Evaluation of NCHRP 747 pavement forensic guide for the Georgia Department of Transportation's adoption

GEORGIA DOT RESEARCH PROJECT 14-13 FINAL REPORT
Evaluation of NCHRP 747 Pavement Forensic Guide for GDOT's Adoption
OFFICE OF PERFORMANCE-BASED MANAGEMENT AND RESEARCH 15 KENNEDY DRIVE
FOREST PARK, GA 30297

1.Report No.: FHWA-GA- 2. Government Accession No.: 16-14-13

3. Recipient's Catalog No.:

4. Title and Subtitle: Evaluation of NCHRP 747 Pavement Forensic Guide for GDOT's Adoption

5. Report Date: April 2018 6. Performing Organization Code:

7. Author(s): S. Sonny Kim, Catherine Johnson, Mi Geum Chorzepa, Stephan A. Durham, Jidong Yang 9. Performing Organization Name and Address: University of Georgia, Athens, GA Kennesaw State University, Marietta, GA
12. Sponsoring Agency Name and Address: Georgia Department of Transportation Office of Performance-Based Management & Research 15 Kennedy Drive, Forest Park, GA 30297-2534 15. Supplementary Notes:

8. Performing Organ. Report No.:14-13
10. Work Unit No.:
11. Contract or Grant No.: RP 14-13; PI# 0013345 13. Type of Report and Period Covered: December 2014 December 2016 14. Sponsoring Agency Code:

16. Abstract:

This report presents the recommendation for whether the Georgia Department of Transportation

(GDOT) should adopt the National Cooperative Highway Research Program (NCHRP) Report

747 (Guide for Conducting Forensic Investigations of Highway Pavements) as a guide to

conduct forensic investigations in Georgia. This report documents the evaluation of three

pavement types using the NCHRP 747 guide: Jointed Plain Concrete (JPC), Continuously

Reinforced Concrete (CRC), and Hot Mix Asphalt (HMA). Each pavement type consisted of an

evaluation of two sites, one in "good/fair" condition and the other in "poor" condition. Non-

destructive testing was performed using Ground Penetration Radar (GPR) and Falling Weight

Deflectometer (FWD). Destructive testing (coring) and on-site field testing was performed

consistent with the recommendations of the forensic guide. Laboratory tests were conducted to

determine material properties of the existing pavement. These results were combined with traffic

data and weather information to form conclusions about the cause(s) of pavement distress in

sections of "poor" condition. Based on the successful investigations, it is recommended to adopt

the NCHRP Report 747 for use in Georgia.

17. Key Words: Forensic Investigation, Pavement, 18. Distribution Statement:

Ground Penetration Radar, Falling Weight

Deflectometer, Jointed Plain Concrete,

Continuously Reinforced Concrete, Superpave.

19. Security Classification 20. Security

21. Number of 22. Price:

(of this report):

Classification

Pages: 130

Unclassified

(of this page):

Unclassified

Form DOT 1700.7 (8-69) ii

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GDOT Research Project No. 14-13
Final Report
Evaluation of NCHRP 747 Pavement Forensic Guide for GDOT's Adoption
Prepared by
S. Sonny Kim, Ph.D., P.E. Associate Professor
Civil Engineering, College of Engineering University of Georgia
Catherine Johnson Graduate Research Assistant Civil Engineering, College of Engineering
University of Georgia
Mi G. Chorzepa, Ph.D., P.E. Assistant Professor
Civil Engineering, College of Engineering University of Georgia
Stephan Durham, Ph.D., P.E. Associate Professor
Civil Engineering, College of Engineering University of Georgia
Jidong Yang, Ph.D., P.E. Assistant Professor
Civil Engineering, Kennesaw State University
Contract with Georgia Department of Transportation
In cooperation with U.S. Department of Transportation Federal Highway Administration
April 2018
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DISCLAIMER The contents of this report reflect the views of the authors, who are solely responsible for the facts and accuracy of the data, the opinions, and the conclusions presented herein. The contents do not necessarily reflect the official view or policies of the Georgia Department of Transportation (GDOT) and Federal Highway Administration (FHWA). This report does not constitute a standard, specification, or regulation, and its contents are not intended for construction, bidding, or permit purposes. The use of names or specific products or manufacturers listed herein does not imply endorsement of those products or manufacturers.
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ACKNOWLEDGMENTS This project was conducted in cooperation with the Georgia Department of Transportation. The authors would like to gratefully acknowledge the contributions of many individuals to the successful completion of this research project. This especially includes Mr. Binh Bui, Mr. Ian Rish, Ms. Gretel Sims, Mr. Yusuf Ahmed, Ms. Jewell Stone, Ms. Neoma Cole, and Dr. Moussa Issa who have helped the research team by coordinating and conducting field investigations with research team, and Mr. Gulden, who advised the team to successfully complete the study.
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EXECUTIVE SUMMARY
State agencies and civil engineers are responsible for the safe travel of millions of vehicle passengers. The roads traveled must be structurally sound and provide a smooth ride. Surely newer roads satisfy these requirements, but throughout the years, roads worsen and need to be either resurfaced, rehabilitated, or reconstructed. Additionally, transportation agencies are starting to discover that some pavements stay in good condition over time, while others have deteriorated significantly. The University of Georgia (UGA) and the Georgia Department of Transportation (GDOT) have collaborated to investigate the cause of this phenomenon.
To discover the cause of these pavement conditions, the National Cooperative Highway Research Program (NCHRP) Report 747 (Guide for Conducting Forensic Investigations of Highway Pavements) was used as a guide. In the absence of an official document for conducting forensic investigation in Georgia, GDOT desires to evaluate and review this latest document for compatibility with current GDOT practices. If discrepancies exist, modifications will need to be developed and presented to GDOT for acceptance.
This report is composed of the evaluations of three types of pavements using NCHRP Report 747: Jointed Plain Concrete Pavement (JPCP), Continuously Reinforced Concrete Pavement (CRCP), and Hot Mix Asphalt (HMA) Pavement. Each pavement was investigated through a site investigation that contained visual inspection and non-destructive/destructive testing. Non-destructive methods include a visual inspection, Ground Penetration Radar (GPR), and Falling Weight Deflectometer (FWD). Destructive testing includes coring samples and laboratory tests performed on the respective samples. Cored specimens were tested to measure the material's physical and strength properties. A series of tests for concrete cores includes the measurement of coefficient of thermal expansion, rapid chloride permeability, compressive strength, modulus of elasticity, alkali-silica reactivity, and carbonation reactivity. Asphalt cores were also tested to determine susceptibility to rutting and stripping, maximum specific gravity, bulk specific gravity, air void content, and binder content.
Based on the experience of conducting a forensic investigation using the NCHRP 747 Report through this study, it is recommended for GDOT's adoption of the NCHRP 747 Report as the Forensic Pavement Guide for Georgia, with the following additions/recommendations:
A comprehensive forensic investigation is very extensive, expensive, and time consuming. Precautions should be exercised to determine whether a full investigation is vii

needed. It is recommended to determine the level of forensic analysis based on the "Phased Approach to Forensic Investigations" diagram in the NCHRP 747 Guideline (Appendix A). Rather than using NCHRP visual condition survey form, it is recommended to use the GDOT's visual inspection forms that have been used for PACES update. However, development of new methodology to assess PACES rating for CRCP is strongly recommended as current methodology does not reflect the functional condition evaluation of CRCP properly. It is believed that new methodology to assess PACES rating for CRCP will be developed through RP 15-02, "Developing a Comprehensive Pavement Condition Evaluation System for Rigid Pavements in Georgia". Based on this RP 14-13 study, flow charts for pavement forensic investigations were developed (Appendices D, E, and F). The flow charts will provide the GDOT engineers with a systematic procedure when pavement forensic investigations are deemednecessary. Traffic information along with pavement service life has large impact on pavement design and performance. To accurately investigate pavement performance, it is recommended that traffic information is efficiently archived and easily accessible. This includes traffic volumes, traffic loads/load spectra, traffic growth, seasonal trends, load restrictions, and any related traffic information during entire pavement service life. It is recommended that all construction documents be efficiently archived and easily accessible when forensic investigations are started. This includes all construction drawings, rehabilitation history, mix design, and other construction information.
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TABLE OF CONTENTS
1. INTRODUCTION ................................................................................................................. 1
1.1 PROBLEM STATEMENT ...................................................................................................... 1 1.2 OBJECTIVES....................................................................................................................... 1
2. LITERATURE REVIEWS ................................................................................................... 3
2.1 GDOT NATIONWIDE SURVEY ........................................................................................... 3 2.1.1 INTRODUCTION AND MOTIVATION .................................................................................... 3 2.1.2 ADOPTION OF PAVEMENT FORENSIC GUIDE ...................................................................... 4 2.1.3 FORENSIC TECHNOLOGIES................................................................................................. 5 2.1.4 REHABILITATION METHODS .............................................................................................. 5 2.1.5 OTHER PUBLISHED FORENSIC PAVEMENT GUIDES AND RESOURCES................................. 8 2.1.6 ADDITIONAL COMMENTS PROVIDED BY PAVEMENT ENGINEERS ...................................... 9 2.1.7 DISCUSSION..................................................................................................................... 10 2.2 PAVEMENT TYPES REVIEW ............................................................................................. 11 2.2.1 JOINTED PLAIN CONCRETE PAVEMENT(JPCP) ................................................................ 11 2.2.2 CONTINUOUSLY REINFORCED CONCRETE (CRC) PAVEMENT ......................................... 11 2.2.3. HOT-MIX ASPHALT (HMA) HMA PAVEMENT ............................................................... 12
3. TESTING METHODOLOGY ........................................................................................... 13
3.1 VISUAL INSPECTION/OBSERVATION ................................................................................ 13 3.2 REVIEW OF PAVEMENT FORENSIC TECHNOLOGIES NON-DESTRUCTIVE........................ 13 3.2.1 FALLING WEIGHT DEFLECTOMETER ............................................................................... 14 3.2.2 GROUND PENETRATION RADAR ........................................................................................ 15 3.2.3 OTHER NON-DESTRUCTIVE TESTING TECHNIQUES .......................................................... 16 3.3 REVIEW OF PAVEMENT FORENSIC TECHNOLOGIES DESTRUCTIVE ................................ 16 3.3.1 CORING ........................................................................................................................... 16 3.3.2 ROLLING DYNAMIC DEFLECTOMETER (RDD)................................................................. 17 3.3.3 DYNAMIC CONE PENETROMETER (DCP)......................................................................... 18 3.4 LABORATORY TESTING METHODS FOR CONCRETE PAVEMENTS ..................................... 18 3.4.2 ALKALI SILICA REACTION (ASR) AND COEFFICIENT OF THERMAL EXPANSION (CTE) .. 18 3.4.3 CARBONATION ................................................................................................................ 18 3.4.4 RAPID CHLORIDE PERMEABILITY (RCP) ......................................................................... 18 3.5 LABORATORY TESTING METHODS FOR HOT MIX ASPHALT PAVEMENTS ........................ 19 3.5.1 BULK SPECIFIC GRAVITY (GMB), THEORETICAL MAXIMUM SPECIFIC GRAVITY (GMM). 19 3.5.2 HAMBURG WHEEL TRACKING TEST ................................................................................ 20 3.5.3 BINDER CONTENT ........................................................................................................... 21
4. JOINTED PLAIN CONCRETE PAVEMENT ................................................................ 22
4.1 INTRODUCTION................................................................................................................ 22
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4.2 TEST SITE AND FIELD SETUP ........................................................................................... 23 4.3 NON-DESTRUCTIVE TESTING .......................................................................................... 26 4.4 DESTRUCTIVE TESTING CORING AND FIELD TESTING .................................................. 29 4.4.1 SR-22 Section Coring and On-site Testing ..................................................................................32 4.4.2 I-75 Section Coring and On-site Testing.......................................................................................32 4.5 DESTRUCTIVE TESTING LABORATORY TESTING ........................................................... 33 4.6 PETROGRAPHIC EXAMINATION........................................................................................ 34 4.7 ANALYSIS OF TESTING RESULTS ..................................................................................... 35 4.8 FINITE ELEMENT ANALYSIS OF THE DISTRESS ................................................................ 37
5. CONTINUOUSLY REINFORCED CONCRETE PAVEMENT ................................... 41
5.1 INTRODUCTION................................................................................................................ 41 5.2 TEST SITE AND FIELD SETUP ........................................................................................... 42 5.3 NON-DESTRUCTIVE TESTING .......................................................................................... 45 5.4 DESTRUCTIVE TESTING CORING AND FIELD TESTING .................................................. 47 5.4.1 MP 45 Section Coring and On-site Testing..................................................................................52 5.4.2 MP 55 Section Coring and On-site Testing..................................................................................52 5.5 DESTRUCTIVE TESTING LABORATORY ......................................................................... 52 5.6 PETROGRAPHIC EXAMINATION........................................................................................ 55 5.7 ANALYSIS OF TESTING RESULTS ..................................................................................... 56
6. HOT MIX ASPHALT (HMA) PAVEMENT SUPERPAVE ........................................ 58
6.1 INTRODUCTION................................................................................................................ 58 6.2 TEST SITE AND FIELD SETUP ........................................................................................... 60 6.3 NON-DESTRUCTIVE TESTING .......................................................................................... 62 6.4 DESTRUCTIVE TESTING CORING AND FIELD TESTING .................................................. 66 6.4.1 SR-38 Coring and On-site Testing..................................................................................................66 6.4.2 SR-54 Coring and On-site Testing SR-22 Section Coring and On-site Testing................67 6.4.3 AIR CONTENT ANALYSIS................................................................................................. 69 6.4.4 BINDER CONTENT ANALYSIS .......................................................................................... 70 6.4.5 SIEVE ANALYSIS ............................................................................................................. 71
7. CONCLUSIONS .................................................................................................................. 74
7.1 JOINTED PLAIN CONCRETE (JPC) PAVEMENT - CONCLUSIONS AND RECOMMENDATIONS74 7.2 CONTINUOUSLY REINFORCED CONCRETE (CRC) PAVEMENT - CONCLUSIONS AND RECOMMENDATIONS .................................................................................................................. 74 7.3 HOT MIX ASPHALT (HMA) PAVEMENT - CONCLUSIONS AND RECOMMENDATIONS ....... 75
8. NCHRP RECOMMENDATIONS ..................................................................................... 76
9. REFERENCES .................................................................................................................... 78
APPENDICES
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LIST OF TABLES Table 1 - Survey Results: States and Canadian Providences with a Forensic Pavement Investigation Guide ......................................................................................................................... 4 Table 2 - Survey Results: Non-destructive and Destructive Testing Methods Used...................... 6 Table 3 Survey Results: Rehabilitation Methods Used. ............................................................... 7 Table 4 Other Forensic Investigation/Rehabilitation Methods Provided during the Survey....... 8 Table 5 Resources shared by state DOTs during the survey. ...................................................... 9 Table 6 - JPCP Conditions............................................................................................................ 24 Table 7 - JPCP NDT Results and Design Parameters................................................................... 26 Table 8 - Summary of Core Test Results...................................................................................... 35 Table 9 - CRC Conditions............................................................................................................. 43 Table 10 - CRC NDT Results and Design Parameters. ................................................................ 45 Table 11 - Summary of Core Test Results.................................................................................... 54 Table 12 - Site Condition and Pavement Profile .......................................................................... 61 Table 13- Subgrade modulus, Effective and Required SN. .......................................................... 65 Table 14 Summary of Pavement Information for Selected HMA Sites ..................................... 71 Table 15 - SR 38 C-4 (Outside Lane) .......................................................................................... 72 Table 16 - SR 54 C-2 (Outside Lane) .......................................................................................... 72 Table 17 - SR 54 C-4 (Inside Lane)............................................................................................ 73
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LIST OF FIGURES
Figure 1 - Survey Responses in North America. ............................................................................ 3 Figure 2 - Falling Weight Deflectometer...................................................................................... 15 Figure 3 - Ground Penetration Radar............................................................................................ 16 Figure 4 - Coring machine ............................................................................................................ 17 Figure 5 - Hamburg Wheel Tracking Machine at UGA ............................................................... 21 Figure 6 JPCP Site Locations .................................................................................................... 22 Figure 7 - General Site Conditions: (a) SR 22 (good condition); (b) I-75 (poor condition)......... 24 Figure 8 - I-75 Typical Distress (Poor Condition)........................................................................ 25 Figure 9 - Typical GPR scans showing single joint...................................................................... 27 Figure 10 - Selected ISM Plots determined from FWD tests ....................................................... 28 Figure 11 - Typical Cores at Joints ............................................................................................... 29 Figure 12- 3D View of Coring Locations and JPCP details for SR 22 (good condition)............. 30 Figure 13- 3D View of Coring Locations and JPCP details for I-75 (poor condition)................. 30 Figure 14 - All cores retrieved from JPCP sections...................................................................... 31 Figure 15- ASR damage found in I-75 section (poor JPCP) ........................................................ 33 Figure 16 - FEA strain results ....................................................................................................... 39 Figure 17- CRCP Site Locations................................................................................................... 42 Figure 18 - Site Photos of CRC Pavement.................................................................................... 42 Figure 19 - I-85 Typical Transverse Crack Pattern (Cluster Cracking)........................................ 44 Figure 20 - GPR scans in the direction of traffic: ......................................................................... 46 Figure 21 - ISM Plots for CRC Pavements................................................................................... 47 Figure 22 - Typical Cores at Rebar Locations, (a) Core sample; (b) Coring machine; (c) Inside view of a cored pavement. ............................................................................................................ 48 Figure 23 - 3D View of Pavement Design Parameters for Fair CRC (I-85 MP 45-44) ............... 49 Figure 24 - 3D View of Pavement Design Parameters for Poor CRC (I-85 MP 55-54) .............. 50 Figure 25 - All cores extracted...................................................................................................... 51 Figure 26 - Construction Signs of Distress* on I-85 MP 55-54 (Poor Condition) ....................... 56 Figure 27 - AC Site Locations ...................................................................................................... 59 Figure 28 - Site Photos (AC pavements) ...................................................................................... 59 Figure 29 - Typical Distress.......................................................................................................... 61
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Figure 30 - SuperPave pavement scan of (a) SR-38 and (b) SR-54 ............................................. 63 Figure 31 - ISM Plots for AC pavements ..................................................................................... 64 Figure 32 - Typical Cores at Joints (SR-38) ................................................................................. 67 Figure 33 - Typical Cores at Joints (SR-54) ................................................................................. 68 Figure 34 - All Cores (a) SR 38 and (b) SR 54.......................................................................... 69 Figure 36 - Asphalt Sample after Ignition Burning ...................................................................... 70
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APPENDICES Appendix A NCHRP Guide 747 "Phased approach to forensic investigations" Appendix B Visual Assessment Form for AC Pavements Appendix C Visual Assessment Form for PCC Pavements Appendix D Flow Chart for Forensic Investigation of Asphalt Pavement Appendix E Flow Chart for Forensic Investigation of Joint Plain Concrete Pavement Appendix F Flow Chart for Forensic Investigation of Continuous Reinforced Concrete Pavement
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ABBREVIATIONS LIST

Abbreviation

AASHTO American Association of State Highway and Transportation Officials

AC

Asphaltic Content

AGBS Aggregate Base

BCO

Bonded Concrete Overlay

Gmb

Bulk Specific Gravity

Caltrans California Department of Transportation

CDOT Colorado Department of Transportation

CRC

Continuously Reinforced Concrete

DCP

Dynamic Cone Penetrometer

DOT

Department of Transportation

DT

Destructive Testing

FDR

Full Depth Repair

FHWA Federal Highway Administration

FWD GPR HMA
HWT ISM JOR JPC NCHRP NDT
PDR
RCP RDD RWD SP SSD STI Gmm TRB UCO

Falling Weight Deflectometer Ground Penetration Radar Hot Mix Asphalt
Hamburg Wheel Tracking Impulsive Stiffness Modulus Joint Repair Jointed Plain Concrete National Cooperative Highway Research Program Non-Destructive Testing
Partial Depth Repair
Rapid Chloride Permeability Rolling Dynamic Deflectometer Rolling Wheel Deflectometer Superpave Saturated Surface Dry Stitching Theoretical Maximum Specific Gravity Transportation Research Board Unbonded Concrete Overlay

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1. INTRODUCTION
1.1 Problem Statement The National Cooperative Highway Research Program (NCHRP) Report 747 (Guide for
Conducting Forensic Investigations of Highway Pavements) was released in 2013. The report explored the process for conducting forensic investigation of pavements to help understand the reasons behind premature failures or exceptionally good performance. The report recommended performing both functional and structural evaluation of pavements for forensic study. It provides general guidance on the organization and planning of the forensic investigation, sampling and testing requirements, analysis of results, and the decision making process. In the absence of a guide for conducting forensic investigation in Georgia, the Georgia Department of Transportation (GDOT) desires to evaluate and review this latest document for compatibility with current GDOT practices. If discrepancies exist, modifications will need to be developed and presented to GDOT for acceptance.
The Michigan Department of Transportation (DOT) conducted a similar research study by evaluating six concrete pavement systems with materials-related distress (Sutter et al. 2010). Factors contributing to concrete pavement distress included extensive alkali-silica reactivity and freeze-thaw deterioration related to poor entrained air-void parameters. The Ohio DOT performed a forensic investigation in 2006 to determine the reasons for differences in performance of ten flexible pavements (Qin et al. 2013). Despite numerous research projects in this field, state transportation agencies seldom provide a formally written forensic pavement investigation guide.
Current forensic pavement investigation techniques consist of non-destructive and destructive tests applicable to both rigid and flexible pavement systems. These techniques are necessary to determine the strength and serviceability of a pavement system. Without on-going and well-structured forensic pavement investigation programs to detect current issues and prevent damage, unwanted downtime and loss of money will be inevitable to mitigate neglected problems (Rens et al. 1997).
1.2 Objectives The primary goal of this research study is to evaluate the NCHRP 747 for GDOT's
adoption by performing functional and structural evaluations of existing asphalt/concrete
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pavements. Specific objectives for this study include: (1) Conduct functional and structural evaluation to identify causes of distress on asphalt and concrete pavements based on the NCHRP 747 Forensic Guide; (2) Provide a recommendation whether the Georgia guide is warranted based on the functional and structural evaluation in accordance with the Forensic guide; (3)If warranted, develop a GDOT version of the Pavement Forensic Guide by considering GDOT practices, the unique characteristics of pavements, materials, and weather conditions in Georgia.
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2. LITERATURE REVIEWS 2.1 GDOT Nationwide Survey 2.1.1 Introduction and Motivation
Before conducting pavement forensic investigations, a national survey was conducted to help the research team understand and possibly enhance forensic evaluation methods. The survey was distributed to each state DOT in North America. Questions were specifically engineered to inquire whether the participant used a pavement forensic guide to examine the functional and structural condition of existing rigid and/or flexible pavement. The survey also asked what specialized tests were used for pavement forensic analysis (Falling Weight Deflectometer (FWD), Ground Penetration Radar (GPR), Rapid Chloride Permeability (RCP) tests, etc.) and inquired about methods for maintenance and/or rehabilitation such as Full Depth Repair (FDR), Partial Depth Repair (PDR), Bonded Concrete Overlay (BCO), Unbonded Concrete Overlay (UCO) (FHWA 2003) and Joint Repair (JOR). The survey participants were provided an opportunity to attach supporting documentation and/or give additional comments. In total, responses were received from 32 state DOT's as shown in Figure 1. Four responses were received from provinces in Canada.
Figure 1 - Survey Responses in North America.
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The following sections present survey results of state practices and a review of available forensic pavement investigation techniques. The primary purpose of the survey was to research the most commonly used forensic investigation methods that other state DOTs use and study the causes of pavement distresses and/or failure contributing to differences in performance (average, below average, above average) among rigid and flexible pavement systems in other states. Therefore, it should be noted that this survey focuses on structural distress types and possible causes in pavement systems. Functional distresses such as riding quality and skid resistance can vary widely from state-to-state, by climate, and pavement types. Thus, they are not intended to be a part of this survey although participants of this survey have shared a few functional evaluation methods.

2.1.2 Adoption of Pavement Forensic Guide When asked if the respondent's DOT uses a pavement forensic guide to examine the
functional and structural condition of existing rigid and/or flexible pavement, only 4 participants (12.5%) responded that their DOT maintained a pavement forensic guide as shown in Table 1. However, 39% of DOTs without a guide are interested in considering one. For the DOTs that did have a forensic guide, they all displayed positive views of their respective guides. Additionally, 3 DOTs (Colorado, Wyoming, and Quebec) have adopted the NCHRP 747 into their pavement practices. Colorado has a neutral opinion of the guide. Wyoming felt they have not had a chance to fully evaluate the guide. Quebec has their own procedures to conduct forensic investigations, but are evaluating the guide to see if it contains any information that they can add to their procedures.

Table 1 - Survey Results: States and Canadian Provinces with a Forensic Pavement Investigation Guide

Response Yes No
Total*

Respondent 5** 27 32

Percentage 15.6 % 84.4 % 100.0 %

Note: * includes 28 US states and 4 Canadian provinces. ** States/Provinces with a guide - Colorado, Maryland, Montana, Saskatchewan, and Quebec.

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2.1.3 Forensic Technologies Subsequently, the participants were asked whether certain forensic pavement testing
technologies were in use by their DOTs, as shown in Table 2. FWDs were the most widely used technology, with 91% of DOT's confirming their use and 96% stating they would recommend the technology. Other technologies include the GPR (Usage=59%, Recommendation=95%), RCP Test (Usage=22%, Recommendation=50%), Dynamic Cone Penetrometer (DCP) (Usage=50%, Recommendation=81%), and the Rolling Dynamic Deflectometer (RDD) (Usage=0%, Recommendation=40%). Although RDD is recommended by multiple state DOTs, no usage was reported in the survey. In addition, the respondents were allowed to add any additional testing that was not listed on the survey. 10 DOTs listed technologies such as Rolling Wheel Deflectometer (RWD), boring, skid resistance, pipe cameras, and base/subgrade samples. Six (6) DOTs specifically mentioned that they use coring.
2.1.4 Rehabilitation Methods Subsequently, the participants were asked whether certain pavement rehabilitation
technologies were in use by their DOT, which is shown in Table 3. The top three used rehabilitation methods are PDR (Usage=97%, Recommendation=97%), FDR (Usage=91%, Recommendation=100%), and JOR (Usage=84%, Recommendation=96%). Other rehabilitation technologies include: BCO (Usage=25%, Recommendation=63%), UCO (Usage=59%, Recommendation=80%), and Stitching (STI) (Usage=47%, Recommendation=76%). The respondents were allowed to add any additional method that was not listed on the survey. Nine DOTs mentioned rehabilitation methods such as Dowel Bar Retrofitting, Rubblization (TRB 2006), Asphalt-Concrete Overlay, Diamond Grinding (FHWA 2016d), and Pavement Preservation Treatments. Table 4 summarized these methods.
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Table 2 - Survey Results: Non-destructive and Destructive Testing Methods Used

State/Province Alberta Arizona Arkansas Colorado
Connecticut Georgia Idaho Illinois Indiana Iowa Kansas Kentucky Louisiana Maine Manitoba Maryland Michigan
Mississippi Missouri Montana Nebraska New Jersey North Dakota Oregon Quebec Rhode Island Saskatchewan South Carolina South Dakota
Utah Virginia Washington Wyoming Responses Percentage

FWD GPR

RCP

DCP









































































































































































































































































29

19

7

16

91% 59% 22% 50%

Note: Yes; No (or No Response)

RDD 0 0%

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Table 3 Survey Results: Rehabilitation Methods Used.

State/Province Alberta Arizona Arkansas Colorado
Connecticut Georgia Idaho Illinois Indiana Iowa Kansas Kentucky Louisiana Maine Manitoba Maryland Michigan
Mississippi Missouri Montana Nebraska New Jersey North Dakota Oregon Quebec Rhode Island Saskatchewan South Carolina South Dakota
Utah Virginia Washington Wyoming Responses Percentage

FDR PDR BCO UCO









































































































































































































































































29

31

8

19

91% 97% 25% 59%

Note: Yes; No (or No Response)

STI









15 47%

JOR





27 84%

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Table 4 Other Forensic Investigation/Rehabilitation Methods Provided during the Survey.

State/Province Colorado Illinois Indiana Iowa Kentucky Louisiana
Maryland
Michigan
Missouri New Jersey
Oregon Quebec South Carolina

Forensic technologies

Rehabilitation methods

Hamburg and French Rut tests

Diamond Grinding

Coring / lab testing Pavement Coring


Asphalt Overlays
Retrofit dowel bars & Retrofit underdrain crack & Seat & overlay Rubblize & overlay Preventive and functional overlay
Diamond grinding

Rolling Wheel Deflectometer, Laboratory
testing of field acquired specimens, Component method outlined in 1993
AASHTO guide, and MEPDG. Cores and Borings
Pipe cameras, HMA sampling/recovery, Concrete petrographic analysis, Coring
Lab testing samples extracted from the project: Composition analysis, APA rut,
Overlay test, binder testing, etc.
Coring and Base/Subgrade Samples
Skid Resistance

Dowel Bar Retrofit
Rubblization and AC overlay, and numerous pavement preservation treatments
A whole host of other pavement preservation treatments
Joint resealing Crack sealing/filling HMA milling/resurfacing HMA overlay Chip seal Microsurface Dowel bar retrofit Diamond
grinding Crush and shape/resurfacing Aggregate lift/resurfacing Fog seal Paver
placed surface seal Dowel Bar Retrofit

Localized punch-out repairs, which are fulldepth
Near the end of the CRCP service life, overlay the CRCP with 2 to 6 inches of asphalt".

Visual observation of cores



Note: No Response

2.1.5 Other Published Forensic Pavement Guides and Resources Respondents were encouraged to upload resources or send a pavement forensic guide if
they had one or were willing to share one. Table 5 contains the resources and guides provided during the survey. Nine DOTs responded and attached a guide or web links: Alberta (Canada), Colorado, Illinois, Louisiana, Maryland, Michigan, Montana, South Carolina, and Quebec (Canada). A few DOTs provided links to their DOT website. Alberta, Illinois, Quebec, and South Carolina uploaded copies of their supporting forensic pavement literature.

8

State Alberta
Colorado
Illinois
Louisiana Maryland Michigan Montana Quebec
South Carolina

Table 5 Resources shared by state DOTs during the survey.
Resources shared (based on the survey conducted between June 2015 and January 2016).
GUIDELINES FOR ASSESSING PAVEMENT PRESERVATION TREATMENTS AND STRATEGIES (web link) http://www.transportation.alberta.ca/Content/docType233/Production/gappts.pdf PROCEDURES FOR FORENSIC STUDY OF DISTRESS OF HOT MIX ASPHALT AND PORTLAND CEMENT CONCRETE (web link) https://s.qualtrics.com/ControlPanel/File.php?F=F_2OGvlIdbj3iHZsg Chapter 53- PAVEMENT REHABILITATION, BUREAU OF DESIGN & ENVIRONMENT MANUAL. (web link) http://www.idot.illinois.gov/Assets/uploads/files/Doing-Business/Manuals-Split/Design-AndEnvironment/BDE-Manual/Chapter%2053%20Pavement%20Rehabilitation.pdf Pavement research (web link) http://www.ltrc.lsu.edu/preview/research_pavement.html Pavement & Geotechnical Design Guide (web link) http://sha.md.gov/OMT/MDSHA-Pavement-Design-Guide.pdf Pavement Design and Selection Manual (web link) http://www.michigan.gov/mdot/0,1607,7-151-9622_11044_11367---,00.html Methods of Sampling and Testing, MT 329-04 - Procedure for Evaluating Plant Mix Surfacing Failures (web link) http://www.mdt.mt.gov/other/webdata/external/materials//materials_manual/329.PDF Rigid Pavement Maintenance and Rehabilitation Guide & Rigid Pavement Distress Identification Manual (web link) http://www3.publicationsduquebec.gouv.qc.ca/produits/ouvrage_routier.fr.html Pavement Design Guidelines (web link) http://www.scdot.org/doing/technicalPDFs/materialsResearch/PavementDesignGuide2008.pdf

2.1.6 Additional Comments Provided by Pavement Engineers The most frequent comment was that other DOTs would like to see the survey results.
Many DOTs are evaluating the NCHRP 747 report for adoption as a forensic pavement guide or are interested in making their own.

Illinois DOT has attached Chapter 53 of their Bureau of Design and Environment Manual. Although it has not been adopted as a formal forensic pavement guide, it is used for pavement evaluation and rehabilitation.
Indiana uses various treatments, depending on the project and "type of roadway". Louisiana stated that they are very experienced in conducting forensic evaluations
and regard NCHRP 747 as an "excellent resource" and recommend it for "new engineers". Michigan is reviewing NCHRP 747 for possible use in their DOT practices, but is not considering creating a new forensic pavement guide. Mississippi utilizes "pavement cores and FWD data" to conduct forensic evaluations on flexible pavement, but they do not have a published forensic pavement guide.

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Nebraska commented that "Many of the principles outlined in the NCHRP forensic guide are part of the pavement design process and are documented in our Pavement Design Manual."
Oregon is primarily a Continuously Reinforced Concrete Pavement (CRCP) state, and therefore Oregon DOT has not had a need for the types of rehabilitation presented in Table 3. It conducts "localized punch-out repairs, which are full-depth". Near the end of the CRCP service life, Oregon DOT traditionally will "overlay the CRCP with 2 to 6 inches of asphalt".
Virginia DOT does not have a published forensic pavement guide, but uses the "Materials Division's Manual of Practice" to conduct pavement investigations and rehabilitate pavement.
Wyoming commented that they have "had limited success with Bonded Concrete overlays on concrete, but have been very successful with Bonded Concrete on plant mix pavement".
2.1.7 Discussion Because only four agencies use a forensic guide for pavement investigation, it is
difficult to conclude which techniques recommended in the NCHRP 747 report are preferred for implementation for use in a pavement investigation guide. However, investigation techniques currently used by multiple highway agencies prevail. Although FWD and GPR methods are used by 29 and 19 states/provinces, respectively, these methods are generally considered practical. For pavement rehabilitation, it was discovered that PDR (FHWA 2016c) and UCO are more popular than FDR (USDOT 2015) and BCO, respectively. Furthermore, JOR is common which suggests that improved maintenance and design processes are necessary.
It was discovered that states including Texas, New Mexico, and California provide a pavement investigation guide or maintenance program although they did not participate in the survey. Texas DOT appears to have a well-organized forensic pavement assessment process as well as rigid and flexible pavement rehabilitation methods available on its website (TxDOT 2015). The NCHRP report includes the Caltrans' guide as well (2003). Moreover, California provides a well-organized Pavement Management System or PaveM (Caltrans
10

2016) which includes an Automated Pavement Condition Survey (APCS). The survey consists of collecting surface pavement sensor and image based distress data and analyzing data in conformance with the Department's APCS Manual. In addition, GPR technology is used to collect continuous layer thickness data.
New Mexico DOT has illustrated the benefits to pavement design, maintenance, and management through the use of non-destructive pavement testing technology, namely FWD and GPR, rather than destructive coring. Furthermore, the agency's effort and interest was also found in a recently completed research report (Bandini et al. 2012) for improving New Mexico DOT's pavement distress survey methodology and developing correlations between FHWA's Highly Polymer Modified (HPM) pavement distress data and Pavement Management System (PMS) data and pavement assessment projects (NMDOT 2016).
2.2 Pavement Types Review This section provides a brief explanation of each pavement type.
2.2.1 Jointed Plain Concrete Pavement (JPCP) Jointed Plain Concrete Pavement (JPCP) is a concrete slab that contains contraction joints
in the transverse and longitudinal direction. These contraction joints control where the pavement cracks occur at specific locations. JPCP is commonly used in roadway construction as an economical choice. The performance depends on the load transfer efficiency and design parameters such as slab thickness, concrete strength, and dowel/joint spacing. Additionally, the pavement is known to have potential issues such as cracking (corner, longitudinal, transverse), faulting, and joint failure (Rada, 2013). These distresses can be prevented through a combination of proper design, construction, and/or material choice.
2.2.2 Continuously Reinforced Concrete (CRC) Pavement Continuously Reinforced Concrete Pavement (CRCP) sections contain longitudinal
reinforcement throughout the entire section. CRCP is known to maintain performance under heavy traffic loadings and challenging environmental conditions, provided proper design and quality construction practices are utilized (FHWA, 2012). This pavement has intentional longitudinal cracks that are held together tightly by the extensive reinforcement. The cracks, no larger than 0.02 inches, prevent moisture from penetrating the slab and damaging the
11

pavement (PI, 2008). The most frequently observed distress in CRC pavements are punchouts (Rada, 2013). Closely spaced transverse cracks can be observed, although they are not necessarily detrimental to Georgia pavements. 2.2.3. Hot-Mix Asphalt (HMA) HMA Pavement Superior Performing Asphalt Pavement System (SuperPave) was created in 1993 by the Strategic Highway Research Program (SHRP) (FHWA, 2010). This pavement is regarded as superior because it combines "asphalt binder and aggregate selection into the mix design process, and considers traffic and climate as well" (PI, 2011). An HMA pavement is typically constructed from a subgrade soil, subbase course, base course, and surface course. As the impact loading strikes the surface course, the load is distributed through each layer of material. The HMA flexes under loading, giving it the classification "flexible pavement". HMA Pavements are susceptible to distresses such as cracking (alligator, transverse, longitudinal, and block), rutting, potholes, and raveling (Rada, 2013).
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3. TESTING METHODOLOGY
3.1 Visual Inspection/Observation Visual observation identifies patterns that reveal pavement deficiencies. The pavement
distress is generally organized in a report that details the severity of the damage and how far the damage extends across the pavement. As part of the NCHRP Report 747, a visual inspection form for Asphalt Concrete (AC) and Portland Cement Concrete (PCC) pavement is provided as a guideline. A copy of these visual inspection guidelines can be viewed in Appendix 2 and 3.
GDOT has developed their own visual inspection method, Pavement Condition Evaluation System (PACES). Depending on the type of distress, the cause can be attributed to a certain factor, such as environmental conditions, poor construction practices, or increased traffic loading. For example, alligator cracks on flexible pavement surfaces generally indicate a loadrelated failure whereas block cracks largely result from an environmental-related failure. Linear cracking and corner breaks normally result from a load-related failure in rigid pavement surfaces while durability cracking is mostly due to an environmental-related failure. Generally, the condition of the pavement surface has been visually inspected periodically by experienced engineers for the purpose of computing the PACES rating. The PACES rating gives a numerical indicator that rates the surface condition of the pavement from 100 (Excellent Condition, no distress) to 0 (The worst Condition). Although the evaluation process may vary widely by jurisdiction, it provides a measure of pavement conditions based on the distress observed on pavement surfaces, as well as a practical indication of functional pavement condition and structural integrity.
3.2 Review of Pavement Forensic Technologies Non-destructive Although many performance problems show on the surface of the pavement, the cause is
often attributed to issues within the pavement structure. Non-destructive testing (NDT) allows these issues to be located with precision, resulting in efficient repair. Furthermore, NDT is responsible for identifying problems that have not appeared on the pavement surface. The most common NDT technologies are Ground Penetrating Radar (GPR), Falling Weight Deflectometer (FWD), friction testers, and profilometers (Rada 2013). GPR and FWD technologies deal more with internal problems such as structural capacity and material properties, whereas friction
13

testers and profilometers deal with external problems such as ride quality and road safety for functional evaluation (Rada 2013). It is necessary to describe each forensic investigation method in this section, in order to properly discuss the state DOT survey results. 3.2.1 Falling Weight Deflectometer
The need for non-destructive testing will usually be decided based on a visual assessment. A Falling Weight Deflectometer (FWD) is a device that applies a load to a pavement section and measures the resulting deflections (FHWA 2006). Figure 2 shows an image of the FWD harnessed to the back of a van. FWD equipment can quantify structural issues by means of measuring deflections. These deflections are measured in at least 7 locations along the test section using sensory instrumentation according to the American Society for Testing and Materials (ASTM), "Standard Test Method for Deflections with a Falling-Weight-Type Impulse Load Device" (ASTM-D4694, 2003). The standard gives instructions on conducting FWD tests to assess AC pavements and their respective parameters such as deflection, structural number, and elastic modulus, etc. (Bilodeau 2012). For site investigations, the FWD test is typically performed in one lane, unless there are thickness variations between lanes. The sections are then interpreted through software to give material properties and the pavement bearing capacity. Unfortunately, test location and temperature can influence FWD measurements and must be accounted for when calibrating the equipment. The Impulse Stiffness modulus (ISM) of the pavement sections is defined as the applied load (in kN) divided by the maximum deflection of the loading plate (in millimeter) (USDOT FAA 2011). Impulse Stiffness Modulus (ISM) plots display the stiffness over the length of the pavement, providing a simplified way to check for the overall strength of the pavement section.
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Figure 2 - Falling Weight Deflectometer
3.2.2 Ground Penetration Radar A Ground Penetration Radar (GPR) uses an antenna to send energy waves through
pavement and monitors the surface reflection, or dielectric (ASTM-D6432 2011). A picture of a GPR is shown in Figure 3. The GPR rapidly and effectively analyzes layer thickness and detects problems such as "debonding, presence of moisture, voids under concrete slabs, and other issues that are normally assessed through coring" (Rada 2013; Zhao et al. 2016). This technology has been used by many DOTs to discover problematic areas in pavement. Using a GPR is very effective in detecting moderate to severe stripping in hot-mix asphalt (HMA) (Chen 2003). The GPR energy waves can penetrate approximately three feet (one meter) and can be operated at highway speeds, when attached to a vehicle, making it a useful addition to non-destructive testing technologies (Chen 2008). Unfortunately, the data results decrease in quality as the highway speeds increase, which may require road closures to receive accurate results. In addition, interpreting GPR data requires a technician with special training (Rada 2013). The GPR is wheeled over the pavement sections and the results are collected in the form of images that use colors to distinguish the variations of dielectric signals that differentiate material properties (Morey 1998). These images are then compared with core samples to verify pavement thickness.
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Figure 3 - Ground Penetration Radar
3.2.3 Other Non-destructive Testing Techniques The NCHRP report recommends the following non-destructive tests to explain issues or
functional distress types being investigated: Profilometer (Pratic and Vaiana 2015), Skid Resistance/Friction (Rezaei and Masad 2013), Tire-Pavement Noise at the Source (Porras 2015), Texture Meter, Permeameter (Huang and Huang 2014), and Magnetic Tomography Technology (Stryk et al. 2013; Hoegh et al. 2012).
3.3 Review of Pavement Forensic Technologies Destructive 3.3.1 Coring
Destructive testing (DT) is utilized where NDT techniques indicate potential pavement failures. Coring is a process where a 102 or 152-mm diameter cylindrical section is extracted from the pavement section. A coring machine is shown in Figure 4. A core sample shows a wide range of pavement layers (e.g., Subbase, Base, Subgrade, Concrete, and Asphalt mixture) that can be analyzed. When the core is taken, a borescope can photograph problem areas, such as voids. Layer thickness and/or cause of distress can be measured from taking core samples. Laboratory testing is conducted on cored specimens to reveal and confirm problems. In terms of the FHWA, the most common testing methods for concrete specimens are "compressive strength, modulus of elasticity (MOE), rapid chloride permeability (RCP), Alkali-Silica Reaction (ASR),
16

Carbonation, and alternating current loop impedance" (Mallela 2006; Salgado and Yoon 2003). Air-void content, dynamic modulus test, Hamburg wheel track test, binder content, aggregate grading and properties, and resilient modulus are common for cores from flexible pavement. To address specific problems associated with pavement, state DOTs conduct many laboratory tests on freshly cored pavement samples.
Figure 4 - Coring machine 3.3.2 Rolling Dynamic Deflectometer (RDD)
A Rolling Dynamic Deflectometer (RDD) was developed as a non-destructive method for determining continuous deflection profiles of pavements in Texas (Nam et al. 2013). Unlike other commonly used pavement testing methods, the RDD performs continuous rather than separate measurements. Due to the low speed of measurements (< 3 mph), however, the use of RDD is not common.
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3.3.3 Dynamic Cone Penetrometer (DCP) A Dynamic Cone Penetrometer is used to determine underlying soil strength by
measuring the penetration of the device into the soil after each hammer blow (Mejias-Santiago et al. 2015). DCP testing has been used to measure the relative strengths of stabilized and unstabilized aggregate base layers, and evaluate existing pavement base and subgrade layer strength during rehabilitation evaluations (MnDOT 2016).
3.4 Laboratory Testing Methods for Concrete Pavements
3.4.2 Alkali Silica Reaction (ASR) and Coefficient of Thermal Expansion (CTE) Other on-site chemical tests such as carbonation and ASR tests and laboratory tests
including petrographic analysis are recommended in the NCHRP 747 report (Rada 2013). It is known nationwide that a high percentage of slab cracks in concrete pavement systems may be attributed to high coefficient of thermal expansion (CTE) while the contributing factor for map cracking is generally the ASR (Kim 2012). This reaction causes the formation of a swelling gel of calcium-silicate-hydrate (CSH) and can ultimately cause serious cracking in concrete pavement. This gel increases in volume with water, and applies an expansive pressure inside the cementitious material, causing spalling and loss of strength, resulting in its structural failure.
3.4.3 Carbonation A carbonation reaction results in a densification of the paste. The product mineral, calcite,
is relatively insoluble in pore solution and its presence results in a permanent reduction in the capillary porosity of the paste (FHWA 2016b). Consequently, in a carbonation test, a diluted epoxy dye will penetrate into these areas, and they will exhibit little to no fluorescence compared to the uncarbonated areas of the same concrete, which would show high fluorescence (FHWA 2016b). Carbonation damage is rarely seen in Georgia pavements.
3.4.4 Rapid Chloride Permeability (RCP) The Rapid Chloride Permeability (RCP) test is performed by monitoring the amount of
electrical current that passes through a sample, a slice of a pavement core, which is 50 mm thick by 100 mm in diameter. The standardized testing procedures are provided in ASTM C 1202 (2012) or AASHTO T 277 (2008). A 60V DC voltage is maintained across the ends of the sample throughout the test. One lead is immersed in a 3.0% NaCl (salt) solution and the other in
18

a 0.3 Molar concentration NaOH (sodium hydroxide) solution. Based on the charge (coulombs) that passes through the concrete sample, a qualitative rating is made of the concrete's permeability: High (>4000), moderate (2000 to 4000), Low (1000 to 2000), Very low (100 to 1000), and negligible (<100). Generally, high levels of penetrability relate to a decrease in pavement quality. RCP testing is not commonly conducted on pavements in Georgia.
3.5 Laboratory Testing Methods for Hot Mix Asphalt Pavements
3.5.1 Bulk Specific Gravity (Gmb), Theoretical Maximum Specific Gravity (Gmm) Gmb is the ratio of a dry specimen's weight to the weight of an equal volume of water (PI,
2011). The test is performed according to AASHTO Standard T 166 "Bulk Specific Gravity of Compacted Asphalt Mixtures using Saturated Surface-Dry Specimens" (AASHTO T 166, 2015). The test involves weighing the sample to record a dry weight. Next, the sample is immersed in water for 4 minutes and weighed underwater. Lastly, the sample is quickly dried and then measured for SSD weight. These parameters are then used to calculate the Gmb using the following formula:

Bulk Specific Gravity (Gmb)= A

(1)

B - C

Where A = Weight in grams of the specimen in air B = Weight in grams, surface dry C = Weight in grams, in water

Theoretical Maximum Specific Gravity (Gmm) is the specific gravity of a sample when there are no air voids. This is possible by testing the asphalt sample in "rice form" (AASHTO T209, 2015). Each sample is weighed to record a dry weight. Next, the material is placed inside the container and filled with water to a point of approximately 1 inch above the sample. Next, the container is sealed and a vacuum pressure of 25 to 30 mm Hg is applied for 15 minutes. Every 2 minutes, the container is agitated with a hammer to release any air bubbles. After the 15 minutes, the pressure is released and the sample is left undisturbed for 10 minutes. Afterwards, the sample is weighed underwater. These parameters are then used to calculate the Gmm using the following formula:

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Theoretical Maximum Specific Gravity (Gmm)= A

(2)

A+D-E

Where A = mass of oven-dry sample in air D = mass of container filled with water at 77F E = mass of container filled with sample and water at 77F

The air content of as sample is calculated from by the Gmb and Gmm values using the following formula:

Air

Voids

(Va)

=

(1

-

)


100

(3)

3.5.2 Hamburg Wheel Tracking Test A Hamburg Wheel Tracking Test measures rutting and stripping in asphalt pavements by
continuously rolling a steel wheel over the pavement surface (CDOT, 2014). During testing, the sample is submerged in 50C water to evaluate moisture susceptibility. After testing, the rut depth of the sample is compared with the amount of wheel passes before failure (20,000 max). The result is used to determine the rate of pavement deformation, by approximating the stripping inflection point (SIP). The SIP is known as the point where "moisture damage starts to dominate performance" (FHWA, 2007). This value is formed by the intersection of the creep slope and the stripping slope. The creep slope refers to the slope of the graph before SIP, whereas the stripping slope is the slope after SIP has occurred (Izzo, 1999). A Hamburg Wheel Tracking Test machine can be viewed in Figure 5.

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Figure 5 - Hamburg Wheel Tracking Machine at UGA 3.5.3 Binder Content
To determine the binder content of an asphalt specimen, the sample is heated to a high temperature (538oC) using an ignition furnace, where all binder will burn away. The difference between the starting and ending weights is used to determine the binder content. Before ignition, samples are heated to a temperature of 230 9F for a minimum time 25 minutes. To determine the binder content of asphalt for this study, an NCAT Asphalt Content Furnace was used to conduct binder content tests in accordance with the AASHTO T 308 "Determining the Asphalt Binder Content of Hot Mix Asphalt (HMA) by the Ignition Method". The furnace has an internal scale that automatically calculates binder content as the sample is burning. After the test is finished, the sample is removed and cooled. Proper safety precautions were strictly enforced throughout this entire process.
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4. JOINTED PLAIN CONCRETE PAVEMENT 4.1 Introduction
Jointed Plain Concrete Pavement (JPCP) is characterized by its concrete slabs that contain steel dowels to efficiently transfer load from traffic. However, transportation agencies find that some JPCPs stay in good condition over time, while others have deteriorated significantly. According to the NCHRP 747 guidelines, JPCP is known to be susceptible to distresses such as transverse cracking, joint faulting, and spalling (Rada, 2013).
In this study, two JPCP sites have been selected in consultation with GDOT as shown in Figure 6: SR-22 in `good' condition and I-75 in `poor' condition. The field investigations were performed at the JPCP sites in two phases: non-destructive and destructive investigations. The non-destructive site investigation involved a visual inspection, Ground Penetration Radar (GPR) scanning and Falling Weight Deflectometer (FWD) testing. Destructive field testing involved collecting pavement cores from the sites and conducting laboratory tests on the cored specimens.
Figure 6 JPCP Site Locations 22

4.2 Test Site and Field Setup A mile-long section from each site was investigated. The first test site is located on State
Route (SR) 22 (Westbound) in Muscogee County, Georgia. The road from milepost 8 to 7 is reported to be in a `good' condition, which shows no visible deficiencies. The second site is located on Interstate (I) 75 (Southbound) in Clayton County, Georgia. The road from milepost 226 to 228 is in `poor' condition, with multiple deficiencies observed on its surface. A visual comparison of both sites is shown in Figure 7. Table 6 shows a comparison of site conditions and pavement profile/construction parameters in the two JPCP sections. In Georgia, roadway sections are rated by district offices and are given a PACES rating (taken in 2015). Ratings of 70 or below generally warrant rehabilitations. The JPCP sections, SR-22 and I-75, have a PACES rating of 100 and 40, respectively, as summarized in Table 6. Deductions from I-75 are from Linear Cracking, Ruptured Slabs, and Joint Spalling.
SR-22 was constructed in 2008 with a design speed of 60 miles per hour. The section is composed of 9 inches of Portland Cement Concrete (PCC) and 8 inches of Graded Aggregate Base (GAB) (see Table 6). SR-22 is composed of two lanes in one direction. The Average Annual Daily Traffic (AADT) in 2013 for the site is 26,630 vehicles with 985 trucks (3.7%). The slab has skewed joints. The test section between MP 8 to MP 7 was selected because it shows relatively good concrete pavement condition in both the fast and slow lanes.
I-75 is believed to have been constructed in 1968 with the earliest documented rehabilitation occurring in 1989. This section is composed of an existing road that was widened from 2 lanes to 3 lanes in one direction with a design speed of 55 miles per hour. The outside lane (lane #3) is designed to have 10.5 inches of Portland Cement Concrete (PCC) over a layer of 6.5 inches of unbonded concrete with GAB underneath. The inside lane (lane #1) is composed of 10 inches of PCC over an Asphalt Concrete (AC) layer of 4 inches with GAB underneath. The inside lane consists of a different concrete composition than the outside lane. The AADT for the site is 115,000 vehicles with about 8,050 trucks (7%). During visual inspection, the inside lane was observed to have fewer signs of failure. The inside lane also experienced a lower volume of trucks.
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Figure 7 - General Site Conditions: (a) SR 22 (good condition); (b) I-75 (poor condition)

Table 6 - JPCP Conditions.

Parameters
Condition Current Condition Rating (PACES) (2014-
2015)

SR 22

Outside

Inside

Good

100

Visual Distress Observed

None

Age (years) Pavement Structure
(in.) AADT (% Trucks) (taken in2013)

48 (1968)

9" PCC/

9" PCC/

8"GAB

8"GAB

26,630 (3.7% trucks)

I-75 Outside
Poor

Inside Fair

40

Primary Distress: Longitudinal Cracking Secondary Distress: Transverse Cracking, Punchouts, Joint
Spalling, and Shattered Slabs 26 (1990)

10.5"PCC/6.5"PCC/10"GAB

10"PCC/4"AC/10"GAB

115,000 (7% trucks)

Condition & Profile

24

In Georgia, roadway sections are rated by district offices and are given a PACES rating (taken in 2015). Ratings of 70 or below generally warrant rehabilitations. The JPCP sections, SR-22 and I-75, have a PACES rating of 100 and 40, respectively, as summarized in Table 6. Deductions for I-75 are from Linear Cracking, Ruptured Slabs, and Joint Spalling. During the visual inspection of I-75, many deficiencies were noted of which spalling, transverse cracks, and longitudinal cracks were most common (and can be seen in Figure 8). In the outside lane, longitudinal cracks running parallel to the wheel paths are the most frequently observed distress type. Small aggregate delamination was occasionally observed, as well as spalling.
Figure 8 - I-75 Typical Distress (Poor Condition) (a) Spalling Repairs and Longitudinal Cracking; (b) Longitudinal Cracking through joints.
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4.3 Non-Destructive Testing
As described in previous section, nondestructive testing (NDT) methods, such as FWD and GPR, are widely used to evaluate in-situ material characteristics of in-service pavements. More information on these technologies can be found in Section 3.2 - Review of Pavement Forensic Technologies Non-destructive.
Table 7 shows a summary of pavement structure determined from the GPR scans. This Table also includes saw cut depth, clear cover depth, rebar size, dowel spacing, and slab aspect ratio. The GPR results for both SR-22 and I-75 are fairly consistent, with a pavement thickness that is representative of their design data (Figure 9). Both sites have consistent compaction, as shown by their consistent layers in the GPR scan. The dowel bars are shown towards the center of the graph. It should be noted that dowels in the outside lane of the I-75 were placed slightly below the centerline.

Table 7 - JPCP NDT Results and Design Parameters.

Parameters
Joint Efficiency (%)
Average ISM (kip/in) Back-calculated subgrade
reaction (pci)
Surface Texture
Saw Cut Depth (in.) Dowel Depth (Clear Cover) (in.)
Actual Dowel Diameter Epoxy Coated Rebar Dowel Spacing (in. on center) Dowel Length (in.) Joint Spacing (ft) Slab Dimensions Length by Width (ft)
Slab Aspect (L/W) Ratio Slab Length-to-Thickness Ratio

SR 22 (Good)

Outside

Inside

92

90

2000

2000

105

115

Transverse Tining
2.5 4.25 (5 from core)
1.125" (#9) Yes 12 18 20
20 by 12 1.67 26

I-75 (Poor)

Outside

Inside

92

85

2500

3000

138

162

Transverse Tining (Worn) 2 6.5
1.25" (#10) Yes

Transverse Tining (Worn) 2 3
1.25" (#10) Yes

12

12

18

18

15

15

15 by 12

15 by 12

1.25

1.25

17

18

FW D

JPCP Design Parameters

26

Figure 9 - Typical GPR scans showing single joint (a) JPCP scan of SR 22 (good condition); (b) JPCP scan of I-75 (poor condition) in the direction
of traffic.
27

The ISM plots created from the FWD testing are shown in Figure 10. Compared to the ISM plot in SR-22, the ISM plot from I-75 shows a certain degree of variation along with distance, that might be interpreted as a construction variability. Using the FWD data, a modulus of subgrade reaction, k was back-calculated based on the 1993 AASHTO design guide (AASHTO, 1993) and is summarized in Table 7.
Figure 10 - Selected ISM Plots determined from FWD tests (a) SR-22 (good condition); (b) I-75 (poor condition) 28

4.4 Destructive Testing Coring and Field Testing Typical cores and crack depths at joint locations, as well as photos of cores retrieved
from joint locations are shown in Figure 11. Figures 12 and 13 illustrate coring locations for the two JPCP sections. Pavement cores were extracted in order to confirm the existing pavement thickness, dowel size, joint design, and crack depth. Based on the recommendations in the NCHRP 747 report, the cores were taken on the centerline of the slab, wheel paths in slow and fast lanes, and cracks to document the crack depth. Further, the non-destructive test data and visual inspection were reviewed to determine the coring locations for both sites as shown in Figures 12 and 13. For I-75, a 4-inch core drill was used for laboratory tests, although a 6-inch core bit was utilized to observe dowel locations. For SR-22, a 4-inch core drill was used for all extractions. Photos of all cores extracted are shown in Figure 14. As shown in Figure 14, cores show consistent compaction and few voids.
Figure 11 - Typical Cores at Joints (a) SR 22 core at the joint (good condition); (b) I-75 core (poor condition); (c) I-75 core (poor
condition) showing a full-depth longitudinal crack. 29

Figure 12- 3D View of Coring Locations and JPCP details for SR 22 (good condition).
Figure 13- 3D View of Coring Locations and JPCP details for I-75 (poor condition). 30

Figure 14 - All cores retrieved from JPCP sections (a) SR 22 cores (good condition); (b) I-75 cores (poor condition) (c) I-75 cores at joints (poor
condition). Note: Core samples shown in (a) and (b) are re-assembled after conducting the laboratory tests for this Figure.
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4.4.1 SR-22 Section Coring and On-site Testing The core (J-3MD) was extracted from a joint at the SR 22 location and tested for carbonation using a chemical testing kit. The test result showed a negative reaction, which means no carbonation was observed. The saw cut on the sample measured 2.5 inches (See Figure 14 (a)). The remaining cores maintained a consistent measurement of 9 inch PCC with GAB underneath. The dowel began at a clear-cover depth of 5 inches below the pavement surface. In this section, the asphalt concrete shoulders were sealed to prevent moisture from entering.
4.4.2 I-75 Section Coring and On-site Testing At the I-75 site, the inside lane showed fewer signs of joint failure, as opposed to the outside lane which showed many deficiencies. The two lanes also show a visible difference in mix design, which strongly indicates that they were constructed at different times. As indicated in Figure 14 (c), the saw cut on the sample measured 2 inches. The second core sample taken in the middle of the slow lane (C-1M) was tested for an Alkali-Silica Reaction (ASR). There was a bright yellow reaction around aggregates as shown in Figure 15 (a), and thus on site testing revealed that there was evidence of ASR. This core sample was selected for a petrographic analysis. A core sample (C-2W-2) was taken from a rehabilitation patch and 6.5 inches of existing PCC was discovered underneath the new PCC. Sample J-W2 was tested for carbonation, which indicated positive on the surface of cracks. As shown in Figure 14 (b), cores taken from the fast lane were discovered to have approximately 4 inches of an asphalt concrete layer beneath the PCC layer. The reinforcement began at a clear-cover depth of approximately 3.5 in. below the pavement surface. Small particle delamination was observed on the site. Sample J-M4 contained a dowel and was subsequently tested for carbonation, which was not found and epoxy coated dowels were in good condition.
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Figure 15- ASR damage found in I-75 section (poor JPCP) (a) On-site field test; (b) Photomicrograph of ASR gel and a crack filled with ettringite in thin
section; (c) Photomicrograph of the typical air void structure from a core.
4.5 Destructive Testing Laboratory Testing A summary of laboratory test results is described in this section. More information on these specific technologies can be found in Section 3.4 Laboratory Testing Methods. The CTE tests were conducted using cored specimens in accordance with AASHTO T 336. The CTE of Portland cement concrete (PCC) generally ranges between 4.4 and 5.5 microstrains/F (AASHTO, 2011). The measured CTEs are within an acceptable range for pavement design in Georgia (Kim, 2012). The measured CTE values for the two test sections are shown in Table 8.
The RCP tests were performed according to ASTM C1202-12: Electrical Indication of Concrete's Ability to Resist Chloride Ion Penetration (ASTM, 2012). As shown in Table 8, the RCP values in the SR-22 and I-75 were determined to be low and high, respectively.
The Modulus of Elasticity (MOE) measures the elastic relationship of stress to strain for a given material. More specifically, it measures material stiffness. The MOE tests for the JPCP specimens were conducted in accordance with the ASTM C469: Standard Test Method for Static Modulus of Elasticity and Poisson's Ratio of Concrete in Compression (ASTM, 2003). The MOE for I-75, particularly for the slow lane, was relatively low, although the average
33

compressive strength was comparable to values determined from SR-22, as shown in Table 8. Both I-75 and SR-22 meet the requirements for minimum compressive strength.
4.6 Petrographic Examination Two cores (one from each site) were selected for petrographic analysis. The petrographic
analysis of selected cores (C9W from SR-22 and CM-1 from I-75) was performed by TEC Services, Inc. located in Lawrenceville, Georgia. This test involves taking an in-depth examination of selected cores to determine multiple construction and material parameters that are not available otherwise. The analysis of the sample from SR-22 indicated that the material makeup of the section consisted of a nominal maximum aggregate size (NMAS) of 3/4 inch crushed granite as coarse aggregate and natural quartz for fine aggregate. The water-to-cement ratio ranged between 0.45 and 0.49, and no fly ash/slag was included. The concrete is airentrained, resulting in a 3%-6% air content. In reference to quality acceptance criteria from GDOT, the water-to-cement ratio is acceptable. The design air content range is between 4.0 to 5.5, so the concrete from SR-22 may meet the design requirements (GDOT 430.3.06, 2013).
The analysis of the sample from I-75 revealed that the material makeup of the section consisted of a NMAS of 5/8 inch crushed granite as coarse aggregate. Manufactured sand was used for fine aggregate. The paste was identified as good quality with a water-to-cement ratio of 0.4 and contained no slag or fly ash. The paste was described as well-hydrated, but mottled and unevenly distributed, which can be attributed to poor construction practices. An air-entraining agent was not found, and a low air content (2%) was found. The air was entrapped as shown in Fig. 15(c), which is indicative of a poor quality mixture. In reference to quality acceptance criteria from GDOT, the water-to-cement ratio is acceptable. The design air content range is between 4.0 to 5.5, so the concrete from I-75 does not meet the design requirements (GDOT 430.3.06, 2013).
Due to the presence of ASR, the concrete used in I-75 is unlikely to be durable for freeze-thaw cycles. Several micro-cracks were visible, and few contained alkali-silica reactivity (ASR) gel. Any deterioration of concrete by ASR or freeze-thaw action accelerates the rate at which ettringite leaves its original location and recrystallize in larger spaces such as voids or cracks (Suksawang, 2014). Although little ASR gel was found in the core sample from I-75, the ettringite formation at voids/cracks is indicative of ASR. This was identified as a major concern, as many of the cracks traveled through the aggregate as shown in Fig. 15(b). These micro-cracks
34

and ettringite formation may be associated with heat of hydration damage during concrete placement or temperature-gradient related damage (PCA, 2001).

Table 8 - Summary of Core Test Results.

Condition

Parameters
Good/Fair/Poor

SR 22 (Good)

Outside

Inside

Good

Good

I-75 (Poor)

Outside

Inside

Poor

Fair

On-site Field Testing

ASR

No

No

Low/Moderate

Low

Laboratory Testing

Petrographic Analysis

Carbonation MOE (ksi) f'c (psi)
RCP (Coulomb) CTE ( in/in/F) Coarse Aggregate
Maximum Aggregate Size Fine Aggregate
W/C ratio Fly ash Paste
Air entrained
Air content
Cracks
Other distresses to note

No

No

No*

No

4189 9,500 2,845

N/A 7,700 2865

3755 7,600 5997

4712 5,600 6328

5.10

5.10

Crushed Granite 3/4" The aggregate is well distributed
and well graded.
Natural quartz; The maximum sand particle size is 1/8"

0.45-0.49 No fly ash or slag

The paste is of good quality.

4.65

4.47

Crushed Granite

5/8"; Well gradation; no segregation

Manufactured Sand
0.4 No fly ash or slag The paste is of good quality.

Air entrained The air varies from 3-6% and is not evenly distributed. The majority of the
air is of good quality. There are occasional cracks in the aggregate that do not appear to be
significant.
Concrete is well hydrated and the paste is hard.

No Air entrained Approximately 2% and many void are entrapped. The air is of poor
quality.
Many microcracks visible; These cracks contain ASR gel and ettringite.
Microcracks visible in thin section, often filled with ettringite (see Fig. 15(b)). Concrete is unlikely to resist freeze thaw cycles in a saturated
condition.

Notes: * Carbonation was discovered within the crack surfaces of the concrete sample.

4.7 Analysis of Testing Results A low/medium level of ASR, as noted in Table 8, was observed at the surface of I-75.
Neither site experienced carbonation, although surfaces of cracks exposed to air were carbonated.
35

The MOE results were unexpectedly lower in I-75 compared to SR-22. The RCP test results show that values for I-75 ranged from 4100 to 7600, with an average of 6000. This indicates very high chloride ion penetrability. The values changed sporadically throughout the section. In contrast, values for SR-22 ranged from 1800 to 3600, with an average value of approximately 3000 throughout the section. This indicates low or moderate chloride ion penetrability. The compressive strength for both sections ranged between 5600 and 7600 psi for I-75, whereas it ranged between 7700 and 9500 psi for SR-22. Relative to SR-22, I-75 has a thicker concrete slab with comparable compressive strength. However, it is concluded from the field and laboratory test results that the concrete in I-75 is depicted by poor material composition including microcracks, ettringite, poor air-entrainment, and ASR damage.
The NCHRP 747 guide prescribes possible causes of longitudinal and corner cracking, similar to the distress observed in I-75. Longitudinal cracking may be caused by low PCC strength, high CTE, thermal deformation due to warping and curling, and poor load transfer to tied shoulder. The causes of failure are fairly consistent with the Caltrans' JPCP design guide (Caltrans, 2008) in that longitudinal cracks occur parallel to the centerline of the pavement and are often caused by a combination of heavy load repetitions on pavement with unsatisfactory roadbed support, thermal curling, faulting, shrinkage, and moisture induced warping stress. Furthermore, the linear cracks running along the centerline of panels (see Figure 8) can develop due to a range of factors (Pavement Interactive, 2012). These include overloading, thermal expansion and contraction, moisture stresses, slab curling, and loss of support underneath the slab. When a combination of distress factors are involved, traffic loads are known to exacerbate these problems.
In comparison to each other, SR-22 and I-75 have very different amounts of traffic. The AADT (2013) for SR-22 is 26,630 vehicles with 985 trucks (3.7%). SR-22 has two lanes in each direction. The AADT (2013) for I-75 is 115,000 vehicles with about 8,050 trucks (7%). I-75 has 3 lanes in one direction. Even when lane distribution is taken into account, I-75 experiences a much higher amount of traffic. During visual inspection, the outside lane also experienced a higher volume of trucks.
The field and laboratory tests indicated that the concrete in I-75 is not likely to be durable, despite a reasonable compressive strength. Therefore, in addition to the distresses found in the concrete materials, another distress factor is suspected when non-destructive and destructive test
36

results indicated no major deficiency in the concrete performance (strength and stiffness) of the sections. It can be concluded from the previous traffic analysis that the distress may be attributed to increased AADT. There are national guidelines available to evaluate JPCP design options such as the AASHTO 1993 design guide (AASHTO, 1993) and Pavement ME (Mu, 2015; ARA, 2004; Pierce, 2014). However, it was not possible to consider a combination of factors, such as thermal deformation and traffic loads, while providing a diagnosis of the full-depth longitudinal cracks found in I-75. Therefore, a nonlinear finite element analysis (FEA) model was constructed to simulate the cracking mechanism observed in I-75, which is discussed in the following section.
4.8 Finite Element Analysis of the Distress
A finite element analysis (FEA) model was constructed using the ANSYS v18.2 software with the objective of simulating the distress conditions found in I-75. In this analysis, the modulus of subgrade reaction determined from the FWD test was used for simplicity by providing compression-only springs at the bottom face of the JPCP section. It is intended that a single slab of I-75 be analyzed to diagnose the causes of pavement distress (or longitudinal cracks) in a three-dimensional FEA model using the best engineering judgment.
A typical three-lane JPCP slab with a uniform lane width of 12 feet was considered for modeling, and one lane was modelled for analysis as shown in Figure 16 (a). A joint spacing of 15 feet was selected for this study as shown in Table 7. For the purpose of illustrating the cause of distress in a clear manner, the entire concrete panel was analyzed, despite the axis of symmetry in a single panel. Furthermore, the two adjacent panels in the direction of travel are modeled half way between joints using the centerline as an axis of symmetry in order to accurately evaluate the behavior of joints. Joint dowels and concrete panels are modeled with solid elements, and dowels are assumed perfectly bonded to the one side of two adjoining concrete slabs. The joint model is illustrated in Figure 16(a) and includes a small gap between the two concrete slabs. A single wheel load of 9,000 lb. of an equivalent 18,000 lb. single axle load was considered in this study. An uniform contact pressure of 100 psi was applied over a rectangular area, as illustrated in Figure 16(b). The 100 psi pressure was applied to reflect the minimum cold pressure for a 9000 lb single wheel load.
Curling occurs in the form of a three-dimensional deformation which provides a positive curvature in two directions. A positive curvature from a temperature gradient mainly occurs in
37

the direction of travel. Generally, in the stress analysis of JPCP, traffic load is applied at the midspan to simulate transverse cracks for positive curling in the longitudinal direction. However, in a relatively square concrete slab, a positive curvature could also become noticeable in the transverse direction due to thermal restraints provided by the adjacent lane and shoulder. Therefore, the critical traffic loading was placed close to the joint locations as shown in Figure 16 (b).
The uniform temperature of 70F was applied to the FEA model, with a gradient temperature of 30F through the slab thickness, to account for convection and solar radiation representing a summer-weather condition. The top surface of the slab was simulated warmer (100F) than the bottom of the slab (70F). The structural model reads the temperature profiles determined from the thermal analysis, and a structural analysis is performed to evaluate stress and strain solutions. Figure 16 (c) shows a schematic diagram of principal strains in the concrete slab for combined thermal and wheel loads (18kip single axle load). Thermal stress relieved by concrete cracking was not considered in this study.
In this analysis, it is determined that the concrete slab develops a tensile crack when the principal elastic tensile strain exceeds 0.00012 in/in because concrete generally cracks when the tensile strain exceeds 0.010 to 0.012 percent. Curling of the JPCP slab due to a daytime positive temperature difference combined with a critical traffic loading position results in high tensile strain (greater than 0.00012 in/in) at joints and initiates a crack in the direction of travel parallel to the centerline of the joint (Figure 16(d)).
Based on the FEA analysis, it is ascertained that thermal deformation combined with structural deformation from the wheel loads causes longitudinal cracks at joints parallel to the centerline of the concrete slabs. The analysis did not account for the microcracks developed during the concrete placement, minor ASR damage in the concrete material, or an increased cover depth during construction found in the I-75 site investigations. The extent of cracking may have been exacerbated if these effects were taken into consideration in the material model. Many of these problems are not common in Georgia pavements, therefore these conclusions apply only to I-75. A full report of conclusions and recommendations can be viewed in Section 8 Conclusions.
38

(a) Typical Joint Model
(b) Isometric view of the FEA analysis model under traffic loading Figure 16 Applied pressure and FEA strain results.
(note: The deformation is magnified by a factor of 500). 39

(c) Principal strain plot of the middle slab under combined traffic and thermal loading
(d) Enlarged joint view Figure 17 Continued Applied pressure and FEA strain results (note: The element mesh is removed from the view for clarity and deformation magnified by a
factor of 500). 40

5. CONTINUOUSLY REINFORCED CONCRETE PAVEMENT 5.1 Introduction
Continuously Reinforced Concrete Pavement (CRCP) consists of a concrete slab reinforced throughout its entire length by longitudinal reinforcement. The continuous steel reinforcement eliminates the need for contraction joints, while efficiently distributing load. CRC is susceptible to issues such as longitudinal cracking, which can induce punchouts in the pavement.
Two trends have been observed between multiple CRC pavements. Over time, many CRC roads stay in fair condition, while others deteriorate quickly. To study this phenomenon, a forensic investigation has been conducted to find the underlying causes of fair and poor pavement performance. As a guideline, the National Cooperative Highway Research Program (NCHRP) Report 747- Guide for Conducting Forensic Investigations of Highway Pavements document is utilized to understand the performance of two CRC sites.
Interstate 85 stretches across the southeast region of the United States. Two pavement sections from this interstate have been investigated as shown in Figure 17. At a distance of 10 miles apart, one pavement site exhibits fair pavement performance, while the other pavement shows poor performance. A forensic site investigation has been performed at each site, including nondestructive, destructive, and laboratory testing.
41

Figure 18- CRCP Site Locations 5.2 Test Site and Field Setup
The two sections used for this study are part of Interstate (I) 85 which runs through Coweta County, Georgia. The site that exhibits fair pavement performance is located between mileposts 45-44. The site showing poor performance is located between mileposts 55-54. A visual comparison of both sites is shown in Figure 18. Table 9 includes a comparison of site conditions and pavement profile/construction parameters in the two CRC sections. Currently, the PACES rating for CRCP is calculated based on the JPCP distress types (i.e., faulting), which is invalid for CRCP condition evaluations. Therefore, the CRCP PACES rating was not taken into the consideration for the site investigations. For the remainder of the CRCP section, I-85 milepost 45-44 will be referred to as MP 45 and I-85 milepost 55-54 will be referred to as MP 55.
Figure 19 - Site Photos of CRC Pavement . (a) I-85 MP 45-44 (Fair Condition) (b) I-85 MP 55-54 (Poor Condition).
42

Condition & Profile

Parameters Condition
Visual Distress Observed
Crack Spacing (in.) Age (years)
Pavement Structure (in.) AADT

Note: Cracks enhanced for clarity.

I-85 MP 45-44 (Fair)

Outside

Inside

Fair

None

I-85 MP 55-54 (Fair/ Poor)

Outside

Inside

Fair

Poor

None

Longitudinal Cracking, Punchouts, Joint Spalling, and
Corner Breaks

3.5 - 13

10 (2006)

11.5"PCC/

11.5"PCC/

12"PCC/

3.5"AC/GAB 3.5"AC/GAB

3"AC/GAB

50,400

Table 9 - CRC Conditions

3.5 - 13 10 (2006)
12.5"PCC/ 2.5"AC/GAB 71,700

MP 45 is in fair condition and has a profile consisting of approximately 11.5 in. of Portland Cement Concrete (PCC), 3.5 in. of Asphalt-Concrete (AC). MP 55 is composed of 12" CRC, followed by 3"AC, and 12" AGBS underneath. The outside lane of MP 55 is in fair condition while the inside lane is poor condition. I-85 is composed of 3 lanes in one direction. However, the inside lane (lane #1), appears to be composed of a better mixture than the middle and outside lanes (lanes #2 and #3). Closely spaced transverse cracking (cluster cracking) is seen throughout all three lanes in both sections, as shown in Figure 19. These cracks vary in length from 8 to 36 inches. Signs of pavement distress (punchouts, spalling, and delamination) were occasionally seen throughout the inside lane of MP 55.
Several recommendations on crack spacing are available to prevent unnecessary damage. To minimize cluster cracking, the Federal Highway Administration recommends a crack spacing between 2 feet to 8 feet (FHWA, 2012). Caltrans has a similar recommendation for crack spacing, with a distance between 3 feet and 7 feet between cracks (Caltrans, 2007). The Texas DOT warns that a crack spacing less than 2 feet could "be a precursor to punchouts" (TxDOT, 2011). With respect to crack spacing, cases of cluster cracking and Y-cracking are unique aspects of short crack spacing that can be problematic in terms of their contribution to localized failures including punchouts. These types of cracking are generally more associated with certain inadequate construction activities such as localized weak support, variable slab base friction,
43

inadequate concrete consolidation, and/or variation in the quality of concrete curing (FHWA, 2016).
In the MP 45 section, several transverse cracks were observed directly above the transverse reinforcement. The cracks measured approximately 3.5 inches in depth and 0.5 to 1 millimeter in width. In between the 3 ft. rebar spacing, 2 or 3 longitudinal cracks were also observed. In the MP 55 section, crack spacing was observed to be very similar to MP 45 in that most of the cracks ranged from 3.5 inches to 13 inches. Neither pavement sections meet the recommended crack spacing from other DOT's, but they are not seen as a sign of distress in Georgia pavements.
Figure 20 - I-85 Typical Transverse Crack Pattern (Cluster Cracking) 44

5.3 Non-Destructive Testing Non-destructive testing was carried out by using a Falling Weight Deflectometer (FWD)
and Ground Penetration Radar (GPR). More information on these technologies can be found in Section 3.2 - Review of Pavement Forensic Technologies Non-destructive. A summary of information acquired from NDT testing is shown in Table 10. The GPR data shows consistently level pavement layers. The transverse rebar spacing is also identified as 3 feet on center, as shown in Figure 20. When the GPR machine scans metal rebar, the resulting image is slightly distorted. This results in arrow-like shapes seen below the rebar in Figure 20.

Table 10 - CRC NDT Results and Design Parameters.

I-85 MP 45-44 (Fair)

I-85 MP 55-54 (Fair/ Poor)

Parameters

Outside (Lane 3)

Inside (Lane 1)

Outside (Lane 3)

Inside (Lane 1)

Average ISM (kip/in)

9400

3800

3600

4100

Back-calculated subgrade reaction (pci)

460

221

--

--

Surface Texture Epoxy Coated Rebar Longitudinal Rebar Depth (Clear Cover) (in.) Longitudinal Rebar Diameter (No.) Transverse Rebar Depth (Clear Cover) (in.) Transverse Rebar Diameter (No.) Longitudinal Rebar Spacing (ft.) Transverse Rebar Spacing (ft.)

Transverse Tining

No

No

3.75

3.75

0.75" (#6) 4.25
0.5" (#4) 0.45 to 0.5
3

0.75" (#6) 4.25
0.5" (#4) 0.45 to 0.5
3

Transverse Tining

No

No

3.25

4.5

0.75" (#6) 4
0.5" (#4) 0.42 to 0.46
3

0.75" (#6) 5.75
0.5" (#4) 0.42 to 0.46
3

CRC Design Parameters

45

Figure 21 - GPR scans in the direction of traffic: (a) I-85 MP 55-54 -Fast Lane; (b) I-85 MP 45-44 -Fast Lane;
Using the FWD data, a modulus of subgrade reaction, k was back-calculated based on the 1993 AASHTO design guide (AASHTO, 1993). ISM results and the back-calculated subgrade reaction are summarized Table 10. As seen in Figure 21, the outside lane of MP 45 has an unusually high ISM value and irregular variation, which might be interpreted as a possible
46

structural variation. After taking coring samples, a very stiff subgrade was located underneath the slow lane (lane 3). This results in an abnormally high ISM value, as seen in Figure 21.
Figure 22 - ISM Plots for CRC Pavements (a) I-85 MP 45 (b) I-85 MP 55
5.4 Destructive Testing Coring and Field Testing The coring process, including the machine used to drill cores, is shown in Figure 22. For
both sites on I-85, a 4-inch core drill was used for laboratory tests and a 6-inch core bit was 47

utilized to observe existing pavement thickness and reinforcement size & location. Based on the recommendations in Section 7.3 of the NCHRP 747 report, the cores were taken on the centerline of the slab, wheel paths in slow and fast lanes, and cracks to document the crack depth (Rada, 2013). Additionally, the coring locations for both sites were reviewed from the nondestructive test data and visual inspection information. The locations of cored specimens are shown in Figures 23 and 24 which provide a 3D schematic of the pavement section.
Figure 23 - Typical Cores at Rebar Locations, (a) Core sample; (b) Coring machine; (c) Inside view of a cored pavement.
48

Figure 24 - 3D View of Pavement Design Parameters for Fair CRC (I-85 MP 45-44) 49

Figure 25 - 3D View of Pavement Design Parameters for Poor CRC (I-85 MP 55-54) 50

Photos of all cores extracted are shown in Figure 25. As seen in the Figure, the reinforcement depth varies by 0.5 inches. MP 45 shows relatively consistent consolidation with few voids. MP 55 has consolidation problems in the slow lane, more specifically, sample C1MTR. A visible difference can be seen when comparing the concrete from the outside and inside lanes from MP 55. More details on these two material differences are explained in section 5.6 -Petrographic Examination.
Figure 26 - All cores extracted (a) Fair CRC (I-85 MP 55-54) (b) Poor CRC (I-85 MP 45-44)
51

5.4.1 MP 45 Section Coring and On-site Testing
The core (C8M-TR) was extracted from the MP 45 location and tested for carbonation, as well as alkali-silica reaction using a chemical testing kit. Both test results showed a negative reaction, which means no carbonation or alkali-silica reaction was observed. The remaining cores maintained a relatively consistent measurement of 11.5 inches, with an occasional variation no more than 0.5 inches. The longitudinal reinforcement depth remained consistent in the outside lane. In the inside lane, however the longitudinal depth varied by as much as 0.75 inches. Variations in reinforcement depth can be caused by leveling on pavement surface. It was also observed that neither longitudinal nor transverse reinforcement were epoxy coated.
5.4.2 MP 55 Section Coring and On-site Testing
Visually, many transverse cracks were discovered during coring and on-site testing. Two cores, one from the outside lane and one from the inside lane, were tested for carbonation and alkali-silica reaction using a chemical testing kit. Both test results showed a negative reaction, meaning no carbonation or alkali-silica reaction was observed. A core sample (C-1M-TR) was taken over a transverse crack, to determine the crack depth (5 in.). The crack was observed to propagate through the coarse aggregate, not around it.
Neither longitudinal nor transverse reinforcement were epoxy coated. During the site investigation, it was observed that the seal has worn between the inside lane (lane 1) and the adjacent lane (lane 2). It was also noticed that the seal was missing between the outside (lane 3) and shoulder. Lack of a proper seal could result in water seeping underneath the pavement layer and penetrating the soil below, causing erosion of the soil particles over an extended period of time.
5.5 Destructive Testing Laboratory A summary of laboratory test results is described in this section. More information on these specific technologies can be found in Section 3.4 Laboratory Testing Methods.
The CTE tests were conducted using cored specimens in accordance with AASHTO T 336 (AASHTO T 336, 2011). The CTE of Portland cement concrete (PCC) generally ranges
52

between 4.4 and 5.5 microstrains/F. The measured CTE values for MP 45 and MP 55 are 4.73 and 4.6, respectively. These values are within their recommendations.
RCP tests were performed according to ASTM C1202-12: Electrical Indication of Concrete's Ability to Resist Chloride Ion Penetration (ASTM C1202-12, 2012). As shown in Table 11, the RCP values in sections MP 45 and MP 55 were determined to be low and high, respectively.
The MOE tests for the JPC specimens were conducted in accordance with the ASTM C469: Standard Test Method for Static Modulus of Elasticity and Poisson's Ratio of Concrete in Compression (ASTM C469, 2014). The MOE for MP 45 showed reasonable values. MP 55 showed particularly low stiffness, although the average compressive strength was comparable to values determined from MP 45 (Table 11). To investigate the possible reasons, petrographic analyses were performed. The next section presents a petrographic analysis and results from the cored specimens.
53

Condition

Parameters Good/Fair/Poor
ASR

Table 11 - Summary of Core Test Results.

I-85 MP 45-44 (Fair)

Outside

Inside

Fair

Fair

I-85 MP 55-54 (Poor) Outside
Fair

No

No

No

Inside Poor No

On-site Field Testing

Carbonation

No

No

No

No

Laboratory Testing

MOE (ksi) f'c (psi)
RCP (Coulomb) CTE ( in/in/F)
Coarse Aggregate Maximum Aggregate Size
Fine Aggregate
W/C ratio Fly ash
Paste
Air entrained

3687 7,400 2085 4.73

3417 7,300 3058
4.6

See I-85 MP 55-54 Fast Lane

3125 7,700 3382 5.25
Crushed Granite and Amphibolite

2450 7,900 3909 5.34
Crushed Granite

3/8"

3/4"; Segregation at the surface

Natural quarts; The max sand particle size s 3mm 0.4-0.45
Class C fly ash and no slag in the cement
The paste is of fair quality

Natural quartzite and gray quartz; The maximum sand
particle size is 1/5"
0.4-0.45
Class C fly ash and no slag in the cement
The paste is of fair quality. The paste is somewhat soft as it can
be scratched by a Mohs 3 hardness point.

No

Yes

Petrographic Analysis

Air content
Cracks Other distresses
to note

Approximately 3% air consisting of mostly entrapped voids.; The air is not evenly distributed as there is more air in the middle of the core.

Approximately 5-7%. Mostly air entrained air voids. There is frequent ettringite in the voids.

Rare microcracks in the paste.
No corrosion is present at the periphery of the rebar. It has 3and3/4 inches of top surface
concrete cover

There are occasionally internal cracks in the aggregate. These cracks could present durability issues but do not appear to be
presently detrimental.

54

5.6 Petrographic Examination Two cores from this site were selected for petrographic analysis, one in the outside and
inside lane of MP 55. The outside lane of the MP 55 has a concrete mixture that is visually similar to the pavement from MP 45. Therefore, no cores were selected from MP 45. The petrographic analysis of selected cores (C3W-LR and C8M-LR from I-85 MP 55-54) was performed by TEC Services, Inc. located in Lawrenceville, Georgia. This test involves taking an in-depth examination of selected cores to determine multiple construction and material parameters that are not available otherwise. The analysis of the sample from the outside lane of MP 55 indicated that the material makeup of the section consisted of a nominal maximum aggregate size (NMAS) of 3/4 inch crushed granite as coarse aggregate and natural quartzite and gray quartz for fine aggregate. The water-to-cement ratio ranged between 0.4 and 0.45. Class C fly ash was included, but no slag was included in the mixture. The concrete is air-entrained, resulting in a 5%-7% air content. In reference to quality acceptance criteria from GDOT, the water-to-cement ratio is acceptable. The design air content range is between 4.0 to 5.5, so the concrete from MP 45 may meet the design requirements (GDOT 430.3.06, 2013).
The analysis of the CRCP from the inside lane of MP 55 revealed that the material makeup of the section consisted of a NMAS of 3/8 inch crushed granite and amphibolite as coarse aggregate. Natural quartz was used for fine aggregate. The paste was identified as fair quality with a water-to-cement ratio of 0.4 and 0.45. Class C fly ash was included. Low air content was observed (3%). In reference to quality acceptance criteria from GDOT, the water-tocement ratio is acceptable. The design air content range is between 4.0 to 5.5, so the concrete from MP 55 does not meet the design requirements (GDOT 430.3.06, 2013). The air was entrapped and described as being "not evenly distributed" and having "more air in the middle of the core". The poor air distribution can be attributed to poor consolidation, as shown in Figure 26(a). Although the paste was reported to be of fair quality, it was much softer than the aggregate, as seen in Figure 26(b). Also, segregation issues can be seen in Figure 26(c), which can be attributed to excessive vibration.
55

Figure 27 - Construction Signs of Distress* on I-85 MP 55-54 (Poor Condition)
5.7 Analysis of Testing Results A summary of the test results is shown in Table 11. MP 45 has a CTE value of 4.6-4.73,
and MP 55 exhibited a value of 5.25-5.34. Both results are within an acceptable range (Kim, 2012).
RCP tests were run on MP 45 in the inside and outside lanes. Values ranged from 2000 to 3500, with an average value of approximately 2100 for the outside lane and 3100 for the inside lane. This indicates a low-to-moderate chloride ion penetrability. RCP tests run on MP 55 in the inside and outside lanes resulted in values from 2800 to 3900. The average value was approximately 3400 for the slow lane and 3900 for the fast lane, respectively. This indicates a moderate chloride ion penetrability.
The compressive strength for both sections ranged between 7700 and 7900 psi for MP 45 section, whereas it ranged between 7300 and 7400 psi for MP 55. Both sites are well within the
56

acceptable ranges of 3,000 psi for Class 1 and 3,500 for Class 2 mixtures (GDOT 430.3.06, 2013).
Several punchout sections were observed within the inside lane of MP 55. The NCHRP 747 guide prescribes possible causes of punchouts in CRCP can be attributed to "low PCC strength" or "steel reinforcement corrosion". The same guide states that longitudinal cracks in CRCP may result from "high stabilizer contents in [the] base". Pavement Interactive reports that punchouts can be caused by "steel corrosion, inadequate amount of steel, excessively wide shrinkage cracks or excessively close shrinkage cracks" (Pavement Interactive, 2012). The causes of punchout failure are a clear result of closely spaced transverse cracks (FHWA, 2012; Caltrans, 2007; TxDOT, 2011). It is also warned that if the cracks widen more than 0.02 inches, moisture can infiltrate the pavement (Pavement Interactive, 2012). A full report of conclusions and recommendations can be viewed in Section 8 Conclusions.
57

6. HOT MIX ASPHALT (HMA) PAVEMENT SUPERPAVE 6.1 Introduction
The NCHRP 747 Guideline reports that AC pavement is often susceptible to distresses such as rutting, roughness, potholes, excessive noise, and skid resistance (Rada, 2013). Additionally, AC pavement often experiences many cracks, such as alligator, transverse, longitudinal, and block cracking. Most deficiencies observed nationwide include: rutting, alligator cracking, transverse cracking, longitudinal cracking, block cracking, roughness, potholes, excessive noise, and frictional characteristics (Rada, 2013). Long-term aging increases the viscosity of asphalt, causing it to become hard and brittle. Combined with vehicle traffic, these effects can lead to various types of distress within asphalt pavements.
To investigate how HMA pavements behave in Georgia, a forensic investigation was conducted using the NCHRP 747 report as a guideline. Two HMA sites have been investigated, SR-38 in `fair' condition and SR-54 in `poor' condition (Figure 27). SR-38 section shows less severe signs of longitudinal cracking and raveling (Figure 28(a)). Similarly, SR-54 shows visual signs of severe distress, mainly longitudinal cracking and raveling(Figure 28(b)). Field investigations were performed in two phases: non-destructive and destructive investigations. The non-destructive site investigation involved a visual inspection, Ground Penetration Radar (GPR) testing and Falling Weight Deflectometer (FWD) testing. Destructive field testing involved collecting pavement cores from the sites and conducting laboratory tests on the cored specimens.
58

Figure 28 - AC Site Locations
Figure 29 - Site Photos (AC pavements) (a) SR 38 (fair condition) (b) SR 54 (poor condition)
59

6.2 Test Site and Field Setup State Route (SR) 38 in Long County is composed of multiple layers of AC as shown in
Table 12. In addition, soil cement is used instead of GAB. The state route consists of four-lane divide highway (two lanes in a single direction). This section was intended to be observed as a section containing SP in "fair" condition, however, upon inspection, the road was observed to have experienced significant deterioration. Numerous surface cracks of a moderately high severity were observed running through most of the pavement. These surface cracks consisted of longitudinal cracks which ranged in moderate to severe conditions over the majority of the section. Intersection cracks occasionally resulted from the amount of transverse and longitudinal cracks. A moderate level of particle loss was also observed in the left wheel path of the outside lane (Figure 29(a)). Most damage was observed in the outside lane, which typically experiences more truck traffic. The PACES data for this road shows a steady decline from a 98 rating on 2008 to 71 in 2013. After 2013, the pavement quality significantly decreased to 58 due to an increase in load cracking and block cracking.
State Route (SR) 54 (Eastbound) in Fayette County is composed of AC with a densely packed Superpave (SP) surface layer. The road is a four-lane divided highway (two lanes in a single direction), with moderate levels of traffic. In addition, SR 54 contains many stoplights and frequently experiences traffic congestion. A section between MP 5 to MP 4 was selected for this evaluation as it showed poor pavement performance in both fast and slow lanes. The test section exhibited severe longitudinal cracking along the wheel-paths of the road that extended throughout a majority of the section with occasional transverse cracking in both fast and slow lanes. Severe longitudinal cracking and raveling were the most commonly observed signs of distress (Figure 29(b)). Potholes, patching, block cracking, reflective cracking, and alligator cracking were observed occasionally during the visual site investigation. The PACES rating for this section sharply decreased from 85 in 2010 to 50 between 2012 to 2014. In 2015, the pavement was seen to increase from 50 to 54. This small increase is considered to be the result of pavement rehabilitation in the form of patches and the filling of potholes. A comparison of site conditions and pavement profiles of the two HMA pavement sections is shown in Table 12.
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General

Table 12 - Site Condition and Pavement Profile

Parameters

SR 38 (Fair Condition)

Outside

Inside

SR 54 (Poor Condition)

Outside

Inside

Condition Age (years) Total Pavement Structure
(inches)
Visual Distress Observed

Poor

Good

N/A

1.75 (12.5mm SP)/

6.5 (19mm SP)/

2 (25mm SP)/

0.75 (12.5mm SP)/

0.75 (19mm SP)/ 6" Soil Cement

Longitudinal Cracking and

raveling near the left wheel path

of the outside lane (see Figure

28a)

Poor

Poor

26 (1990)

1.5 (12.5mm SP)/ 2 (19mm SP)/
4 (25mm SP)/ 10" GAB

6.5 (12.5mm SP)/ 7.75 (19mm SP)/ 8.75 (37.5mm SP)

Severe Longitudinal and Transverse Cracking, Raveling

PACES Score (2015), %

72

64

ADT (% Trucks)

5,860 (9.5% Trucks)

21680 (5% Trucks)

Traffic

Figure 30 - Typical Distress (a) SR-38 (b) SR-54
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6.3 Non-Destructive Testing Non-destructive testing was carried out by using a Falling Weight Deflectometer (FWD)
and Ground Penetration Radar (GPR). More information on these technologies can be found in Section 3.2 - Review of Pavement Forensic Technologies Non-destructive. A representative scan from SR-38 and SR-54 is shown in Figure 30. The scan of SR-38 (Figure 30(a)) shows surface, base, and subgrade profiles with density information. As seen, the GPR scan color code of density is uniform, which is expected for less variability in pavement condition. However, SR54 shows an irregular GPR scan color code of subgrade (Figure 30(b)). Variability of subgrade density and moisture level is expected, which can result in problems such as longitudinal and fatigue cracking, as well as rutting and potholes (Rada, 2013).
The ISM plots for SR-38 and SR-54 are shown in Figure 31. The ISM plot of SR-38 has an average ISM value of 1100 and 1200 kip/in for the inside and outside lane, respectively. The ISM plot of SR-54 shows an irregular trend in the inside lane (Figure 31(b)). The ISM value is steady around 1100, but rapidly increases to a value close to 3000. Three coring samples were taken within this irregular area. It was discovered that the total length of the extracted cores varied from 12 inches to 23. These irregular cores contained very thick binder and base mixes, with no GAB underneath. The most logical explanation is that the previous roadway underwent a full-depth rehabilitation that left some pieces of the existing roadway in place. It is assumed that the road was most likely widened at that time, which explains why the outside lane has a steady ISM value. The average ISM value for the outside lane is 900 kip/in, which is lower than the value of pavement from SR-38 (around 1100 kip/in).
62

Figure 31 - SuperPave pavement scan of (a) SR-38 and (b) SR-54 63

Figure 32 - ISM Plots for AC pavements (a) SR-38 and (b) SR-54
64

The subgrade modulus for the subgrade layer of each pavement section was backcalculated using the AREA-based method described in the USDOT-FAA Advisory Circular (USDOT, 2004). This method uses the area of the radial deflection of the pavement found during the FWD procedure to estimate the subgrade modulus (Esubgrade) of the pavement layers. The value for Esubgrade may then be used to calculate the design thickness required for the pavements to carry specific load conditions.
Additionally, the design Structural Number (SN), which represents an index of required pavement depths, was calculated for each pavement section using the AASHTO pavement design guide (1993). For these evaluations, 2 million and 1.3 million Equivalent Single Axle Loads (ESALs) were used to determine the required SN number for the SR-38 and SR-54 AC sections, respectively. ESALs were obtained from the traffic records provided. A summary of the calculated SN and required subgrade base depths are shown in Table 13. SR-38 meets the requirements for SN, meaning that the pavement is structurally sound to hold its loading. However, SR-54 does not meet the SN requirements, meaning that the pavement need a rehabilitation.

Table 13- Subgrade modulus, Effective and Required SN.

Parameter Subgrade Modulus, Esubgrade (psi) Effective Structural Number, SNeff
ESAL SN, Required SNreq'd > SNeff

SR 38 9,776 5.13 2 Million 3.85 Yes

SR 54
4,714 4.30 1.3 Million 4.60 No

The subgrade soil modulus for SR-54 was determined to be 4,714 psi, which indicates silty-clay type soils (CL, CH, ML, MH) normally found in Fayette county, Georgia. However, the subgrade modulus for SR-38 was 9,776 psi and significantly higher than the modulus determined for SR 54 AC section. The sandy soils (SW, SP, SM, SC) may be present in SR 38 pavement section. This observation matches with soil survey of Georgia, which indicates that sandy soils are generally found in Long county, Georgia (USDOA, 1982).

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6.4 Destructive Testing Coring and Field Testing 6.4.1 SR-38 Coring and On-site Testing
When coring the samples from SR-38, the cores contained compacted soil cement below their respective AC layer. The use of soil cement is typical in South Georgia to save GAB material and haul costs as most of quarries for GAB are located in North Georgia. Figure 32 shows typical cores takes at joints from SR-38. Figures 32(a) and 32(b) show a core sample before and after extraction. As shown in Figure 32(c), there are several AC lifts within the cored specimen. This could be attributed to milling and overlay rehabilitation. All cores extracted from SR-38 and SR-54 are shown in Figure 34. Cores from SR-38 (Figure 34a) appear very similar in length and layer density.
As previously mentioned, SR-38 exhibits moderate raveling and fatigue cracking on the left side of the outside lane (Figure 29(a)). Due to the unique location of longitudinal cracking, it is suspected that the distress may be initiated by reflective cracking and deteriorated further due to traffic. Observation of cored specimens from SR-38 confirms that cracking is reflected from soil cement. Reflective cracking is a common distress among pavements when a soil cement is used as the soil cement typically experiences shrinkage cracks, which is reflected upward to the pavement surface (Adaska, 2004).
66

Figure 33 - Typical Cores at Joints (SR-38) (a) Unremoved core sample (b) Pavement with core sample removed (c) Core sample
6.4.2 SR-54 Coring and On-site Testing SR-22 Section Coring and On-site Testing
All of the SR 54 coring samples taken contained large cracks. Many cracks initiated from either the bottom or top, and several samples were extracted in pieces. Figure 33 shows images from the coring process on SR-54. A large, irregularly shaped void was discovered when coring sample C-7 (Figure 33(b)). The void was also part of the extracted sample, as seen in Figure 33(c). The void is assumed to be the result of an organic material (e.g. wood) displaced during construction. All cores extracted from SR-38 and SR-54 are shown in Figure 34. The core samples from SR-54 are consistent in the outside lane. However, the fast lane shows cores of irregular lengths (Figure 33(c)). As mentioned previously, the 4th, 6th, and 7th samples in Figure 34(b) show full depth asphalt composed entirely of asphalt mixes. No GAB was found underneath these samples.
67

Design drawings were not available for SR-54. The irregular length of coring samples from the inside lane of SR-54 can lead to the conclusion that, the inside lane is composed of an existing pavement that contained an asphalt base (Figure 33c). The existing road underwent a full-depth rehabilitation on partial sections of the road. The two pavements are joined at the wheel path locations in the pavement. It seems that the large cracks shown in Figure 29 (b) initiated from this joint.
Figure 34 - Typical Cores at Joints (SR-54) 68

Figure 35 - All Cores (a) SR 38 and (b) SR 54
6.4.3 Air Content Analysis The air content observed in sample SR-38 is highly irregular (Table 14). The air void content of the surface lift is 7.3%, which is close to the general guideline of 4 to 7%. The binder lifts each had varying air contents, which are most likely not representative of the sample. SR 54 sample C-2 was taken in the slow lane, and shows a very high air content (11.3%), which is most likely indicative of raveling distress (Table 14). SR 54 sample C-2 taken from the fast lane exhibits a high air content (7.8%), which is also indicative of raveling distress. However, the binder lift
69

below the surface has a low air content (4.0%), which may be the result of compaction from traffic loading. 6.4.4 Binder Content Analysis
The binder content was measured in accordance with AASHTO T 308 "Determining the Asphalt Binder Content of Hot Mix Asphalt (HMA) by the Ignition Method". Each sample was ignited at a temperature of 538C until the internal scale reached a constant weight (approximately 60 to 90 minutes). Figure 36 shows how samples look after burning in the ignition furnace. The binder content is calculated by the ignition oven and this information can be viewed in Table 14.
The surface course from SR-38 (sample C-2) contained a binder content of 5.1%, which is 17% higher than the binder content of SR 54 Sample C-2. The binder course has an average binder content of 5.96%, which is 28% higher than the binder content of SR 54 Sample C-2. SR 54 Sample C-2 and SR 38 Sample C-4 also have a differing binder content for their base course, with a 16% relative difference.
Figure 36 - Asphalt Sample after Ignition Burning
70

Table 14 Summary of Pavement Information for Selected HMA Sites

Crack

Condition Pvmt Material

Site

Type

/Lane Layer Type

Material Sub-Type

Thickness, (in.)

Gmb

Gmm

Air Void (%)

1

AC

1/2 in NMSA

LC SR
BC 38
RV C-4
RT

Fair/ Inside

2

AC

3/8 in NMSA

3

AC

3/8 in NMSA

4

AC

1/2 in NMSA

5

AC

3/4 in NMSA

Soil

6

Soil Cement

Cement

LC

1

SR

BC

Poor/

54

2

RV

Outside

C-2

3

RT

4

AC
AC AC GAB

1/2 in NMSA
3/4 in NMSA 1 in NMSA
GAB

LC SR
BC 54
RV C-4
RT

Poor/ Inside

1 Surface 1/2 in NMSA

2 Binder 3/4 in NMSA

3

Base

3/4 in NMSA

4

GAB

GAB

(Not

(Not

2

2.4928

conducted)

conducted)

1.5

2.2562

2.5194

10.4499

2

2.3692 2.4358

2.7338

3

2.4316 2.4505

0.7731

2.5

2.2468 2.4906

9.7865

6

--

--

--

(Not

(Not

1.5

2.5163

conducted)

Conducted)

2

2.3781 2.5261

5.86

4

2.4302 2.5199

3.56

10

--

--

--

(Not

(Not

1.5

2.5020

conducted)

conducted)

2.25

2.4071 2.5067

3.97

3

2.3645 2.5272

6.44

10

--

--

--

Asphalt Content
(%)
5.12%
5.29% 6.51% 6.07% 4.78%
--
4.58%
4.64% 4.13%
--
4.38%
4.82% 4.50%
--

Note: LC=Load Cracking, BC=Block Cracking, RV=Raveling, RT=Rutting
6.4.5 Sieve Analysis After burning, each sample was weighed and sieved according to ASTM C136 "Standard
Test Method for Sieve Analysis of Fine and Coarse Aggregates". Samples were sieved to determine the Nominal Maximum Aggregate Size (NMAS). The sieve results from each layer were compared according to NMAS by the GDOT Standard Specifications for the Construction of Transportation Systems (GDOT 828.2.03, 2013). The sieve analysis results can be seen in Tables 15 through 17. In SR-38, all layers meet the GDOT requirements, with the exception of the 4th lift. In SR-54, sample C-2 meets all grading requirements. However, it was observed that gradation of Layer 1 in sample C-4 is out of the GDOT specification range. A full report of conclusions and recommendations can be viewed in Section 8 Conclusions.
71

Sieve Size
1 3/4 1/2 3/8 4 8 10 16 Pan

Layer 1 (NMAS 1/2 in) 100% 100%
96% 82% 52% 35% 32% 27% 0%

GDOT Spec (1/2
in.) 100% 100% 90-100% 70-85%
-34-39%
----

Table 15 - SR 38 C-4 (Outside Lane)

Layer 2 (NMAS 3/8 in) 100% 100%
99% 98% 70% 43% 39% 29% 0%

GDOT Spec (3/8
in.) 100% 100% 100% 90-100% 55-75% 42-47%
----

Layer 3 (NMAS 3/8 in) 100% 100% 100%
98% 68% 46% 42% 33% 0%

GDOT Spec (3/8
in.) 100% 100% 100% 90-100% 55-75% 42-47%
----

Layer 4 (NMAS 1/2 in) 100% 100%
98% 88% 65% 47% 44% 35% 0%

GDOT Spec (1/2
in.) 100% 100% 90-100% 70-85%
-34-39%
----

Layer 5 (NMAS 3/4 in) 100% 100%
76% 64% 45% 35% 32% 26% 0%

GDOT Spec (3/4
in.) 100% 90-100% 60-89% 55-75%
-29-34%
----

Sieve Size
1 1/2 1 3/4 1/2 3/8 4 8 10 16
Pan

Table 16 - SR 54 C-2 (Outside Lane)

Layer 1 (NMAS 1/2
in)

GDOT Spec (1/2 in.)

Layer 2 (NMAS 3/4
in)

GDOT Spec (3/4 in.)

100% 100% 100% 97% 81% 49% 33% 30% 24% 0%

100% 100% 100% 90-100% 70-85%
-34-39%
----

100% 100% 98% 75% 57% 37% 30% 28% 24%
0%

100% 100% 90-100% 60-89% 55-75%
-29-34%
----

Layer 3 (NMAS 1
in)
100% 99% 85% 66% 47% 33% 26% 25% 21% 0%

GDOT Spec (1 in.)
100% 90-100% 55-89% 50-70%
--25-30 ----

72

Sieve Size
1 3/4 1/2 3/8 4 8 10 16 Pan

Table 17 - SR 54 C-4 (Inside Lane)

Layer 1 (NMAS 1/2
in)

GDOT Spec (1/2 in.)

Layer 2 (NMAS 3/4
in)

GDOT Spec (3/4 in.)

Layer 3 (NMAS 3/4
in)

GDOT Spec (3/4 in.)

100% 100% 94% 70% 40% 27% 24% 19% 0%

100% 100% 90-100% 70-85%
-34-39%
----

100% 99% 85% 66% 45% 35% 31% 26% 0%

100% 90-100% 60-89% 55-75%
-29-34%
----

100% 97% 75% 60% 39% 30% 28% 24% 0%

100% 90-100% 60-89% 55-75%
-29-34%
----

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7. CONCLUSIONS 7.1 Jointed Plain Concrete (JPC) Pavement - Conclusions and Recommendations
A forensic investigation was conducted on two JPCP sections, SR-22 and I-75, in `good' and `poor' condition. SR-22 shows no signs of distress. The distress in I-75 is mainly depicted by longitudinal cracks running full-depth along the centerline or wheel paths. Based on the findings of this investigation:
1. The cause of the observed distress in I-75 is the result of a combination of factors including traffic load, poor material composition, and environmental conditions such as thermal (or moisture-related) expansion/contraction and weather cycles.
2. The relatively high RCP results of the core samples and petrographic analysis in I-75 section suggests that the potential for concrete material degradation and punch-out distress is high. The microscopic examination of core samples obtained from I-75 documented the presence of microcracks and ettringite, which is conclusive evidence of ASR damage and temperature-related deformation. Furthermore, these distresses increase the potential for concrete tensile failure, which might have ultimately caused the observed distress, specifically longitudinal cracks.
3. The distresses found on I-75 are unique in that they are not commonly observed on pavements in Georgia although it should be noted that the I-75 JPCP section is an "old" section beyond its design life (>20 years).
7.2 Continuously Reinforced Concrete (CRC) Pavement - Conclusions and Recommendations The distress in I-85 MP 54-55 in "poor" condition is mainly depicted by transverse cracks
spaced at intervals less than 1 foot on center. Based on the findings of this investigation:
1. The cause of the observed distress on I-85 MP 54-55 in "poor" condition is the result of a combination of factors including poor material composition, aggregate segregation, soft paste (of Mohs 3 hardness), and environmental conditions such as thermal (or moisturerelated) expansion/contraction and weather cycles.
74

2. Improper consolidation and irregularity in rebar cover depth may be attributed to roadway profiling, workmanship, and construction processes.
3. Closely spaced crack spacing (cluster cracking) is normal for CRC pavements in Georgia. However, the punchout locations in MP 55 inside lane should be investigated in more detail.
4. It is highly recommended to develop a 5 year monitoring program of CRCP sections in Georgia, in order to systematically identify signs of distress (e.g., crack width, longitudinal cracks, and punchout distress) and recognize the right (most economical) time for providing any rehabilitation, if needed. Although GDOT currently maintains concrete pavements on its interstate highways and state routes using CPACES, assessment of CRCP rating is based on distress types, which are more critical to JPCP rating assessment (I.e., faulting). As critical distress types to assess JPCP and CRCP conditions are quite different, development of a systematic CPACES rating methodology for Georgia CRCP are recommended to optimize the most economical time for maintenance and rehabilitation.
7.3 Hot Mix Asphalt (HMA) Pavement - Conclusions and Recommendations
A forensic investigation of two HMA sections in "fair" and "poor" condition was conducted. The distress observed in both pavement sections is mainly depicted by longitudinal cracking and raveling. Based on the findings of this investigation:
1. SR-38 shows longitudinal cracking and this cracking seems to be reflected from the soilcement layer. It seems that the reflected longitudinal cracking in the left wheel path of the outside lane has been worsened by traffic.
2. Although SR-38 contains raveling and longitudinal cracking, the pavement is structurally sound based on FWD evaluation. In areas where longitudinal cracks are prevalent, it is recommended to mill and overlay the affected areas.
3. In SR-54, the extreme longitudinal cracking and raveling may have occurred as a result of widening between two existing pavement layers that were constructed at different times. The distresses have been worsened by increased traffic loadings thereafter. Based
75

on AASHTO 1993 design guide, a major rehabilitation is recommended on this test section.
8. NCHRP RECOMMENDATIONS Using the National Cooperative Highway Research Program (NCHRP) Report 747
(Guide for Conducting Forensic Investigations of Highway Pavements) was very helpful throughout this investigation. The guide contains a very structured method for carrying out each step of the forensic investigation. Information is clear and easy to follow for pavement engineers who may not have much experience. In regard to recommended testing, each pavement type (JPCP, CRCP, HMA) is covered in meticulous detail. The guide also provides recommendations on how to analyze causes of pavement distress. Based on the experience of conducting a forensic investigation using the NCHRP Report 747, it is highly recommended for GDOT's adoption as the Forensic Pavement Guide for Georgia, with the following additions/recommendations:
A comprehensive forensic investigation is very extensive, expensive, and time consuming. Precautions should be exercised to determine whether a full investigation is needed. It is recommended to determine the level of forensic analysis based on the "Phased Approach to Forensic Investigations" diagram in the NCHRP 747 Guideline (Appendix A).
Rather than using NCHRP visual condition survey form, it is recommended to use the GDOT's visual inspection forms that have been used for PACES update (Appendices B and C). However, development of new methodology to assess PACES rating for CRCP is strongly recommended as current methodology doesn't reflect the functional condition evaluation of CRCP properly.
Based on the GDOT RP 14-13 study, flow charts for pavement forensic investigations were developed (Appendices D, E, and F). The flow charts will provide the GDOT engineers with a systematic procedure when pavement forensic investigations deemed necessary.
Traffic information along with pavement service life has large impact on pavement design and performance. To accurately investigate the pavement performance, it is
76

recommended that traffic information is efficiently archived and easily accessible. This includes: traffic volumes, traffic loads/load spectra, traffic growth, seasonal trends, load restrictions, and any related traffic information during entire pavement service life. It is recommended that all construction documents be efficiently archived and easily accessible when forensic investigations are started. This includes: all construction drawings, rehabilitation history, mix design, and other construction information.
77

9. REFERENCES
1. AASHTO (American Association of State Highway and Transportation Officials). (1993). "Guide for Design of Pavement Structures." Volume 1. Washington, D.C.
2. AASHTO, T 277 (2008). "Standard Method of Test for Electrical Indication of Concrete's Ability to Resist Chloride Ion Penetration". Standard Specifications for Transportation Materials and Methods of Sampling and Testing.
3. AASHTO, T 308 (2010). Determining the Asphalt Binder Content of Hot Mix Asphalt (HMA) by the Ignition Method. Standard Specifications for Transportation Materials and Methods of Sampling and Testing.
4. AASHTO, T 336 (2011). Coefficient of Thermal Expansion of Hydraulic Cement Concrete. Standard Specifications for Transportation Materials and Methods of Sampling and Testing.
5. AASHTO, T 166 (2015). Bulk Specific Gravity of Compacted Asphalt Mixtures using Saturated Surface-Dry Specimens. Standard Specifications for Transportation Materials and Methods of Sampling and Testing.
6. AASHTO, T 209 (2015). Theoretical Maximum Specific Gravity and Density of Hot Mix Asphalt. Standard Specifications for Transportation Materials and Methods of Sampling and Testing.
7. Adaska, Wayne S., and David R. Luhr. (2004). Control of reflective cracking in cement stabilized pavements. Proceedings of 5th International RILEM Conference on Cracking in Pavements.
8. ARA, Inc. ERES Division (2004). Guide for Mechanistic-Empirical Design of New and Rehabilitated Pavement Structure, Final Report NCHRP 1-37A, Transportation Research Board of the National Academies, Washington, D.C.
9. ASTM (American Society for Testing and Materials) D 4694 (2003). "Standard Test Method for Deflections with a Falling-Weight-Type Impulse Load Device." 1996 (Reapproved 2003). ASTM International, PA, USA.
10. ASTM, D 6432 (2011). "Standard Test Method for Deflections with a Falling-WeightType Impulse Load Device." ASTM International, PA, USA.
11. ASTM, C. (2012). 1202-12. "Standard Test Method for Electrical Indication of Concrete's Ability to Resist Chloride Ion Penetration." ASTM International, PA, USA.
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12. Bandini, P., Halter, S. B., Montoya, K. R., Pham H. V., and Migliaccio, G. C. (2012). "Improving NMDOT's Pavement Distress Survey Methodology and Developing Correlations between FHWA's HPMS Distress Data and PMS Data." New Mexico Department of Transportation Report No. NM10MNT-01.
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24. FHWA. (2006) "Long-Term Pavement Performance Program Manual for Falling Weight Deflectometer Measurements." (FHWA-HRT-06-132). Version 4.1. Washington, D.C.
25. FHWA. (2007). "Technical Report: Hamburg Wheel-Tracking Database" FHWA/TX05/0-1707-7 Washington, DC, FHWA.
26. FHWA. (2010). "TechBrief: Superpave Mix Design and Gyratory Compaction Levels" FHWA-HIF-11-031. Washington, DC, FHWA.
27. FHWA. (2012). "TechBrief: Continuously Reinforced Concrete Pavement Performance and Best Practices" FHWA-HIF-12-039 Washington, DC, FHWA.
28. FHWA. (2016). "Testing the Chloride Penetration Resistance of Concrete: A Literature Review, completed under Contract DTFH61-97-R-00022." <https://www.fhwa.dot.gov/publications/research/infrastructure/structures/chlconcrete.pdf> (Feb. 15, 2016).
29. FHWA. (2016b). "Chapter 13.2.3 Porosity Related to Carbonation." <http://www.fhwa.dot.gov/publications/research/infrastructure/pavements/pccp/04150/ch apt13.cfm#por> (Feb. 15, 2016).
30. FHWA. (2016c). "Pavements- Partial-Depth Repairs." https://www.fhwa.dot.gov/pavement/-concrete/repair04.cfm. (Feb. 15, 2016).
31. FHWA. (2016d). "Pavements- Concrete Pavement Rehabilitation Guide for Diamond Grinding." <https://www.fhwa.dot.gov/pavement/concrete/diamond.cfm> (Feb. 15, 2016).
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34. Huang, C., & Huang, X. (2014). "Effects of pavement texture on pavement friction: a review." International Journal of Vehicle Design, 65(2-3), 256-269.
35. Huang, Y. H. (1993). Pavement Analysis and Design. Pearson Education Inc., U.S.A. 36. INDOT (2013). Design Manual.
http://www.in.gov/indot/design_manual/files/Ch52_2013.pdf. Accessed on July 20, 2016.
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37. Izzo, Richard, and Maghsoud Tahmoressi. (1999) "Use of the Hamburg wheel-tracking device for evaluating moisture susceptibility of hot-mix asphalt." Transportation Research Record: Journal of the Transportation Research Board 1681.76-85.
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APPENDIX A
NCHRP Guide 747 "Phased approach to forensic investigations"

Figure A4.1. Phased Approach to Forensic Investigations.

APPENDIX B
Visual Assessment form for AC pavement

APPENDIX C
Visual Assessment form for PCC pavement

APPENDIX D
Flow Charts for Forensic Investigation of Asphalt Pavement

Table D.1. GPR Performing Details.

GPR

Location

Identical to FWD location

Frequency

2 Scans/Mile (for thickness) 20 Scans/mile (for distress and problem identification)

Radar Frequency

> 1 GHz

Scan Depth

< 3ft

Dielectric Value

3 to 5.

Table D.2. FWD Performing Details.

FWD

50 ft., if Section Length < 2 miles

Location and interval

100 ft., if : 2 miles <Section length < 4 miles 250 ft., if :Section Length > 4 miles 3 to 15 ft. (1 to 5 m) in defined problem areas; offset in adjacent lanes

The surface temp. > 60F (15C)

Table D.3. NDT on Asphalt Surfaced Pavements.

Table D.4. Example NDT Intervals. Table D.5. Example Modulus Ranges for Different Layer Types.

Table D.7. Field Testing Activities for Collecting Supplemental Data. Table D.8. Tests for End-State Physical Properties of Pavement Materials

Figure D.1. Core Locations for LTPP-AC Surfaced Test Section Figure D.2. Crack Core Locations for LTPP AC Test Section

Figure D.3. Trench Locations for LTPP Test Section
Figure D.4. Dynamic Cone Penetration, Falling Weight Deflectometer, Nuclear Density Gauge, and Saw-Cut Locations

APPENDIX E
Flow Chart for Forensic Investigation of Joint Plain Concrete Pavement

Table E4.2. Examples of NDT on Concrete Surfaced Pavements. Table E4.3. Example NDT Intervals.

Table E6.3. Examples of Laboratory Testing Requirements for Concrete Pavement Investigations

Figure E4.11(a). Example FWD Test Locations on Jointed Plain Concrete Pavements.
Notes: On Concrete pavements, test location on the slab will depend on the issues being investigated. Load transfer efficiency is measured across the joints in the wheel paths, stiffness is measured in the center of the slab, and curling is measured across the joint at the slab corners. Example test locations for jointed concrete pavements are shown in Figure 4.11

Figure E4.11(b). Example FWD Test Locations on Jointed Plain Concrete Pavements. Figure E7.2. Examples of Core Locations for Jointed Plain Concrete Sections.

APPENDIX F
Flow Chart for Forensic Investigation of Continuous Reinforced Concrete Pavement

Table F.1. GPR Performing Details.

Location
Frequency
Radar Frequency Scan Depth
Dielectric Value

GPR Identical to FWD location
2 Scans/Mile (for thickness and concrete cover depth) 20 Scans/mile (for punchout area) > 900 MHz < 3ft 3 to8.

Table F.2. FWD Performing Details.

Location and interval
The surface temp. LTE of CRCP cracks

FWD 50 ft., if Section Length < 2 miles 100 ft., if : 2 miles <Section length < 4 miles 250 ft., if :Section Length > 4 miles 3 to 15 ft. (1 to 5 m) in defined problem areas; offset in adjacent lanes < 77F (23C) LTE must be greater than 75 percent.

Table F.3. NDT on Concrete Surfaced Pavements Table F.4. Example NDT Intervals.

Table F.5. Example Modulus Ranges for Different Layer Types

Table F.7. Field Testing Activities for Collecting Supplemental Data Table F.7. Field Testing Activities for Collecting Supplemental Data

Figure F.1. Core Locations for Continuously Reinforced Concrete Sections. Figure F.2. Test Pit Layout.