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: Maintenance treatments for flexible pavements.
• SPS-4: Maintenance treatments for rigid pavements.
• SPS-5: Rehabilitation of AC pavements.
• SPS-6: Rehabilitation of jointed concrete pavements.

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:

• Thin overlay.
• Slurry seal.
• Crack seal.
• Chip seal.

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:

• Joint and crack sealing.
• Joint undersealing.

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:

• Climatic zone: Temperature and moisture.
• Subgrade type: Fine-grained and coarse-grained.
• Subbase type: Granular and stabilized.

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:

• Climatic zone: Wet versus dry and freeze versus no-freeze.
• Existing pavement condition: Fair versus poor.
• Surface preparation: Intense versus minimum.
• Overlay material: Recycled versus virgin HMA.
• Overlay thickness: Thin 2 inches (51 mm) versus thick 5 inches (127 mm).

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:

• Climatic zone: Wet versus dry and freeze versus no-freeze.
• Pavement condition: Fair versus poor.
• Type of concrete pavement: JPCP versus JRCP.
• Overlay thickness: 4 inches (102 mm) versus 8 inches (203 mm).

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:

• Inventory: Section location, pavement characteristics, and material characteristics.
• Materials testing: Material properties and characteristics from field and laboratory tests.
• Climatic: Temperature, humidity, precipitation, cloud cover, and wind statistics.
• Maintenance: Activities performed since inclusion in the LTPP program.
• Rehabilitation: Major improvements since inclusion in the LTPP program.
• Traffic: Annual traffic summary statistics for a study lane since it was opened to traffic.
• Monitoring: FWD, profilometer, surface distress, skid, and transverse profile.
• Dynamic load response: Only available from the instrumented SPS-1 and SPS-2 test sections in Ohio and North Carolina.

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:

• Inventory: INV_AGE:TRAFFIC_OPEN_DATE.
• IRI monitoring: MON_PROFILE_MASTER.
• AC distress survey monitoring: MON_DIS_AC_REV.
• AC rutting survey monitoring: MON_T_PRF_INDEX_SECTION.

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:

• Inventory: INV_AGE:TRAFFIC_OPEN_DATE.
• IRI monitoring: MON_PROFILE_MASTER, MON_T_PRF_INDEX_SECTION.
• PCC faulting monitoring: MON_DIS_JPCC_FAULT_SECT.
• PCC distress survey monitoring: MON_DIS_JPCC_REV, MON_DIS_ PADIAS42_JPCC.

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:

• Inventory: INV_AGE:TRAFFIC_OPEN_DATE.
• SPS: SPS5_PMA_CONSTRUCTION:DATE_COMPLETE.

Traffic data were as follows:

• Traffic: TRF_MONITOR_LTPP_LN:TRUCKS_LTPP_LN.
• Traffic: TRF_MON_EST_ESAL:AADT_TRUCK_COMBO.
• Traffic: TRF_MONITOR_LTPP_LN:TRUCKS_LTPP_LN.

Material data were as follows:

• Material_Test: TST_L05B: CONSTRUCTION_NO, LAYER_NO, LAYER_TYPE, REPR_THICKNESS.
• Material_Test: TST_L05B: MATL_CODE.
• Inventory: INV_SUBGRADE:AASHTO_SOIL_CLASS – reference:CODES:AASHTO_SOIL_CLASS.
• Inventory:INV_UNBOUND:AASHTO_SOIL_ CLASS – reference:CODES:AASHTO_SOIL_CLASS.

Monitoring data were as follows:

• IRI: MON_PROFILE_MASTER.
• Rutting surveys: MON_T_PRF_INDEX_SECTION.
• Cracking surveys: MON_DIS_AC_REV.

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:

• Inventory: INV_AGE:TRAFFIC_OPEN_DATE.
• SPS: SPS6_PMA_CONSTRUCTION:DATE_COMPLETE.

Traffic data include the following:

• Traffic: TRF_MONITOR_LTPP_LN:TRUCKS_LTPP_LN.
• Traffic: TRF_MON_EST_ESAL:AADT_TRUCK_COMBO.
• Traffic: TRF_MONITOR_LTPP_LN:TRUCKS_LTPP_LN.

Material data include the following:

• Material_Test: TST_L05B: CONSTRUCTION_NO, LAYER_NO, LAYER_TYPE, REPR_THICKNESS.
• Material_Test: TST_L05B: MATL_CODE.
• Inventory: INV_SUBGRADE:AASHTO_SOIL_CLASS – reference:CODES:AASHTO_SOIL_CLASS.
• Inventory: INV_UNBOUND:AASHTO_SOIL_ CLASS – reference:CODES:AASHTO_SOIL_CLASS.

Monitoring data include the following:

• IRI: MON_PROFILE_MASTER.
• Rutting survey: MON_T_PRF_INDEX_SECTION (for sections with AC overlay).
• Faulting surveys: MON_DIS_JPCC_FAULT_SECT.
• PCC distress surveys: MON_DIS_JPCC_REV, MON_DIS_PADIAS42_JPCC.

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