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Publication Number: FHWA-RD-03-040
Date: July 2002

Researcher's Guide to The LTPP Layer Thickness Data

Foreword

This guide summarized the layer material type and thickness data structure in the Long-Term Pavement Performance (LTPP) database. Summaries of layer thickness within-section data variablility and constructed thickness deviations from the target thickness are also provided for LTPP sections; the guide provides several benchmark values for both of these data elements for different material types. Guidelines are also presented to search for the most appropriate thickness information for different research purposes.

This guide will be of interest to highway agency engineers and reearchers involved in pavement design, performance modeling, and construction quality assurance.

 

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

 

Notice

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

The United States Government does not endorse products or manufacturers. Trade or manufacturers' names appear herein only because they are considered essential to the objective of the document.


Technical Report Documentation Page

Technical Report Documentation Page
1. Report No.
FHWA-RD-03-040
2. Government Accession No. 3. Recipient's Catalog No.

4. Title and Subtitle
Researcher's Guide to the Long-Term Pavement Performance Layer Thickness Data

5. Report Date July 30, 2002
6. Performing Organization
7. Author(s)
Y. Jane Jiang, Olga I. Selezneva, and Goran Mladenovic
8. Performing Organization Report No.
9. Performing Organization Name and Address
ERES Division of Applied Research Associates, Inc.
9030 Red Branch Road, Suite 210
Columbia, Maryland 21045
10. Work Unit No.
11. Contract or Grant No.
DTFH61-96-C-00003
12. Sponsoring Agency Name and Address
Office of Infrastructure Research and Development
Federal Highway Administration
6300 Georgetown Pike
McLean, Virginia 22101-2296
13. Type of Report and Period Covered
Final Report
14. Sponsoring Agency Code
15. Supplementary Notes
Contracting Officer's Technical Representative (COTR): Cheryl Allen Richter, HRDI
Work was conducted as part of the LTPP Data Analysis Technical Support Contract.

16. Abstract
The accuracy of layer thickness data has a great impact on the outcome of practically all analyses of pavement performance. A large amount of data related to layer material type and thickness data have been collected as part of the Long Term Pavement Performance (LTPP) Program. The main purposes of this researcher's guide for the LTPP thickness data are to:

  1. Explain to the LTPP data users what and where different types of layer material type and thickness data reside in the LTPP database, as well as the limitations of the data.
  2. Present LTPP thickness within-section variability.
  3. Summarize as-designed versus as-constructed layer thickness comparisons.
  4. Provide guidelines to search for the most appropriate thickness information for different research purposes.

Field sampling, materials testing, and other layer thickness data collection activities utilized by LTPP are discussed, along with the characterization of the within-sectin thickness variation and designed versus constructed thickness data variations for the LTPP sections. Findings from this study are applicable to pavement design reliability and construction quality assurance applications.

17. Key Words
Asphalt pavements, concrete pavements, LTPP, layer thickness, thickness variation, sampling
18. Distribution Statement
No restrictions. This document is available to the public through the National Technical Information Service, Springfield, Virginia 22161.
19. Security Classif. (of this report)
Unclassified
20. Security Classif. (of this page)
Unclassified
21. No. of Pages
65
22. Price

 

SI* (Modern Metric) Conversion Factors


 

Contents

LIST OF FIGURES

LIST OF TABLES

LIST OF ABBREVIATIONS

Table of Contents

  1. INTRODUCTION

  2. LTPP LAYER THICKNESS DATA

  3. LTPP THICKNESS DATA WITHIN-SECTION VARIABILITY

  4. VARIATION IN AS-DESIGNED AND AS-CONSTRUCTED LAYER THICKNESS DATA

  5. RECOMMENDED LAYER THICKNESS DATA SOURCES IN THE LTPP DATABASE

  6. ADDITIONAL INFORMATION

    REFERENCES

List of Tables

Table 1. Code list and code descriptions for "DESCRIPTION."

Table 2. Code list and code descriptions for code "MAT_TYPE."

Table 3. Code list and code descriptions for code "VISUAL_ACPC."

Table 4. Code list and code descriptions for code "COMMENT."

Table 5. Sampling requirements for visual examination and thickness of AC cores.

Table 6. Detailed SPS sampling requirements for visual examination and thickness of AC cores.

Table 7. Summary of the sampling and testing plan for thickness measurement and visual examination of PCC cores.

Table 8. Detailed SPS sampling requirements for PCC core visual examination and length measurement.

Table 9. Code list and code descriptions for code "MATERIAL."

Table 10. Code list and code descriptions for code "LAYER_TYPE."

Table 11. Code list and code descriptions for code "MEASURE_TYPE."

Table 12. Code list and code descriptions for code "L05B_COMMENT_CODES."

Table 13. Summary of layer thickness COV and standard deviations based on core measurements.

Table 14. Summary of layer thickness COV and standard deviations based on SPS elevation measurements.

Table 15. Design layer thicknesses for the SPS-1 experiment.

Table 16. Design layer thicknesses for the SPS-2 experiment.

Table 17. Design layer thicknesses for the SPS-5 experiment.

Table 18. Design layer thicknesses for the SPS-6 experiment.

Table 19. Design layer thicknesses for the SPS-7 experiment.

Table 20. Design layer thicknesses for the SPS-8 experiment.

Table 21. Summary of differences between mean elevation thickness measurements and target thicknesses.

Table 22. Summary of differences between mean core thickness measurements and target thicknesses.

Table 23. Distribution of the mean thickness deviations from the design thickness based on kurtosis and skewness tests.

List of Figures

Figure 1: Chart. Example distribution of layer thickness measurements along the section for AC surface and binder layer for the SPS-1 Section 55-0118.

Figure 2: Chart. Example distribution of layer thickness measurements along the section for PCC surface layer for the SPS-8 Section 39-0809.

Figure 3: Chart. Example of normally distributed thickness deviations (elevation data, LC, target thickness 152 mm [6 in]).

Figure 4: Chart. Example of a skewed distribution for layer thickness deviation (core data, PCC, target thickness 279 mm [11 in]).

List of Abbreviations

AC = Asphalt concrete (surface course).
AASHTO = American Association of State Highway and Transportation Officials.
ASTM = American Society for Testing and Materials.
ATB = Asphalt-treated base (dense-graded, generally similar to the AC surface course).
COV = Coefficient of variation.
CRCP = Continuously reinforced concrete pavement.
CTB = Cement-treated base.
DGAB = Dense-graded aggregate base (unbound).
DGATB = Dense-graded asphalt-treated base (bound).
FHWA = Federal Highway Administration.
FWD = Falling Weight Deflectometer.
GB = Granular base.
GPR = Ground Penetrating Radar.
GPS = General Pavement Studies.
HMAC = Hot-mix asphalt concrete.
JPCP= Jointed plain concrete pavement.
JRCP= Jointed reinforced concrete pavement.
LC= Lean concrete (base).
LTPP= Long Term Pavement Performance [program].
OD = Outside diameter.
PCC = Portland cement concrete.
PATB = Permeable asphalt-treated base.
QA = Quality assurance.
QC = Quality control.
RSC = Regional Support Contractor.
SHRP = Strategic Highway Research Program.
SB = Surface and binder [layer].
SPS = Specific Pavement Studies.


The Federal Highway Administration (FHWA) is a part of the U.S. Department of Transportation and is headquartered in Washington, D.C., with field offices across the United States. is a major agency of the U.S. Department of Transportation (DOT).
The Federal Highway Administration (FHWA) is a part of the U.S. Department of Transportation and is headquartered in Washington, D.C., with field offices across the United States. is a major agency of the U.S. Department of Transportation (DOT). Provide leadership and technology for the delivery of long life pavements that meet our customers needs and are safe, cost effective, and can be effectively maintained. Federal Highway Administration's (FHWA) R&T Web site portal, which provides access to or information about the Agency’s R&T program, projects, partnerships, publications, and results.
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