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Publication Number: FHWA-HRT-10-049
Date: August 2010

LTPP Specific Pavement Studies (SPS) Materials Action Plan Final Report

Chapter 1. Introduction

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1.1 Genesis of the SPS Materials Action Plan

The Long-Term Pavement Performance (LTPP) program was begun in the late 1980s to study pavement performance and the factors that affect it over a period of 20 years or more. One of the program's goals is to provide research-quality data to explain how pavements perform and why they perform as they do. More than 2,500 pavement test sections have been established on in-service public highways and roadways throughout North America. These test sections are subjected to the same traffic loads and environmental conditions as other pavements in the public transportation system. A broad range of data are collected from LTPP test sections based on past and current engineering principles of pavement performance, distress development, load factors, and construction/maintenance effects.

The availability of accurate and reliable data to properly characterize an as-constructed pavement structure and the engineering properties of its materials is crucial to understanding why pavements perform as they do. Field material sampling, field material tests, and laboratory test plan guidelines were developed by the LTPP program for each of the Specific Pavement Studies (SPS) included in the LTPP program. Individual field and laboratory test plans were also developed by the program for each SPS experimental project site. Due to budget limitations, highway agencies that voluntarily agreed to participate in the LTPP SPS experimental program by constructing LTPP test sections on public roads in their jurisdictions were assigned responsibility for the majority of these materials-related tests.

In 1996, LTPP conducted a mid-course program assessment to determine corrective actions needed to enhance the ability of the program to meet its goals. The focus of this assessment was the inventory of LTPP test sections and the data that had been collected. A major finding from that assessment was that there were gaps in the LTPP database, including significant gaps in the available SPS materials information.

Consequently, in 1997, LTPP undertook a program-improvement campaign that sought to determine the status of the database shortages and whether they could be filled. Although progress was made, significant materials data gaps still remained at the conclusion of the effort.

The magnitude of the SPS materials data problem was summarized in a handout provided by the Federal Highway Administration (FHWA) to the Transportation Research Board (TRB) LTPP Materials and Falling Weight Deflectometer Data Collection and Analysis Expert Task Group (referred to as the Materials ETG) at its April 29-30, 2002, meeting in Woods Hole, MA. Overall, 48 percent of the requested SPS materials test data were missing, clearly limiting the use of data from the SPS experiments in some important research investigations.

In 2002, the LTPP program renewed its effort to address the SPS materials data gaps. This effort included further pursuit of missing materials data from the responsible highway agencies, reconciliation of all materials data submitted to the LTPP program, and acceleration of hot-mix asphalt (HMA) and unbound granular (UG) resilient modulus testing performed by the LTPP laboratory test contractor using program funds.

While the 2002 effort provided positive results and more available materials data, significant data needs still existed. This need led the LTPP program to develop the Materials Action Plan (MAP) to address priority materials data needs on SPS project sites. The details of the final MAP were contained in the internal LTPP document LTPP SPS Materials Data Resolution: Update and Final Action Plan, August 2004.

The MAP addressed three major areas of need with the following priorities:

To optimize the use of LTPP program funds in 2004, the MAP was focused on the following SPS project sites, which were designed to extend the findings from LTPP General Pavement Study sites with the addition of controlled pavement design factors and/or environmental load factors:

The other test sections classified in the LTPP SPS experimental program were excluded from the MAP for the following reasons:

1.2 MAP Task Structure

The MAP consisted of the following nine defined tasks:

  1. Award of new central LTPP laboratory test contract.
  2. Preparation of project data needs reports and other required documentation.
  3. Preparation of detailed materials sampling and testing (MS&T) plans.
  4. Creation of tables in LTPP database for new tests.
  5. Implementation of field portion of MS&T plans.
  6. Implementation of laboratory portion of MS&T plans.
  7. Entry of materials data into LTPP database.
  8. Collection of samples for LTPP MRL.
  9. Preparation of final LTPP materials availability report.

The formal implementation of the MAP began in 2004 and was completed in 2009 with delivery of the final material test data sets from the LTPP laboratory test contractor.

The original intent of task 9 was to document the results of the MAP and perform a detailed assessment of the availability of materials data for all LTPP test sections. Due to LTPP program funding constraints, this report presents summary statistics and other metrics to document the results of the MAP.


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