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Publication Number: FHWA-RD-07-052
Date: September 2007
QC of the laboratory test data was divided into four basic sets of procedures. These steps included the following:
These QC/QA procedures required input from all parties involved in the LTPP program. The FHWA (and prior to that SHRP) included requirements for the laboratory selected to do the testing as part of the Request for Proposal. The laboratory used an internal quality control procedure in performing the testing. The Regional contractors and the Technical Support contractor both provided data review.
These QC/QA methods evolved over time from those initially implemented under SHRP to improve the overall quality of data in the PPDB. Table 2.1 provides a basic list of these QC/QA procedures along with the group responsible for performing the checks and the year that this portion of the quality program was implemented as well as the year of any major change in that overall procedure.
|QC/QA Procedure||Responsible Party||Year Implemented|
|Laboratory Accreditation and Requirements||FHWA/SHRP||1988|
|Laboratory Quality Control Program||Laboratory Contractor||1988|
|Laboratory Start-Up Procedure performed in addition to Accreditation||Technical Support Services Contractor||1996|
|Independent Review of Data||Regional Support Contractor||1988|
|Technical Support Services Contractor||1996 – Protocol P462001 – Protocol P072005 – MAP Testing|
|Automated Quality Assurance Checks||Regional Support Contractor||1988|
The QC/QA procedures implemented by the laboratory were required by contract with FHWA and prior to that SHRP. The laboratory capabilities were reviewed as part of their proposal to perform the work. These capabilities were specified in the Request for Proposals prepared by the contracting agency and included items such as minimum level of experience and education of personnel to supervise and perform the testing.
The steps required under the original SHRP contract required that the laboratories be accredited through the AASHTO program.(13) The purpose of the AASHTO Accreditation Program (AAP) was to review the competency of the laboratory to perform specific tests on construction materials. As part of the AAP, the laboratory quality system was assessed for compliance with AASHTO Standard Practice R18.(14) Test procedures on PCC, asphalt materials, and unbound materials are included in the program; however, the AAP did not include every kind of test that could be performed on each of these materials.
Since some of the tests not included in the AAP were considered critical to the LTPP testing plan, a set of proficiency programs were developed and used for these procedures. These programs were initially implemented under SHRP and included the following five areas:
The SHRP-P-687 report provides a complete description of these programs and how they were implemented.(1)
SHRP required that the lab contractors have their own in-house QC/QA programs as well as experienced and capable personnel committed to carrying out these procedures. These QC/QA documents were to include provisions for each of the following facets of a laboratory testing program:
This requirement continued under FHWA. However, the requirement could only be enforced for the laboratories contracted to FHWA that were performing the resilient modulus and associated testing. The State laboratories performing the remaining testing on the SPS projects and GPS overlays were not required to have such a document in place.
Under FHWA, a laboratory start-up procedure was developed and used prior to allowing any resilient modulus testing of LTPP samples.(15) This program was first initiated in 1996. This procedure reviewed the dynamic performance of the testing system to make sure that the values measured by the system were in fact the loads, displacements, and pressures applied to the sample. Checks were made of the individual system components to ensure that the output met the expected ranges.
The proficiency program was expanded under this procedure to incorporate review of the personnel performing the testing to make sure that they were following the test procedures. Under this portion of the procedure, laboratory personnel were evaluated as they performed each step of the test procedure by a member of the Technical Support contract team. At the same time, the settings within the test system were also reviewed to make sure that they were appropriate and complied with the test protocol.
The Lab Guide was created to provide the first step of the QC/QA process. The Guide provided a uniform set of procedures to be followed by all laboratories participating in the LTPP testing program. The protocols and sample handling procedures included in the Guide were developed to be as specific as possible such that the variation in test results between laboratories would be as small as possible.
Additionally, procedures within the Guide included quality control activities for the assignment of layer numbers to each pavement structure, identification of both samples and layers, performance of lab tests and review of test data, review of layer data, and storage and handling of samples. More information about these procedures is provided in the following chapters.
Quality assurance of the laboratory data was performed in part through timely transmission of information using the standard set of forms provided by the lab guide. A full set of these forms and accompanying descriptions are provided in the following chapters of this version of the Guide.
Under SHRP, the Regional Engineer was responsible for providing QA on layering assignments, field data, and laboratory data. Generally, the Regional Engineer utilized Regional contractor staff to provide input on this QA.
This review involved evaluating the consistency of the data with other information that had been obtained from the test section or project. The review also included comparing the tests conducted with those planned and examining the data from a particular test section for variability. Some variation may have existed with the specifics of these reviews between regions, but all of the Regional reviews contained these same general components.
When FHWA took control of the LTPP program, the Regional staff became directly responsible for reviewing data obtained for the State designated laboratories. These laboratories were performing all of the testing on the SPS projects and GPS overlays except the resilient modulus testing. These reviews consisted of the same components as they had under SHRP.
The responsibility for review of the resilient modulus testing under FHWA was placed on the Technical Support contractor. To that end, in 1997, P46CHECK was created to assist in the review of resilient modulus data from unbound (base, subbase, and subgrade) materials.(16) The software provided a way to keep uniformity in the review and ensure that all aspects of the data were evaluated.
The software identified that all 16 data files were present. It also checked that the files were complete and identified the presence of noise in the raw data. Conformance with test method procedures was also verified. Finally, the summary data were reviewed to ensure that the calculations were performed correctly and that the material response followed expected trends.
Similar to P46CHECK, P07CHECK was developed in 2001 and used for evaluating the resilient modulus testing of asphalt materials.(17) The operating characteristics and checks performed by this software were quite similar to those for P46CHECK. Although it was not initially used until 2001, all of the asphalt resilient modulus data contained in the PPDB were evaluated using the P07CHECK software.
Laboratory test data collected under the MAP were also reviewed by the Technical Support contractor. Primarily, this review identified that the data were complete and fell within reasonable ranges. This review did not preclude any review performed by the Regional contractor as well.
Once the data were entered into the PPDB, they were put through a series of data quality checks using several automated QC programs. Specifically, there were three levels of checks to which the data were subjected. The first, or Level-C, checks were to identify any records for which critical data elements were missing. For instance, this check might have identified records in the TST_AC02 table with a missing value for the bulk specific gravity. The Level D checks identified the validity and reasonableness of the data entered in a particular field. For example, an asphalt content entered in table TST_AC04 of 52 percent would have been flagged by this check. Level E checks examined the data for consistency between fields and tables. Among other level E checks performed, these checks made sure that the data entered in tables for asphalt materials corresponded to a layer with an asphalt material code in the TST_L05A table. Additional information about these QC checks was provided in the Data User’s Guide.(18)
Once the data were entered into the regional database and checked using the automated QC programs, the data were uploaded on a regular basis to the PPDB. Prior to allowing these data to be released to the general public, the data were reviewed by the Technical Support contractor. In particular, this review evaluated the consistency of the data collected between the regions. The review identified the consistency of the application of procedures and definitions between the varying agencies performing and reviewing the laboratory testing.
The QC/QA procedures used within the LTPP program were considered to be a critical element to the laboratory testing program. These procedures extended to all parties involved in the LTPP program. They also extended from the time of proposing on the laboratory contract to after the laboratory data had been uploaded to the PPDB. It was one of the goals of the LTPP program to provide research quality materials characterization for each the test sections under study.
Topics: research, infrastructure, pavements and materials
Keywords: research, infrastructure, pavements and materials, Asphalt cement, asphalt concrete, field sampling, General Pavement Studies, laboratory testing, LTPP, material properties, pavement layering, Pavement Performance Data Base, portland cement concrete, protocol,Specific Pavement Studies, subbase, subgrade, treated base, unbound base
TRT Terms: research, facilities, transportation, highway facilities, roads, parts of roads, pavements