Rehabilitation of Jointed Portland Cement Concrete Pavements: SPS-6, Initial Evaluation and Analysis

Chapter 2. SPS-6 EXPERIMENTAL PLAN

Rehabilitation of Jointed Portland Cement Concrete Pavements: SPS-6, Initial Evaluation and Analysis

Chapter 2. SPS-6 EXPERIMENTAL PLAN

This chapter describes the SPS-6 experimental plan, including a detailed discussion to define the SPS-6 experimental design matrix and the current status of the design cells (constructed sections) as nominated. It is important to note that even if a site is nominated to a specific cell of the design matrix, the actual properties of the site, such as climatic factors, may result in the site not meeting the originally nominated characteristics. For example, a site nominated as being in the dry-freeze zone may have too much annual precipitation to be classified as "dry"and is actually "wet" resulting in a wet-freeze site rather than the nominated dry-freeze site.

ORIGINAL DESIGN FACTORIAL

The SPS-6 experiment examines the effects of climatic factors (wet-freeze, wet-no freeze, dry-freeze, or dry-no freeze), type of concrete pavement (plain or reinforced), condition of existing pavement (fair or poor), and traffic rate (as a covariant) on pavement sections incorporating different methods of rehabilitation with and without AC overlays. Table 1 shows the number of sites that are required to complete the original design factorial as established by the LTPP program. The shaded area was not included because there are no JRCP sections in that area of the country. Note that there are two replicate experiments planned within most cells.

REHABILITATION ALTERNATIVES

There are eight different rehabilitation alternatives incorporated into each site of the SPS-6 experiment. These eight rehabilitation alternatives are referred to as the eight core sections of the experiment. Every site constructed as part of the SPS-6 experiment must contain the eight core pavement sections. These rehabilitation alternatives include variations in pavement preparation, restoration, AC overlay thickness, and additional treatments (saw and seal).

Table2 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 the overlay thickness. It was also required that at least six of these core sections have 152-meter (m) (499 foot) nondestructive performance monitoring areas and that two have 305-m (1,000 foot) areas, with an additional 15 m (49 feet) on each end for destructive testing. In addition, traffic in the test lane must also exceed 200,000 equivalent single-axle loads (ESALs) per year (rigid ESALs).

1 mm =.039 inch

If desired by the participating SHA, additional sections incorporating other types of rehabilitation variations in pavement preparation, other treatments, or overlay thicknesses were included. For example, the supplemental sections included variations in the crack/break and seat dimensions, rubblized pavements, varying AC overlay thicknesses, use of fabrics and fibers, and other features. The State-selected supplemental sections are discussed in more detail later in this chapter.

A discussion of the various levels of preparation, other treatments, and AC overlays follows.

Portland Cement Concrete (PCC) Pavement Preparation

The control section received routine maintenance, including joint and crack sealing, and limited patching. In addition to the control section, three levels of pavement preparation were applied: minimum preparation, maximum preparation, and crack/break and seat. The preparation techniques are discussed below:

Minimum Preparation: Consists of routine maintenance, which includes limited patching (filling potholes), crack repair and sealing, and stabilization of joints. This level of rehabilitation is typical of the current practices of many highway agencies prior to overlay. Note that some of these minimum-preparation sections also included diamond grinding when faulting was severe.

Maximum Preparation: Consists of several activities, depending on pavement distress and condition. This level represents a premium level of pavement preparation, including subsealing, subdrainage, joint repair and sealing, full-depth repairs with restoration of load transfer, diamond grinding (nearly always), and shoulder rehabilitation. Diamond grinding and joint and crack sealing were not performed on sections that received an AC overlay and, in at least one case, not on the bare concrete sections.

Crack/Break and Seat: Uses mechanical means to reduce slab size to minimize or eliminate reflection cracking in the AC overlay. The cracking and seating process is used with JPCP and the breaking and seating process is used with JRCP. The fracturing (cracking and/or breaking) is intended to produce hairline cracks through the full depth of the PCC slab, plus fractures in any reinforcing steel, when present, so that all reinforcing materials are completely separated.

Other Treatments

The only other special AC overlay reflection treatment included in the core experiments is saw and seal. For the SPS-6 section ***604, with a 102-millimeter (mm) (4-inch) -thick AC overlay, sawing was performed directly above the existing joints and cracks of the PCC pavement. No other treatments were included as part of the core experiment; however, several SHAs provided supplemental sections using other treatments, such as fabric interlayers or fibrous AC overlays.

AC Overlays

The study design includes two overlay thicknesses (102 and 203 mm (4 and 8 inches)). The 102-mm (4-inch) overlays were placed on sections receiving the minimal restoration level of pavement preparation, the maximum restoration, and the crack/break and seat pavement preparation. In addition, a minimum-rehabilitation section with a 102-mm (4-inch) overlay, in which joints are sawed above the existing PCC joints and then sealed, was included. Also included in the experiment is a 203-mm (2-inch) overlay placed on the cracked/broken and seated section.

The overlays allowed for use on the sections were constrained to ensure a reasonable level of consistency as indicated below:

• All overlays must use virgin AC material.
• Application does not incorporate stress-absorbing membrane interlayer (SAMI) or any type of reinforcement (e.g., fibers and geotextiles).

AS-NOMINATED DESIGN FACTORIAL

As of August 1999, the SPS-6 experiment had 14 sites located throughout the United States. The distribution of the currently constructed SPS-6 sites by State and geographical region is shown in figure 1. Table 3 provides a list of all of these sections, including the core and State supplemental sections. Each site has the same core of eight standard test sections. In addition, many State agencies have included additional sections, which are referred to as State supplemental sections. Currently, a total of 112 core sections and 59 State supplemental sections have been constructed for SPS-6 experiments.

Each site was nominated to fill a specific cell of the design matrix. Table 4 shows how each of the nominated/constructed SPS-6 sites fills the design matrix. Cells containing one or more asterisks highlight a missing site in the design matrix. These asterisks clearly show that 11 sites were not constructed. Unfortunately, no additional SPS-6 sites will be constructed. Therefore, the empty portion of the design matrix will remain unfilled. These missing sections will ultimately impact the potential for rehabilitation findings for these site conditions. A detailed description of each SPS-6 section, including the supplemental sections, is provided in appendix A. This information highlights the rehabilitation efforts performed and any significant deviations from the initial experimental design factorial.

Figure 1. States participating in SPS-6 PCC rehabilitation study.

• Each indicates that an additional site is needed to complete the original design matrix.
• the first site is designated as MO.

STATE SUPPLEMENTAL SECTIONS

In addition to the eight core sections required by the SPS-6 experiment, the SHAs have included additional experiment sections (referred to as State supplemental sections). Table 5 lists the design variables selected by a given SHA for nonfractured PCC pavements, and table 6 lists the supplemental sections with fractured PCC pavements as a form of rehabilitation. Based on the number of supplemental sections in these tables, it appears that there is interest by the SHAs in the performance of fractured PCC pavements as a rehabilitation alternative

Both of these tables highlight rehabilitation design variables that interest the SHAs. Many SHAs are interested in the performance of design features that were not included within the eight core sections of the experiment to determine their potential influence on the performance of the rehabilitated pavement section.

SUMMARY

• Twenty-four SPS-6 sites were planned; however, only 14 were actually constructed. These 14 sites will provide performance data for some major areas of the United States where JPCP and JRCP exist.
• The central portion of the United States was well covered (wet-freeze and wet-no freeze); however, portions of the west and east coasts were generally not covered (particularly dry climatic areas).
• Many additional State supplemental sections were added to the core sections. These typically emphasize reflection crack control sections.

Each represents one experiment section. 1 mm =.039 inch