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.

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.

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Contents

LIST OF FIGURES

LIST OF TABLES

LIST OF ABBREVIATIONS

Table of Contents

1. INTRODUCTION
   • Background
   • Purpose and Scope of the Guide
   • Guide Organization
   
   
   
2. LTPP LAYER THICKNESS DATA
   • Inventory Layer Thickness Data
   • Rehabilitation Layer Thickness Data
   • Laboratory Core Examination Data
   • Field Elevation Measurements
   • Field Layer Material Type and Thickness Measurements
   • Layer Material Type and Thickness Summary Data
   
   
   
3. LTPP THICKNESS DATA WITHIN-SECTION VARIABILITY
   • Data Sources
   • Typical Values for Variability Indicators from LTPP
   • Layer Thickness Distribution Type
   • Summary of Layer Thickness Variability Assessment
   
   
   
4. VARIATION IN AS-DESIGNED AND AS-CONSTRUCTED LAYER THICKNESS DATA
   • Data Sources
   • Typical Deviations Between the Mean Measured and the Design Thicknesses
   • Analysis Results From Designed Versus Constructed Thicknesses Comparisons
   
   
   
5. RECOMMENDED LAYER THICKNESS DATA SOURCES IN THE LTPP DATABASE
   • Recommended Layer Thickness Data Sources for Section-Level Analyses
   • Recommended Layer Thickness Data Sources for Location-Specific Analyses
   • Recommended Layer Thickness Variability Data Sources
   
   
   
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.