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Federal Highway Administration Research and Technology
Coordinating, Developing, and Delivering Highway Transportation Innovations
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Publication Number: FHWA-RD-01-169
Date: October 2005
Rehabilitation of Jointed Portland Cement Concrete Pavements: SPS-6, Initial Evaluation and Analysis
Chapter 1. INTRODUCTION
The Specific Pavement Studies 6 (SPS-6) experiment,"Rehabilitation of Jointed Portland Cement Concrete Pavements," was designed as a controlled field experiment that focuses on the study of specific rehabilitation design features of jointed plain concrete pavements (JPCP) and jointed reinforced concrete pavements (JRCP). The successful completion of this experiment will lead to improvements in rehabilitation design procedures and standards for jointed concrete pavements. These improvements will contribute to achieving the overall goal of the Long-Term Pavement Performance (LTPP) program: increased pavement life and better use of resources.
This goal will be achieved through investigation of the effects of the specific experimental rehabilitation design features (overlay thickness and restoration activities) and site conditions (existing pavement condition, subgrade soil, traffic, and climate) and their interactions on pavement performance. This will make it possible to evaluate existing rehabilitation design methods and performance equations; develop new and improved rehabilitation design equations; and calibrate mechanistic models, including the 2002 Guide for the Design of New and Rehabilitated Pavement Structures (hereafter known as the 2002 Design Guide).
The SPS-6 experimental plans were originally designed to incorporate project sites in all four LTPP climatic regions and on both fine-grained and coarse-grained subgrades. This requirement makes it potentially possible to cover a large inferential space of the continental United States. A major effort was made by the Strategic Highway Research Program (SHRP), the State highway administrations (SHAs), and the Federal Highway Administration (FHWA) to identify appropriate SPS-6 sites and to construct all the sections according to their original experimental design. A wide range of specific data was collected during construction. Extensive field monitoring data (traffic, profile, cracking, etc.) have been collected from these sections over time.
The original expectations for the LTPP program are summarized in a SHRP report.(1) Originally, the following objectives were established for the LTPP program:
The experimental designs for various LTPP experiments were developed with a clear relationship to these objectives. The following products were identified for the LTPP program:(1)
General Products: Evaluation of existing design methods and performance equations, new and improved design equations, and calibration of mechanistic models.
Specific Products: Effects of the specific experimental design features (asphalt concrete (AC) overlay thickness, pre-overlay repair, etc.) and site conditions (subgrade, traffic, and climate).
Other Products: Test methods developed specifically for SPS test sections, correlations among material properties determined by different methods, study of other features and materials, and technology transfer.
The following objectives of the SPS-5 (Rehabilitation of Flexible Pavements) and SPS-6 (Rehabilitation of Jointed Portland Cement Concrete Pavements) experiments are stated in the same report:(1)
"The primary objective of the experiments on rehabilitation of asphalt concrete and jointed portland cement concrete pavements is to develop conclusions concerning the effectiveness of different rehabilitation techniques and strategies and their contribution to pavement performance and service life."
While the LTPP program has been oriented toward research, the client agencies (SHAs) expect "down-to-earth" implementable products that will help the agencies better manage their highway networks. Specifically, the highway agencies expect that the overall LTPP program and, specifically, the SPS experiments will contribute significantly toward improving knowledge in the following areas:
As the SPS experiments have been constructed and monitored over time, concerns have been expressed regarding their ability to satisfactorily meet these expectations. These concerns include:
It is known that some of these SPS projects were not constructed in some climatic areas because of lack of interest by the SHAs or lack of suitable sites, leaving a portion of the desired inferential space with no performance data. It is also known that some of the SPS projects, as constructed, are not in complete conformity with the original experimental plans. Despite best efforts, the amount of inventory and monitoring data that has been collected from these sections during construction and for several years afterward may be deficient.
The full extent of the deviation and the potential impact of that deviation have not yet been fully evaluated for most of the SPS experiments. Thus, this study was initiated to conduct a comprehensive review of all SPS-6 experiment sites. This review compares the experiment sites as they exist today with the original expectations and, in addition, compares these projects as they exist today with any new expectations for the 21st century. For example, there is a greater emphasis on mechanistic-based design now than existed a decade ago. This review provides a sound basis for:
Issues of experimental design (e.g., existence of planned SPS projects), construction quality, data quality, and data completeness (with respect to both current data collection guidelines and anticipated pavement engineering needs) should be addressed.
The SPS-6 projects were constructed between 1989 and 1998 and, thus, many are fairly young and may not yet directly support analytical activities to improve the level of knowledge in many of the areas listed above. However, a number of the SPS-6 sections have exhibited distress, allowing some preliminary evaluations to be made. However, no indepth assessment has yet been undertaken to determine to what extent the SPS-6 experiment will provide the necessary data to ensure that the broader expectations of each experiment are attained.
This evaluation of SPS-6 is being conducted at the same time and in coordination with the evaluation of SPS-1 (new flexible pavement), SPS-2 (new rigid pavement), and SPS-5 (rehabilitated flexible pavement).
This review concentrates on the core experiment sections that were included in the experimental design for the SPS-6 project. In addition, the SHAs often added supplementary sections to each SPS-6 project that do not fit any formal controlled experimental plan. The value of these sections was also evaluated.
The objectives of this study are:
This report first focuses on the original SPS-6 experimental design and compares this to the SPS 6 projects actually constructed. Chapter 3 reviews the availability and completeness of the SPS-6 experiment data. Chapter 3 also includes a detailed discussion of the quantity and percentage of level E (releasable to the public) data available in the Information Management System (IMS) database. Chapter 4 presents achieved versus required testing frequency at these sites. Chapter 5 compares the designed versus constructed section parameters. Chapter 6 contains a status assessment of each of the SPS-6 experimental projects. Initial evaluations of the key performance trends are then discussed in chapter 7. Chapter 8 provides a summary, conclusions, and recommendations. Appendix A presents a summary of the SPS-6 projects that were constructed. The materials testing information is summarized in appendix B. Finally, all of the monitoring activities from IMS are listed in appendix C.