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

Chapter 4. MAP Accomplishments

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4.1 Test Results

The number of tests ordered from the laboratory contractor and the number of test results obtained are shown in table 5. The difference between tests ordered and results obtained is due to inadequacy of specimens for the requested tests. Approximately 95 percent of the MAP material tests ordered from the LTPP contract material test laboratory were able to be tested following the rigorous LTPP test protocols. It is common in pavement field and laboratory testing to obtain samples that cannot be tested in the laboratory due to a number of practical constraints, such as inadequate material, damaged cores, or too-thin layers.

Table 5. Comparison of MAP tests ordered versus delivered data results.

Specimens for the Superpave^®-related binder tests (AE07, AE08, and AE09) were planned for testing by a related national HMA pavement research program but were not tested by 2009. Test specimens for PCC thermal coefficient of expansion (PC03) were sent to FHWA's Turner‑Fairbank Highway Research Center for testing consideration. While some of these specimens may have been tested, they were not included in the official MAP tracking system since these tests were performed under voluntary participation by the test laboratories.

A comparison of the number of available and missing material test results by material type and test method between 2004 and 2009 is shown in table 6. The numbers presented in this table were generated using database queries based on general rules for material data requirements. Due to the myriad details associated with each SPS project site, the numbers do not necessarily represent missing data needed to characterize a pavement structure based on other potential data inferences. This comparison was intended to provide an "apples-to-apples" time comparison for management purposes based on a macro business rules approach that takes into account rule changes. The numbers in the 2004 columns are from the internal report LTPP SPS Materials Data Resolution, written in August 2004. The numbers in the 2009 column were generated using as similar methodology as possible based on data from LTPP Standard Data Release 24.

Table 6. Comparison of materials test data status by material layer type and test protocol from 2004 to 2009 for SPS projects included in the MAP.

^a A single test may provide results for multiple layers. The numbers provided here are on a per-layer basis.
^b Test was not required prior to 2004.

The numbers in the "missing" columns represent the number of additional tests that would be required to fulfill the following criteria:

• For AC01, AC02, and PC06: Both 2004 and 2009 require at least three tests per test section.
• For PC03: 2004 requires three tests per project layer, and 2009 requires at least two tests per project layer.[1]
• For TB01: 2004 requires three tests per section layer, and 2009 requires three tests per project layer.
• For all other tests: Both 2004 and 2009 require at least three tests per project layer.

In addition, the layer must have at least 1.5 inches in representative thickness in the database for a test to be required (with the exception of thickness measurements in the AC01, PC06, and TB01 tests).

The information in table 6 does not reflect limitations on sampling due to field conditions or the suitability of specimens for the respective test. In the case of treated base materials, these test requirements were determined solely on the basis of the material description previously reported and stored in the database. In some cases, based on the new MAP field sampling, the material was found to be unsuitable for the planned tests. In other situations, the difference between the previously reported pavement structure and the findings from the MAP field investigations did not allow for corrections to be made in the field.

The change in materials data availability is summarized in table 7. Note that the number of required tests increased substantially due to additional layers discovered during the MAP sampling program and to additional required tests such as DCP and specific gravity of unbound materials. Also, the increase in available test results is substantially higher than the 10,280 tests performed by the laboratory contractor. The reasons for this difference are as follows:

• DCP testing is included in table 7 but was performed by the LTPP regional support contractors rather than the laboratory contractor.
• A single AC01 test usually yields data for multiple layers. The numbers in table 7 are tabulated on a per-layer basis.
• The regional support contractors received and entered test results during this period from sources outside the MAP, including State highway agency laboratories.

Table 7. Increase in availability of material test data from 2004 to 2009 on SPS-1, -2, -5, -6, and -8 project sites.

Detailed information on materials data availability by project, section, layer, and specific test designation is tabulated in the appendices.

4.2 Summary of MRL Sample Collection

Although the collection of MRL samples was strongly supported by FHWA, storage of samples in the MRL for potential future use was assigned a lower priority due to financial constraints. The effort was dependent on the highway agencies' generosity in carrying out the sampling.

It was recommended that the same number of cores be obtained for the MRL as for the new and aging tests. Although the goal was to obtain specific numbers of cores that included all asphalt concrete (AC) or PCC layers within the project, this was not always achieved. In some cases, sufficient cores were collected but some or all of them included less than the total layers in the project. Table 8 summarizes the number of project-layer combinations present in the collected core samples. Of the desired samples, 74 percent of the 12-inch core samples and 61 percent of the 4-inch core samples were delivered to the MRL.

Table 8. Status of SPS AC and PCC cores for the MRL.

Additional material in the MRL includes 473 12-inch cores and 1,071 4-inch cores of treated base material as well as 1,488 samples of bulk material.

[1] A project layer is defined as a layer common to more than one test section on a project constructed to the same material and construction requirements. Thus, more than one test section on a project may contain the same project layer.