIONS

Conclusions

1. Structural Capability: Most airfield pavements are capable of supporting current mission requirements. There is only one section (T19A) on Taxiway Alpha with AGL limitations based on the C-130H primary mission aircraft. However, the AGL tables in Appendix H should be used to check structural adequacy of more damaging aircraft than the C-130H found in Load Group 4.

Based on current use, T19A is recommended for reconstruction based on its limited structural capacity. Overall, the runway and taxiway networks are in satisfactory condition and suffer from few load-related distresses. The “Using the Structural Results” section of the reference file provides general examples of how to use the AGL tables to answer specific questions. These techniques will help airfield managers and base leadership make informed decisions on pavement use and overload scenarios to preserve pavement life while balancing mission requirements. The standard PCNs published in National Geospatial-Intelligence Agency (NGA) references for U.S. Air Force airfields are based on the most restrictive primary runway section (full width over 1,000 feet at the ends and the 75-foot-wide keel section for the entire length of the runway) and maximum-weight C-17 aircraft at 50,000 passes. For the Maxwell AFB primary runway and paved assault strip, the recommended PCNs for publication are:

Runway 15/33: 66 R/B/W/T

Assault Runway 009/189: 56 R/B/W/T

2. Surface Condition: The overall surface condition of the airfield pavements at Maxwell AFB ranged from SERIOUS to GOOD, with the majority of pavements by area in GOOD condition.

Most pavements will only require routine M&R to sustain the condition. However, the pavements that rated FAIR or worse are due for more major M&R; however, complete reconstruction is not anticipated for these sections. Of the 56 sections surveyed (not including shoulders and closed pavements), 30 are PCC, 25 are AC, and one is DBST.

a. Concrete Distresses: The primary distresses observed on the PCC pavements included joint seal damage, faulting, and small patches.

b. Asphalt Concrete Distresses: The primary distresses observed on the AC pavements included low- and medium-severity weathering, block cracking, and longitudinal and transverse cracks.

Recommendations

1. Asphalt Concrete Sections

a. Reconstruct Taxiway A section T19A to provide long-term structural support for mission aircraft (C-130H).

b. Accomplish a mill and overlay project on Runway 15/33 sections R05A1, R04C1, and R09C.

c. Accomplish a selective crack-sealing project on Assault Runway 009/189 (R02A), including the turn-around taxiway (T06A).

d. Program a mill and overlay project for section T06A in FY17. Particular attention should be paid to correcting slope deficiencies between the Assault Runway and Runway 15/33 to restore positive drainage.

e. Apply an asphalt surface treatment to the shoulder sections of Runway 15/33 and shoulders of Assault Runway 009/189.

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f. Program a demolition project to selectively remove portions of closed asphalt pavements adjacent to operational surfaces. Removing these pavement sections will prevent excess moisture from infiltrating into the subgrade and becoming trapped in the pavement structure. Additionally, removing these non-operational pavements will allow for re-grading efforts along Runway 15/33 and Assault Runway 009/189 that should mitigate current ponding issues on shoulder pavements.

2. Portland Cement Concrete Sections

a. If not already programmed, schedule a project to provide M&R of global crack and joint sealant on all PCC pavement sections identified with medium- and high-severity longitudinal/transverse cracking or joint sealant damage. This will slow deterioration of the PCC pavement and reduce spalling. See the extrapolated distress report in Appendix F to identify concrete pavements with Distress Code 63 or 65 at high or medium severity. Focus efforts on Runway 15/33, Assault Runway 009/189, the Maintenance Hangar Access Apron, the West Apron, Taxiway Alpha, and the North Apron.

b. Continue replacing slabs as necessary and sealing cracks on various pavement sections, focusing funds on the Runway 15/33 (R03A1) and the West Apron (A05B).

c. Continue to perform maintenance repairs in accordance with UFC 3-270-03 and UFC 3- 270-04. Discontinue use of silicone joint sealant products to mitigate faulting patches.

Faulting, or otherwise failing, patches should be removed and replaced with an approved pavement repair material. A list of current packaged, cementitious and polymeric material for concrete airfield repair is maintained at:

https://transportation.erdc.dren.mil/cacsites/TriService/pavement_repair.aspx.

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ATTN: MR. ERIC RODEN

ERIC.RODEN.CTR@US.AF.MIL

ELECTRONI…