Long Term Pavement Performance Project Laboratory Materials Testing And Handling Guide

Chapter 1. Introduction

1.1 History of LTPP Laboratory Testing

The Long Term Pavement Performance (LTPP) program was a twenty-year study begun in the late 1980s to evaluate pavement performance and the factors that affect it. LTPP’s goal was to provide the data necessary to explain how pavements perform and why they perform as they do. To meet this goal, nearly 2,500 pavement test sections were established on in-service highways throughout North America and hence subjected to real traffic loads and a wide range of environmental conditions. At each test section, general inventory, pavement performance monitoring, materials,traffic, climatic, and maintenance and rehabilitation data were collected.

A critical element to the successful accomplishment of the LTPP goal was the collection of accurate and reliable materials data. These data were needed to define the properties of each of the structural pavement layers of the test sections within the program.

Originally, the LTPP materials testing program under the direction of the Strategic Highway Research Program (SHARP) was conducted by one of five laboratory contractors as indicated by Figure 1.1. Testing of all portland cement concrete (PCC) materials was performed by one central contractor under the direct supervision offshore. Testing of the asphalt and unbound materials was performed by one of four laboratories under the management of the Regional Engineer assigned by SHRP to each of the four regions. The Regional Engineer was assisted in the contract management by the Regional contractor. The field sampling and laboratory testing for the General Pavement Studies (GPS) test sections was conducted under the contracts identified in Figure 1.1 with the exception of the resilient modulus testing and testing of overlays placed after these contracts ended. At the end of the SHRP oversight of the LTPP program, a five-year report was prepared which provides a complete review of the field sampling and laboratory testing activities performed under SHRP.⁽¹⁾

The field sampling efforts were performed in accordance with the SHRP-LTPP Guide for Field Materials Sampling, Testing, and Handling, Operational Guide No. SHRP-LTPP-OG-006.⁽²⁾Each GPS experiment had a sampling plan specific to that experiment. The Field Guide provided each of these individual sampling plans. It also covered the requirements associated with sample naming, labeling, identification, and shipping.

The Specific Pavement Studies (SPS) projects differed from the GPS test sections in that each SPS project incorporated several test sections at a location. Field sampling and laboratory testing plans were developed for each specific SPS project. These sampling and testing plans were based on the general set of sampling and testing plans developed for each SPS experiment and as identified in the experiment specific guidelines. (See references 3–9.) Only the latest version of each of these documents was identified in the reference list. Revisions were made to most of these documents at some point during their use and can be found using the LTPP Guidelines for Data Collection.⁽¹⁰⁾

Figure 1.1 Organizational Chart for Laboratory Testing Under Conducted SHRP

Testing for the LTPP program was carried out in accordance with the SHRP-LTPP Interim Guide for Laboratory Materials Handling and Testing (PCC, Bituminous Materials,Aggregates, and Soils), Operational Guide No. SHRP-LTPP-OG-004.⁽¹¹⁾ The Guide was prepared for the SHRP Laboratory Testing Contractors responsible for laboratory material handling and testing of material specimens and samples of asphalt materials, PCC, aggregates and soils under the supervision of the SHRP Regional Engineers and the SHRP Regional Coordination Office Contractor staff and SHRP Authorized Representatives. It was first release din November 1989 and served as a contract document providing the required information for sample receipt, testing plans for the GPS experiments, test protocols, sample disposal and invoicing.

Under the Federal Highway Administration (FHWA), testing efforts were consolidated under two contracts. The objective of these two contract laboratories was to perform testing of the SPS projects and complete the resilient modulus testing for the GPS test sections. Additional testing to be performed under these contracts included testing of any overlays constructed on the GPS test sections as time progressed. Due to lack of funding, the testing requirements for these laboratories were reduced to the resilient modulus and supporting tests for the SPS projects and GPS test sections. Because of these funding limitations, the remainder of the testing requirements were taken on by the State departments of transportation (DOTs) constructing the SPS projects and GPS overlays. After approximately one year, one of the FHWA contract laboratories released their contract due to potential conflict of interest with a separate contract held by the same company.

The Laboratory Materials Testing Guide was in a state of constant evolution over the life of the LTPP program and was revised over the years to more fully encompass the needs of the LTPP program. In 1993, updates were made to provide for the SPS project testing and appropriate forms for these projects. Updates were made to various testing procedures to clarify existing procedures. In particular, the protocols for resilient modulus testing for both the asphalt and unbound materials were re-written to provide a more robust means to perform these tests. Revisions to the Guide beginning in 1993 were made by directives from FHWA. The LTPP Customer Support Service Center may be contacted to obtain copies of these directives.

As part of a program assessment conducted in the late 1990s,a review of the available materials data indicated that there were gaps in the available data. An effort was undertaken to fill in these gaps of missing data and improve the overall quality of the available data. As part of this effort, the document LTPP SPS Materials Data Resolution: Update and Final Action Plan was developed to fully document the existing gaps and the proposed methods for resolving them.⁽¹²⁾ Due to further funding limitations, some of the desired testing originally identified in the Materials Action Plan (MAP) was removed from the plan. The FHWA awarded a laboratory contract to perform the testing identified in the MAP.

The objective of this document is to provide information to analysts regarding the methods used in obtaining research quality laboratory data for the LTPP program.

1.2 Document Outline

This version of the laboratory materials testing guide represents a major revision to previous versions of the guide. This version consists of five chapters. The objective of the first chapter is to provide an overview of the history of the guide and the objective of this version. The second chapter provides a summary of the quality control/quality assurance (QC/QA) program used by the LTPP program to assure the quality of the results. Chapter 3 provides the series of forms (L01 to L04) used to alert the FHWA of receipt of data and assign tests to individual samples. Chapter 3 also provides the methods used in splitting samples to obtain the sample used for testing. Chapter 4 provides the protocols, associated forms, and codes used in completion of those forms. Finally, Chapter 5 provides the guidelines for completing the section layering information in the L05 series forms. The last two sections of the document contain a glossary of common terms used throughout the Guide and the references for other relevant LTPP documents.

As the protocols used by the laboratories in performing testing for the LTPP program provide the largest portion of this document, a list of these protocols, test designations, and titles are provided in Table1.1. Some of the protocols listed in Table 1.1 were developed as new tests to be performed as part of the action plan to provide a more complete set of the materials data in the LTPP Pavement Performance Data Base (PPDB) for the SPS projects. Due to funding issues, these new tests were eliminated from the MAP and no data were collected using these protocols (P27, P28, P29, and P70). Additionally, the protocols beginning with the letter "H" were used for testing materials from the SPS-3 and SPS-4 experiments concerning the effectiveness of maintenance on asphalt concrete pavements and jointed concrete pavements,respectively.

Notes: ^# Testing using protocol P24 was cancelled effective December 1997.
* No testing was performed for the LTPP program using this protocol.
⁺ These tests were used for testing samples from the SPS-3 and SPS-4 projects exclusively.

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