Skip to contentUnited States Department of Transportation - Federal Highway Administration FHWA Home
Research Home   |   Pavements Home
REPORT
This report is an archived publication and may contain dated technical, contact, and link information
Publication Number: FHWA-HRT-10-066
Date: October 2011

 

Impact of Design Features on Pavement Response and Performance in Rehabilitated Flexible and Rigid Pavements

Chapter 3. Overview of LTPP Maintenance and Rehabilitation Experiments

Introduction

Data from LTPP SPS-5 and SPS-6 experiments provided information to gain an understanding of the effects of design and construction features on pavement response and performance of rehabilitated flexible and rigid pavements. In addition, SPS-3 and SPS-4 experiments contain pavement performance data collected over the years for the sections subjected to different preventive maintenance treatments. The data from these experiments were used as primary data source for this study as follows:

SPS-3 and SPS-4 experiments were constructed in 1990 to evaluate the effectiveness of and to determine the optimum timing for applying preventive maintenance treatments for flexible and rigid pavements. SPS-5 and SPS-6 experiments provide critical information to support pavement rehabilitation decisions. The primary objective of these experiments was to develop conclusions concerning the effectiveness of rehabilitation techniques and strategies and their contribution to pavement performance and service life.

SPS-3 Experiment

Experimental Design

An experimental design for SPS-3 was developed to help determine the impact of important factors on the pavement performance changes caused by selected preventive maintenance treatments. Major factors included environment, traffic, subgrade type, structural capacity, and condition prior to treatment for the test sections applied to flexible pavements.

At each site, SPS-3 examined the performance of four preventive maintenance treatments on flexible pavement sections: thin overlay, slurry seal, crack seal, and chip seal. The experiment design stipulated that the effectiveness of each of the four treatments be evaluated independently. The effectiveness of combinations of treatments was not considered; therefore, each test site included the following four treated test sections in addition to a control section:

SPS-3 Sections

SPS-3 experiments were initiated at 81 sites in the United States and Canada in 1990 and 1991. In many cases, these sites were linked to a GPS section that served as a control section. Most of these GPS control sections were from the GPS-1, GPS-2, and GPS-6 experiments.

The sections with thin overlays were nominally 1.5 inches (38.1 mm) thick and were placed
by State and Provincial highway agencies using their own AC mixes. The slurry seals and chip seals were placed by four different contractors, one from each LTPP region. The material specifications were the same for all four regions. Crack sealing was executed by four different crews-one from each LTPP region. The material used for crack sealing was the same for all sites in all regions, but crack sealing application procedures varied.

A summary of SPS-3 sites and conditions is provided in table 7. The climate condition was defined based on the freeze index and average rainfall for each site. Sites with an average annual rainfall greater than 39 inches (1,000 mm) were classified as wet, and those with less than
39 inches (1,000 mm) of rain were catalogued as dry. Similarly, the sites with a freeze index greater than 140 °F (60 °C) were classified as a freezing climate and those with a freeze index less than 140 °F (60 °C) were designated as a no-freeze climate. By March 1, 2006, all SPS-3 sites were deassigned from the experiment, and data collection stopped. The LTPP database contains information for 370 core SPS-3 sections.

Table 7. SPS-3 categorization.

Condition at Beginning of Experiment

Wet

Freeze

No-Freeze

Fine Subgrade

Coarse Subgrade

Fine Subgrade

Coarse Subgrade

Low Traffic

High Traffic

Low Traffic

High Traffic

Low Traffic

High Traffic

Low Traffic

High Traffic

Good

21-A300

 

26-C300

   

5-A300

47-B300

 

24-A300

 

27-A300

   

48-F300

48-A300

 

42-B300

 

29-B300

     

48-I300

 

17-A300

 

36-B300

     

28-A300

 

Fair

19-A300

18-A300

   

47-A300

47-C300

 

1-A300

21-B300

26-B300

   

48-H300

40-C300

 

1-C300

26-D300

           

40-B300

             

48-G300

Poor

 

51-A300

17-B300

36-A300

 

48-B300

53-C300

1-B300

 

87-A300

27-B300

42-A300

     

12-B300

 

87-B300

27-D300

89-A300

     

12-C300

 

29-A300

 

26-A300

       
     

27-C300

       

Dry

Good

16-A300

   

16-B300

48-K300

 

48-J300

48-D300

     

49-C300

   

48-A300

48-M300

     

16-C300

       
     

83-A300

       

Fair

30-A300

 

56-A300

32-B300

48-Q300

   

4-D300

31-A300

 

6-A300

32-C300

48-E300

   

48-N300

Poor

20-B300

90-A300

56-B300

53-A300

 

40-A300

 

4-A300

8-A300

 

49-A300

90-B300

     

4-B300

20-A300

 

49-B300

       

4-C300

8-B300

 

32-A300

       

48-L300

   

53-B300

         

Note: The numbers in each cell represent the State code followed by the site ID. Blank cells indicate that data are not available.

SPS-4 Experiment

Experimental Design

The purpose of the SPS-4 experiment was to assess the effects of selected rigid pavement maintenance treatments, joint/crack sealing, and joint undersealing on performance relative to the performance of untreated control sections. The experiment design stipulated that the effectiveness of each of the two treatments be evaluated independently at each SPS-4 site.

The experimental design for the main SPS-4 experiment incorporated the same primary experimental factors as in the GPS experiments: climatic zone, subgrade type, and traffic level. The original experimental design for SPS-4 included two second-level factors: type of subbase (granular or stabilized) and condition at the time of treatment (good, fair, or poor). The following maintenance treatments were considered:

Both JPCP and JRCP were included in the study. The treatment sections on joint/crack
sealing test sites consisted of one section in which all joints had no sealant and one in which a watertight seal was maintained on all cracks and joints. Undersealing was included as an optional experiment factor and was performed only on the sections in which the need for undersealing was indicated.

As originally designed, the matrix of cells for this experiment could not be filled out because some agencies were unwilling to provide sites for the SPS-4 study. A primary concern was the use of undersealing as a preventive maintenance treatment. Therefore, the SPS-4 study was modified to allow agencies to participate in installation of sections with joint/crack sealing and undersealing, joint/crack sealing only, or undersealing only. As a result, the standard experiment layout included a test section with silicone sealant and a control section with unsealed joints. In addition, separate undersealed test sections were constructed at eight test sites.

The final experiment design for SPS-4 was reduced to the following factors for JPCP:

For JRCP, only the wet moisture level was considered.

The SPS-4 experiment included 35 sites in the United States and Canada during 1990 and 1991 and 1 site in Colorado in 1995. Table 8 shows SPS-4 experimental factorials using as-built information.

Table 8. SPS-4 experimental design.

Experimental Factors

Freeze

No-Freeze

Fine Subgrade

Coarse Subgrade

Fine Subgrade

Coarse Subgrade

Plain

Wet

Dense

   

19-A400

19-B400

40-A400

     

Stabilized

18-A400

21-A400

39-A400

39-B400

48-A400

     

Dry

Dense

46-A400

 

6-B400

8-A400

   

4-A400

6-A400

   

31-B400

32-A400

   

48-C400

 
   

49-C400

49-D400

       
   

49-E400

         

Stabilized

31-A400

31-C400

           

Reinforced

Wet

Dense

29-A400

29-B400

       

5-A400

5-B400

42-A400

42-C400

       

48-E400

 

Stabilized

       

5-C400

28-A400

   
       

48-B400

48-D400

   

Dry

Dense

20-B400

             

Stabilized

20-A400

             

Note: The numbers in each cell represent the State code followed by the site ID. Blank cells indicate that data are not available.

By March 1, 2006, all SPS-4 sites were deassigned from the experiment. The LTPP database contains information for 79 core SPS-4 sections.

SPS-5 Experiment

Experiment Design

The objective of the LTPP SPS-5 experiment was to help develop improved methodologies and strategies for the rehabilitation of flexible pavements. The experiment was designed to evaluate common rehabilitation techniques currently implemented in the United States and Canada. The factors considered in the experiment included the structural and functional condition of the pavement before overlay, the environmental and traffic loading of the test sections, and the various treatment applications.

The SPS-5 experiment provides a means to compare rehabilitated HMA pavement performance using different surface preparation intensities, overlay thicknesses, and overlay mixtures. It also can be used to determine the appropriate timing of rehabilitation and to evaluate the life-cycle cost of different rehabilitation actions.

The experiment was designed to compare the effect of the following variations on performance of rehabilitated pavements:

Variation of surface preparation alternatives, overlay material, and overlay thickness led to eight design combinations at each SPS-5 site (see table 9). One additional section was assigned as a control section and did not receive any overlay, except for routine maintenance, for a total of nine experimental sections. All test sections were designed to be 500 ft (152.4 m) long over a fine-grained subgrade with minimum annual traffic over the test sections of 85,000 equivalent single axle loads (ESALs).

Table 9. Core sections of SPS-5 experiment.

LTPP ID

Overlay Type

0501

Control: No treatment

0502

Thin overlay (2 inches): Recycled HMA mix

0503

Thick overlay (5 inches): Recycled HMA mix

0504

Thick overlay: Virgin mix

0505

Thin overlay: Virgin mix

0506

Thin overlay: Virgin mix with milling

0507

Thick overlay: Virgin mix with milling

0508

Thick overlay: Recycled mix with milling

0509

Thin overlay: Recycled mix with milling

1 inch = 25.4 mm

Final Factorial of SPS-5 Experiment

A total of 18 SPS-5 projects were constructed between 1989 and 1998. The as-built status of the SPS-5 design factorial is shown in table 10. All projects are located in the appropriate cells based on the actual environmental data. Additionally, all of the cells have at least two projects except for the wet no-freeze fair condition and the dry freeze poor condition. A total of 210 test sections (162 core test sections plus 48 supplemental sections) were built as part of the SPS-5 experiment.

Table 10. Constructed SPS-5 sites for the experimental factorial.

Pavement Condition

Soil Classification

Climate, Moisture/Temperature

Wet Freeze

Wet
No-freeze

Dry Freeze

Dry
No-freeze

Fair

Coarse/fine

Georgia

 

Colorado

 

Coarse

New Jersey

 

Alberta, Canada

New Mexico

Montana

Fine

   

Minnesota

Oklahoma

Texas

Poor

Coarse/fine

   

Manitoba, Canada

California

Coarse

Maine

Florida

 

Arizona

Alabama

Fine

Maryland

Mississippi

   

Missouri

Note: Blank cells indicate data are not available.

One major deviation from the original SPS-5 experimental plan was the subgrade soil type. Originally, the subgrade soils for all SPS-5 projects were supposed to be fine-grained soils. Only six of the SPS-5 projects actually had fine-grained soils. Four SPS-5 projects had soils that varied between fine and coarse grained. The subgrade soils for the remaining eight SPS-5 projects were classified as coarse grained.

SPS-6 Experiment

Experimental Design

The goal of the SPS-6 experiment was to develop improved methodologies and strategies for the rehabilitation of concrete pavements. The experiment was designed to investigate the effects of the specific experimental rehabilitation design features on pavement performance.

The factors considered in the experiment were overlay thickness, various restoration activities, and site conditions such as existing pavement condition, subgrade soil, traffic, and climate. The interactions of these factors also were considered.

The SPS-6 experiment included both JPCP and JRCP. The experiment design examined the effects of the following factors:

The SPS-6 experimental plans were originally designed to incorporate project sites in all four LTPP climatic regions and on both fine- and coarse-grained subgrades. Every project constructed as part of the SPS-6 experiment had eight core pavement sections that represented eight different rehabilitation alternatives. These rehabilitation alternatives included variations in pavement preparation, restoration, AC overlay thickness, and additional treatments (saw and seal and crack and seat).

Table 11 lists the eight core experiment sections required for an SPS-6 project. Each section varies by a combination of the extent of pavement preparation, other treatments (saw and seal of the AC overlay and crack and seat), and the overlay thickness. It was also required that at least six of these core sections had 500-ft (152-m) nondestructive performance monitoring areas and that two had 1,000-ft (305-m) areas with an additional 49 ft (15 m) on each end for destructive testing. In addition, traffic in the test lane should have exceeded 200,000 ESALs per year.

Table 11. Core sections of the SPS-6 experiment.

Strategic Highway Research Program (SHRP) ID

Overlay
Thickness (mm)

PCC Preparation

0601

-

Routine maintenance (control)

0602

-

Minimum restoration

0603

102

Minimum restoration

0604

102

Minimum restoration (saw and seal AC over joints)

0605

-

Maximum restoration

0606

102

Maximum restoration

0607

102

Crack/break and seat

0608

203

Crack/break and seat

1 inch = 25.4 mm
Note: The dashes indicate that the section did not receive an overlay.

Final Factorial of SPS-6 Experiment

The SPS-6 experiment contained 14 sites constructed between 1989 and 1998. Table 12 shows the constructed SPS-6 sites in relation to the experiment factorial. A total of 112 core sections and 58 State supplemental sections have been constructed for the SPS-6 experiment.

Table 12. As-built SPS-6 sites for the experimental factorial.

Pavement Type

Pavement Condition

Climate/Moisture/Temperature

Wet Freeze

Wet
No-freeze

Dry Freeze

Dry
No-freeze

JPCP

Fair

Missouri*

Alabama and Tennessee

South Dakota*

 

Poor

Indiana*

Arkansas*

Arizona and California

 

JRCP

Fair

Iowa, Michigan, and Pennsylvania

Oklahoma*

 

N/A

Poor

Illinois and Missouri

   

N/A

* Represents a single additional site that is needed to complete the original design matrix.
N/A indicates data are not available because there were no JRCP sections in that area of the country.
Note: Blank cells indicate that no section was available at the combination of climate and pavement conditions
for that particular pavement type.

Overview of the LTPP Data Relevant to this Study

Information in the LTPP database is divided into the following modules:

Each of these modules contains tables that provide information on the various design features and performance measurements of a particular pavement section. For the data elements identified, the LTPP data were examined to determine the extent of availability for all the data elements. The most current LTPP data release was used (23d released in January 2009).

Data extracted from the LTPP database were imported to a Microsoft Access® file and stored in relational databases so that they could be manipulated and linked together for different analyses.

Assessment of SPS-3 Data

Various tables containing data pertinent to the SPS-3 experiment were examined. Table 13 provides a summary of SPS-3 data availability including the location, number of surveys, number of treatments, and the observation period for each section. For example, all sections of the 1-A300 project were surveyed six times except for the control section, which was surveyed five times. The sections receiving thin overlay, slurry seal, and crack seal were treated twice, while chip seal and control section were treated once. The difference between the first and the last survey was 9 years for all sections except for the control section, which was 8 years. There were no data available for the cells left blank. The tables from the LTPP database used for this assessment were as follows:

The sample size for the SPS-3 experiment should allow for meaningful conclusions and should not just allow comparisons between treatments but also comparisons for the effectiveness of treatments for different conditions (e.g., environmental conditions).

Table 13. Data availability for SPS-3 sites.

State Code

SHRP ID

Number of Surveys

Number of Treatments

Number of Years

Thin Overlay

Slurry Seal

Crack Seal

Control Section

Chip Seal

Thin Overlay

Slurry Seal

Crack Seal

Control Section

Chip Seal

Thin Overlay

Slurry Seal

Crack Seal

Control Section

Chip Seal

1

A300

6

6

6

5

6

2

2

2

1

1

9

9

9

8

9

1

B300

5

5

5

5

5

2

2

1

0

1

7

7

7

7

7

1

C300

8

8

8

8

5

1

1

7

0

3

12

12

12

12

7

4

A300

3

3

3

3

3

1

1

1

1

1

4

4

4

4

4

4

B300

 

1

1

5

1

 

2

1

4

2

 

0

0

9

0

4

C300

4

2

3

3

4

2

2

2

0

1

6

1

3

3

4

4

D300

3

1

2

5

1

1

2

2

2

1

6

0

3

12

0

5

A300

8

8

 

8

8

1

1

 

1

1

13

13

 

13

13

6

A300

6

7

7

7

7

2

3

1

0

1

12

13

13

13

13

8

A300

2

2

2

2

2

1

1

2

0

1

3

3

3

3

3

8

B300

2

2

2

3

2

1

1

1

0

2

0

0

0

3

0

12

A300

6

6

6

6

6

1

1

1

0

1

6

6

6

6

6

12

B300

4

4

4

6

4

1

1

1

1

1

4

4

4

9

4

12

C300

7

6

6

6

6

1

3

4

7

1

7

6

6

6

6

16

A300

5

5

5

6

5

1

1

1

1

1

14

14

14

14

14

16

B300

6

6

6

7

6

1

1

1

0

1

14

14

14

14

14

16

C300

4

4

4

14

4

1

1

1

0

1

7

7

7

7

7

17

A300

8

8

8

8

8

1

1

2

0

1

14

14

14

14

14

17

B300

8

7

7

7

7

2

1

2

1

1

14

14

14

14

14

18

A300

6

7

6

6

6

1

1

1

0

1

4

5

4

4

4

19

A300

4

4

4

4

4

1

1

1

0

1

3

3

3

3

3

20

A300

6

6

6

5

6

2

2

2

0

2

10

10

10

9

10

20

B300

6

6

6

6

6

1

2

2

0

1

7

7

7

7

7

21

A300

4

4

5

4

4

1

1

1

0

1

3

3

4

2

3

21

B300

6

6

5

4

4

1

1

1

0

1

7

7

4

3

3

24

A300

7

7

7

7

7

1

1

1

0

1

8

8

8

8

8

26

A300

4

5

5

5

4

2

1

1

1

1

4

5

5

5

3

26

B300

5

5

5

5

5

1

1

1

1

2

5

5

5

5

5

26

C300

5

5

5

5

5

1

1

1

0

1

5

5

5

5

5

26

D300

5

5

5

5

5

1

1

1

0

1

5

5

5

5

5

27

A300

3

3

3

3

3

1

1

1

0

1

5

5

5

5

5

27

B300

4

4

4

4

4

1

1

1

0

1

5

5

5

5

5

27

C300

4

3

3

3

2

1

1

1

0

1

5

5

5

5

5

27

D300

4

3

1

3

4

2

1

1

0

1

2

4

0

4

5

28

A300

5

5

5

13

5

1

1

2

2

1

8

8

8

11

8

29

A300

8

8

8

8

8

2

2

2

0

1

14

14

14

14

15

29

B300

8

7

7

7

7

1

1

1

0

1

13

13

13

13

13

30

A300

5

5

5

5

5

1

1

1

0

1

8

8

8

8

8

31

A300

5

6

6

6

6

1

1

1

0

1

5

5

5

5

5

32

A300

4

3

3

3

4

1

3

3

1

2

6

6

6

6

6

32

B300

3

3

3

3

3

1

2

1

0

1

6

6

6

6

6

32

C300

2

2

2

4

2

1

1

1

2

1

1

1

1

6

1

36

A300

7

7

7

7

7

2

1

1

1

1

7

7

7

7

7

36

B300

6

6

6

6

6

1

1

1

0

1

7

7

7

7

7

40

A300

 

5

5

5

5

 

1

0

0

1

 

6

6

6

6

40

B300

6

6

6

7

6

1

1

2

0

1

8

8

8

13

8

40

C300

4

4

4

2

4

1

3

1

1

1

4

4

4

3

4

42

A300

7

7

7

7

7

1

1

1

1

1

6

6

6

6

6

42

B300

6

 

7

6

7

1

 

4

0

2

8

 

11

11

11

47

A300

3

3

3

10

1

2

2

3

2

1

4

4

4

16

0

47

B300

4

4

4

6

4

1

1

2

0

1

6

6

6

8

6

47

C300

4

4

4

9

4

1

1

2

4

3

4

4

4

15

4

48

A300

7

7

7

7

 

1

1

0

0

 

9

9

9

9

 

48

B300

9

9

9

8

9

2

2

1

0

3

13

13

13

12

13

48

D300

5

5

4

5

5

2

2

3

3

2

5

5

3

5

5

48

E300

5

4

5

6

4

2

4

3

0

4

4

3

4

4

3

48

F300

7

6

6

5

5

1

2

3

0

3

7

5

5

5

4

48

G300

6

6

6

7

5

1

1

0

0

4

8

8

8

14

6

48

H300

5

5

5

5

5

1

1

2

0

1

6

6

6

6

6

48

I300

6

7

7

7

7

1

1

0

0

1

8

8

8

8

8

48

J300

9

9

9

9

9

2

2

1

1

2

11

11

11

11

11

48

K300

9

9

9

9

9

2

2

0

0

2

8

8

8

8

8

48

L300

8

8

8

8

8

2

2

1

0

2

12

12

12

12

12

48

M300

8

8

8

8

8

2

2

1

2

1

6

6

6

6

6

48

N300

5

5

5

5

5

1

2

5

1

1

2

2

2

2

2

48

Q300

8

8

8

8

8

1

1

0

0

2

11

11

11

11

11

49

A300

4

4

4

5

4

1

1

1

1

1

7

7

7

13

7

49

B300

6

2

6

5

6

2

1

2

2

2

10

2

10

10

10

49

C300

6

6

6

6

6

1

1

1

0

1

11

11

11

11

11

51

A300

7

7

7

7

7

1

1

1

0

1

7

7

7

7

7

53

A300

2

2

2

7

2

1

1

2

1

1

3

3

3

13

3

53

B300

5

5

5

5

5

1

1

2

0

1

9

9

9

9

9

53

C300

4

4

5

4

5

1

1

2

1

1

6

6

6

6

6

56

A300

3

3

3

20

3

1

1

1

2

1

7

7

7

13

7

56

B300

6

6

6

8

6

1

1

1

2

1

11

11

11

12

11

83

A300

7

7

7

8

7

3

3

4

2

2

14

13

13

14

14

87

A300

4

4

4

4

4

1

1

1

0

1

2

2

2

2

2

87

B300

6

6

6

6

 

1

2

1

0

 

7

7

7

7

 

89

A300

6

6

6

6

6

1

1

1

0

1

5

5

5

5

5

90

A300

5

6

4

6

7

1

2

1

5

2

4

5

3

5

5

90

B300

5

6

6

6

6

1

2

2

2

2

8

9

9

9

9

Note: Blank cells indicate data are not available.

Assessment of SPS-4 Data

Tables containing data relevant to the SPS-4 experiment were examined. Table 14 summarizes data availability for SPS-4 sections, including the location, number of surveys, number of treatments, and the observation period for each section. The sample size for SPS-4 was not as large as the sample size for the SPS-3 experiment. Moreover, the number of sections with undersealing treatment may not lead to statistically significant conclusions for this experiment. In this case, the research team will attempt to analyze the individual sections to draw some conclusions. The LTPP tables used for this assessment were as follows:

Table 14. Data availability for SPS-4 sites.

State Code

SHRP ID

Number of Surveys

Number of Treatments

Number of Years

 Sealing

Undersealing

Control Section

Sealing

Undersealing

Control Section

Sealing

Undersealing

Control Section

4

A400

4

 

4

1

 

0

7

 

7

5

A400

4

 

3

1

 

0

7

 

7

5

B400

3

 

3

1

 

0

6

 

6

5

C400

3

 

3

1

 

0

6

 

6

6

A400

5

4

5

1

1

0

12

12

12

6

B400

5

5

5

1

1

0

9

9

9

8

A400

4

 

4

1

 

1

7

 

7

18

A400

5

 

5

1

 

1

13

 

13

19

A400

1

 

1

1

 

0

0

 

0

19

B400

2

 

2

1

 

0

5

 

5

20

A400

2

 

2

1

 

0

2

 

2

20

B400

3

 

3

1

 

0

5

 

5

21

A400

3

 

3

6

 

0

7

 

7

28

A400

4

 

4

1

 

0

6

 

6

29

A400

3

 

3

2

 

2

4

 

4

29

B400

4

 

4

1

 

0

13

 

13

31

A400

4

 

4

1

 

0

9

 

9

31

B400

4

 

4

1

 

0

9

 

9

31

C400

4

 

4

2

 

0

9

 

9

32

A400

3

4

3

1

1

0

8

9

8

39

A400

4

 

4

1

 

0

11

 

11

39

B400

3

 

3

1

 

1

4

 

4

40

A400

5

5

5

1

1

0

8

8

8

42

A400

5

 

5

2

 

3

9

 

9

42

C400

6

 

6

2

 

1

12

 

12

46

A400

5

4

4

1

1

1

11

11

11

48

A400

4

4

4

1

1

0

7

7

7

48

B400

8

8

8

1

1

0

11

11

11

48

C400

7

7

7

4

7

4

9

9

9

48

D400

7

7

7

1

1

0

10

10

10

48

E400

7

7

7

1

2

1

10

10

10

49

C400

6

 

6

1

 

0

13

 

13

49

D400

4

 

4

2

 

1

9

 

9

49

E400

6

 

6

1

 

0

14

 

14

Note: Blank cells indicate data are not available.

Assessment of SPS-5 Data

The availability of SPS-5 experiment data was assessed in different modules of the LTPP database. Available data needed for the analysis of the experiment and the data needed for running MEPDG were extracted from different modules and stored in a new database. The tables from the LTPP database used to gather information are listed below.

Inventory data were as follows:

Traffic data were as follows:

Material data were as follows:

Monitoring data were as follows:

Inventory Data

Table 15 presents relevant data on the SPS-5 sites. The sites were constructed between 1965 and 1982, and they were rehabilitated based on SPS-5 standard specifications between 1989 and 1998.

Table 15. Original construction, traffic open, and major rehabilitation dates for SPS-5 projects.

State Code

Construction Date

Traffic Open Date

Rehabilitation Date

1

06/1976

06/1976

12/1991

4

07/1968

09/1968

05/1990

6

06/1966

06/1966

04/1992

8

10/1974

10/1974

10/1991

12

04/1971

12/1971

04/1995

13

06/1978

06/1978

06/1993

23

11/1972

11/1972

06/1995

24

11/1971

11/1971

06/1992

27

07/1969

07/1969

06/1990

28

09/1973

09/1973

09/1990

29

10/1981

10/1981

09/1998

30

09/1982

09/1982

09/1991

34

11/1968

08/1972

08/1992

35

06/1965

07/1965

09/1996

40

07/1973

07/1973

07/1997

81

06/1977

06/1977

10/1990

83

09/1971

09/1971

09/1989


Traffic Data

Available traffic data for the SPS-5 experiment were reviewed and analyzed. The TRF_MON_EST_ESAL and TRF_HIST_EST_ESAL tables include the annual traffic counts and estimates of each site for a number of years. Using the data available from these tables, the average annual daily truck traffic (AADTT) at rehabilitation date, growth rate, and growth method were calculated as presented in table 16. These data are needed to run the
MEPDG software.

Table 16. Traffic data for the SPS-5 experiment.

State Code

Construction Year

Rehabilitation Year

AADTT at Rehabilitation Date

Growth Rate

Growth Method

1

1976

1991

500

5.06

Compound

4

1968

1990

530

8.27

Compound

6

1966

1992

2,478

0

-

8

1974

1991

781

12.7

Linear

12

1971

1995

131

14.9

Linear

13

1978

1993

3,689

21.9

Linear

23

1972

1995

600

4.9

Linear

24

1971

1992

615

7.37

Linear

27

1969

1990

188

7.9

Linear

28

1973

1990

1,155

5.65

Compound

29

1981

1998

630

0

-

30

1982

1991

751

3.9

Linear

34

1972

1992

1,530

28.9

Linear

35

1965

1996

3,483

14.4

Linear

40

1973

1997

-

-

-

81

1977

1990

270

18.6

Linear

83

1971

1989

207

7.6

Linear

- Indicates data are not available.

Some data are missing from the traffic module. For example, the database does not contain any traffic data for Oklahoma (State code 40). The axle distribution data are missing from Georgia (13) and Missouri (29), and monthly adjustment factors are not available for California (6) and Georgia (13).

Material Data

As shown in the sample in table 17, the State code, SHRP ID, layer number, layer type, and material description are obtained from the LTPP database. The construction number reveals if any major rehabilitation was applied to the site. For example, layer 5 was removed and was replaced with two layers of HMA with 1- and 2-inch (25.4- and 51-mm) thicknesses. As a result, the construction number is changed to 2. Construction 1 always refers to the original construction, and construction 2 is the rehabilitation work. Some sections have received several rehabilitation and maintenance treatments.

Table 17. Sample materials with project information for the SPS-5 experiment.

STATE_CODE

SHRP_ID

CONSTRUCTION_NO

LAYER_NO

LAYER_TYPE

Material Description

REPRESENTATIVE_
THICKNESS (inches)

1

506

1

1

SS

Coarse-grained soil: silty sand

 

1

506

1

2

GS

Other (specify, if possible)

5.4

1

506

1

3

GB

Crushed gravel

10.6

1

506

1

4

AC

Hot mixed, hot laid AC, dense graded

2.2

1

506

1

5

AC

Hot mixed, hot laid AC, dense graded

1.5

1

506

2

5

AC

Hot mixed, hot laid AC, dense graded

0

1

506

2

6

AC

Hot mixed, hot laid AC, dense graded

1

1

506

2

7

AC

Hot mixed, hot laid AC, dense graded

2

1 inch = 25.4 mm
Note: The blank cell indicates that there is no thickness for subgrade.

Monitoring Data

Different monitoring data were collected from SPS-5 sites. Distress surveys were obtained and summarized from all experiment sections to compare performance.

Table 18 depicts the number of surveys available for each experiment, the number of treatments applied to each experiment, and the number of years the section was under inspection. The table summarizes the data available from the MON_DIS_AC_REV table from the LTPP database. As shown, distress data have been collected for up to 17 years. Some sites have survey data for up to 12 inspections.

Table 18. Available monitoring (distress) data.

State Code

501

502

503

504

Number of Surveys

Number of Treatments

Number of Years

Number of Surveys

Number of Treatments

Number of Years

Number of Surveys

Number of Treatments

Number of Years

Number of Surveys

Number of Treatments

Number of Years

1

7

2

12

11

2

15

11

2

15

11

2

15

4

2

1

4

10

6

11

11

5

11

11

5

11

6

11

5

14

11

4

14

11

4

14

11

2

14

8

5

3

8

5

3

8

5

3

8

5

3

8

12

10

1

15

10

2

12

10

2

12

10

2

12

13

     

10

2

12

10

2

12

10

2

12

23

9

3

9

9

3

9

9

3

9

9

3

9

24

10

2

14

12

3

15

12

3

15

11

3

15

27

11

3

15

11

4

15

9

4

15

12

4

15

28

4

1

8

4

2

8

4

2

8

4

2

8

29

4

1

3

7

2

6

7

2

6

7

2

6

30

7

3

13

6

3

13

7

3

13

7

3

13

34

9

2

12

10

2

14

11

2

14

10

2

14

35

6

7

7

9

2

10

9

2

10

9

3

10

40

9

3

9

9

3

9

9

3

9

9

3

9

81

12

3

15

12

3

15

12

3

15

12

2

15

83

6

6

9

10

5

17

10

5

17

10

5

17

State Code

505

506

507

508

509

Number of Surveys

Number of Treatments

Number of Years

Number of Surveys

Number of Treatments

Number of years

Number of Surveys

Number of Treatments

Number of years

Number of Surveys

Number of Treatments

Number of Years

Number of Surveys

Number of Treatments

Number of Years

1

11

2

15

11

2

15

11

2

15

11

2

15

11

2

15

4

11

6

11

11

6

11

11

4

11

11

5

11

11

6

11

6

11

4

14

11

4

14

11

2

14

11

3

14

11

3

14

8

5

3

8

5

3

8

5

3

8

5

3

8

5

3

8

12

10

2

12

10

2

12

10

2

12

10

2

12

10

2

12

13

10

2

12

10

2

12

10

2

12

10

2

12

10

2

12

23

9

3

9

9

3

9

9

3

9

9

3

9

9

3

9

24

11

3

15

11

2

15

11

2

15

12

3

15

11

2

15

27

11

5

15

12

5

15

12

5

15

11

4

15

11

4

15

28

4

2

8

4

2

8

4

2

8

4

2

8

4

2

8

29

7

2

6

8

2

8

8

2

8

8

2

8

8

2

8

30

7

3

13

7

3

13

7

3

13

7

3

13

7

3

13

34

10

2

14

10

2

14

11

2

14

11

2

14

10

2

14

35

9

2

10

9

3

10

9

3

10

9

3

10

8

3

9

40

9

3

9

9

3

9

9

3

9

9

3

9

9

3

9

81

12

2

15

12

2

15

12

2

15

12

2

15

12

3

15

83

10

5

17

10

4

17

8

5

17

9

5

17

7

4

17

Note: Blank cells indicate data are not available.

Rutting data are recorded in the MON_T_PROF_INDEX_SECTION table from the LTPP database. Table 19 summarizes the number of rut measurements taken at each site. IRI is another monitoring index measured in SPS-5 sites. The IRI measurements are available from the MON_PROFILE_MASTER table from the LTPP database. The number of IRI measurements taken at each site is presented in table 19. For the sites where there is a considerable difference in available data for each experiment within the site, a range of available surveys is specified.

Table 19. Number of rutting and IRI surveys conducted at SPS-5 sites.

State Code

Rutting

IRI

1

13

11

4

17

14

6

18

15

8

8

10

12

13

9

13

14

9

23

13

10

24

17

15–19

27

12–18

14

28

6

6

29

10–12

5

30

12

16

34

18

17–20

35

12

7

40

13

9

81

14

17

83

13

15

Assessment of SPS-6 Data

Inventory Data

The SPS-6 experiment was conducted in 14 States throughout the United States. The sites were originally constructed between 1962 and 1978, and they were rehabilitated according to SPS-6 specifications between 1989 and 1998. Table 20 shows the States included in the study and their corresponding historic dates. The LTPP tables used to gather the information are as follows:

Inventory data include the following:

Traffic data include the following:

Material data include the following:

Monitoring data include the following:

Table 20. Original construction, traffic open, and major rehabilitation dates for SPS-6 sites.

State Code

Construction Date

Traffic Open Date

Rehab Date

1

05/1966

06/1966

06/1998

4

09/1966

01/1967

10/1990

5

12/1978

01/1979

12/1996

6

08/1977

11/1977

09/1992

17

06/1964

04/1965

06/1990

18

01/1972

01/1974

08/1990

19

11/1965

11/1965

09/1989

26

06/1958

06/1958

05/1990

29

07/1975

10/1975

08/1992

29A

07/1969

08/1969

09/1998

40

11/1962

01/1963

08/1992

42

09/1968

09/1968

10/1992

46

04/1973

10/1973

09/1992

47

06/1964

07/1964

05/1996


Traffic Data

Similar to the SPS-5 experiment, available traffic data for the SPS-6 experiment were obtained from the TRF_MON_EST_ESAL and TRF_HIST_EST_ESAL tables, including the annual traffic counts and estimates of each site for a number of years. Using the data available from these tables, the AADTT at rehabilitation date was obtained. The growth model with a better fit and the growth rate are presented in table 21.

Table 21. SPS-6 traffic growth.

State

Construction Year

Rehab Year

AADTT at Rehab Date

Growth Rate

Growth Method

1

66

98

N/A

   

4

66

90

38

14.47

Compound

5A

78

96

N/A

   

6

77

92

1,436

0

No growth

17

64

90

391

11.25

Linear

18

72

90

110

59

Linear

19

65

89

441

11.11

Linear

26

58

90

476

1.2

Linear

29

75

92

637

4.35

Compound

29A

69

98

62

12.9

Linear

40

62

92

630

2.9

Compound

42

68

92

1,594

2.5

Linear

46

73

92

121

5

Linear

47

64

96

N/A

   

N/A indicates data are not available.
Note: Blank cells indicate missing traffic data.

Traffic data are missing from Alabama (1), Arkansas (5), and Tennessee (47). The axle distribution data were missing from Missouri (29), Oklahoma (40), and Pennsylvania (42). Also, Missouri (29) is missing axle per truck data from the database.

Material Data

Pavement structure information for SPS-6 sites and the sequence of the changes made to each site over time were extracted from the LTPP database. Table 22 provides a sample table with project information.

Table 22. Sample materials with project information for the SPS-6 experiment.

State Code

SHRP ID

Construction Number

Layer Number

Layer Type

Material Description

Representative Thickness (inches)

1

0606

1

1

Subgrade (untreated)

Coarse-grained soil: clayey gravel

 

1

0606

1

2

Unbound (granular) layer

Crushed stone

6

1

0606

1

3

Portland cement concrete layer

PCC (JPCP)

10.3

1

0606

2

1

Subgrade (untreated)

Coarse-grained soil: clayey gravel

 

1

0606

2

2

Unbound (granular) layer

Crushed stone

6

1

0606

2

3

Portland cement concrete layer

PCC (JPCP)

10.3

1

0606

2

4

AC

Hot mixed, hot laid AC, dense graded

2.2

1

0606

2

5

AC

Hot mixed, hot laid AC, dense graded

1.3

1 inch = 25.4 mm
Note: The blank cell indicates that there is no thickness for subgrade.

Monitoring Data

Table 23 summarizes the basic information about the monitoring data collected during the SPS-6 study. Distress surveys were obtained and summarized from all experiment sections to compare performance. The table shows the number of surveys available for each experiment, the number of treatments applied to each experiment, and the number of years the section was inspected.

Table 23. SPS-6 available monitoring (distress) data.

State Code

601

602

603

604

No. of Surveys

No. of Treatments

No. of Years

No. of Surveys

No. of Treatments

No. of Years

No. of Surveys

No. of Treatments

No. of Years

No. of Surveys

No. of Treatments

No. of Years

1

9

1

8

9

1

8

9

1

8

9

1

8

4

1

0

0

1

1

0

7

3

11

7

2

11

5

10

6

11

10

4

11

10

1

11

11

1

11

6

     

10

6

12

11

4

12

11

5

12

17

10

6

12

10

8

12

11

4

15

11

5

15

18

2

0

1

9

4

14

10

4

14

11

3

14

19

6

6

15

6

9

15

8

6

15

8

5

15

26

3

0

3

3

1

3

4

1

6

4

1

6

29

6

7

9

6

9

9

9

2

13

9

2

13

29A

8

3

8

8

2

8

8

2

8

7

2

6

40

13

5

15

13

2

15

13

3

15

13

3

15

42

11

2

15

11

1

15

11

2

15

11

2

15

46

10

7

14

9

3

14

9

3

14

9

3

14

47

8

3

8

8

4

8

8

1

8

8

1

8

State Code

605

606

607

608

No. of Surveys

No. of Treatments

No. of Years

No. of Surveys

No. of Treatments

No. of Years

No. of Surveys

No. of Treatments

No. of Years

No. of Surveys

No. of Treatments

No. of Years

1

9

1

8

9

1

8

9

5

8

9

1

8

4

2

1

0

7

2

11

7

3

11

7

3

11

5

10

4

11

10

1

11

10

1

11

10

1

11

6

8

7

12

11

4

12

11

4

12

11

3

12

17

10

7

12

11

9

15

11

6

15

11

3

15

18

8

4

13

10

4

14

11

4

14

10

4

14

19

6

10

15

8

4

15

9

5

15

10

4

18

26

3

1

3

4

1

6

4

1

6

4

1

6

29

6

9

9

9

1

13

2

2

3

9

3

13

29A

7

2

6

9

2

8

8

2

8

7

1

6

40

13

9

15

13

3

15

13

6

13

13

2

15

42

11

1

15

11

1

15

11

1

15

11

1

15

46

9

4

14

9

3

14

9

5

14

9

4

14

47

8

6

8

8

1

8

6

1

6

8

1

8

Rut measurements were collected several times from the SPS-6 sites. Table 24 summarizes the number of surveys conducted for each site. The number of surveys available from the database was not the same for all the sections of a site. Therefore, a range is presented for most of the sites. The number of IRI measurements available from the experiment also is provided.

Table 24. Number of rutting and IRI surveys conducted at SPS-6 sites.

State Code

Rutting Surveys

IRI Surveys

1

11      

8

4

11

3–14

6

7–17

11

17

7–18

9–12

18

6–17

2–17

19

12–16

9–12

26

3–8

4–9

29

3–16

4–11

40

5–14

9–10

42

4–14

14–16

46

6–16

10–11

47

2–11

4–7

5A

1–12

8–10

29A

3–11

6

 


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.
FHWA
United States Department of Transportation - Federal Highway Administration