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Publication Number: FHWA-RD-01-168
Date: July 2006

Rehabilitation of Asphalt Concrete Pavements: Initial Evaluation of The SPS-5 Experiment-Final Report

Chapter 2. General Overview of Experiment

The first step in evaluating the SPS-5 experiment assessed how much of the experiment actually was constructed and what effect any missing sites might have on the experiment. This chapter discusses the original SPS-5 experiment design, the experimental sites constructed as of the time of this report, the effects of the missing experimental design cells, and the information available from the supplemental sites. The January, 2000, release of the IMS that contained only Level E data was used for the detailed review.

ORIGINAL SPS-5 EXPERIMENT DESIGN

The SPS-5 experiment examines the effects of climatic factors (wet versus dry and freeze versus no-freeze) and pavement condition (fair versus poor) on pavement sections incorporating different rehabilitation structural features. The features include:

The original SPS-5 experiment factorial is shown in table 1. A site is defined by the environmental conditions shown within the design. Nine combinations of rehabilitation factors are presented by the factorial. In table 1, intensive surface preparation denotes those test sections in which 51 mm of the surface was milled off and patching was performed as needed to rectify localized failures. Minimum surface preparation indicates that only patching was performed. The experimental plan specified that the recycled mixtures should contain 30 percent RAP and that the RAP incorporated into the mix should be the material that was milled from the intensive surface preparation test sections.(2) As part of the experiment design, one section was to have no treatment and serve as the control section for the project.

Two projects were required for each of the nine combinations of rehabilitation factors. Table 1 illustrates which State projects were nominated initially to fill specific design cells of the factorial. As shown, at least two projects were nominated for each cell with the exception of the dry-freeze-poor condition cell of the factorial. Some cells contain triplicate sections. As of August 1999, the SPS-5 experiment had 18 projects located throughout the United States and Canada. A map of the selected sections is shown in figure 1. These projects are well distributed across North America.

Table 1. Factorial used in SPS-5 experiment design.
Rehabilitation ProceduresFactors for Moisture, Temperature, and Pavement Condition
Surface PrepOverlay MaterialOverlay Thickness mmWetDry
FreezeNo-FreezeFreezeNo-Freeze
FairPoorFairPoorFairPoorFairPoor
Routine Maintenance (Control) N/A0 MD,MNNJMEMOTXGAMS,FLALCO,ABMTMB  NMOKAZCA
MINIMUMRecycled AC51MD,MNNJMEMOTXGAMS,FLALCO,ABMTMB NMOKAZCA
127MD,MNNJMEMOTXGAMS,FLALCO,ABMTMB NMOKAZCA
Virgin AC51MD,MNNJMEMOTXGAMS,FLALCO,ABMTMB NMOKAZCA
127MD,MNNJMEMOTXGAMS,FLALCO,ABMTMB NMOKAZCA
INTENSE
Recycled AC51MD,MNNJMEMOTXGAMS,FLALCO,ABMTMB NMOKAZCA
127MD,MNNJMEMOTXGAMS,FLALCO,ABMTMB NMOKAZCA
Virgin AC51MD,MNNJMEMOTXGAMS,FLALCO,ABMTMB NMOKAZCA
127MD,MNNJMEMOTXGAMS,FLALCO,ABMTMB NMOKAZCA

Figure 1. Map. Location of the SPS-5 projects.

This is a schematic chart showing the S P S-5 project locations in the United States and Canada. The project sites are located in Alabama, Arizona, California, Colorado, Florida, Georgia, Maine, Maryland, Mississippi, Missouri, Montana, New Jersey, New Mexico, Oklahoma, Texas, Wisconsin, and Alberta and Manitoba Canada.

Each test section has an identifying number that is common for all of the SPS-5 projects, and this test section number indicates the following characteristics:

Requirements set for all test sections on each project are as follows:

SUPPLEMENTAL SECTIONS

In addition to the nine core sections located at each project, the States were allowed to add supplemental sections that would be monitored by LTPP. These supplemental sections are usually a variation of the experiment and represent typical rehabilitation practices by the individual agency. Table 2 provides a list of the SPS-5 projects and the number of supplemental sections that were built at each. These supplemental sections represent a much more diverse range of overlay materials and rehabilitation strategies than were considered in the core experiment. The 48 supplemental sections are considered a valuable source of data for future pavement engineering needs.

CURRENT STATUS OF DESIGN FACTORIAL

The status, as of the year 2000, of the SPS-5 design factorial is provided in table 3. All projects have been located in the appropriate cells based on the actual environmental data, which will be discussed in detail in chapter 4. As shown, all of the cells have at least two projects, except for the wet-no-freeze, fair condition cell and the dry-freeze, poor condition cell. The distribution of these projects across North America represents the diverse environmental conditions required for this experiment. In summary, a total of 210 test sections (162 core test sections of the experiment plus 48 supplemental sections) had been built as part of the SPS-5 experiment.

Table 2. Supplemental sections constructed on SPS-5 projects.
STATESHRP IDREHABILITATION
ALABAMA056351 mm milling and inlay with virgin mix
056451 mm milling and inlay with RAP mix
ARIZONA055951 mm milling and inlay with RAP mix
056051 mm milling and inlay with asphalt rubber asphalt concrete
CALIFORNIA0559Chip seal on 51 mm virgin mix
056051 mm virgin mix on pavement-reinforcing fabric
065151 mm rubberized mix on pavement-reinforcing fabric
056251 mm rubberized mix
066351 mm rubberized mix on stress absorbing membrane interlayer (SAMI)
056451 mm virgin mix on SAMI
056519 mm open-graded mix on SAMI on virgin mix
056619 mm open-graded mix on 51 mm virgin mix
0567100 mm virgin mix
056851 mm virgin mix on 100 mm virgin base mix
056951 mm Stone Mastic Asphalt with Vestoplast®
057051 mm modified stone mastic asphalt
057151 mm dense graded overlay
COLORADO0559159 mm virgin mix
056051 mm polymer modified mix on 108 mm virgin mix
FLORIDA056189 mm RAP mix
056289 mm virgin mix
0563Mill inlay with virgin mix
0564Mill inlay with RAP mix
0565Mill and inlay, overlay with 89 mm RAP mix
0566Mill and inlay, overlay with 89 mm virgin mix
GEORGIA0560Planned treatment
056189 mm RAP mix
056289 mm virgin mix
0563Mill 51 mm and inlay 51 mm virgin mix
0564Mill 51 mm and inlay 51 mm RAP mix
0565Mill 89 mm and inlay 89 mm RAP mix
0566Mill 89 mm and inlay 89 mm virgin mix
0567Second control section
MAINE055932 mm virgin mix on 19 mm virgin shim layer
MARYLAND055951 mm agency mix design
056064 mm Arbocel® modified stone mastic asphalt
056164 mm Vestoplast modified stone mastic asphalt
056264 mm Styrelf® modified stone mastic asphalt
056364 mm Styrelf and Arbocel modified stone mastic asphalt
MINNESOTA055938 mm virgin mix
0560Milling of transverse cracks only and overlay with 38 mm virgin mix
0561Overlay with type 41 mix on type 31 mix
MISSISSIPPI056076 mm virgin overlay with fabric underseal and slurry seal
MONTANA0561127 mm mill and inlay with Polybuilt® modified mix
056051 mm mill and inlay with Kreton modified mix
NEW JERSEY0559Mill 51 mm and overlay with 51 mm RAP on 64 mm virgin mix
0560Mill 51 mm and overlay with 25 mm rubblized wearing course on 64 mm virgin mix
OKLAHOMA0560Mill and inlay, 89 mm virgin overlay

Note: Unmentioned states and provinces had no supplemental sections.

There is one major difference or deviation from the SPS-5 experimental plan. The subgrade soils for all SPS-5 projects were to be fine-grained soils. However, the soils for many of the projects are classified as coarse-grained soils. Table 3 identifies those projects that have fine-and/or coarse-grained soils. Only five of the SPS-5 projects have fine-grained soils: Maryland, Minnesota, Mississippi, Oklahoma, and Texas. The soils supporting the Missouri project were not yet classified. Four projects have soils that vary between fine- and coarse-grained: California, Colorado, Georgia, and Manitoba. The subgrade soils for the remaining eight projects are classified as coarse-grained. Although this is considered a significant deviation from the experimental plan, it is not believed to be detrimental to achieving the overall expectations for this experiment.

Table 3. Final factorial for the SPS-5 experiment design.
Pavement ConditionSoil ClassificationClimate,Moisture-Temperature
Wet-FreeWet-No-FreezeDry-FreezeDry-No-Freeze
FairCoarse/fineGA (8) 6.2 CO (2) 7.9 
CoarseNJ (2) 7.0 AB (0) 8.9
MT (2) 8.0
NM (0) 2.9
Fine MN (3) 8.9OK (1) 2.1
TX (0) 7.8
PoorCoarse/fine MB (0) 10.0CA (13) 7.3
CoarseME (1) 4.1FL (6) 4.3
AL (2) 7.7
AZ (2) 9.2
FineMD (5) 7.2
MO* (0) 0.0
MS (1) 8.9

Note: The numbers in parentheses indicate supplemental sections, which are followed by the age of the project as of January 2000.

*Missouri is located in the cell for which it was nominated because the data for determining the correct cell assignment were unavailable as of the time of this report.

 


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