Structural Factors for Flexible Pavements—Initial Evaluation of The SPS-1 Experiment Final Report

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Foreword

This report documents a study undertaken to conduct a detailed review of the Long-Term Pavement Performance (LTPP) Special Pavements Study–1 (SPS-1) experiment to determine to what extent it will provide the necessary data to ensure that the objectives and expectations from this experiment are attained.  The SPS-1 experiment entitled Strategic Study of Structural Factors for Flexible Pavements is one of the key experiments of the LTPP program. Its goal is to develop improved methodologies and strategies for the construction of flexible pavements.  The review concentrated on the core experimental test sections with secondary emphasis on the supplemental test sections that were built by the individual agencies for each SPS-1 project. 

As a result of this work, the data availability and completeness for the SPS-1 experiment are fairly complete with two exceptions.  The two critical elements or parameters found to have significant deficiencies are the traffic and materials test data.  These data deficiencies need to be addressed before a comprehensive analysis of the SPS-1 experiment is conducted.  The majority of the SPS-1 data that have been collected are at level E.

This report will be of interest to highway agency engineers involved in the collection, processing, and analysis of SPS-1 data to improve the design procedures and standards for constructing hot-mix asphalt-surfaced pavements.

T. Paul Teng, P.E.
Director, Office of Infrastructure
Research and Development

NOTICE

This document is disseminated under the sponsorship of the U.S. Department of Transportation in the interest of information exchange.  The U.S. Government assumes no liability for its contents or use thereof.  This report does not constitute a standard, specification, or regulation.

The U.S. Government does not endorse products or manufacturers.  Trade or manufacturers’ names appear herein only because they are considered essential to the objective of this document.

TABLE OF CONTENTS

1. INTRODUCTION
   • BACKGROUND
   • STUDY OBJECTIVES
   • SCOPE OF REPORT
2. GENERAL OVERVIEW OF EXPERIMENT
   • ORIGINAL SPS-1 EXPERIMENT DESIGN
   • STATE SUPPLEMENTAL SECTIONS
   • CURRENT STATUS OF DESIGN FACTORIAL
3. PROJECT REQUIREMENTS
   • CONSTRUCTION MATERIAL REQUIREMENTS
   • MATERIALS SAMPLING AND TESTING
   • MONITORING REQUIREMENTS
4. EXPERIMENT ASSESSMENT—DATA AVAILABILITY AND COMPLETENESS
   • LTPP DATA QUALITY CONTROL CHECKS
   • DATA ELEMENT CATEGORIES
   • GENERAL SITE INFORMATION
   • DESIGN VERSUS ACTUAL CONSTRUCTION REVIEW
   • MATERIALS TESTING
   • TRAFFIC
   • MONITORING DATA
   • DYNAMIC LOAD RESPONSE DATA
   • SUMMARY
5. ANALYSIS OF EARLY PERFORMANCE OBSERVATIONS
   • GRAPHICAL COMPARISONS FROM TIME-SERIES DATA
   • ANALYSIS OF VARIANCE
   • EFFECT OF KEY EXPERIMENTAL FACTORS ON PERFORMANCE
   • SUMMARY
6. SUMMARY AND CONCLUSIONS
   • SPS-1 EXPERIMENT STATUS
   • DESIGN VERSUS ACTUAL CONSTRUCTION
   • DATA AVAILABILITY AND COMPLETENESS
   • EARLY PERFORMANCE TRENDS
   • EXPECTATIONS FROM THE STATES
   • CAN THE SPS-1 EXPERIMENT MEET EXPECTATIONS?
   • RECOMMENDATIONS FOR FUTURE ACTIVITIES

APPENDIX A.—SPS-1 PROJECT SUMMARIES

• APPENDIX A. SPS-1 PROJECT SUMMARIES (continued)

• APPENDIX B.—SUMMARY OF CONSTRUCTION DATA (continued)

LIST OF FIGURES

Figure

1. Location of the SPS-1 projects
2. LTPP data collection and data movement flowchart
3. Thickness histograms for the thin HMA layer (102 mm) from tables SPS1_LAYER  (construction data) and TST_L05B
4. Thickness histograms for the thick HMA layer (178 mm) from tables SPS1_LAYER (construction data) and TST_L05B
5. Thickness histograms for the thin ATB layer (102 mm) from tables SPS1_LAYER (construction data) and TST_L05B
6. Thickness histograms for the thick ATB layer (203 mm) from tables SPS1_LAYER (construction data) and TST_L05B
7. Thickness histograms for the PATB layer from tables SPS1_LAYER (construction data) and TST_L05B
8. Thickness histograms for the 102-mm DGAB layer from tables SPS1_LAYER  (construction data) and TST_L05B
9. Thickness histograms for the 203-mm DGAB layer from tables SPS1_LAYER (construction data) and TST_L05B
10. Thickness histograms for the 305-mm DGAB layer from tables SPS1_LAYER  (construction data) and TST_L05B
11. Histogram of air voids measured on the HMA surface layer
12. Histogram of air voids measured on the HMA binder layer
13. Histogram of air voids measured on the ATB layer
14. Histogram of the material passing the number 4 sieve, PATB layer
15. Histogram of material passing the number 200 sieve, PATB layer
16. Histogram of material passing the number 200 sieve, HMA surface layer
17. Histogram of material passing the number 200 sieve, ATB layer
18. Area of fatigue cracking measured over time comparing test sections with and without permeable base layers for all SPS-1 projects combined
19. Total length of transverse cracks measured over time comparing test sections with and without permeable base layers for all SPS-1 projects combined
20. IRI values measured over time comparing test sections with and without permeable  base layers for all SPS-1 projects combined
21. Rut depths measured over time comparing test sections with and without permeable  base layers for all SPS-1 projects combined
22. Longitudinal cracking in the wheel paths measured on different dates for the core test sections of the Alabama project
23. Longitudinal cracking outside the wheel paths measured on different dates for the core test sections of the Alabama project
24. Transverse cracking measured on different dates for the core test sections of the Alabama project
25. Graphical illustration of the average amount of fatigue cracking observed on each of the projects, as of January 2000
26. Percentage of the core test sections that exceed an IRI value of 1.2 m/km
27. Percentage of the core test sections that exceed 8 mm of rutting
28. Percentage of test sections that exceed an IRI value of 1.2 m/km
29. Percentage of core test sections that have fatigue cracking

LIST OF TABLES

Table 

1. Factorial for the SPS-1 experimental design and the sites/projects originally nominated for each cell within the experiment
2. Supplemental sections constructed on SPS-1 projects
3. Final factorial for the SPS-1 experiment design
4. Required testing for the SPS-1 experiment
5. Summary of SPS-1 data elements and their importance to experimental expectations
6. SPS-1 project site information and report availability
7. SPS-1 subgrade classification
8. Summary of key factor values for the SPS-1 projects
9. Summary of materials testing on the subgrade soils
10. Summary of materials testing on the unbound aggregate base materials
11. Summary of materials testing on the permeable asphalt treated base mixtures
12. Summary of materials testing on the asphalt treated base mixtures
13. Summary of materials testing on the HMA mixtures
14. Summary of materials testing completed by material type for the core test sections,  percent complete
15. Summary of climatic and traffic data for the SPS-1 project sites
16. Summary of the minimum number of distress and other performance indicator measurements made at each project site
17. Summary of the average time interval between the different performance indicator surveys   
18. Summary of Level E dynamic load response data for the Ohio SPS-1 project
19. Summary of the overall construction difficulties and deviations, and the adequacy code for the projects included in the SPS-1 experiment
20. Percentage of the SPS-1 core test sections with distress magnitudes exceeding  the value noted
21. Summary of the average area of fatigue cracking observed at each project
22. Summary of p-values from a one-way ANOVA to determine the effect of experimental factors on selected performance indicators
23. Average performance differences of the test sections between the different soil types included in the SPS-1 experiment
24. Average performance differences of the test sections between the different  types of base layers included in the SPS-1 experiment
25. Average performance differences of the test sections between the different drainage conditions included in the SPS-1 experiment
26. Average performance differences of the test sections between the different HMA layer thickness included in the SPS-1 experiment
27. Summary of missing or limited data for the SPS-1 experiment
28. Deficiencies and action items for each SPS-1 project
29. Identification of future research studies from the SPS-1 experiment—initial analysis of the individual factorial cells and companion projects
30. Identification of future research studies from the SPS-1 experiment—overall effect of the main experimental factors on performance
31. Identification of future research studies from the SPS-1 experiment—benefits of drainage
32. Identification of future research studies from the SPS-1 experiment—effect of thickness variations on performance
33. Identification of future research studies from the SPS-1 experiment—effect of base material type on pavement performance
34. Identification of future research studies from the SPS-1 experiment—effect of seasonal changes on pavement response and material responses related to performance
35. Identification of future research studies from the SPS-1 experiment—effect of soil type and stiffness on pavement performance
36. Identification of future research studies from the SPS-1 experiment—effect of base condition on pavement performance
37. Identification of future research studies from the SPS-1 experiment—effect of HMA properties on pavement performance
38. Identification of future research studies from the SPS-1 experiment—quantification of remaining life of cracked or damaged HMA layers
39. Identification of future research studies from the SPS-1 experiment—identify those properties and conditions most conducive to the development of surface initiated fatigue cracks
40. Identification of future research studies from the SPS-1 experiment—applicability of the subgrade protection criteria for use in design of flexible pavements
41. Identification of future research studies from the SPS-1 experiment—confirm the C-values or differences between laboratory measured resilient modulus and back calculated elastic layer modulus
42. Identification of future research studies from the SPS-1 experiment—mechanistic analysis of the SPS-1 sites
43. Summary of key project monitoring data for the Alabama SPS-1
44. Summary of available materials testing data on the Alabama SPS-1
45. Summary of key project monitoring data for the Arizona SPS-1
46. Summary of available materials testing data on the Arizona SPS-1
47. Summary of key project monitoring data for the Arkansas SPS-1
48. Summary of available materials testing data on the Arkansas SPS-1
49. Summary of key project monitoring data for the Delaware SPS-1
50. Summary of available materials testing data on the Delaware SPS-1
51. Summary of key project monitoring data for the Florida SPS-1
52. Summary of available materials testing data on the Florida SPS-1
53. Summary of key project monitoring data for the Iowa SPS-1
54. Summary of available materials testing data on the Iowa SPS-1
55. Summary of key project monitoring data for the Kansas SPS-1
56. Summary of available materials testing data on the Kansas SPS-1
57. Summary of key project monitoring data for the Louisiana SPS-1
58. Summary of available materials testing data on the Louisiana SPS-1
59. Summary of key project monitoring data for the Michigan SPS-1
60. Summary of available materials testing data on the Michigan SPS-1
61. Summary of key project monitoring data for the Montana SPS-1
62. Summary of available materials testing data on the Montana SPS-1
63. Summary of key project monitoring data for the Nebraska SPS-1
64. Summary of available materials testing data on the Nebraska SPS-1
65. Summary of key project monitoring data for the Nevada SPS-1
66. Summary of available materials testing data on the Nevada SPS-1
67. Summary of key project monitoring data for the New Mexico SPS-1
68. Summary of available materials testing data on the New Mexico SPS-1
69. Summary of key project monitoring data for the Ohio SPS-1
70. Summary of available materials testing data on the Ohio SPS-1
71. Summary of key project monitoring data for the Oklahoma SPS-1
72. Summary of available materials testing data on the Oklahoma SPS-1
73. Summary of key project monitoring data for the Texas SPS-1
74. Summary of available materials testing data on the Texas SPS-1
75. Summary of key project monitoring data for the Virginia SPS-1
76. Summary of available materials testing data on the Virginia SPS-1
77. Summary of key project monitoring data for the Wisconsin SPS-1
78. Summary of available materials testing data on the Wisconsin SPS-1

ABBREVIATIONS

AASHTO—American Association of State Highway and Transportation Officials

AC—Asphalt Concrete

ANOVA—Analysis of Variance

AGG—Aggregate bases, identical to dense graded aggregate base

ATB—Asphalt Treated Base

AVC—Automated Vehicle Classification

AWS—Automated Weather Stations

DGAB—Dense Graded Aggregate Base, identical to aggregate base

ESAL—Equivalent Single Axle Load

FHWA—Federal Highway Administration

FWD—Falling Weight Deflectometer

GPS—Global Positioning System

HMA—Hot-Mix Asphalt

HMAC—Hot-Mix Asphalt Concrete

IMS—Information Management System

IRI—International Roughness Index

LTPP—Long-Term Pavement Performance

NAA—National Aggregate Association

NCHRP—National Cooperative Highway Research Program

NIMS—National Information Management System

NOAA—National Oceanic and Atmospheric Association

PATB—Permeable Asphalt Treated Base mixtures

QC/QA—Quality Control/Quality Assurance
RCO—Regional Coordination Office

RIMS—Regional Information Management System

SHA—State Highway Agency

SHRP—Strategic Highway Research Program

SPS—Special Pavement Studies

WIM—Weigh-in-Motion

SPS-1 Project Name Abbreviations